# Destroyers.....



## Lucky13 (Jun 14, 2009)

Here goes lads....which is the top dog from any of these destroyer classes? 8)

Fantasque Class v. 
Narvik Class v. 
Soldati Class v.
Akizuki Class v. 
Soobrazitelny Class v. 
L and M Class v. 
Fletcher Class v.


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## Amsel (Jun 16, 2009)

I really like the Fletcher class. Some of my favorite ships are from the Fletcher class including DD-557 USS Johnston and the USS Hoel. The Fletcher class was really at an advantage for surface fighting due to the same radar-assisted Mark 37 Gun Fire Control System used on the BB's, and its Mark 1 Fire Control Computer from Ford. It was used up until 1969.

The Fletchers will always be among y favorite due to the Battle off Samar and the tough resistance Taffy 3 put up against Kuritas powerful Center Force.


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## Glider (Jun 16, 2009)

1 Fletcher
Best all round destroyer of the group
2 Akizuki
DP main weapons and the best torpedos
3 LM
Best British Fleet Destroyer but I would go for the 8 x 4in not the 6 x 4.7in version
4 Fantastique
Best armed destroyer for Surface to Surface fighting.
5 Narvik Class
On paper a heavier gun armament than the Fantastique but 5.9 shells were too heavy and the ships unbalanced
6 Soldati
Good little destroyers which needed a DP main armament 
7 Soobrazitelny
Dreadfull vessels that were a follow on from an earlier design which could not face up to a heavy sea. A clue is that one captain was given a medal for keeping his destroyer at sea for three days, also they sank nothing in the entire war, not even a merchant ship.


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## Juha (Jun 16, 2009)

Agree totally with Amsel.
Fletcher was really good class and look the number produced, 175 IIRC. And yes the fight of Johnston, Hoel and Hermann plus those couple DEs was really outstanding.

Juha


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## Vassili Zaitzev (Jun 16, 2009)

I recoginze the Flecther from that list. Sorry, I don't have any knowledge on those other class of Destroyers.


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## vikingBerserker (Jun 16, 2009)

Juha said:


> And yes the fight of Johnston, Hoel and Hermann plus those couple DEs was really outstanding. Juha



A classic. I have to go with the Fletcher as well


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## comiso90 (Jun 16, 2009)

Were there other Destroyers besides The Fletcher?

.


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## timshatz (Jun 17, 2009)

One thing that should be mentioned about the speeds on ships, especially Destroyers. Once you get north of 25 knots, in any kind of weather, it is almost impossible to stand on those things, much less fight. When people talk about a top speed of this or that, it should be taken into consideration that those speeds are only good for calm water. Once the seas build, forget it. You're not going over 25knots and getting anything done.

Realize it hasn't been brought up yet but it's something people miss when talking about those old destroyers. A little different now with stabelizers and whatnot. But not much. 

My vote is for the Fletchers. Good all around Destroyer.


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## Glider (Jun 17, 2009)

timshatz said:


> One thing that should be mentioned about the speeds on ships, especially Destroyers. Once you get north of 25 knots, in any kind of weather, it is almost impossible to stand on those things, much less fight. When people talk about a top speed of this or that, it should be taken into consideration that those speeds are only good for calm water. Once the seas build, forget it. You're not going over 25knots and getting anything done.
> 
> Realize it hasn't been brought up yet but it's something people miss when talking about those old destroyers. A little different now with stabelizers and whatnot. But not much.


True to a degree. When HMS Cavalier the last british WW2 destroyer was in her last few years of service she was pitched against the newest destroyer in a race as part of a publicity stunt, as you can guess it didn't go according to plan and the Cavalier won the race.
According to everyone on board she was rattling and shaking herself to bits but managed 37 kts in I think 1970, not bad for an old lady.

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## renrich (Jun 17, 2009)

Tim, good remarks. I go with Fletcher, a good balanced design.


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## ToughOmbre (Jun 17, 2009)

The "Fletchers" are to DDs what the "Iowas" are to BBs.

And good looking ships to boot!

TO


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## Torch (Jun 17, 2009)

Good website for info........History of the World's Navy's


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## timshatz (Jun 17, 2009)

Glider said:


> True to a degree. When HMS Cavalier the last british WW2 destroyer was in her last few years of service she was pitched against the newest destroyer in a race as part of a publicity stunt, as you can guess it didn't go according to plan and the Cavalier won the race.
> According to everyone on board she was rattling and shaking herself to bits but managed 37 kts in I think 1970, not bad for an old lady.



I was thinking of time I spent on a Gearing (Fletcher on steroids). In any weather other than flat, she pitched. Not bad, but it was noticeable. Especially as she was top heavy. The higher the seas, the worse the ride. We got stuck in a gig where we were going after a Columbian AF C-130 that had ditched North of Bermuda. We started out in 12ft seas and ended up in 20-25ft seas. Even in 12ft, it was pointless to go over 23-24kts, it was throwing people out of their racks. Seas got worse, speed came down. And guys were throwing up all over the place. Even had puke on the overhead. It was nutz. 

I was thinking of that (and other similar events) in terms of the affect of speed and whatnot. Whilethe numbers are impressive (we could do 33kts sustained but it was a rough ride), the trade off in weight usually means the ship is lite, top heavy and not a good gunnery platform at high speeds. 

Might be different now with new ships.


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## Juha (Jun 17, 2009)

Hello
looked on Glider's list and tended to agree with him, Akizuki's weak point is its AAA, 25mm AAA gun wasn't very good, and when they added more of them, they removed the second DT which was IMHO a bad move, after that it could engage only one target in time with its 100mm guns. But IIRC Japanese industry had difficulties to deliver enough of those DTs, which were very good, almost as good as US Mk 37.

Juha


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## Glider (Jun 18, 2009)

comiso90 said:


> Were there other Destroyers besides The Fletcher?
> 
> .



Apologies for missing your question.
The Standard production destroyer for the USN at the start of the war was the Benson class. Designed for 5 x 5in, 10 x TT and 6 x HMG they normally ended up with 4 x 5in, 10 x TT, 2 x 40 (1 x 2), 4 x 20mm ( 4x1). Very few were built as designed, if I remember correctly about 4 almost all being built with 4 x 5in. There were considerable differences between individual vessels as the war progressed.

After the Fletcher the standard production destroyer was the Allen M Summner. 6 x 5in (3x2), 12 x 40mm (2x4, 2x2), 11 x 20mm (11 x 1) and 10 x TT. In some ways these were not a success as they tended to be slower than designed around 33 knots not 36 and were top heavy from the start.


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## beaupower32 (Jun 18, 2009)

Fletcher Class for me here also. Im kinda fond of the USS Kidd. I have visited her numerous times in Louisiana. 


USS KIDD Veterans Memorial


The KIDD's first voyage was one of some notoriety. Under the command of Cdr. Allan B. Roby, the destroyer moved across New York Harbor for delivery to the Brooklyn Naval Shipyards . . . flying the skull and crossbones of the Jolly Roger high from the foremast. The edition of TIME magazine that week carried a photo of KIDD, announcing that it had been one hundred years since the Jolly Roger had flown in New York Harbor. The crew quickly adopted the pirate Captain Kidd—who ironically hailed from New York—as their mascot and hired a local cartoonist to paint the famed buccaneer's image high of the forward smokestack. Not wishing to dishonor RADM Kidd, however, the crew obtained permission from Mrs. Kidd first. The Admiral's nickname at the Naval Academy had been "Cap" (as in "Captain Kidd") and he had gone by this nickname his entire life. So on the crew's behalf, Mrs. Kidd obtained official permission from the powers-that-be in the Navy for them to paint the pirate on the stack and fly the Jolly Roger. The KIDD would become the only vessel in the history of the United States Navy to ever have such leave granted to fly the flag of piracy.

During a simulated torpedo attack in September of that year, KIDD was struck by two star-shells fired from the NORTH CAROLINA (BB-55). As fortune had it, her forward damage control party was exercising in the immediate vicinity with a make-believe casualty strapped into a stretcher. One of the shells entered the compartment and crossed just above the chest of the pretended casualty. The sailor suffered a minor abrasion from a fleck of debris. The skipper reported to the task force commander: "KIDD claims to be the best prepared ship in the Navy. We had a victim already strapped in the stretcher when he was wounded.

It was early on at this point in her career when she picked up the nickname that would become her trademark. Taking their mascot pirate to heart, crew members began to "ransom" rescued pilots for ice cream mix and other delicacies from their comrades aboard aircraft carriers so that her reputation grew as the "Pirate of the Pacific." Other destroyers conducted this practice, but KIDD did so with a certain flair. The Pirates were one of the first "tin cans"—destroyers—to have their very own ice cream machine, something usually reserved for the larger vessels of the fleet.

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## Amsel (Jun 18, 2009)

Great story.


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## renrich (Jun 18, 2009)

Tim it is always good to hear from someone who has practical experience. Adds a little reality to the discussion and your remarks and observations are much appreciated. I was always an admirer of the Gearing class (from looking at pictures) probably because of their heavy armament. They were big DDs with lots of guns and torpedoes, perhaps too many.


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## Amsel (Jun 18, 2009)

I have heard a few references to the officers and sailors of the DD's and DE's being the real navy.


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## Lucky13 (Jun 18, 2009)

So I'm not the only one with a soft spot for the "pirate ship" USS Kidd DD-661 then?


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## Messy1 (Jun 18, 2009)

Good story beau! Funny!


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## timshatz (Jun 18, 2009)

My pleasure Ren. To tell the truth, I'd forgotten about most of it. When I was writing that, a lot of memmories came back. When I was on it, she was a very old ship and not as top heavy as when originally designed (took off two 5" mounts and all the 40MM, replaced with ASROC and a hanger for a helicopter in the Fram 2 rework). But she was still pretty top heavy. Probably had something to do with the inch of armor she carried on the main deck. That and the superstructure. 

One thing Colin mentioned about in his story was how the ship he heard about practically shook itself to bits on a speed run. It was prety common for the older ships to have troubles when they got to speed. Just too many miles under the bow. Stuff like that was always happening to the ship I was on. We jokingly refered to them as the "sink by themselves" class because they were 38 years old and had things breaking all the time. Had many occasions when we were steaming and the ship just broke. Lights went out, engineering lost steam and the props stopped. No big deal in most cases, but when you do it in the middle of the Delaware River on a weekend in Summer (with tons of guys cruising around you in their speedboads), it gives the scene a weirdness all it's own. 

Chicks, Beer, Speedboats, Broken Navy Destroyer-which one of these things is out of place?


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## comiso90 (Jun 18, 2009)

It's a flippin crime that we sent our guys to war with inferior torpedoes.....


.


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## tomo pauk (Jun 18, 2009)

The Japs did have Long Lances, but the US destroyers had everything.


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## vikingBerserker (Jun 18, 2009)

That's a fricken awesome story - lol


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## beaupower32 (Jun 18, 2009)

Lucky13 said:


> So I'm not the only one with a soft spot for the "pirate ship" USS Kidd DD-661 then?




Nope, I got a soft spot for the Kidd as well. I have visited her a couple of times, and I enjoy it more and more every time.


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## renrich (Jun 19, 2009)

It is very educational to hear accounts of the nitty gritty of naval affairs. Us land lubbers tend to look at performance specs for ships( just like we do with air planes) and take all else for granted. In reading about the British BCs at the Falklands, it was said that the vibration, while steaming at 25 knots, was so bad in the high directors that they could hardly focus on the German armored cruisers. At the Kormondorskis, in WW2, Salt lake City fired the equivalent of 80 ten gun 8 inch salvos. The vibration was so bad that light bulbs all over the ship broke and much of the electronic equipment quit working. Jellicoe, commander of the Grand Fleet in WW1, because the Fleet was steaming outside of Scapa Flow much of the time because of the Flow's poor security, lost whole divisions of dreadnoughts because of breakdowns in machinery. More to it than meets the eye!


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## timshatz (Jun 19, 2009)

I'll drop a war story in hear along the same lines.

Out on the gun line one day, firing the forward and after mount in sequence ('cause everyone knew it was a bad idea to fire a broadside from a Destroyer that old) and I'm up in CIC at battlestations. The Chief of our section is in there and he has a bug up his ass. Starts yelling at us all that we're sloppy and telling us to get it together. In the middle of the speech, the Capt decides to fire a broadside just to see if the old girl could do it. "BANG!" go the guns, whole ship shakes and, predictable, the lights go out due to the vibration, which is also so bad it unhinges a battle lantern (those yellow plastic flashlight things all over the place inside US ships that are designed to come on when the lights go out) right over the Chief's head and drops it squarely on his noggin. He goes down in a head on the deck, out cold. 

For a few seconds, we all just sat there with this, "Wow, did you just see that ****!" look on our face. Then we got the Chief back on duty. He was groggy for a while. Forgot to finish his speech.


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## Messy1 (Jun 19, 2009)

Like that story Tim!


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## renrich (Jun 19, 2009)

Great story! Many thanks.


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## batcocan (Jun 21, 2009)

Hi all,
Although those are some mighty fine ships you've listed I have to suggest the Tribal Class destroyers-Considered to be almost pocket cruisers with their firepower and speed. There is still one in existence "HMCS Haida" check her out at HMCS HAIDA - Intro
I had an uncle who served on her sister HMCS Athabaskan (G07) and my wife's grandfather served on the postwar replacement HMCS Athabaskan (R79) 
I'm not a boat person but just my two cents
Cheers,
Matthew


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## renrich (Jun 22, 2009)

Comis, the US was not the only WW2 power that had faulty torpedoes. The Germans had problems also. U boat skippers early in the war were often frustrated with poor torpedo performance. I am not sure if the problems were as great as those encountered with those in the USN, but I think were similar.


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## parsifal (Jun 29, 2009)

Like all these sorts of discussions, it is very difficult to emphatically say which is best, unless there are some parameters set down as to the mission and the operating conditions that the ships will be operating under

The following is just an example of that problem:


During the war, the Germans built a class of Destroyer which the the British refer to as "the narviks". They were designed with an exceptionally heavy gun armment, and also a very heavy torpedo armement as well. Their main armament was essentially equivalent to that of a cruiser, being 5.9" caliber, in a fully enclosed gun turret.

The design was produced in response to the French Contre torpilleurs being built just before the war, the Mogadors and earlier to that, the Le Fantasque classes. Germany had seen France rather than Britiain as her most likely enemy at that time, and had been designing her navy to counter the capabilities of the French rather than the British navies

Once the war did break out it was soon the case that it was the Royal Navy that was the Kriegsmarines main opponent, and it was found that the waters that the KM was most regularly fighting in were the rougher waters of the Arctic rather than the calmer waters of the Baltic and the moderate latitudes of Europe.

However, at the time these destroyers were being transferred to the north, it was felt that the heavy armament of the Narviks would assist in redressing the numerical balance that the RN enjoyed, and that the larger destroyers of the KM could also take on the numerous british Light Cruisers with some measure of confidence.

As it turned out, the narviks were largely a failure. In the rough conditions of the Polar oceans, the heavy weight of the forward turret caused the ships to plunge heavily, rendering them often unsuitable for operations in conditions that were of only marginal inconvenience to their lighter British cousins. The idea that they could engage British Light cruisers was also a misguided assumption. The destroyers lacked the fire control and gun laying capabilities of the british cruisers, meaning they were not as accurate under rough conditions. 

In terms of rate of fire the narviks could not compete as well. I forget the exact ROF of the 5.9 inch, but compared to the 4.7 and 4.5 inch guns of the RN, I vaguely recall it to be about half that of the lighter britisg guns. In rough conditions, a high rate of fire increases the chances of a hit, and any hit has a good chance of knocking out a ship the size of a DD. 

The Narviks also enjoyed a theoretical range advantage, about 18000 yds to about 13000 , but again in the arctic this was a theoretical advantage , during the critical years of 1941-3 the narviks had a practical engagement range that was really no greater than that of the british Destroyers.

So, in the finish, the Germans ended up with a lesser number of big destroyers, which in terms of cost were about 2.5 times more expensive than their British counterparts but in my opinion no more effective. On the basis of cost versus effectivebness, the Narviks have to be considered a failure, in my opinion.

The same sorts of arguments can be levelled at every class of warship and every class of DD you care to mention, so, the lesson to be learnt is that it simply depends on the conditions and the mission you find your ships operating in. If the Narviks had been able to fight under the conditions they were originally designed for, they would have been a success, and today we would be arguing about just how brilliant the Germans wereat designing really good destroyers. Instead we tend to write off the narviks as a failuyre, and that is the reult of them having to fight under conditions that they were not suited to


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## Lucky13 (Jun 30, 2009)

Good post Parsifal!


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## timshatz (Jun 30, 2009)

Good points and a good post.


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## Juha (Jul 1, 2009)

Hello Parsifal
I’d be more harsh on Narviks, it didn’t do well on Biscay either. Nor at the western end of English Channel. And North Sea can be very rough too
The most famous engagement on Biscay was 28 Dec 43 when 5 Narviks and 6 big torpedo boats were engaged by 2 RN light cruisers, a modern Town class and an old E-Class. End result was that one Narvik and 2 of the big torpedo boats were sunk.

Juha


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## stug3 (Feb 2, 2013)

From U-boat Archive - U-581 - Interrogation Report

Royal Navy Destroyer HMS Westcott, rammed U-581 in the straits between the islands of Pico and Fayal, 2nd February, 1942.


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## vinnye (Feb 2, 2013)

I am pleased someone has mentioned the RN Tribal Class - served with distinction in very inhospitable conditions. Sometimes engaging enemy ships with heavier armament. I like the 8 x 4 inch armament - gives a good chance to fire two salvos - meaning better chance of hitting what your are firing at.


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## Juha (Feb 2, 2013)

Tribals original main gun armament was 8 x 4.7 in, soon modified to 6 x 4.7 in + 2 x 4 in. Their weak points were the weak torpedo armament of 1 x quad launcher of 21 in torpedos and its quad 2 pdr was somewhat wooded.

Juha


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## vinnye (Feb 3, 2013)

Juha - you are of course correct, the Canadian Tribals had the 8 x 4 inch fitted as standard.


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## parsifal (Feb 3, 2013)

British DDs, even the tribals were not as competitive as many other Navies until later in the war. The RN determined that the overwhelming issue was numbers, and accordingly designed an built their DDs until the latter part of the war (1944-45), to the idea of sacrificing quality to an extent, in favour of numbers. Even the L&M class were nuilt to budgetry constraints....a limited displacement, no unit machinery arrangement SP guns. The "Z" , "Ca", "Ch', Co", Cr" classes had a superior DP weapon, a decent torpedo broadsise, but farly light LAA, they had machinery arranged in a unit style arramgment, but were about 1000 tons lighter than a Fletcher.

Battle Class (both the 1st and second groups) had standard displacements of 2400tons (compared to the fletchers 2300 tons), but a deep load displacement of 3300 tons to the Fletchers 2900 tons. This had a great impact on the stability comparisons for the two classes. There was no comparison. Ive trained with gearing classes (a close relative to the fletchers) in a Daring Class ( a bigger brother to the Battles), and in any kind of rough seas, the Gearings were quickly forced to lose speed, whereas the Darings were able to maintain close to full speed. The CG of the Darings was much lower than the Geariigs and topweight much less. There really is not any comparison in stability. Moreover the flush deck (ie lack of a raised weather forecastle) generally made the fletchers very wet in any sort of sea.

So, whilst I think the Fletcher was a heavily armed DD, that provided the weather was not too rough could do all things pretty well, it did have some limitations. Its 5/38s were an excellent all ropund general purpose weapon, but compared to more modern DPs was not as good at either the AA or the surface role. The Fletcher had great strength in the hull, but limited internal space brought about by the flush deck arrangements. 

Fletchers were excellent all rounders, but this should not be confused with the idea that they were the best at everything. They were just a well balanced design


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## Glider (Feb 3, 2013)

I agree with a lot of the previous statement by Parsifal. At the outbreak of war the UK dcided to build their destroyers to a standard design to help speed production. The hull was based on the JKN class and this really didn't change much until the Battle class. The guns, light AA and torpedos were modified here and there but the basic design wasn't changed much. 
A similar decison was made re light cruisers where war built ships were based on the town class cruisers.

Considering the war service the RN destroyers and Light Cruisers faced in a multitude of situations the decision worked pretty well.

The Fletchers were almost certainly the best balanced destroyer design of the war but generally speaking the USN were not quite as concerned about their ships being top heavy. The massive rise in LAA and radar only added to the problem.

Fletchers were designed for 4 x 1.1in and 6 x 20mm and some ended up with 10 x 40mm and 7 x 20mm. Add the radars, extra directors, ready use ammo and I hate to think how much weight was added topside. Stability had to give


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## vinnye (Feb 3, 2013)

Most of the British designs were intended for fleet protection if I remember correctly. They would screen heavier units and engage enemy destroyers - hence the heavy firepower and decreased torpedo banks?
As war broke out, it became clear that these types were often going to have to work in isolation or in small task groups - frequently coming under air attack. These showed their weakness in AA capability and hence a number of modifications taking place when possible. It is probably fair to note that several losses whilst undertaking near suicidal missions up to late 1941 may have helped to clarify both RN and other navies thinking regarding AA fitments. Maybe the USN took note of these actions and made improvements to their designs?
I have also read that the RN destroyers were capable of maintaining quite high speeds during severe weather.


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## Glider (Feb 3, 2013)

The Tribal Class were designd to take on other Destroyers hence the priority given to firepower over torpedo's but it was recognised that this wasn't the correct balance. The following JKN class switched to 6 x 4.7 and 10 x TT which was a very good balance without being top heavy.

As for their AA fire British warships at the outbreak of war had better LAA guns and more of them than most if not all the major navies. The problem was that it wasn't sufficient, for the simple reason no one knew what sufficient was. The scale of air attack that warships had to face was beyond the imagination of pre war navies.

US Destroyer design did learn from the lessons of the European war plus their vessels were designed for the extra ranges involved when fighting in the Pacific. This made their warships bigger which then gave more deck space to fit additional LAA guns.


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## davebender (Feb 3, 2013)

I've never understood why Britain diverted resources to development of 4.5" and 5.25" naval rifles. 4.7" (120mm) is ideal for DD use and weapons that size were mounted on RN DDs during 1918. Britain could have continued 4.7" development during 1920s and 1930s. By mid 1930 a proper 4.7" DP gun should have armed all British built destroyers as well as secondary weapon on KGV class battleships.


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## Glider (Feb 3, 2013)

The bit that I never understood was that pre war the RN had a DP 4.5in (on Ark Royal) and a DP 4.7in (on Nelson). Why they stop there develop one or both of these as a proper DP gun I will never know


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## parsifal (Feb 3, 2013)

It does seem a bit of a mystery. I suspect that neither the 4.7DP or the 4.5DP whilst functional weapons had quite the optimal performance they were looking for. But then, one could hardly argue the 5.25" was an ideal weapin either. 

In the case of the 4.7 SP weapon, I think it was simply a case of a number of factors. At the top wa cost....having developed the 4.7SP as the principal DD weapon there was probably little money for further development.

But money would have been found if true extent of threat to surface ships by a/c had been appreciated. Like a lot of contenntal Navies, the threat from a/c was grossly under-estimated. The 4.7 offered better anti-surface results over both the 4in and the US 5/38. The light AA suites were probably seen as enough protection. If so, a serious miscalculation.

The development of a good large calibre DP weapon remained problemtaic. The French had difficulties with their DP mounts, as did the italians. The Japanese DP mount was nearly useless, whilst the germans never attempted a DP mount in the interwar context. their 4.1 was an AA mount, whilst their 5.9 was an anti-surface weapon. Their 5 in DD mount was SP. I think most of the protagonisits found the development of a true DP mount a bit of a challenge. The US did develop the 5/38, and various mounting types to go with it, but while the 5/38 was an excellent gun, it did give up a lot in range and hitting power to achieve that. More than the surface battle focussed Navies of Europe and Japan were prepred to give.


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## Shortround6 (Feb 4, 2013)

There was a lot more to designing and working with DP guns that a few calibers of barrel length and just getting the gun to elevate. The higher velocity guns used larger propelling charges and larger (heavier) cartridge cases. Higher velocity guns could need more room for the barrel to recoil, nor a problem at 30 degrees or under but a big problem at 45 degrees and above. The trunnions need to be higher off the deck. You also need room to load, Most (all?) of these guns used fixed or semi-fixed loading, Shell and cartridge rammed as one unit. It is tough to load while kneeling. AA guns not only need to elevate they need a high rate of fire. By the time you get a high velocity gun high enough off the deck to act as an AA gun it can wind up too high to a be a good surface gun. Instead of being loaded at waist/chest height it has to be loaded at shoulder/head height. 

Picture of US 5in/25 figure how high the breech would be if the gun was level or slightly depressed. 






5in/38 pedestal mount





Note height and rotating platform. It is the simplest 5in/38 mount, yet is larger and more complicated than the British 4.7in single mounts. It is also about 4-5 tons heavier.


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## Glider (Feb 4, 2013)

I agree with what you say but the twin 4.5 as mounted on the pre war Ark Royal weighed in at approx 30 tons, the twin 4.7 as mounted on the JKN was about 25 tons. 
The hull of the standard RN destroyer was based on the JKN so you could have had 4 x 4.5in DP instead of 6 x 4.7in SP and left yourself approx 15 tons for light AA. A quad 2pd was about 10 tons. So with no additional development costs or increase in weight you could have had a standard war built destroyer in 1939 with
4 x 4.5in DP, 2 x quad 2pd, 6 x quad 0.5 and 10 x TT. Sorry but that seems like a better all round job than was built


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## fastmongrel (Feb 4, 2013)

Glider said:


> The bit that I never understood was that pre war the RN had a DP 4.5in (on Ark Royal) and a DP 4.7in (on Nelson). Why they stop there develop one or both of these as a proper DP gun I will never know



The 4.5" on Ark Royal and the 4.7" on Rodney and Nelson were pure AA guns. They could engage surface targets but that wasnt there job and the mounts were only capable of depressing -5 degrees not enough for a DP gun especially when mounted so high above the waterline on the Ark Royal. 

There was an experimental 4.7" +60 to -10 degree DP mount trialled in at least 2 ships but it was a victim of early thirties defence cuts and was never developed as it probably should have been. The RN decided that it wanted lots of small destroyers around the 1400 ton mark and it wasnt possible to build a small destroyer pre war with 4 x DP guns and 10 torpedo tubes and have good seakeeping. With the benefit of hindsight the RN would have been better off mounting 3 or 4 twin 4" DP mounts as the RCN did with its later Tribal builds.


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## Glider (Feb 4, 2013)

I don't think that the -5 degree would be a problem as all the wartime 4.5in guns only had a depression of -5 degrees and I have never heard of an issue with this. 
You are correct about the between the wars going for a 1,400 ton DD but when war broke out they went for a larger hull based on the JKN design. As shown by my previous posting I believe that we could have done better than we did with what we had available.


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## davebender (Feb 4, 2013)

Germany 12.7 cm/61 (5") KM40 (Flakzwilling 40)
German 12.7cm/61 was potentially the best DP destroyer weapon of WWII yet the German Navy did not put it on a ship. It would have been a good weapon for Zerstörer 1936A class rather then historical 15cm/48 naval rifle. Would also make a good DP weapon for German battleships.


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## parsifal (Feb 4, 2013)

Indeed. a formidable weapon. But too late in its navalized form to make any difference.


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## davebender (Feb 4, 2013)

12.8 cm FlaK 40 - Wikipedia, the free encyclopedia


> Development of the gun began in 1936
> 
> first prototype gun was delivered for testing in late 1937 and completed testing successfully.


Naval version of this weapon could have been in production by 1939 if Admiral Raeder wanted it. Early enough for Z1936A class DD and Bismarck class dreadnoughts.


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## parsifal (Feb 4, 2013)

Not really. I am surprised that the gun was ready in 1937, Campbell says it did not begin naval rtrials until after 1940. In any event the 1936A (Z23-34) were already being launched in 1940, and were designed for a 5.9" main armament. The KM would have (mistakenly) considered a reversion to a 5" calibre as a backward step.


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## DonL (Feb 5, 2013)

Neither the german 12.7cm/61, nor the german 12.8 cm FlaK 40 are DP weapons or to my opinion good designs for a DP weapon.
They were FLAK weapons not DP weapons.

The germans had to my opinion since 1934 a good 12,7cm DP weapon.
Germany 12.7 cm/45 (5") SK C/34

This gun had better ballistics then the USA 5"/38 (more muzzle velocity is better in the AA role), was reliable and a good gun for anti ship, which it showed on the Zerstörer 1934/34a and later Zerstörer 1936B Mob (Z35,Z36, Z43, Z44, Z45), which were back to the 12,7cm/45 sk34.

The germans totaly overslept to develop a proper turret (single or double mount), whith an elevation till 80 degrees (AA role), high training rates through motors and semi rammers, similar to the 5"/38.

From my research I have done till now, there were no technical problems to develop the 12,7cm/45 SK34 to a DP gun (with proper turrets), similar to the 10,5cm/45 C/32, which was a developed anti ship gun with AA turrets and which proved good performance at the AA role (with less good ballistics compare to the 12,7cm/45 sk34)
Germany 10.5 cm/45 (4.1") SK C/32

This gun was mounted on the Flottentorpedoboat 1939, which are to my my opinion the best german destroyers from a balanced design and seakeeping performance
Elbing-class torpedo boat - Wikipedia, the free encyclopedia

To my research Admiral Fuchs has also his hands on the not developed 12,7cm/45 sk34 in to a proper DP gun, as he has his hands on the not introduction of the Bofors 4cm AA instead of the 3,7cm/83 sk C/30 at 1936, as the major flaws of the 3,7cm were indentificated and the KM wanted an other AA in the 4cm region.


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## davebender (Feb 5, 2013)

> Flottentorpedoboat 1939, which are to my my opinion the best german destroyers


I agree. Germany should have built these inexpensive ships like hot roll starting in 1934 rather then building more expensive fleet destroyers.

http://www.german-navy.de/kriegsmarine/ships/index.html
RM 13 million to RM 13.7 million. German fleet destroyers.
RM 5.7million. FTB1939 class.

4 x 10.5cm DP main guns.
4 x 3.7cm AA guns.
2 to 9 20mm AA guns.
6 x 21" torpedo tubes.
50 mines.
32 knots. 2,400 miles @ 19 knots.
.....IMO exactly what you need for coast defense and the price is dirt cheap. You can build two FTB1939s for the price of one fleet destroyer and have a bit of change left over.


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## parsifal (Feb 5, 2013)

They certainly look impressive, but the first was not available until the beginning of 1942. 

How do they compare to the Hunt Class? Type II appears to be the nearest equivalent with the following characterisitics


Displacement:

1,050 long tons (1,070 t) standard
1,435 long tons (1,458 t) full load
Length: 85.3 m (279 ft 10 in) o/a
Beam: 10.16 m (33 ft 4 in)
Draught: 3.51 m (11 ft 6 in)
Propulsion:2 Admiralty 3-drum boilers, 2 shaft Parsons geared turbines, 19,000 shp (14,000 kW)
Speed: 27 knots (31 mph; 50 km/h), 25.5 kn (29.3 mph; 47.2 km/h) full
Range: 2,350 nmi (4,350 km) at 20 kn (37 km/h)
Complement: 168
Armament: 

• 6 × QF 4 in Mark XVI guns on twin mounts Mk. XIX
• 4 × QF 2 pdr Mk. VIII on quad mount MK.VII
• 2 × 20 mm Oerlikons on single mounts P Mk. III
• 4 × 0.5 in Vickers machine guns on twin mounts Mk. V, later replaced by 4 × 20 mm Oerlikons on twin mounts Mk. V
• 3 × 21 in (533 mm) torpedo tubes
• 40 depth charges, 2 throwers, + 1 rack


cost £352,000


By comparison, the Elbings were as follows:


Displacement: 1,295 long tons (1,316 t) (standard), 1,755 long tons (1,783 t) (maximum)
Length: 97 m (318 ft 3 in) (w/l), 102.5 m (336 ft 3 in) (o/a)
Beam: 10 m (32 ft 10 in)
Draft: 3.22 m (10 ft 7 in)
Installed power: 32,560 shp (24,280 kW)
Propulsion: 2 × Wagner geared steam turbines, 2 × shafts
Speed: 32.5 kn (60.2 km/h; 37.4 mph)
Range: 2,400 nmi (4,400 km; 2,800 mi) at 19 kn (35 km/h; 22 mph)
Complement: 205
Armament: 

4 × 105 mm (4.1 in) guns
4 × 37 mm (1.46 in) anti-aircraft guns
9 × 20 mm (0.79 in) anti-aircraft cannons
6 × 533 mm (21.0 in) torpedo tubes
50 × mines


It looks to me these two classes would have been very evenly matched . The Elbing was larger, and faster, but i think the Hunt is more heavily armed, except for torpedoes. Probably the british design was a more efficient ASW platform and with slightly deeper draught may have been more stable, although not necesarily. The German design was slightly longer ranged.

An interesting match up in my opinion.


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## DonL (Feb 5, 2013)

@ parsifal

The german Torpedoboats 1935 and 1937 (not E-Boats) prequels to the Flottentorpedoboat 1939, were Vessels after the London naval treaty, not larger then 600ts. To construct a Torpedoboat only with 600ts was impossible, as the Torpedoboats 1935 and 1937 has shown.

So the Flottentorpedoboat 1939 were in reality destroyers not Torpedoboats and were constructed after this worse experience with the Torpedoboats 1935and 1937 much more to destroyer standards. (So the Flottentorpedoboat 1939 was also a vialotion of the naval treatys).

The german had one realy intresting design with the training ship Bremse (1931).
German training ship Bremse - Wikipedia, the free encyclopedia
Bremse (1931)
http://www.marineoffizier.eu/KRIEGSMARINE/07-Kiel-Wiek-II/ASS_Bremse/images/hp-ass-bremse-fahrt.gif

It was a full designed destroyer without torpedo tubes (but which were planed to add later) and diesel engines.

To my opinion this design would be a realy interesting basic design for a reliable smal to mid destroyer class with very long range.
Bremse had at the beginning problems with it's seakeeping abilitys, but was rebuilt at 1934 and after that, was a realy good seaship, which could get full speed even at bad weather conditions. The diesel engines were quite interesting for the range, to escort the larger vessels.

To my opinion an improved Bremse design (with more power) would have had much more advantages to the KM then the large destroyer classes 1934/34A and Narvik class with it's unreliable powerplant and bad seakeeping performances.


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## davebender (Feb 6, 2013)

Apples and oranges.

Hunt class were ASW vessels for convoy escort. FTB1939 were designed for coast defense. That's why Hunt class carry depth charges and FTB1939 class carry mines.


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## parsifal (Feb 6, 2013)

davebender said:


> Apples and oranges.
> 
> Hunt class were ASW vessels for convoy escort. FTB1939 were designed for coast defense. That's why Hunt class carry depth charges and FTB1939 class carry mines.


 


err nope. They were rated as escort destroyers. They were intended to have sufficient speed to work with the fleet, and were intended to operate in the coastal waters around Europe. They did not have the range or the sea keeping capbilities to work as ASW escorts. They also were not optimized for ASW, with only a limited number of DCs throwers and rails fitted to the class. 

As coastal destroyers, I would think they had exactly the same role as the Elbings


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## davebender (Feb 6, 2013)

Laying mines to keep Soviet ships out of the Baltic? I don't think so. Were Hunt class ships ever employed as high speed mine layers?


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## parsifal (Feb 6, 2013)

Not sure. I dont see why they copuldnt, then again a ZDD of this size would not be an optimal minlelayer, limited numbers of mines being the main problem. 


Converting a ship to lay mines does not entail a large modification for any ship, especially ships already configured to carry DCs.


There was an operational need for the KM to lay a mine barrier in the gulf of Bothnia and elsewhere to botle up the Soviet Navy. The heavy losses suffred by the Baltic Fleet in 1941-2 more than vindicates that approach. The allies had at their disposal vasatly greater and better resources for minelaying, principally dedicated minelaying ships and aircraft, that were able to lay approximately ten times the number of mines compared to the Axis, In the baltic and the North Sea that effort accounted for about a million tons of shipping. But the need to risk Destroyers laying mines was not as great for the RN as it was for the KM because of those other resources


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## Shortround6 (Feb 6, 2013)

They didn't need to be. The RN had other ships that could do that job. Although with some of them carrying up to 110 depth charges there seems to be some capacity to swap that weight/space for mines. 

The Elbings were about 23% heavier than the Hunts standard displacement and 22% heavier full load they _should_ have more capability than a Hunt. 

Try comparing the Elbings to the British war emergency destroyers which were about 19-30% heavier standard displacement to see how much difference it can make. 

The Elbings were a continuation of the German ideas of torpedo craft. Their main offensive weapon was the torpedo battery. They were low silhouette (which wasn't quite as important with radar becoming more prevalent) for low visibility. They may have been a fit for what the Germans needed but if they had been the _standard_ German destroyer the Germans would have been in big trouble.

Many of the between wars British destroyers could be fitted for mine laying should the need arise. 1 or 2 of the 4.7 in guns and the torpedo tubes were landed and 60-72 mines carried. I believe the intention was that alternating flotillas would be fitted as either high speed mine sweepers or as mine layers.


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## DonL (Feb 6, 2013)

> They may have been a fit for what the Germans needed but if they had been the standard German destroyer the Germans would have been in big trouble.



Why?

They had better seakeeping abilitys, a better AA capacity, better engines and also more range then the Fleet destroyers of the germans.
I can't see the throuble.......


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## parsifal (Feb 6, 2013)

DonL how did the Elbings fare in the arctic waters? That is the acid test for me regarding seakeeping. You seem well aware of the p[roblems the KM fleet destroyers had in rough arctic seas. I dont have information on the performance of the elbings in those conditions, but they could hardly have been any worse than the big DDs 

What were these ships like for topweight? They look pretty good to me....


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## Shortround6 (Feb 6, 2013)

The Germans mucked up the sea keeping of the bigger destroyers. They got it up to pretty good with the Z 17 but then blew it with the twin 15cm turret. 

You also have to try and figure out what good sea keeping was, and it usually varied with the size of the ship. People expected 2800 ton ships to have better sea keeping than 1400 ton ships. Just like light cruisers had better sea keeping than even big destroyers. And does sea keeping mean the ability to maintain speed in a head sea? does it mean being able to fight the forward guns at speed in a head sea? Does it mean being able to keep up a decent rate of fire even with the aft guns or is the ship pitching and rolling too much? 

The only advantage the Elbings had for AA was the higher elevation of the main guns. If built earlier they would have had the same crap 37mm as the early destroyers. Did the Elbings have a high angle director for the 10.5 cm guns? without a high angle director the actual usefulness of the 10.5 cm guns for AA work is greatly diminished. (British fitting of a single 12dpr of 4 in AA gun on destroyers was as much for morale as it was for actual effect). 

I am not sure were the better engines come from. they used boilers operating at 70 atmospheres. 

Sources are all over the place on range although it does seem the Elbings were better. Question is was 20% better or 100% better? 

Trouble comes in the form of low gun power, four 4.1 in guns is no better than what the British had on the WW I V&W destroyers except they had an A-B-X-Y gun arrangement rather than A-Q-X-Y. The British B gun being workable in seas that prevented the use of A gun ( although practical accuracy in such seas is very low). The limited firing arcs of the Q gun counts against it. Practical range of the 4in guns are lower than the 4.7in-5in guns of other navies. Forget the listed max range of the gun.


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## parsifal (Feb 7, 2013)

I know that the hunts were used in the Arctic Convoys, but lacked the endurance to undertake the full run. they could only undertake escort for part of the way. For example JW51A.....the target of the Battle of Barents Sea was escorted by three Hunts, HMS Blankney, HMS Ledbury, and HMS Chiddingford. They were present with the convoy on the day of the battle. earlier 5 hunts had been used to escort PQ18. The Hunts were particularly favoured in the arctic escort because of their good AA fits. but they dont seem to have had much issue being effective in poor weather, or potentially poor weather.

I simply dont know if the Elbings had similar capability.......I expect that they could, but im unaware of them actually being used above the Arctic Circle


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## Glider (Feb 7, 2013)

I suspect that its true to say that the range of a destroyers guns is limited by the ability of the destroyer to provide a good gun platform at sea. The nominal effective range of the gun is not a factor. I don't see the 4in as being that much worse than a 4.7 despite the smaller shell as they normally had a faster rate of fire and a 4in can do quite a lot of damage vs a destroyer.

I see the main difference being the torpedos the two ships carried. Hunts normally had either 6 x 4in *or *4 x 4in and 3 x TT. This would give the edge to the German vessel that had 6 x TT. The last two units did have the originally designed 6 x 4in and 3 x TT but were a little bigger

As for sea keeping I would give the edge to the Hunts but only because the RN designed these ships for the N Atlantic and didn't concentrate on speed. Its worth noting that the Hunts were equipped with stabalisers which would have helped. I think was the first time these were fitted to any warship. These were often removed so that additional fuel could be carried for escort work


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## tomo pauk (Feb 7, 2013)

Maybe an interesting tidbit: in Russian nomenclature, the destroyer is 'mine carrier' (mino-nosets), literary. The fleet destroyers (Эскадренные миноносцы - eskadreny minonostsy) carry the same name, even when armed with Mach 3 anti ship missiles.


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## Shortround6 (Feb 7, 2013)

Glider said:


> I suspect that its true to say that the range of a destroyers guns is limited by the ability of the destroyer to provide a good gun platform at sea. The nominal effective range of the gun is not a factor. I don't see the 4in as being that much worse than a 4.7 despite the smaller shell as they normally had a faster rate of fire and a 4in can do quite a lot of damage vs a destroyer.



It is not only the need for a good gun platform, it is the ability to spot the shell splashes at long range. The smaller shells don't make a big enough splash to be spotted well at longer ranges. There is one source that says the early French super destroyers with 5.5in guns had a theoretical range of 19,000 meters but with their 3 meter range finder spotting of the splashes was almost impossible over 13,000 meters.

Part of it is the distance to the horizon which varies with the observers height above the surface. at 10 meters height the observer can see 11,300 meters. Granted you many not need to see the targets water line but trying to "aim" ( range take and figure course) on just bridge and funnel/s may be a bit chancy. 

This all assumes perfect weather, the 4in guns coming into their own at night, in haze, rain or snow squalls. 

However even at moderate ranges the 4.7/5 in guns have a bit of an advantage over 4 in guns in rough and ready shooting. Their heavier shells loose velocity slower and they have a larger danger space. More important when in local control or on ships with simple fire control equipment.


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## Vincenzo (Feb 7, 2013)

tomo pauk said:


> Maybe an interesting tidbit: in Russian nomenclature, the destroyer is 'mine carrier' (mino-nosets), literary. The fleet destroyers (Эскадренные миноносцы - eskadreny minonostsy) carry the same name, even when armed with Mach 3 anti ship missiles.



i thinked that in this case "mino" was for torpedo


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## Milosh (Feb 7, 2013)

The early (23 ships) Hunts had a stability problem fixed by 50t of permanent ballast and replacing X turret with a multibarrel pom-pom. The nexy 53 ships had the beam increased by 12".

Man o' War #4


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## tomo pauk (Feb 7, 2013)

Vincenzo said:


> i thinked that in this case "mino" was for torpedo



You might be somewhat right there. The 'mina' ('mine' in English), in this context, was at 1st the explosive attached into a pole that would be rammed at enemy ship, at least Wikipedia says so.
The term is still very much in use even today, when the torpedo outfit is of maybe tertiary importance, despite the calibre of 533mm on the ships.


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## Glider (Feb 7, 2013)

Milosh said:


> The early (23 ships) Hunts had a stability problem fixed by 50t of permanent ballast and replacing X turret with a multibarrel pom-pom. The nexy 53 ships had the beam increased by 12".
> 
> Man o' War #4


Thats right. I think it was the first four ships were built to the original 6 x 4in and 3 x TT and this was quickly stripped down. The last two built had the original weapons but were made larger to cater for the original weight


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## DonL (Feb 7, 2013)

Compare to the Fleet destroyers, the Elbing's were flush-decker with buckling ribs at the bow.

No Elbing was at ther artic sea but they were stationed at the Biscaya and english channel to escort merchant ships and U-Boats and I think the rough seas are equal.
From all primary sources, this ships were very good seakeeping ships and not top heavy, also they were permanent in action, much more then their larger Fleet destroyer colleagues.

Also to the engines.

Shortround 6 permantley claimed that all german vessels used boilers operating at 70 atmospheres even the Battleships!

*That's wrong!*

There is much bogus in secondary sources about the german high pressure steam turbines.
For startes:

The were three different boiler systems at major german vessels.

Wagner Boilers: Bismarck, Tirpitz, Scharnhorst, Gneisenau operating on 50-55 atmospheres 
Wagner La Mont Boiler: Hipper Class operating on 70 atmospheres.
Benson Boilers: Graf Zeppelin and much of the Zerstörer 34 and 34a operating on 70 atmospheres.
Later Wagner Boilers: Zerstörer 1936, 1936a, 1936 mobA, 1936 mobB and Flottentorpedoboat 1939 operating on 50-60 atmospheres.

All boilers had troubles at the beginnings, but the Benson and Wagner La Mont Boilers were much worser.
The Wagner Boilers were much more stable and at the Battleships (accept Scharnhorst) were reliable, also at the later destroyer classes, which changed from Benson to Wagner boilers.

The Fleet destroyers since the 1936a Class had much more problems with their sea keeping performances and instabilities, then with their machinary.
For example all Fleet destroyers since 1934 class had fuel bunkers up to 700ts, but could only consume 70% of this, because of their instabilities.
THe Elbings hat 516ts max bunker and had no problems to consume till 90-95%.

Also I could not understand this claimimgs about range finders and AA capacity!

The Elbings had a normal 3m range finder above their superstructure, similar to the destroyers, also they had the same FC AA controls as the destroyers and also were fitted with AA radar.

They had numerous battles with allied vessels and could stand their man for two years alone at the Biscaya and the Channel, could sink light cruisers and Fleet destroyers.
They were tough fighting ships from realife action.


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## davebender (Feb 7, 2013)

Why would anyone operate such small destroyers in the Arctic when larger destroyers were available? 

FTB1939 had good sea keeping for a 1,700 ton ship but size does matter when operating in an Arctic gale.


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## parsifal (Feb 7, 2013)

Hi DonL

Having never been on a ship in the Arctic waters, I cant comment about the comparison of conditions to the Bay of Biscay. However, i have served in the southern Oceans. There is no comparison in the roughness of the seas in the latitudes 50 degeees or below to those above 50. From 40 degree latitudes, there are constants winds that generally have the potential to whip the oceans up to 2 or 3 times that which are encountered in lower latitudes. Of course in the tropical latitudes you can get tropical storms, but they are not as frequent as in the high latitudes, Moreover, from about 50 degrees, you start to get icing issues, which, combined with the winds, and cold produce difficult conditions not seen further north (north for us is closer to the equator, maybe south for you guys).

I stood watches in ships where for 6 or 8 days straight the winds have been above 100kmh and the seas are in the storm category. It is very common to have rollers in excess of 60 feet high in those higher latitudes. I was on ships fully stabilzed and in excess of 6000 tons (there were two ships, one was the Nella Dan (which was later wrecked off Macquarie island in 1987) , which I volunteered to crew whilst still a serving officer, and later in 1987 on a similar ship the Icebird (but as a civilian), when we picked up the recued crew of the Dan from Macquarie island in 1987). I also spent time in the Antarctic waters on Training Ship Jervis Bay (a converted vehicle ferry, about 10000 tons and stabilized), earlier still on a modified Daring Class (the Vampire), an Adamas class DDG and an 18000 ton light fleet carrier. These various ships handled the conditions to diferent standards of proficiency. By far the worst was the American ship, far too top heavy to handle the conditions, and not good at deicing at all) without a doubt the re-supply ships were most suited.

So, getting back to the ships we are meant to be talking about, being of such small size, and if lacking stabilizers and/ or de-icing equipment (which I dont think was all that common back then) it would be critically important to make sure top weight was well down to maximise stability. Milosh has already pointed out that the earlier Hunts needed to lose a lot of fire power and have permanent ballast fitted to solve their stability issues. i bet that was because they were expected to operate in the rougher northern waters. it also explains why so many were sent to the med (along with their good AA capabilities). If the allied experiences are anything to go by, the Elbings would not have been suitable, unless changes were made to their upper deck configuration and top weight. If there was any reliability issues whatever with the engines, real or perceived, the crews would not have been confident to take into rough arctic conditions .

Finally, from research i have done, by 1942 the amount of Axis shipping in the channel and Biscay areas fell right away in the latter part of 1941. The elbings were not commissioned until 1942, so Im a bit perplexed or curious about how much escort work they were actually doing. They did a lot of good work in these areas, dont get me wrong, but you seem to be painting a picture of "business as usual" in the channel and French coast for Axis shipping, which was not the case even for warships by 1942.


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## DonL (Feb 7, 2013)

As I said the Elbings had *no problems *with their top weight and their supertructure, which comes through the construction as a flush-decker with buckling ribs at the bow. THe layout is very similar to the Fletcher Class.

Anyway I think and agree that they were perhaps to small for the artic sea, but were much better seakeeping ships at the north sea and north atlantic as the german Fleet destroyers, that was mentioned in many primary sources.
Also the Bay of Biscay and the Channel are famous for their rough seas and often bad weather conditions.

The main duty of the Elbings from 1942-1944 at the Bay of Biscay and the Channel was to escort all blockade breakers and all merchant ships that needed escort, also they escort incomming and outgoing U-Boats.
Several sources claim, that they were permanent at missions, because they were next with the E-Boats the only warships from germany at this region and they were only 8 ships. 

Anyway my intention is and was, that I think the german would had much more benefits, if they had begun to built such a balanced destroyer class (or something like Bremse) at 1934 to practise destroyer building, and get experience with a smal- to mid destroyer classes.
Such destroyers are cheaper and it isn't this worse, if a construction isn't that good, as you blow up a whole fleet destroyer class.
They could built fleet destroyers later, after experience with smal- to mid destroyer classes. (from 1937).

Also what is totaly incomprehensible, is the fact, that all fleet destroyers were built from shipyard with no experience in destroyer construction.
Schichau/Elbing had this experience through their destroyer building at the WWI.
SMS S113 - Wikipedia, the free encyclopedia

- and they built the much better and balanced design at WWII with the Elbing class destroyer.

I can't understand why this way was gone, because for example, all E-Boats were built from Lürssen, which had the most experience with E-Boats and the german E-Boats were the best at WWII.


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## Juha (Feb 7, 2013)

Elbings were not much smaller than the British E and F classes, which were c. 1400 tons standard/ c. 1940 tons full load and which were widely used in Arctic water.

Juha


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## parsifal (Feb 7, 2013)

Fletchers were not good sea boats in heavy seas because of their flush deck configuration. A raised forecastle is necessary in rough waters, if you want to move through that ocean at any speed. The design of the bow is also important as it can affect the direction and severity of sea spray, and if the sea spray is too much out of control it can affect range finiding and visual communication gear,. it also makes the bridge commanders job much harder. so its not a trivial issue. 

Im not being too critical of the Elbings. I like them as a class, and agree with nearly everything yove said. the one issue I am taking you to task over, is this comparison of temperate waters operations to arctic area operations. German destroyers had some difficulties in the arctic because of the problems with their machinery, their heavy forecastle weight (for the Narviks at least, but even the 5" armed ships had some issues), and the amount of spray that they tended to throw up in heavy seas. They were not comparable ships to some British classes of destroyers (but to be fair, some British ships were poor performers in heavy seas too). I think the Elbings, as a generalization would be better in heavy seas than most other German ships, but the question is, how suitable were they. If they were suitable, or more suitable than the bigger Zerstorers, why werent they sent there (assuming they werent sent to the Arctic).


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## RCAFson (Feb 8, 2013)

parsifal said:


> British DDs, even the tribals were not as competitive as many other Navies until later in the war. The RN determined that the overwhelming issue was numbers, and accordingly designed an built their DDs until the latter part of the war (1944-45), to the idea of sacrificing quality to an extent, in favour of numbers. Even the L&M class were nuilt to budgetry constraints....a limited displacement, no unit machinery arrangement SP guns. The "Z" , "Ca", "Ch', Co", Cr" classes had a superior DP weapon, a decent torpedo broadsise, but farly light LAA, they had machinery arranged in a unit style arramgment, but were about 1000 tons lighter than a Fletcher.
> 
> Battle Class (both the 1st and second groups) had standard displacements of 2400tons (compared to the fletchers 2300 tons), but a deep load displacement of 3300 tons to the Fletchers 2900 tons. This had a great impact on the stability comparisons for the two classes. There was no comparison. Ive trained with gearing classes (a close relative to the fletchers) in a Daring Class ( a bigger brother to the Battles), and in any kind of rough seas, the Gearings were quickly forced to lose speed, whereas the Darings were able to maintain close to full speed. The CG of the Darings was much lower than the Geariigs and topweight much less. There really is not any comparison in stability. Moreover the flush deck (ie lack of a raised weather forecastle) generally made the fletchers very wet in any sort of sea.
> 
> ...



The Tribals, JKN and L-M class destroyers had DP 4.7in guns with on-mount AA fuze setters, that were controlled with the FKC HA FC system. It is true that elevation was limited to 40 or 50 degs, but they were not SP guns, as per the 5"/38 guns on the USN Porter and Somer class, which had no capability for predicted fire against aircraft. The overall AA power of a Tribal or JKLMN class was probably better than the early USN destroyers with 4 or 5 x 5"/38 DP guns, because the RN destroyers had a CIWS of a quad pom-pom and 2 quad .5in mounts versus only 4 x.5in mgs on the USN destroyers.


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## vinnye (Feb 8, 2013)

Information on changes made to Battle class during WW" from Wiki ;
Experiences in the Pacific, in operations against the Japanese, pointed to the limited usefulness of the 4 inch gun abaft the funnel and only the first ships completed, Barfleur, Armada, Trafalgar, Camperdown, Hogue and Lagos were fitted with the gun. In all other ships the gun was replaced by two single 40/60 mm Mk VII giving a total of 14 Bofors, the heaviest light AA armament of any British destroyer and heavier than that carried in many cruisers. In time, all the ships fitted with the 4 inch gun had them removed and replaced with the two single 40/60 mm Mk VII Bofors.

I had not realised that they had so much AA on board!


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## davebender (Feb 9, 2013)

> British E and F classes, which were c. 1400 tons standard/ c. 1940 tons full load and which were widely used in Arctic water


They widely suffered weather related damage in the Arctic too and one has to question combat effectiveness of a ship whose crew were sea sick and half frozen much of the time.


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## Glider (Feb 9, 2013)

davebender said:


> They widely suffered weather related damage in the Arctic too and one has to question combat effectiveness of a ship whose crew were sea sick and half frozen much of the time.


An often ignored benefit of the enclosed gunhouse


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## vinnye (Feb 9, 2013)

I am not surprised they suffered weather related damage in the Artic - but they continued to be there and do their job. To be combat effective, you first have to be there, then deal with the conditions as best you can and be as ready as you can to face whatever opposition shows itself. That is if they can survive the weather.


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## fastmongrel (Feb 9, 2013)

davebender said:


> They widely suffered weather related damage in the Arctic too and one has to question combat effectiveness of a ship whose crew were sea sick and half frozen much of the time.



Name a ship that didnt suffer weather damage in the Arctic. Even Aircaft carriers got battered when operating above the Arctic circle one escort carrier had its deck peeled back like a sardine can and a fleet carrier lost its boats and crane.


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## davebender (Feb 9, 2013)

Aircraft carrier flight decks and aircraft are exceptionally vulnerable to Arctic gales. I wouldn't operate a CV that far north unless I had no choice.


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## Shortround6 (Feb 9, 2013)

The Elbings were sort of in between the WW I V W and the between wars A-I classes. They may have been good for their size but if built "like hot rolls" from the mid 30s on instead of the bigger destroyers the German Navy would still have been in trouble. The fact that the big destroyers were far from perfect does not automatically mean the the Elbings were great. And by 1942 some of their "concept" was outdated. Many Navy's (including the British) in the 20s and 30s thought that torpedo "craft" should have low silhouettes for low visibility, especial night attacks. Some British officers criticized the A-I classes because of their high bows and high bridges. However by 1942 the idea that 1000 tons ships could "sneak" up on radar equipped ships at night to deliver torpedo attacks was fast going away (Japanese used longer ranged torpedoes and their danger was not fully appreciated). The Elbings did not have the gun power to fight their way through an opposing destroyer screen to get to a firing position although they did have a fair rearward firepower to cover their withdrawal. 

The British do claim that the A-I class were some of the best sea boats _of their size_ but this may be a pre-war assessment and may not include the Elbings or some of their own later sloops. 

A flotilla of Elbings that ran into/against a flotilla of A-Is might be in trouble or it might succeed. A Flotilla of Elbings against a flotilla of J,K,L, Tribals and such would be in big trouble. The Germans needed bigger destroyers than the Elbings. 

Wither they should have been the 1936 Mob A design is another story.


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## fastmongrel (Feb 9, 2013)

davebender said:


> Aircraft carrier flight decks and aircraft are exceptionally vulnerable to Arctic gales. I wouldn't operate a CV that far north unless I had no choice.



What choice do you have. Choices are for peacetime.


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## davebender (Feb 9, 2013)

Perhaps none. 

Did anyone try to establish an airfield on Bear Island?

Engines of the Red Army in WW2 - The Northern Route


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## fastmongrel (Feb 9, 2013)

Good luck with the weather and finding enough flat space to build a runway.


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## Glider (Feb 9, 2013)

davebender said:


> Aircraft carrier flight decks and aircraft are exceptionally vulnerable to Arctic gales. I wouldn't operate a CV that far north unless I had no choice.


CVL's operated that far north, with considerable success. You have to take your hats off to the crews that manned those vessels, I wouldn't fancy it.

People often comment on the ineffective AA fire of the RN but the german losses against convoys such as PQ18 were very heavy. The only aircover was 10 Sea Hurricanes


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## davebender (Feb 9, 2013)

Would you rather land on Bear Island or a CV steaming in the vicinity of Bear Island? Same weather but the island isn't pitching and rolling.


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## fastmongrel (Feb 9, 2013)

Its not so much the wind as the 10/10 cloud Bear Island is covered in regulary.

edit Just done a bit of googling and Bear Island is fogbound up to 40% of days in summer. Weather in winter isnt too bad for the Arctic circle but theres no sun between Nov 8th and Feb 5th.


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## RCAFson (Feb 9, 2013)

Royal navy task group in arctic waters:


_View: https://www.youtube.com/watch?v=Mwjrf0gZjIE_

Only the most seaworthy of destroyers can cope with such weather.


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## parsifal (Feb 9, 2013)

davebender said:


> Would you rather land on Bear Island or a CV steaming in the vicinity of Bear Island? Same weather but the island isn't pitching and rolling.



wrong question really. from the pov of the pilot, a land base is much preferred. from an operational pov, a carrier based aircraft is far more useful. Its right thre where its needed. morover,at those time when the carrier aircraft cannot fly, enemy aircraft will also be ineffective. 

Moreover, whilst both sides had aircraft types that could handle rough weather, German training had abandoned blind flying for most crews after 1942. this meant that British aircrews could fly at times that most of the Luftwaffe was grounded. 

Laslty RN CVs and their aircrews developed techniques and skills that enabled their a/c to get off the deck and back down again, at a wider range of weather types than most of their adversaries, and even their allies. What USN carriers ever operated above the arctic circle....none, which is still the case today.


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## parsifal (Feb 9, 2013)

> The Tribals, JKN and L-M class destroyers had DP 4.7in guns with on-mount AA fuze setters, that were controlled with the FKC HA FC system.



Ill have to check, but i think that meant the gun had be depressed below a certain elevation in order to allow it to fire. If correct, thats not a very convincing argument that it was an effective DP mount. Theres a lot more to designing an effective DP mount than simply being able to load and elevate above a certain angle. Ill stand corrected, if you have the details on the design of these mounts. 




> It is true that elevation was limited to 40 or 50 degs, but they were not SP guns, as per the 5"/38 guns on the USN Porter and Somer class, which had no capability for predicted fire against aircraft.



What arrangements did they have built into the mount to allow predicted fire at aircraft. further, what practical rof did they have whilst firing above 45 degrees? What practical or operational evidence is there of this ever being effective

Also, only being able to fire up to 50 degrees is just not enough. At that angle, for aircraft at a typical approach altitude of say 15-20000 feet, (say 5-7000m) they will only be able to be fired at beyond 7000m horizaontal range. That will help, but the shells at that range will not be all that accurate at that altitude, and the firing window so limited as to be of not much use at all. 

If youve got operational information to show effective AA fire from these mounts , I genuinely would like to see it. But Ive always been led to believe they were not a practical or effective AA mount. 



> The overall AA power of a Tribal or JKLMN class was probably better than the early USN destroyers with 4 or 5 x 5"/38 DP guns, because the RN destroyers had a CIWS of a quad pom-pom and 2 quad .5in mounts versus only 4 x.5in mgs on the USN destroyers.




Your comparison is not completely valid. You are comparing either the weapons fit of later RN types, or the war upgrades, to the pre-war fits for some USN types. We should really compare apples to apples, by comparing ships of contemporary design to each other


For example

"A to E" classes to the Farraguts
The "A B" were designed with 2 x pom poms , and 4 x QF MkIXs. The MkIXs had shielding to the deckline, limiting elevation to 30 degrees maximum. Bulldog had an experimental aMk XII mounting with 60 degree elevation fitted, but it was a failure. Those that survived to the midwar period were rearmed....bulldog for example receiving 2 x 4.7 and 6 x 20mm. 

The "C D" classes were similar, but as built had a 3" HA fitted. In 1935-6 Crusader had a quad pom pom tried out, which was successful. 

The "E F" classes had 5 x 4.7 but no light AA. the mounting of the 4.7 in this class was slightlly modified to allow 40 deg elevation. It decribed by Campbell has having a theoretical AA value only, because elevation was only to 40 degrees, and also needed well covers removed in order to fire. No special prediction equipment was carried, which is a real giveaway about what the RN thought about their real AA potential. 

Farraguts were fitted with 4x 5/38 and 4 x 0.5 in MG. Mk 33 directors were fitted, from the beginning, which gave theiur HAA a potent AA potential. War mods saw the MGs replaced by a pair of 40mm Bofors and 5 x 20mm 

Displacement of the RN types was slightly higher than the farraguts. 

If you want to compare the JKNs then you would need to look at the Bensons to make fair comparison. and a JKN does not match up well to a benson in terms of AA capacity. Either designed or actual.


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## Shortround6 (Feb 9, 2013)

"No special prediction equipment was carried, which is a real giveaway about what the RN thought about their real AA potential>"

Or the mounting of a _single_ 12pdr or 4 in gun on a high angle mount in place of one torpedo mount showed what was thought of the four-six 4.7 in guns on 40 degree mounts. And the 12pdr/4in was darn near useless. The ships would have been better served with a few single 2pdr or 20mm or even multiple .5 in MGs.


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## RCAFson (Feb 9, 2013)

parsifal said:


> Ill have to check, but i think that meant the gun had be depressed below a certain elevation in order to allow it to fire. If correct, thats not a very convincing argument that it was an effective DP mount. Theres a lot more to designing an effective DP mount than simply being able to load and elevate above a certain angle. Ill stand corrected, if you have the details on the design of these mounts.
> 
> 
> 
> ...


 
You should start by reading the Wikipedia article on the MK XIX 4.7in twin mount:

4.7 inch QF Mark IX XII - Wikipedia, the free encyclopedia

The 4.7in twin had on mount fuze setters where the time fuze setting as determined by the AA FC computer, was set by the guns crews. The wiki article states 12rpm as the practical maximum rof (navweaps.com states 10rpm in AA fire) and that's a lot of metal being directed against an aircraft.

As for 40 degs not being enough, well that's not true; it all depends on the altitude of the attacking aircraft, obviously against a torpedo bomber or a low altitude level bomber, 40degs is plently, and against dive bombers attacking other ships, the same gun could place a barrage over the ship being attacked. If you read the accounts of the IJNAF attacks on the USN carrier task forces in 1942, you will see that the destroyers could have performed as AA escorts even with 40deg elevation. The key factor is that the guns be controlled in AA mode by a computer that can predict the movement of the target and direct the gun to the correct elevation and deflection while also providing fuze timing, and every RN destroyer from the Tribal class onward could do this. Here's the firecontrol schematic of the Tribal class (this also shows type 285 radar which was being fitted to RN destroyers from mid 1941):




The big problem for RN destroyers and 40 deg elevation guns, came when they had to operate alone or where they became the target of attacking aircraft, and then really only when they faced dive bombers. High altitude level bombing was not very effective against ships anyways, and the RN would have preferred to add an extra quad pom-pom when the dive bombing threat was realized in 1940, but these simply didn't exist so they added (spare) 3in and 4in single HA mount guns on some destroyers to allow for engaging high altitude and divebombers and a twin 4in in lieu of the after upper 4.7in mount on the Tribal class.. Here's an example of HMS Tarter engaging aircraft with computer controlled 4.7in AA fire:


> ... In May Tartar was deployed to defend the Atlantic convoys. During these duties, she was present at the sinking of the German battleship Bismarck. After this, on 28 May Tartar was returning to Scapa Flow with HMS Mashona, when they came under heavy air attack west of Ireland, and Tartar's action report states: "...It is believed that all attacking aircraft were H.E. 111's. Occasionally a F.W. Condor was seen shadowing astern. It is estimated that about 50 aircraft took part in the attacks over a period of 13 hours..."[5] The Mashona was hit and badly damaged, eventually capsizing, but in return Tartar shot down an He 111 bomber.[6] Tartar was able to rescue 14 officers and 215 ratings, and transported them to Greenock. During this engagement " Tartar used her Fuze Keeping Clock to aim her 4.7" guns and "...Every gun was used, the 4.7" in controlled fire and the 4" and close range weapons firing independently. 290 rounds of 4.7", 255 rounds of 4", 1,000 rounds of pom pom and 750 rounds of .5 machine gun ammunition were fired."[7]
> HMS Tartar (F43) - Wikipedia, the free encyclopedia



Controlled fire is the RN term for AA fire directed by the FC computer.

The A class was commission from 1930 and the Farraguts from 1934, but the Farraguts didn't receive their Mk 33 directors until 1936 - Hardly a fair comparison.


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## Glider (Feb 9, 2013)

I agree with a lot of Parsifals last posting. Just some small detail about the pre war destroyers. All the A-I class destroyers had either 2 x 2pd or 2 x quad 0.5in mg's. Most of the Flotilla leaders had 5 x 4.7 instead of 4 x 4.7 but even these had the quad 0.5. These destroyers and the JKN/Tribal destroyers didn't have DP guns. They were SP guns only, if they had been DP why did the tribals have 2 x 4in instead of 2 x 4.7in?


The only RN Fleet destroyers with DP guns were the LM classes of which I think half had 6 x 4.7in DP and the rest 8 x 4in DP

During the war most if not all the A-I class ships were modified for convoy escort duties as new build destroyers came on line. Some of their guns and torpedos were removed and replaced by ASW weapons and some extra LAA gunds.


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## RCAFson (Feb 9, 2013)

Shortround6 said:


> "No special prediction equipment was carried, which is a real giveaway about what the RN thought about their real AA potential>"
> 
> Or the mounting of a _single_ 12pdr or 4 in gun on a high angle mount in place of one torpedo mount showed what was thought of the four-six 4.7 in guns on 40 degree mounts. And the 12pdr/4in was darn near useless. The ships would have been better served with a few single 2pdr or 20mm or even multiple .5 in MGs.



The special prediction gear (FKC, see: Fuze Keeping Clock - Wikipedia, the free encyclopedia ) wasn't ready till 1938, and then first priority went to the new destroyer classes and to the RN's new AA sloops which were fitted with HA 4in guns and the Hunt class destroyer escorts. By Dec 1941, some of the H-I class destroyers had been retrofitted with FKC AA FC, and with no war they might have all been retrofitted. A number of WW1 destroyers were also retrofitted with a full AA outfit and 2 x twin 4in HA mounts, but time and yard space didn't allow for all older destroyers to be retrofitted.


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## RCAFson (Feb 9, 2013)

Glider said:


> the JKN/Tribal destroyers didn't have DP guns. They were SP guns only, if they had been DP why did the tribals have 2 x 4in instead of 2 x 4.7in?



That's completely untrue. The 4.7in twin was a DP mounting, that had all the features required for AA computer control, including on on mount fuze setters, and the Tribal and later class destroyers used a dedicated AA director mounted just aft of the low angle director, which fed targetting info to the AA FC computer - see the schematic I posted earlier.


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## Glider (Feb 9, 2013)

In theory it was a DP gun with all the trimmings but at the end of the day if you cannot get your gun to point at the target then all the director gear in the world will not help you.

As a result of combat experience all surviving Tribals had 2 x 4in installed and the last few had 8 x 4in not 8 x 4.7. All surviving JKN's had a 4in instead of a set of torpedo tubes.

You have to ask yourself why they felt the need to take such drastic action, if the 4.7in was a DP gun in the first place.


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## RCAFson (Feb 9, 2013)

Glider said:


> In theory it was a DP gun with all the trimmings but at the end of the day if you cannot get your gun to point at the target then all the director gear in the world will not help you.
> 
> As a result of combat experience all surviving Tribals had 2 x 4in installed and the last few had 8 x 4in not 8 x 4.7. All surviving JKN's had a 4in instead of a set of torpedo tubes.
> 
> You have to ask yourself why they felt the need to take such drastic action, if the 4.7in was a DP gun in the first place.



you have to realize that it wasn't until VT ammo came along that destroyers could engage aircraft with their main guns, at high elevation with a high probability of success, so a 40. 50 or 55 degree mount was not a huge drawback - because it was the CIWS that had the best probability of success against aircraft attacking a destroyer. The Tribal and later classes, opted to save weight by using a low angle DP main armament and use the weight saved to add a heavy CIWS, just as the USN Porter class used the weight saved to add 2 quad 1.1in mounts, however, unlike the Porter class the RN Tribals and JKM class also added a full AA FC system to their main armament. The plain fact is that destroyers needed more CIWS than they needed higher angle main armament, but large numbers of CIWS guns simply didn't exist, so HA 4in guns were added instead. 

Here's an example of a USN Mk33 equipped destroyer trying to engage dive bombers at Eastern Solomons in Aug 1942:



> Warren Armstrong, standing on the control officer’s platform with his head out of his hatch, tried to coach the Mk-33 around to the diving planes. Jaworski and Serwitz would slew the director frantically by eye with their handwheels until, with Canaday’s advice, they thought they were “on target,” then would drop down to try to catch the plunging planes in their optics. It was an impossible task! At the rangekeeper, Copeland and I watched Warren’s feet and lower torso expectantly as he squirmed about, hoping he’d get the director “locked on” to something so we could shoot. The attack was coming in from high over our section of the screen. The enemy planes were passing over our heads as they bore in on Enterprise. We’d whirl the director to try to get our sights on a Jap, but it takes a big arc of train to make even a small change near the zenith. They’d be over the top and out the other side before we could settle on them. Jaworski on the Pointer’s scope reported “On Target” a couple of times, but he couldn’t follow the fast motion as the attackers dove in. *We never got a shot off!*
> http://destroyerhistory.org/goldplater/ussmaury/index.asp?r=40130&pid=40136



I find it hard to believe that Maury would have done any better in Norway in 1940, or at Crete in 1941 and she entered the war with a much lighter main armament with a much weaker CIWS than the Tribal and JKM classes.


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## parsifal (Feb 10, 2013)

Im afraid I agree with glider on this one (and no, we are not conspiring against you RCAFson) . The article you posted from wiki includes some comments from Vian about the inneffectiveness of the 4.7" DP mount against aircraft. Not a complete waste of time, i will grant you, but not greatly effective either. As i recall Cunningham was similar in his view, though I cannot find at the minute his exact comments. 

There were a number of problems with the 4.7" but more particularly its mount and support equipment. Some of these problems had little to do with the actual gun or the mounts. The RN adopted a faulty method of HA fire control for its medium and heavy batteries. i confess im not 100% certain of the specific types of directors used in given Destroyer classes, though I do know that the Battles were fitted with a "Mk VI" director and another apparatus called a "Mk XL corrector". However Campbell is pretty damning of all British pre-war direectors because of their methods of stabilization....in practice they proved incapable of dealing woith aircraft that were chamging course and or speed or altitude. they were better than nothing, but compared to the USN HA directors, were pretty average affairs. 

For HA Short range weapponary, most work was done as over open sights until late in 1942. After that date , RN DDs began to receive some elementary beam switching gear. Dont ask me to give a detailed explanation, all I know is that it was linked to radars to give a pretty good indication of deflection and other corrections to the gunners of the LAA batteries. But in 1939, director control for the LAA in the RN was almost non existent. 

The other problems with the 4.7 in mountings are squarely to with the gun and the mounts they were put into. The gun mounts, to put it mildly were simply too slow in both training speed and elevation to be effective, and as i suspected, the gun could not be loaded above 40 degrees elevation. The best turrets housing the 4.7 had a training sppeed of 10 degrees per secons and a max elevating speed that was the same. by comparison, the 4.5s in the battles were nearly twice that speed. The USN 5/38 had a traverse speed of 34 degreees per second and and elevating speed of 18 degrees per second. put simply the 4.7 was too slow to be effective, and wasnt well directed until later in the war


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## Glider (Feb 10, 2013)

The Porters had weight problems as they tried to include eight main guns and a full set of torpedos. The Tribals didn't have such a problem as they lost a set of torpedos in the design stage. Don't confude the two. Also the weight of the quad 2pd was about the same as two quad 1.1in mounts.
The Porters didn't have DP guns as that would had pushed the weght further, The Tribals because the RN didn't fit DP guns in DD's at the time.

Switching a twin 4in for a twin 4.7 had nothing to do with weight.


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## RCAFson (Feb 10, 2013)

parsifal said:


> Im afraid I agree with glider on this one (and no, we are not conspiring against you RCAFson) . The article you posted from wiki includes some comments from Vian about the inneffectiveness of the 4.7" DP mount against aircraft. Not a complete waste of time, i will grant you, but not greatly effective either. As i recall Cunningham was similar in his view, though I cannot find at the minute his exact comments.
> 
> There were a number of problems with the 4.7" but more particularly its mount and support equipment. Some of these problems had little to do with the actual gun or the mounts. The RN adopted a faulty method of HA fire control for its medium and heavy batteries. i confess im not 100% certain of the specific types of directors used in given Destroyer classes, though I do know that the Battles were fitted with a "Mk VI" director and another apparatus called a "Mk XL corrector". However Campbell is pretty damning of all British pre-war direectors because of their methods of stabilization....in practice they proved incapable of dealing woith aircraft that were chamging course and or speed or altitude. they were better than nothing, but compared to the USN HA directors, were pretty average affairs.
> 
> ...



Vian states that AA fire from 4.7in guns prevented a single hit from an attack lasting many hours, on a whole convoy moving at 5 knots, through narrow waters - if RN destroyer AA was so ineffective why didn't the bombers press in to low altitude and annihilate the convoy? What was the luftwaffe afraid of? Do you really think that USS Maury could have done any better? Mk 37 wasn't even service in April 1940, and the Mk 33 system on Maury and most of the prewar USN destroyers was an obvious failure as the USN itself admitted.

I have a feeling that the effectiveness of USN AA systems has been greatly exaggerated and this has given the impression that if only the RN had similar systems that all would have been well...yet a read of the two volumes of First Team, will show you that USN AA simply didn't do well and was hardly a factor in the first year of the war, until Santa Cruz, and then it was massed CIWS fire that proved effective, not 5in Mk 37 fire.

I think XL means "cross level" as GXLC means "Gyro cross level corrector" and Campbell states that it was part of the director, not a separate unit. Cross level correction was only really important at very high angles while firing far forward of the beam, and so was not an issue for Tribal class AA although there was a cross level corrector in the LA firing circuit.

No WW2 AA system could deal with aircraft that were changing course or speed and/or changing altitude since all WW2 AA computers could only predict straight-line target motion, and assumed that the target would fly at a steady speed during the prediction cycle. Mk37 could predict motion based upon a steady rate of climb or descent, but only if the target flew level in a straight line at a steady speed. As for 10degs/second traverse, it was plenty to track low elevation targets:



> A 270 knot (500 km/h) target crossing the line of sight at right angles, at 2000 yards (1829 m) range, will move across the line of sight at 4.5 degrees per second. This simple fact of geometry appears to contradict the assertion that a 10-degree-per-second traverse rate was too slow to track a high-speed aircraft.



Higher speeds were only needed against very close range targets ( AFAIK higher speeds are only needed to engage dive bombers that are nearly directly over the ship) but the AA computers, including MK 37 were not effective at such high angles anyways because they were to slow to compute the needed corrections, and MK 37 was not accurate above 70 degs due to it mechanical limits:
Historic Naval Ships Visitors Guide - Computer Mark 1 and Mark 1A
http://www.hnsa.org/doc/computermk1/pg380.htm
After the war electrical computers could do much better.

Beam switching refers to a method of getting accurate bearing information from a radar; the radar beam is switched rapidly between the left and right sides of the antennae and if the radar antennae is not centered on the target, the target will flicker on the display tube. After 1942 beam switching was introduced on type 285 and type 282 radar.

Most RN destroyers used eye shooting for CIWS AA until late war when the Simple Tachymeyric Director ( similar to Mk 51) began to be fitted to some destroyers to control CIWS guns, and some pom-poms were fitted with gyro gunsights similar to the USN Mk 14. USN destroyers began to receive Mk 51 in 1943 to control twin bofors mounts, although the RN Hazemeyer was theoretically far more accurate, it was not very reliable. Almost all RN cruisers and larger ships had director control of pom-pom mounts starting around 1930, where the USN didn't have director control of 1.1in or Bofors guns until 1942.

The USN admitted that MK 33 was a very poor director:


> The USN never considered the Mk 33 to be a satisfactory system, but wartime production problems, and the added weight and space requirements of the Mk 37 precluded phasing out the Mk 33: "Although superior to older equipment, the computing mechanisms within the range keeper (Mk10) were too slow, both in reaching initial solutions on first picking up a target and in accommodating frequent changes in solution caused by target maneuvers. The Mk 33 was thus distinctly inadequate, as indicated to some observers in simulated air attack exercises prior to hostilities. However, final recognition of the seriousness of the deficiency and initiation of replacement plans were delayed by the below decks space difficulty, mentioned in connection with the Mk28 replacement. Furthermore, priorities of replacements of older and less effective director systems in the crowded wartime production program were responsible for the fact the Mk 33's service was lengthened to the cessation of hostilities."[19]
> Ship gun fire-control system - Wikipedia, the free encyclopedia
> 
> and:
> ...


but one would never know about these problems by reading Campbell because he glosses over defects in the USN AA firecontrol, while being highly critical of less serious problems in RN AA fire control.


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## RCAFson (Feb 10, 2013)

Glider said:


> The Porters had weight problems as they tried to include eight main guns and a full set of torpedos. The Tribals didn't have such a problem as they lost a set of torpedos in the design stage. Don't confude the two. Also the weight of the quad 2pd was about the same as two quad 1.1in mounts.
> The Porters didn't have DP guns as that would had pushed the weght further, The Tribals because the RN didn't fit DP guns in DD's at the time.
> 
> Switching a twin 4in for a twin 4.7 had nothing to do with weight.



The Tribals had DP 4.7in guns controlled by an AA FC computer but if HA guns were so important why didn't the Porter/Somers class have their LA guns replaced later in the war? 

The RN didn't want to reduce the gun armament of their destroyers, so they were willing to add guns in lieu of torpedo tubes, but they weren't willing to reduce torpedos to nil, and so on the Tribals they opted to keep the torpedoes and replace a twin 4.7in with a twin 4in (while saving 9 tons of topweight). Adding a 2nd pom-pom would have meant removing all torpedoes or reducing gunpower by by 25%.


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## Glider (Feb 10, 2013)

They did. At the end of the war Porters and Sommers were normally equipped with 4 x 5in (2 x 2) 1 x 5in DP in X turret. 6 x 40mm 8 x 20mm and 8 x TT
It varied a little but B and X turrets were removed to add LAA and the single DP 5in reinstalled in X. It should be noted that some books refer to these vessels as having DP guns from the start but they didn't. The Mk22 mount only had a 35 degree elevation. To save topweight they also lost a director, a deck in bridge height, lowered funnels, lighter masts, a set of torpedos from the Sommers, plus of course the two turrets. 

In brief the USN vessels were top heavy before the war started. The Tribals didn't, they started the war with eight main guns and finished the war with eight main guns. They were able to absorb the war changes with little difficulty because they were a more balanced design from the start.

I am afraid I don't understand your comment about the adding a quad 2pd at the cost of 25% of the guns. They started the war with one quad and finished with one quad 2pd. Had the Tribal spent most of the war in the pacific I have little doubt that the AA fire would have been changed. Quite probably to a similar level as the last Canadian built Tribals 8 x 4in DP, 6 x 40mm, 4 x 20mm and 4 x TT which are a better balance than the Porters


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## vinnye (Feb 10, 2013)

I believe the 25 % reduction in gun armament is achieved by removing a pair of 4.7 inch making a total of 6 still fitted - a 25 % reduction from the 8 originally fitted. 
The removed turret gives space for adding a quad.


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## stug3 (Feb 10, 2013)

Officers on the bridge of a destroyer, escorting a large convoy of ships keep a sharp look out for attacking enemy submarines during the Battle of the Atlantic.







A photograph taken from the bridge of HMS VISCOUNT which gives a good idea of the difficult weather conditions while escorting a convoy during the Battle of the Atlantic. During this operation HMS VISCOUNT and HMS FAME rammed and sank two German U-boats.


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## parsifal (Feb 10, 2013)

> Higher speeds were only needed against very close range targets




No incorrect. Slower travers speeds mean the mount spends more time moving, and less time firing, and when you have second in which to respond that can be critical. A turret capable of traversing at 10 degrees per second can move through an arc 650m every second at a radius of 4000m. in that time an aircraft traveling at 250 miles can move about 150m every second. If the destroyer is being attacked from head on and beam on simultaneously, and if we allow say 5 secs for orders to change targets thats a delay of say 8-10 secs before the guns can be pointed at the initial position of the target aircraft,. however if the target is moving in an arcing movement toward another target, say abaft the Destroyer, then by the time the aircraft will have reduced the range to target by about 1500m in the time it took that DD to move its turrets in the general direction of the target a/c. But now, 8 secs later, the range is down to 2500m (assuming equidistance between the DD and the aircraft, and the a/c target and the aircraft). At that point the DD turrets can arc through only 438m per sec @ range 2500m while it is traversing.....effectively it is now losing 25% of its ROF because 1 in 4 seconds the turret has to move rathe than fire . and this situations just gets worse as the range drops. However even more serious is the loss in enagement time. If the effective torpedo launch range is 2000m the gun now has only 4 secs in which to find a firing solution and fire. assuming it can fire immediately, it might get off 0.7 rounds if its lucky. Effectively thats just one round before launch.....

Now, applying that same battle situation to a US 5/38 mount....it has a traverse rate of 34 degrees per second and an effective rof of around 20 rpm. In that same situation its guns can be moved to the new target in in 6 secs, That places the tartget a/c at a range of about 3000m from the firing gun, and also about 3000m from the target ship (remamber, for simplicity I have assumed equal distances). At 3000m the target a/c has 8-10 before it can launch. The 5/38 only loses another second in that time for traverse adjustments, meaning it has 7-9 secs of firing time. theoretically that means it could get up to three rounds off in that time. 

Effectively, in that situation, disaregarding all the other gizmos and paraphenalia (I can never spell that word), the 5/38 is three times as effective as the 4.7 gun simply because of its better rof and higher traverse speed. 

Traverse speed is a bit like a bombers best speed. Every bit counts. in the case of the bomber, even though it cannot outrun a fighter, every ounce of speed is still importance because of endurance issues. For the AA gun traverse speed is actually critical, because it has only seconds to respond, and every second lost traversing is less lead in the air. and in the end, thats what counts.


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## Shortround6 (Feb 10, 2013)

traverse and elevation speed also get used up compensating for the destroyer's ( or ship mounted on) motion. In this case traverse and elevation acceleration are important but they tend to be _somewhat_ proportional to traverse and elevation speed. Mounts with faster speeds have faster acceleration.


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## RCAFson (Feb 10, 2013)

Glider said:


> I am afraid I don't understand your comment about the adding a quad 2pd at the cost of 25% of the guns. They started the war with one quad and finished with one quad 2pd. Had the Tribal spent most of the war in the pacific I have little doubt that the AA fire would have been changed. Quite probably to a similar level as the last Canadian built Tribals 8 x 4in DP, 6 x 40mm, 4 x 20mm and 4 x TT which are a better balance than the Porters



Many Tribal class did serve in the Pacific (all the RAN ones), but the point is that adding a quad pom-pom either means removing the only TTs or reducing gun power by 25%. The solution was to swap a 4.7in twin for a 4in twin. The last Canadian built Tribals had 6 x 4.7 and 2 x 4in, as did all the wartime Tribals, and unlike the Porters' 5in they could use their 4.7in in controlled fire, giving them a heavy AA armament.


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## RCAFson (Feb 10, 2013)

parsifal said:


> No incorrect. Slower travers speeds mean the mount spends more time moving, and less time firing...



It certainly is possible to create scenarios where high traverse rates are useful, but typical AA engagements involve picking the aircraft up when it was still considerable ways from the target, and usually before the point where it has to steady on it's bomb run, and 10degs/sec is quite adequate for that. This was especially true after radar became widespread in 1941.


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## Glider (Feb 10, 2013)

RCAFson said:


> Many Tribal class did serve in the Pacific (all the RAN ones), but the point is that adding a quad pom-pom either means removing the only TTs or reducing gun power by 25%. The solution was to swap a 4.7in twin for a 4in twin. The last Canadian built Tribals had 6 x 4.7 and 2 x 4in, as did all the wartime Tribals, and unlike the Porters' 5in they could use their 4.7in in controlled fire, giving them a heavy AA armament.



I am sorry but you are wrong.
a) The last two canadian Tribals had 8 x 4in 
b) The Porters did have a combined HA/LA director even though the guns were single purpose like the Tribals
c) Like the Tribals the Porters had a heavy AA gun installed, a single 5in DP in the Porter a twin 4in in the Tribals
d) I certainly agree that the Tribal 4.7 could be used against torpedo bombers and in theory dive bombers after they had dropped their bombsbut against any other kind of air attack they were useless
e) Your theory about the addition of another quad 2pd is I think also wrong. During the war the Australian Tribals were equipped with an addition 6 x 40mm gun which weighed a lot more than one additional quad 2pd
f) If you could supply any evidence to support your theory that the 4.7in was dual purpose I would be very interested to see it. I would also be interested in seeing any evidence that the installation of the 4in was anything to do with weight
Its only fair that I give you my opening support. Its a link to a very well respected website on Naval Weapons. Britain 4.7"/45 (12 cm) QF Mark IX
Please note the opening statement
The lack of a DP function for these weapons was keenly felt throughout the war as more British destroyers were sunk by air attack than from any other cause. _*What little AA capability that these weapons did have*_ was hindered by a lack of a tachymetric (predictive) fire control system and the setting of HE time fuzes by hand. The last single mounting designed, the CPXXII, had a spring operated rammer, but all other single mountings were completely hand worked. The twin mounting had power ramming and used power training and elevation but no RPC gear was installed.


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## RCAFson (Feb 10, 2013)

I meant the last wartime built Canadian Tribal - my mistake.


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## RCAFson (Feb 10, 2013)

Glider said:


> I
> b) The Porters did have a combined HA/LA director even though the guns were single purpose like the Tribals
> c) Like the Tribals the Porters had a heavy AA gun installed, a single 5in DP in the Porter a twin 4in in the Tribals
> d) I certainly agree that the Tribal 4.7 could be used against torpedo bombers and in theory dive bombers after they had dropped their bombsbut against any other kind of air attack they were useless
> ...



B)The Porter/Somers class, as built, had a LA only Mk 35 director with no AA capability - see Friedman's The U. S. Destroyers: An Illustrated Design History, p87.

C

D: Here's the engagement envelope of the 4.7in twin:





The level bombers that attacked HMS Prince of Wales and USS Hornet flew at 9000ft and you can see that a 4.7in Tribal-JKM destroyer could have engaged them continuously, if placed on a screen around the ships being attacked. Dive bombers could be engaged prior to dropping their bombs and during their bomb run via barrage placed over the ship being attacked. A barrage, in naval terms, is created by firing the guns with a fuze setting designed to burst at a fixed point in front of the attacking aircraft's path. 

e) The Australian tribals retained 8 main guns, their quad pom-pom and their TTs. *They didn't reduce their gun armament*. In 1940/41 the RN didn't have the option to fit single Bofors guns.

f) Naval weapons of WW2, p50 shows the fuze receiver on the 4.7in twin mount along with the fuze setting pedestal - just as the schematic states in my earlier post; so it has on mount fuze receiver/setter, and it is controlled by an AA FC computer, which in turn was fed data by a HA director - I have pointed this out and supplied hard data via solid references to back it up and it's time you simply admit that it was a DP mounting.

I don't give a hoot for Navweaps editorial comments. It was a DP gun controlled via an AA FC computer. Navweaps is simply wrong. I've already given examples of 4.7in guns being used against aircraft while being controlled by the AA computer but here's a drawing and photo of the mount showing the AA fuze setter:






I earlier pointed out that Lundstrom's two volume study the USN in the Pacific, First Team, hi-lights the poor showing of USN AA was during 1942, so it seems that the USN simply wasted a lot of weight and money on AA systems that seem advanced, on paper, but as per Maury's experience, just weren't very effective:



> The performance of the 5" A.A. batteries was uniformly poor. There was much wild shooting with no indication of control other than local. Bursts were in most cases short and ineffective. Other than noise effect on morale it may be assumed that this battery was useless for close range melee.The automatic weapons, 1.1 and 20 m.m. although extremely wild were more effective. At least 85% of the fire observed from these weapons was low and trailing. Failure to lead sufficiently and following the tangent of the tracer trajectory were all too apparent. The only solution is believed to be more practice firing from all angles at high speed towed sleeves. Pointers for 20 m.m. guns should be able-bodied, intelligent, marines, trained in "Duck Shooting."
> HyperWar: Battle of Coral Sea--Task Unit 17.2.2 Action Report



I'll bet the above Admiral's comments will never appear on Navweaps or this recommendation from Yorktown after Midway:


> (e) *Replacement of 5"38 caliber guns*, 1.1" guns and 50 caliber machine guns, by a large number of 40mm automatic guns. While smaller caliber automatic guns have proven effective at short ranges, their range is too short to offer effective opposition to attacking planes prior to delivery of their attack. 5"38 caliber guns are very effective at long ranges and should be retained in ships which are used as anti-aircraft screening vessels.
> Battle of Midway: USS Yorktown Action Report


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## RCAFson (Feb 10, 2013)

duplicate


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## parsifal (Feb 10, 2013)

RCAFson said:


> It certainly is possible to create scenarios where high traverse rates are useful, but typical AA engagements involve picking the aircraft up when it was still considerable ways from the target, and usually before the point where it has to steady on it's bomb run, and 10degs/sec is quite adequate for that. This was especially true after radar became widespread in 1941.



True, I agree, but this doesnt change the same basic disadvantage of the 4.7". I ran a different scenario.....which I have sketched and tried to optimise the DDs firing position. I can post the worksheet if you are interested (I wish I had kept some PP plot sheet which are excellent for working this sort of stuff out...of course nowadays its all worked out electronically). This is still an anvil attack, one group from dead ahead and another from the port beam, about 60 deg off the bow. I assumed an initial engagement range of 7000m for both the head on attack and a beam attack, with (as i said) the beam attack 60 deg off the bow coming in on the port side of the target. the target is assumed to be steaming 20kts, whilst the DD is steaming 30 kts. The a/c are attacking at 200mph, launch range is still 2000m. the DD is placed on the port side of the target about 1500m from the target (a typical TD) , so that the attackers will pass just forward of the DD and be in launch position about 600m from the DD. This is about as optimal for a DD in a realitic situation as I can achieve, whilst still also being realistic about the aircraft tactics and capability. 

To get into ideal firing position, the DD has to turn 30 deg to starboard and the guns have to traverse 90 deg. Again assuming a 5 second command delay and as SR points out some estimate of accelaration delay (I am guessing about 3 secs for the slower traversing turret, and about 1 sec for the faster 5/38 turret for a 90 deg traverse), we have a 17 second delay for the 4.7 turret. I calculate that it will take 43 secs for the beam attack to get into firing posn, but firing time for the DD will be reduced to 26 secs after allowing for all of the above. At 10 rpm that means they will get off 4-5 rounds before launch.

For the equivalent 5/38, everything is the same, except time delay and rof. Because of the accelaration issue and higher traverse rate, the gun will be in firing position 9 secs after initial orders are given. That gives them 34secs of firing time, or 17 rounds at max rof.

of course this is all theoretical, but even as atheoretical excercise, it amply demonstrates one of the basic disadvantages of the 4.7 mounting as a "DP" mount. It makes no real difference in relaistic situations the 4.7 will always perform significantly less efficiently than the 5/38.


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## Glider (Feb 10, 2013)

RCAFson said:


> B)The Porter/Somers class, as built, had a LA only Mk 35 director with no AA capability - see Friedman's The U. S. Destroyers: An Illustrated Design History, p87.


 You are correct my info was wrong

C


> D: Here's the engagement envelope of the 4.7in twin:
> View attachment 224306
> 
> 
> The level bombers that attacked HMS Prince of Wales and USS Hornet flew at 9000ft and you can see that a 4.7in Tribal-JKM destroyer could have engaged them continuously, if placed on a screen around the ships being attacked. Dive bombers could be engaged prior to dropping their bombs and during their bomb run via barrage placed over the ship being attacked. A barrage, in naval terms, is created by firing the guns with a fuze setting designed to burst at a fixed point in front of the attacking aircraft's path.


I couldn't open the attachment but get the general picture. Would it be faor to say that your belief is that the would be able to help defend other ships, but with the lack of high angle would be defenceless against dive bombers to defend themselves.



> e) The Australian tribals retained 8 main guns, their quad pom-pom and their TTs. *They didn't reduce their gun armament*. In 1940/41 the RN didn't have the option to fit single Bofors guns.


 Absolutely agree with you. In 1940/41 no one had the chance to rearm with 40mm. The point was that the Tribal as a design could and did accept increased AA guns without losing any of their main weapons because of weight consideration. The Aussie Tribals as you uyourself point aut, confirm that view. 



> f) Naval weapons of WW2, p50 shows the fuze receiver on the 4.7in twin mount along with the fuze setting pedestal - just as the schematic states in my earlier post; so it has on mount fuze receiver/setter, and it is controlled by an AA FC computer, which in turn was fed data by a HA director - I have pointed this out and supplied hard data via solid references to back it up and it's time you simply admit that it was a DP mounting.


 The difference is that the AA director is high angle but the gun isn't. The gun is a low angle that will work against torpedo bombers and as you point out help other ships, but no more.



> I don't give a hoot for Navweaps editorial comments. It was a DP gun controlled via an AA FC computer. Navweaps is simply wrong. I've already given examples of 4.7in guns being used against aircraft while being controlled by the AA computer but here's a drawing and photo of the mount showing the AA fuze setter:
> View attachment 224307


 Here we disagree, all I say is that those fittings would help against a low altitude attack. The problem I have with your argument is that you don't awnser the difficult questions just restate your view. 
Question 1 Why did the RN install a twin 4in HA gun when there was no issue with weight.
Question 2 Why did the RCN build that last two destroyers with 8 x 4in HA guns if the 4.7 was a true DP gun
Question 3 Why did the RN develop proper DP guns if the original ones were true DP guns



> I earlier pointed out that Lundstrom's two volume study the USN in the Pacific, First Team, hi-lights the poor showing of USN AA was during 1942, so it seems that the USN simply wasted a lot of weight and money on AA systems that seem advanced, on paper, but as per Maury's experience, just weren't very effective:


 Your forgetting one mportant thing. In 1942 the USN were new to combat. It would be foolish to pretend that ships crews were fully effective. Also no one would disagree that HAA of any type only became really effective with the proximity fuse.
Its also worth pointing out that in 1941/2 the US 5in and mk 37 director was fitted to HMS Delhi and the RN were so impressed that they tried to purchase more units for fitting in RN warships but production was already committed to USN needs. Cleary the RN who had considerable experience of combat at this stage disagreed with him.


> I'll bet the above Admiral's comments will never appear on Navweaps or this recommendation from Yorktown after Midway:


I admit to not understanding your poosition on this. The quote you posted was very clear 5inL38 guns are very effective at long ranges and should be retained in AA ships


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## RCAFson (Feb 10, 2013)

Glider said:


> You are correct my info was wrong
> 
> C
> 
> ...



a) I'll try again:






They wouldn't be defenceless because they still have a quad 40mm pom-pom, and they can still engage the target to within a minimum range depending on it's altitude

b) But in 1941 adding a quad pom-pom meant removing a gun mount or all the TTs.
c) The RN 50lb 4.7 shell was obsolete (designed pre WW1), with poor streamlining and thus range and no new designs were forthcoming. The RN 4" twin actually out-ranges the 4.7 twin but it has the draw back that it fires a much lighter shell so the RCN must have decided to simply accept the 4in disadvanatges and move to an entire 4in armament. With the advent of VT ammo, high angle, close range fire became a feasible proposition, when it wasn't using mechanical time fuzes.

D) C'mon Coral Sea and Midway were 6 and 7 months into the war - about the same as the RN in Norway. The point is that the USN didn't find AA fire abovc 40degs to be very effective and the CO of Yorktown called for the vaunted 5in/38 to be removed entirely.

e) and at long ranges, 40deg elevation was just fine.
.


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## RCAFson (Feb 10, 2013)

My whole point is that 40 deg guns were not useless - they could and were used to engage aircraft. Adding a heavy, expensive, complex HA mount with complex FC computer didn't turn USN destroyers into invincible AA platforms, and it seems that they didn't really do any better than RN destroyers with FKC FC and 40deg gun elevation.


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## parsifal (Feb 11, 2013)

> My whole point is that 40 deg guns were not useless - they could and were used to engage aircraft.



Yes, you have shown that. I would be happy to agree or concede that point. 



> Adding a heavy, expensive, complex HA mount with complex FC computer didn't turn USN destroyers into invincible AA platforms,



They werent heavy, compared to their nearest equivalents. Id agree they (US DDs) were not invincible AA platforms, but neither can we discount that they were better than the RN. Most contemporary opinions are that they were better. 



> and it seems that they didn't really do any better than RN destroyers with FKC FC and 40deg gun elevation.


 By no stretch of the imgination, no assuaging of the facts, no papering over of the enormous doubts raised in the discussions can you make this claim. From the technical assessment a 40 degree elevation was a big problem, the slow rate of traverse another problem, the slow rof another. all this suggests a less capable weapon system in the AA role. Where you might have a valid point, but have not really brouight the point out, is the inherent weakness of the 5/38 in the anti-surface role. The USN gave a lot of ground in this regard to gain some advantage in the AA role. Despite your valiant attenmpts at rebuttal, my opinion is that you have NOT shown the Brit DDs as comparable AA platforms. i think on the basis of probabilities they (the brit DDs) were significantly weaker in this regard.


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## RCAFson (Feb 11, 2013)

parsifal said:


> Despite your valiant attenmpts at rebuttal, my opinion is that you have NOT shown the Brit DDs as comparable AA platforms. i think on the basis of probabilities they (the brit DDs) were significantly weaker in this regard.



The thing that we haven't looked at, is that the Tribal and later classes had a much heavier CIWS than contemporary USN destroyers, and they were able to do this because they saved weight by having a LA main armament. 

If you think that USN destroyers did better, then where's your proof? We know from Lundstrom that USN destroyer AA just wasn't that effective before VT ammo was introduced. Given all their bells and whistles, USN AA FC must have seemed impressive, but the reality is that it shot down very few aircraft.


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## Glider (Feb 11, 2013)

RCAFson said:


> a) I'll try again:
> 
> View attachment 224333
> 
> They wouldn't be defenceless because they still have a quad 40mm pom-pom, and they can still engage the target to within a minimum range depending on it's altitude.


So you basically agree that the Tribal would be defencless against a dive bomber until the bomber came within range of the 2pd. Which would give the 2pd seconds to shoot it down, at a rough estimate about five seconds.


> b) But in 1941 adding a quad pom-pom meant removing a gun mount or all the TTs..


 But according to your theory the Tribals didn't need to switch to anything. You see the 4.7 as a good DP gun and we know that the Tribal didn't have any weight issues so it wasn't because of that. So why would they want to add a quad 2pd or a twin 4in. When the 4in was installed that only changes to the LAA fire was swopping the 0.5in for 20mm's..


> c) The RN 50lb 4.7 shell was obsolete (designed pre WW1), with poor streamlining and thus range and no new designs were forthcoming. The RN 4" twin actually out-ranges the 4.7 twin but it has the draw back that it fires a much lighter shell so the RCN must have decided to simply accept the 4in disadvanatges and move to an entire 4in armament. With the advent of VT ammo, high angle, close range fire became a feasible proposition, when it wasn't using mechanical time fuzes..


 So now your saying that the 4.7 shell was obsolete which presumably means that the 4.7 as a DP gun was obsolete. The comment you make about the 4in being lighter doesn't hold up, it was of course but it had a much higher rate of fire than would have made up the difference.

.


> D) C'mon Coral Sea and Midway were 6 and 7 months into the war - about the same as the RN in Norway. The point is that the USN didn't find AA fire abovc 40degs to be very effective and the CO of Yorktown called for the vaunted 5in/38 to be removed entirely..


 The issue isn't how long the UA had been at war. The issue is how much combat had the vessels seen. By the nature of georaphy the majority of the ships only fought when the navies sailed into combat at the large set piece combats. In Europe the RN was involved from day one, there was no phoney war for the RN. 
Re your quote where does it say he wants the 5in removed, all I can see is a comment as to how good it is.

.


> e) and at long ranges, 40deg elevation was just fine.
> .


 If fine means being close to defenceless against dive bombers and giving me about 40 seconds to engage and shoot down a level bomber with a gun that has a slow traverse and elevation rate plus an obsolte shell then we have a different definition of the word 'Fine'


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## parsifal (Feb 11, 2013)

guys

its been a very good debate, and we have all had our chance to say our pieces. but the room has gone deathly quiet, and if we go any further with this, we will be crossing a line.

Time to move on.


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## RCAFson (Feb 11, 2013)

Glider said:


> Re your quote where does it say he wants the 5in removed, all I can see is a comment as to how good it is.
> 
> '



I just want to clarify this:


> (e) *Replacement of 5"38 caliber guns*, 1.1" guns and 50 caliber machine guns, by a large number of 40mm automatic guns. While smaller caliber automatic guns have proven effective at short ranges, their range is too short to offer effective opposition to attacking planes prior to delivery of their attack. 5"38 caliber guns are very effective at long ranges and should be retained in ships which are used as anti-aircraft screening vessels.
> Battle of Midway: USS Yorktown Action Report



The first sentence calls for the replacement of 5"/38, 1.1in and .5in guns with 40mm guns. So Yorktown's CO thought that the 5"/38 was less effective than 40mm fire. 

In the same vein: _"In theory, the 5in gun could counter either horizontal or torpedo bombers; it could not fire nearly fast enough to present any threat to dive bombers,which, ironically, were probably the most lethal threat to fast maneuverable craft such as destroyers."_ US Destroyers-An Illustrated Design History, Friedman, p203.

Finally, I've read somewhere where the RN did a study that showed that any engagement of an aircraft prior to bomb release would cause a drastic reduction in bombing accuracy - if this is the case then having some guns that can fire at very high angles might have a deterrent effect, if nothing else, but it seems to me that the same effect would be achieved with a 40mm bofors or pom-pom, and these guns would have a much higher probability of actually scoring a kill.

I guess that to prove anything, we would need to see some hard stats on WW2 naval AA.


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## fastmongrel (Feb 11, 2013)

I think it would be fair to say that the best defence a Destroyer had was speed and manouverability. Destroyers with sea room were very hard to hit and a large number of those sunk were destroyers protecting slow moving vessels they could not leave to manouver independently or were close into shore.


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## Glider (Feb 11, 2013)

RCAFson said:


> I just want to clarify this:
> 
> 
> The first sentence calls for the replacement of 5"/38, 1.1in and .5in guns with 40mm guns. So Yorktown's CO thought that the 5"/38 was less effective than 40mm fire.
> ...



I see where you are coming from on this. Unfortunately you didn't show all the requested chages.
The following listed alterations should be installed. 

(a) A workable hand-powered ammunition supply for 5"38 caliber guns. 
(b) A hand-operated cooling system, as an auxiliary, for the water-cooled automatic guns. 
(c) Automatic fuse setters for 5"38 caliber guns not already so equipped. 
(d) Automatic parallax control for 5"38 caliber fire control installations not already so equipped. 
(e) Replacement of 5"38 caliber guns, 1.1" guns and 50 caliber machine guns, by a large number of 40mm automatic guns. While smaller caliber automatic guns have proven effective at short ranges, their range is too short to offer effective opposition to attacking planes prior to delivery of their attack. 5"38 caliber guns are very effective at long ranges and should be retained in ships which are used as anti-aircraft screening vessels. 
(f) Replace a considerable percentage of the present 20mm explosive projectiles with A.P. projectiles. Observations in this and preceding actions indicate that the present 20mm projectiles seldom reach vital spots, and carry too small a charge to cause serious damage to surfaces against which they explode

The first four suggestions are to do with how to improve the 5in, the fifth a request for them to be removed whilst emphasising how good they were in anti aircraft screening vessels. Its almost as if they are saying please make these changes and until then replace them with 40mm. History shows that they made the changes and kept the 5in.

However this moves us away from the main topic, why did the RN take out 2 x 4.7 and replace them with 2 x 4in. According to your theory the Tribals didn't need to switch to anything as you see the 4.7 as a good DP gun. We know that the Tribal didn't have any weight issues as later in the war it accepted 6 x 40mm with no reduction in firepower.
So why would they want to add a twin 4in if it wasn't because the ships were lacking in AA fire


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## RCAFson (Feb 11, 2013)

Glider said:


> I see where you are coming from on this. Unfortunately you didn't show all the requested chages.
> The following listed alterations should be installed.
> 
> (a) A workable hand-powered ammunition supply for 5"38 caliber guns.
> ...



The deficiencies of the 5in gun mounts were pointed out, but the key factor is that the report still recommends removing the 5in guns without qualification, rather than saying "if these changes are made the guns will be OK against dive bombers". 

We've gone over the Tribal 4in gun situation several times. The only way to augument their HA firepower without unduly reducing surface firepower was to add a 4in twin mount. If the RN felt that the 4.7in was totally inadequate they had the option to replace all the guns with 4in and they didn't do that, except on the 4 of LM class because the 4.7in/50 was not available. 

However, the fact remains that at least some captains in the USN felt that 5in guns were useless for short range AA fire, for example against divebombers - something that Friedman also states.


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## RCAFson (Feb 12, 2013)

parsifal said:


> . I calculate that it will take 43 secs for the beam attack to get into firing posn, but firing time for the DD will be reduced to 26 secs after allowing for all of the above. At 10 rpm that means they will get off 4-5 rounds before launch.
> 
> For the equivalent 5/38, everything is the same, except time delay and rof. Because of the accelaration issue and higher traverse rate, the gun will be in firing position 9 secs after initial orders are given. That gives them 34secs of firing time, or 17 rounds at max rof.



So for a Tribal class with 8 x 4.7in we have 26sec x 8 guns = 34.7 shots 
and for a JKM class, 26 sec x 6 guns = 26 shots 
(assuming 10 RPM/gun)


A Benson or other 4 gun USN destroyer (typical prewar) we have 34 sec x 4 guns = 27 shots
(assuming 12RPM/Gun, the RoF according to Crenshaw of USS Maury )

later class with 4 guns = 34 rounds
(Later USN destroyers had a higher rate of fire, due to a superior fuze setter arrangement and had a RoF of 15RPM/gun)

The RN destroyers will also be able to engage the aircraft with their quad pom-pom. Overall I don't see a huge advantage for the USN destroyers, and if we include the pom-pom, I'd say they were at a disadvantage, because their CIWS = 4 x .5in HMGs.

The other factor is the time for the AA FC computer to generate a solution. Crenshaw says it took about 30 seconds for the Mk 33 computer. My understanding is that the FKC could come to solution very quickly and RN picked FKC and HACS to avoid the slow solution speeds of tachymetric computers as used on USN destroyers.


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## parsifal (Feb 12, 2013)

> So for a Tribal class with 8 x 4.7in we have 26sec x 8 guns = 34.7 shots
> and for a JKM class, 26 sec x 6 guns = 26 shots
> (assuming 10 RPM/gun)
> 
> ...




Its not a fair comparison. you are comparing the theoretical rof of the british DDs with the practical rof for the bensons. The two terms are not interchaneable. The practical rof for the 4.7in was around 4-8 rpm. On that basis the Tribals will get off around 13-14 rounds (from an 8 gun broadside) , whilst the JKN will be propportionally smaller. If you want to compare theoretical maximums, you need to do so for all classes, In that case the rofs are 10rpm for the 4.7 and 24 rpm for the 5/38, which we could arbitarily taken as 20rpm, simply because some sources say its 20rpm. On that basis, the Bensons will get off 54 rounds in the same time as the 13 rounds are fired by by the tribals and about 10 for the JKNs. There is simply no comparison in the ROFs.

Ive served on ships that have the 4.5in as main armament, and observed fire onboard Gearing class DDs. I can assure you there is no comparison when it comes to Practical rofs. I will concede that in reality the theoretical rofs are not a true reflection of actual practical rofs. the po st war 5/54 with auto loader has a theoretical rof of nearly 60 rpm, but in reality could only sustain about 20 rpm. Hand loaded mounts will never do well when it comes to actual sustained rof, and rammed breeches are even worse when the mount is operating in the AA role. 

This is moreso the case for the 4.7 guns, which still required ramming of each round. at elevation the workable rate of fire would have dropped right away, as crews struggled to get each round rammed home and in the chamber. Trying to argue that the British DDs had a comparable ROF to the bensons in an AA role is a complete dud Im afraid. 




> The RN destroyers will also be able to engage the aircraft with their quad pom-pom. Overall I don't see a huge
> 
> advantage for the USN destroyers, and if we include the pom-pom, I'd say they were at a disadvantage, because their CIWS = 4 x .5in HMGs.



Only the 2pdrs can provide any real fire against torpedo bombers, and that is a theoretical capability, not a real one. 20mm weapons and MGs were almost totally impotent against torps fired at normal ranges because they lacked sufficient effective range. They were effective at making torps keep their distance, that i will grant you. 

The 2 pdr was judged an advanced weapon when introduced, but by the outbreak of World War II advances in aircraft would have made it obsolete but for the introduction of a high-velocity round and new director designs (which were not available at the beginning of the war for DDs) . It was intended that the curtain of fire it threw up would be sufficient to deter attacking aircraft, which it could sometimes achieve, but its performance was hampered by the ineffective Mk III director.The MK IV Director with a Gyro Rate Unit and Type 282 radar was an improvement and was introduced on the King George V-class battleships, but not in DDs until much later. 

In January 1941, HMS Illustrious′s Mk VIII mountings performed flawlessly firing 30,000 rounds with very few stoppages (accounting for 2 known kills). When HMS Prince of Wales was attacked and sunk by Japanese aircraft near Singapore, the subsequent RN report judged that a single 40 mm Bofors gun firing tracer was a more effective anti-aircraft weapon than a full eight barrelled pom pom. The Bofors had better range (about double in terms of effective range) and could deliver far more accurate fire, compared to a multiple pom-pom in director control, as the pom-poms did not have tracer ammunition, and the weapon lacked effective range. In the PoWs case, moreover, the pom-pom ammunition had deteriorated badly in their ready use lockers, while the Type 282 radar units also failed in the equatorial heat. In the same action, the Commissioned Gunner of HMS Repulse spent the whole action running from one pom-pom mount to another trying to keep them operational due to the faulty ammunition. The pom-poms on Repulse shot down two of the four confirmed kills made by Force Z, while Prince of Wales′ pom-poms did record hits on enemy aircraft but no kills (the other 2 of the total 4 losses were not lost to british action) . The Royal Navy judged the pom-pom's effectiveness to range from about half that of the Bofors, per gun, against torpedo planes to about equal against Kamikaze attackers. This was because Kamikazes had to penetrate to within the kill zone of the weapon more than anything 

So no, against a torpedo bomber operating at normal range, I would say the CIWs aboard the British ships would make hardlky any difference. They made some difference to Divebombers and Suicide aircraft, but if a D/B or Kamikaze is that close, as to allow the pom poms to be effective, the Pom Pom has failed in its primary deterrent role anyway. 30000 rounds to shoot down 2 aircraft is not a great result, and not evidence of an effective weapon. Compare that to the 14-26 confirmed kills (depending on who you read) from the South Dakota a year or so later at Santa Cruz, and you start to get some idea of the different efficieny levels of the two weapon systems. 



> The other factor is the time for the AA FC computer to generate a solution. Crenshaw says it took about 30 seconds for the Mk 33 computer. My understanding is that the FKC could come to solution very quickly and RN picked FKC and HACS to avoid the slow solution speeds of tachymetric computers as used on USN destroyers.



Thats completely at odds with both campbell and Nav Weapons. this will get down to who you want to believe.....I choose to believe Campbell and Nav weapons. And operational results that we do have, whilst pretty sparse, dont support the claims you make in this regard.


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## RCAFson (Feb 12, 2013)

parsifal said:


> Its not a fair comparison. you are comparing the theoretical rof of the british DDs with the practical rof for the bensons. The two terms are not interchaneable. The practical rof for the 4.7in was around 4-8 rpm. On that basis the Tribals will get off around 13-14 rounds (from an 8 gun broadside) , whilst the JKN will be propportionally smaller. If you want to compare theoretical maximums, you need to do so for all classes, In that case the rofs are 10rpm for the 4.7 and 24 rpm for the 5/38, which we could arbitarily taken as 20rpm, simply because some sources say its 20rpm. On that basis, the Bensons will get off 54 rounds in the same time as the 13 rounds are fired by by the tribals and about 10 for the JKNs. There is simply no comparison in the ROFs.
> 
> Ive served on ships that have the 4.5in as main armament, and observed fire onboard Gearing class DDs. I can assure you there is no comparison when it comes to Practical rofs. I will concede that in reality the theoretical rofs are not a true reflection of actual practical rofs. the po st war 5/54 with auto loader has a theoretical rof of nearly 60 rpm, but in reality could only sustain about 20 rpm. Hand loaded mounts will never do well when it comes to actual sustained rof, and rammed breeches are even worse when the mount is operating in the AA role.
> 
> ...



Where do you get 4-8 rpm for a 4.7in twin? *The twin had power ramming, BTW*, and in trials even the single could achieve close to 18 RPM:
During gunnery trials in 1930, HMS Basilisk'' was able to fire "...five rounds in 17 seconds."
, Kimberly at Narvik: "Salvos fired about 180 in all...drill to guns very good, great part of the action a loading interval of about 5 seconds was achieved..."
4.7 inch QF Mark IX XII - Wikipedia, the free encyclopedia but both above extracts are quotes from British Destroyers, by F. March.

Campbell states a 5 sec firing cycle for the 4.7in twin and Navweaps states: _CPXIX (twin) Mounting: 10 - 12 rounds per minute_ , and I can't see where they state otherwise.
Navweaps states, for the 5"/38: 
_Pedestal and other mounts lacking integral hoists: 12 - 15 rounds per minute_ (mark 33 destroyers)
_Base ring mounts with integral hoists: 15 - 22 rounds per minute_ (later mark 37 destroyers)

I think you need to provide some sources for your assertions, regarding 4.7in RoF. There are many sources that state 10-12 rpm including RN action reports. The first RN 4.5 destroyer twin was not comparable to the 4.7in twin which was a completely different mount. Campbell also states that Illustrious fired 3000 rounds of 4.5in ammo at an average of 12 rounds per gun per minutes during Operation Excess, and her 4.5in twins had a very similar loading system to the 4.7in twin. The pom-pom and 4.5in ammo fired by Illustrious was fired during the entire action including her stay at Malta.

According to Lundstrom the USN made 25 AA kills shared amongst all the USN ships at Santa Cruz (The USN claimed 127 kills at Santa Cruz!). 

In any event, I was comparing the RN and USN destroyers in their original format, not after years of war mods. So the original outfit of the RN destroyers was quad pom-poms and quad .5in mounts versus 4 x .5in MGs for the USN destroyers. Your scenario implied that the aircraft would have to pass close to the destroyer, and if so they would come within pom-pom fire.

Finally, you have to remember that post war AA firing were typically using VT ammo, so they could skip the MT fuzesetter, which sped things up.


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## tomo pauk (Feb 12, 2013)

One can read many interesting things here. Thanks, people.


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## Juha (Feb 12, 2013)

RCAFson said:


> The deficiencies of the 5in gun mounts were pointed out, but the key factor is that the report still recommends removing the 5in guns without qualification, rather than saying "if these changes are made the guns will be OK against dive bombers".
> 
> We've gone over the Tribal 4in gun situation several times. The only way to augument their HA firepower without unduly reducing surface firepower was to add a 4in twin mount. If the RN felt that the 4.7in was totally inadequate they had the option to replace all the guns with 4in and they didn't do that, except on the 4 of LM class because the 4.7in/50 was not available.
> 
> However, the fact remains that at least some captains in the USN felt that 5in guns were useless for short range AA fire, for example against divebombers - something that Friedman also states.


 
For RN 4" gun wasn't a realistic option, because it lacked enough punch for being an adequate surface gun. But it was adequate HA gun. And it was fairly common in the early war emergency DDs. So of 16 O- P-classes DDs only 4 had 4.7" guns and 12 had 4" guns. But as the duel of Petard and Paladin vs IJN I-27 showed, against surface targets 4" was totally inadequate, its SAP round was unable to penetrate pressure hull of I-27.

Juha


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## vinnye (Feb 12, 2013)

The problem with armament is complex and has a lot to do with the role that it is anticipated to do most often.
So a fleet destroyer that was expected to engage enemy destroyers is most likely to have a larger calibre gun eg 4.7 or 5 inch.
But as often happens - the destroyers were called upon to undertake many roles - sometimes acting independent of other units and being exposed to aerial attack. This showed up a deficiency in AA capability - which was not anticipated during the design stage. Hence modifications were carried out to improve AA capability - this often meant HA guns of smaller calibres eg 4 inch. So a compromise is often arrived at that involves a mixture of calibres that enable the ship to have some hope of succes in different roles.


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## parsifal (Feb 12, 2013)

> Where do you get 4-8 rpm for a 4.7in twin? *The twin had power ramming, BTW*, and in trials even the single could achieve close to 18 RPM:
> During gunnery trials in 1930, HMS Basilisk'' was able to fire "...five rounds in 17 seconds."
> , Kimberly at Narvik: "Salvos fired about 180 in all...drill to guns very good, great part of the action a loading interval of about 5 seconds was achieved..."
> 4.7 inch QF Mark IX XII - Wikipedia, the free encyclopedia but both above extracts are quotes from British Destroyers, by F. March.



These are max rates of fire. Practical rates of fire are a lot less than maximums. Usually about half the rate by rule of thumb. Ive got a source somewhere. i wil look it up and post it soon. 



> Campbell states a 5 sec firing cycle for the 4.7in twin and Navweaps states: _CPXIX (twin) Mounting: 10 - 12 rounds per minute_ , and I can't see where they state otherwise.



These are max rates, not practical rates. they are different. 



> Navweaps states, for the 5"/38:
> _Pedestal and other mounts lacking integral hoists: 12 - 15 rounds per minute_ (mark 33 destroyers)
> _Base ring mounts with integral hoists: 15 - 22 rounds per minute_ (later mark 37 destroyers)



Glad that you mentioned Nvweapons, because i the bit you are drawing from it states in full regarding all marks of the 4.7 in weapon

"_The lack of a DP function for these weapons was keenly felt throughout the war as more British destroyers were sunk by air attack than from any other cause. What little AA capability that these weapons did have was hindered by a lack of a tachymetric (predictive) fire control system and the setting of HE time fuzes by hand. The last single mounting designed, the CPXXII, had a spring operated rammer, but all other single mountings were completely hand worked. The twin mounting had power ramming and used power training and elevation but no RPC gear was installed"_. 

With regard to the Bensons, they were not equipped with 4 x 5/38s at thge beginning of the war, they were armed with 5x 5/38s. by the time they landed the 5th 5/38, they were authorised (and generally did carry) 4x 40mm and 8 x 20mm AA weapons. 

Moreover, the Bensons used the mk30 mount,, which was not a pedestal mount. You are misquoting or selectively quoting Navweappons here. Relevantly it states. 

_The Mark 30 mountings made up by far the majority of single mountings built during the war. The Mark 30 enclosed base ring mounts were first introduced on USS Wichita (CA-45). The Mark 30 ran up to Mod 86, with Mod 0 being the original enclosed mounting and Mod 1 being the original open mounting. There were also semi-enclosed mounts which had the upper half of the shield removed as a weight savings but having a canvas cover to protect the interior of the mount. Many of the Mark 30 modifications were trivial in nature. For example, USS Fletcher (DD-445) used Mod 16 in positions 1 and 5, Mod 19 in position 2, Mod 30 in position 3 and Mod 31 in position 4. The differences were mainly related to the elevation and training limitations inherent in the different mounting positions. Escort Carriers (CVE) completed during the war used Mark 30 Mod 80 which was a simplified base ring mounting which lacked shields, axial hoists and RPC. The maximum elevation of this Mod was restricted to +27 degrees as it was installed under the flight deck overhang. The single open Mark 30 Mod 48 and Mark 30 Mod 51 mountings were simplified base-ring types for auxiliaries and merchant ships and lacked integral shell hoists. Trunnion height was 58.0 inches (147 cm) above the loading platform. 55 inches (140 cm) is considered the maximum desirable trunnion height when firing at low elevations for a 50 - 55 lbs. (22.7 - 24.9 kg) projectile. 

*Almost all Mark 25 and Mark 30 base ring single mounts **had an integral shell hoist on the axis of the mounting which allowed shells to be passed directly to the gun at any angle of train*. *Fuzes were automatically set as the shells traveled up the hoist. Cartridges were passed up to the gun through a scuttle also on the rotating mass. These base ring mounts with integral shell hoists and cartridge scuttles had the advantage that projectiles and cartridges were presented to the loaders at exactly the same position and orientation regardless of the mount's elevation or training and thus simplified and sped up the loading procedure*. Both the shell hoist and the cartridge scuttle were on the left side of the mount. Mark 25 and enclosed Mark 30 base ring mountings used a single 10 hp motor to work both elevation and train, a 7.5 hp motor for the hoists and a 7.5 hp or 5 hp motor for ramming. 

8) All twin SP and DP mounts were base ring types and were generally similar to single enclosed base ring mounts. Twin mounts differed from single mounts in that there were twin powder hoists for the cartridges on the rotating structure as well as twin shell hoists. The hoists for the right gun came up through the deck on the left side of the gun while those for the left gun came up on the right side of the gun. Twin mounts took about 27 crewmen in the mount itself and in the upper handling room. Additional personnel were required in the lower handling room during sustained firing periods. 

*All twin DP mountings were equipped with RPC gear *and powered by electric motors through hydraulic gear. Training was by a 4 hp motor while the guns were elevated by a 7.5 or 10 hp motor. Each gun had a 7.5 or 10 hp motor for the hoists and a 5 or 7 hp motor for the rammer. _

So, in comparison to the 4.7 in gun which does not have rpc in the Mk XII mount and had a fussy loading system, and poor turret layouts and design, we have An American system that is designed for the purpose, and stated as the best of its kind in the world at that time. 



> I think you need to provide some sources for your assertions, regarding 4.7in RoF.



Agreed, but it would be a great start if I could get you to understand the difference between Max rof and practical rof. 




> In any event, I was comparing the RN and USN destroyers in their original format, not after years of war mods. So the original outfit of the RN destroyers was quad pom-poms and quad .5in mounts versus 4 x .5in MGs for the USN destroyers.



You were actually kind of allover the place really. You were comparing the Bensons....a Destroyer class that did not start to commission until late 1940-41, but were quoting the main armament after modification and reduction. You were comparing the prewar light AA compopnent which the Americans began to rectify in the first months of their entry . 

And you selectively or outright misquote Navweapons which makes very clear that the 4.7 gun was an inadequate AA weapon, and also very clearly states the 5/38 was the best DP weapon during the war. 



> Finally, you have to remember that post war AA firing were typically using VT ammo, so they could skip the MT fuzesetter, which sped things up


.

True, but in the age of time fuzed shells, the US arrangements according to Navweapons were far more efficient compared to the 4.7 mounts.


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## RCAFson (Feb 12, 2013)

parsifal said:


> These are max rates of fire. Practical rates of fire are a lot less than maximums. Usually about half the rate by rule of thumb. Ive got a source somewhere. i wil look it up and post it soon.
> 
> 
> 
> ...



*Why would navweaps and Campbell state max rates for RN guns and practical rates for USN guns - that makes no sense at all!* Yet you want to hold Navweaps up as gospel. I am willing to agree with their data but not their editorial comments which are not based upon any scientific basis, except simple hearsay.
The data from Navweaps and Wikipedia from Illustrious and HMS Kimberly's action reports showing a 5 sec loading cycle or from Basilysk showing 5 rounds in 17 seconds shows us that average RoF in combat was ~12 rpm.

*We are talking about the twin mountings as used in the Tribal or JKMN classes*, the earlier classes didn't have AA FC and wartime pressures prevented it from being universally retrofitted, and the first wartime fleet destroyers (O-P-Q-R classes) had to continue with the weapons that were in storage or easily produced as wartime Britain didn't have the capacity to introduce more modern designs quickly during the war. 

The Benson class had Mk 37 and integral hoists, but the 1939 and earlier classes did not, but these were the last USN destroyers built to treaty limits, whereas the UK, because of wartime pressures, had to continue building destroyers with treaty based hulls until the Battle class of 1945.


> *All these repeat ships were ordered with only four 5-inch/38s due to severe topweight problems with the initial ships*. Thus differentiated, they were launched as the Bristol (DD 453) class and, less the lead ship (already attached to DesRon 13) and Barton, were organized into Destroyer Squadrons 10, 12, and 14–19. This distinction also disappeared, however, when the first 24 Bensons and Gleaves were modified to match as follows (see also ARMAMENT):
> Ships in DesRon 11 (DesDiv 21, which remained in the Atlantic, and DesDiv 22, the first ships of the class deployed to the Pacific)—and DesRon 13 retained ten torpedo tubes but landed their No. 3 5-inch mount, while increasing their .50 cal armament to twelve guns.
> Ships assigned to DesRon 7 landed their after torpedo tube mounts and added four .50 cal machine guns.
> « « «
> ...


 (I added the info in square brackets)

*No Benson class ships were in commission in April or May 1940 and only one by June 1940.*
The First Sumner class (twin 5"/38 ) didn't enter service until 1944 - only 3 twin mount 5"/38 gunned DDs in commission by Jan 1944)

*The RN entered the war with it's pre-war main armament and CIWS; what would have happened if the USN did the same? How would USN destroyers have fared in Norway or at Dunkirk!*

The problem is that instead of thinking for yourself, you seem to want to simply repeat Navweaps editorial comments - this makes for a pretty poor discussion, when as, I've stated, repeatedly, that I don't agree with their editorial comments. And you also dispute Navweaps data by asking us to pretend that RN RoFs were only half of what they state.


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## RCAFson (Feb 12, 2013)

To bring some reality back into the discusion:


> SECRET
> 
> CYPHER MESSAGE
> 
> ...


 
Again, if we place USN destroyers into the same situation - will they do better? We know that they have HA main armament, but we also know that the Mk 33 is a very slow and clumsy FC system, that was generally hopeless against surprise attack, and we know that USN destroyers have a much lighter CIWS than RN Tribal-JKMN destroyers. It is also apparent that the RN was subjected to a scale of attack unlike anything seen in the Pacific in 1942.


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## RCAFson (Feb 12, 2013)

Some comments on USN RPC (automatic gun drives):

Crenshaw of USS Maury:


> Our training schedule took on more importance and the tempo picked up. As Assistant Gunnery Officer, I attended the Gunnery Officer’s School held on Dixie once a week and heard the Squadron Gunnery Officers expound on the arcane art. One could read all about the technical details of our guns and fire control in the manuals, but hearing how to handle the equipment from the best in the fleet brought it all to reality. *Automatic Gun Drives were still new in the Fleet and were plagued with reliability problems.* The intricacies of the Mk-10 Rangekeeper were baffling to most officers. I found it all fascinating and listened with relish.



So in the Spring of 1941 USN RPC was still unreliable - I wonder what it was like in April 1940? 

Here's some more that backs up Crenshaw:


> Mindell, David A.. Between Human and Machine : Feedback, Control, and Computing before Cybernetics:
> 
> "...The director and the computer formed what one user manual called a "regenerative group," a feedback loop that eased the job of tracking fast-moving targets. 111 However useful and innovative, this feature exceeded the limits of BuOrd's or its contractors' technical knowledge. The feedback loop on the Mark 37,"a previously untried closed-circuit servo," had a stability problem: the output of the computer moved the director, which in turn affected the input to the computer. Both the computer and the power drives had time lags, so the two could push and pull each other and make the system oscillate. How these loops interacted and fed back on each other was poorly understood and caused severe problems in operations. (112) When radar was added in 1940,the noisy, often erratic signals instigated a complete breakdown. But the equipment was already in production, and the navy was preparing for war. The stability problem in the Mark 37 was the most prominent example of a complication arising throughout naval ﬁre control. Wherever sensitive instruments and intricate computers drove powerful servos on heavy gun mounts the systems could become unstable."It is well known," a 1937 report read, that "the guns, because of their enormous inertia, do not respond instantaneously to a signal from the director...for similar reasons the guns tend to swing too far when coming to alignment with the director after such motion, giving rise to 'hunting' or oscillations." (113) Adjustments could make these systems stable, but only at the cost of unacceptably degraded performance. A series of tests identified an "inherent weakness"in the Ford system of control and in the hydraulic speed gear with which it was used. BuOrd's precious machines suﬀered from "insufficient 'stiffness' or 'rigidity' or a lack of prompt response to the director system." (114) Naval ﬁre control systems, for all their precision, ruggedness, and sophistication, had run up against a problem the engineering culture could not solve: how to make a feedback loop move a large mass at high speed without making it unstable. Naval ﬁre control systems, for all their precision, ruggedness, and sophistication, had run up against a problem the engineering culture could not solve: how to make a feedback loop move a large mass at high speed without making it unstable..." p65-66
> 
> ...



and another:


> The Naval Institute guide to world naval weapons systems, 1997-1998, Friedman, p59:
> 
> MK 1 Electromechnical analog computer of the MK37 GFCS (FCS)...MK1 introduced fully automatic rate control to US practice and the MK 37 FCS was the first USN ordnance application of close-loop servo practice (initially experiencing severe problems because its feedback made it unstable) Most US ships used the MK1A version.


 {Mk1A was postwar}

Please tell me why these criticisms don't show up on the Navweaps site? Why does it always praise USN systems and criticize RN systems?

Here's some more that comment on the the slowness of the USN Mk 37 FC system:



> 200,000 Miles aboard the Destroyer Cotten
> June 1944:
> 
> Finally, a new fire control feature had been added that permitted individual 5inch mounts to be controlled by the closest 40-mm directors. This would allow Sky I to take severalattacking kamikazes under fire at the same time with a 40-mm mount and a 5inch mount, both under the same 40-mm director. It was now inescapably apparent that the main battery director and fire control computer of the typical destroyer were ineffective against diving kamikazes. The director was too slow to track a rapidly moving aircraft, and the computer was too slow to develop an accurate solution whenever changes in elevation, deflection, and range were initially rapid.






> U. S. NAVY BUREAU OF ORDNANCE
> IN WORLD WAR II by Rowland and Boyd.
> 
> The development of the Gun Directors Mark 33 and 37 provided
> ...



and I've already mentioned this one:


> "Although superior to older equipment, the computing mechanisms within the range keeper (Mk10) were too slow, both in reaching initial solutions on first picking up a target and in accommodating frequent changes in solution caused by target maneuvers. The Mk 33 was thus distinctly inadequate, as indicated to some observers in simulated air attack exercises prior to hostilities. However, final recognition of the seriousness of the deficiency and initiation of replacement plans were delayed by the below decks space difficulty, mentioned in connection with the Mk28 replacement. Furthermore, priorities of replacements of older and less effective director systems in the crowded wartime production program were responsible for the fact the Mk 33's service was lengthened to the cessation of hostilities."



{my comment regarding Mk 1A}


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## Glider (Feb 13, 2013)

Very interesting stuff RCAF, many thanks


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## RCAFson (Feb 13, 2013)

Glider said:


> Very interesting stuff RCAF, many thanks



This is a very interesting account of AA fire by the light crusier HMS Scylla:
HMS Scylla Story, 1942 - 1943
Note that it claims 16RPM for her 4.5in guns.
Here's Scylla defending PQ18:
CONVOY TO RUSSIA - British Pathé
you can actually watch and time her 4.5in salvos at 5sec intervals. I wouldn't want to fly close to the pom-pom either.


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## fastmongrel (Feb 13, 2013)

RCAFson said:


> Please tell me why these criticisms don't show up on the Navweaps site? Why does it always praise USN systems and criticize RN systems?



Reading some sources you get the impression the RN was so incompetent they should have stayed at anchor. Funny how they seem to have managed to do so well with such archaic equipment.


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## RCAFson (Feb 13, 2013)

fastmongrel said:


> Reading some sources you get the impression the RN was so incompetent they should have stayed at anchor. Funny how they seem to have managed to do so well with such archaic equipment.



Exactly. Considering the scale of attack faced by the RN in Norway, Dunkirk and for 3 years in the Med, the RN would have been wiped out several times over if RN AA was a bad as Navweaps would have us believe. Yet the people who knew best, the Luftwaffe and IAF, seemed to have a very healthy respect for RN AA.


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## vinnye (Feb 13, 2013)

Yes they got a bit of practice didn't they! Some of the situations they worked in were suicidal!
Given the advantages in weight and when they were designed, would it not be a fairer comparison to use the Manxman Class to the USN Fletcher?


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## cherry blossom (Feb 13, 2013)

It may be more important to have good ranges than a perfect predictor (off topic, the Germans had better range finders and a less sophisticated director system at Jutland). RN AA probably improved greatly over 1941 as radar started to give accurate ranges. I suspect that USN AA showed a similar improvement approximately a year later. 

The British also had an automatic 40 mm AA gun Britain 2-pdr [4 cm/39 (1.575")] Mark VIII afloat in fair numbers in 1939. Even the high velocity version only managed 2,300 fps (701 mps) compared to 2,720 fps (829 mps) for the Bofor, which would have been much better, but only the Dutch, Swedish and Norwegian Navies had decided to buy the Bofor. However, the German 37 mm was not automatic in 1939 and France had only equipped one ship with an automatic 37 mm in 1940 France 37 mm/70 (1.46") Model 1935.


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## fastmongrel (Feb 13, 2013)

Thats a lot of ammo, 140 rounds per barrel.


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## parsifal (Feb 13, 2013)

> Why would navweaps and Campbell state max rates for RN guns and practical rates for USN guns - that makes no sense at all! Yet you want to hold Navweaps up as gospel. I am willing to agree with their data but not their editorial comments which are not based upon any scientific basis, except simple hearsay.



Incorrect on two counts

My problem was that in one of your earlier posts you calcuclated the weight of fire on the basis of a rate of fire below the minimum max rof for the 5/38, and at the max rof for the 4.7 mount. It looked as if you were calculating the oputput on the practical rof for the US gun and the max rof for the Brit gun. 

Second error is your claim about Navweapons basing their assesment on Hearsay. Wrong. There are some operational results and losses given, and a very solid technical overview of both guns. They provide a pretty good analysis actually, and then draw logical, inbiased (the author is neither American or British I understand) conslusions from that. 



> The Benson class had Mk 37 and integral hoists, but the 1939 and earlier classes did not, but these were the last USN destroyers built to treaty limits, whereas the UK, because of wartime pressures, had to continue building destroyers with treaty based hulls until the Battle class of 1945




The Z classes onward had similar hull forms to the Battles, so it was from 1942 that the RN started to change its destroyer construction program not 1945. in other words, just behind the USN, but not by much. Bensons incidentally were close to treaty limits, it was from the Fletchers onward that significant departures really began, and they were 1941 designs....




> The RN entered the war with it's pre-war main armament and CIWS; what would have happened if the USN did the same? How would USN destroyers have fared in Norway or at Dunkirk



We will never know, but statisitically they should shoot down more enemy, provide better area defence and suffer a lower loss rate, if we are to believe most sources. 




> The problem is that instead of thinking for yourself, you seem to want to simply repeat Navweaps editorial comments - this makes for a pretty poor discussion, when as, I've stated, repeatedly, that I don't agree with their editorial comments. And you also dispute Navweaps data by asking us to pretend that RN RoFs were only half of what they state.



Im thinking for myself, but I do not misuse or misrepresent the material that is available to achiegve a wanted outcome. If I were to try to get fancy with this, you and others could justificably be baying for blood because what i was stating was just my opinion. Which is exactly what you are doing with this practical rof stuff. i certainly am not disagreeing with Navweapons. They rely on max rofs, which is fine, but if you are going to use figures that are below the max rof for one type, you need to do the same for the other....not pick the highest in the range for one type, and the lowest, or below the range for the other. Thats whats at the heart of this dispiute....colouring the lily with regard to the RN DDs whilst hammering the US type for any litle detail. That makes us no better than the LW Ra Ra boys if we start donig that..... 


Moving onto your next envelope, which includes a very si zable (and generally good account of Aa in Norway. Thereas a lot in the material, and i commend you for the contribution, but this does, if anything underline the weaknesses of the 4.7 as an AA mount.

Though I could critique a lot of the material, it all leads back to the inability of the 4.7 to hit high level targets, and fails to realize that in early 1940, the Germans did not have an effective aerial torpedo. Relevantly it states



> The above remarks also apply to low level bombing (2 to 3000 feet) in conditions where surprise can be effected.


 


Problem is, most LW attacks by their level and divebombers adopted an approach altitude considerably higher than that, typically in the region of 5-6000m. At that height, the 4.7 with 40 deg elevation can only engage a target approaching at 6000m. for a few seconds, and not effectively. The gun has a maximum horizontal range of about 17000 yads, which gives it a max vertical range of about 8000m. Again I have to enter the realm of practicality, because max ceiling is not the same as max effective ceiling. normally, the rule of thumb is that max effective ceiling for an AA gun is 20-30% less than its max ceiling. On that basis, the max effective ceiling for the 4.7 will be about 5-6000m. Anything above 7000m is out of the question. Anything above 5000m is just about impossible for it, and then only for a few seconds at extrem range. Nearly useless in other words. Which is exactly what Navweapons say. Not opinion, or editorial when you stop and think about it. 



> Again, if we place USN destroyers into the same situation - will they do better? We know that they have HA main armament, but we also know that the Mk 33 is a very slow and clumsy FC system, that was generally hopeless against surprise attack, and we know that USN destroyers have a much lighter CIWS than RN Tribal-JKMN destroyers. It is also apparent that the RN was subjected to a scale of attack unlike anything seen in the Pacific in 1942.




we cannot really answer that. Its not valid to say "the US did not upgraqde its CIWs until several year after the war broke out". War for the USN doid not break out until the end of 1941, before that the USN was unready for war because they were still at peace, with elements within the administration dead set against any involvement. If the USN found itself embroiled in the war from 1939, there is no reason to suggest that they would not have taken steps to upgrade their LAA defences in the opening months of their entry into war, as they did historically in 1942. We should draw similar conclusions with regard to their RPC and Director Controls. By way of comparison, the USN also had severe difficulties with the F4F a/c, but these were worked out by the time they went to war. So in response to your question, we dont know, and we cannot draw too many conclusions either. One way of looking at it is certainly to say they would, or could do noting to address the deficiencies, but another is to say they could well have addressed their deficiencies.

One thing I do take issue with hoever, is the elleged effectiveness of British CIWs. The available information is that British CIWs were pretty inneffective.....getting back to the Illustrious experience, there were 30000 rounds expended (according to Wiki) and that, along with the 3000 rounds of 4.5 in expended by the Illustrious and whatever other ammunition expended by her escort, managed to, maybe, shoot down 2 out of 40 aircraft, who in turn hit her with at least 6 bombs. Thats not good. The experiences of the PoW and Repulse are even worse.

And the claim that warfare in the Pacific was somehow easier than in Norway and in the med is highly disputable. numbers maybe, but interms of proficiency, the Japanese in 1942 were able to achieve accuracy levels of around 80% against the British (in the Indian Ocean), and pretty strike rates in other actions


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## RCAFson (Feb 13, 2013)

cherry blossom said:


> It may be more important to have good ranges than a perfect predictor (off topic, the Germans had better range finders and a less sophisticated director system at Jutland). RN AA probably improved greatly over 1941 as radar started to give accurate ranges. I suspect that USN AA showed a similar improvement approximately a year later.
> 
> The British also had an automatic 40 mm AA gun Britain 2-pdr [4 cm/39 (1.575")] Mark VIII afloat in fair numbers in 1939. Even the high velocity version only managed 2,300 fps (701 mps) compared to 2,720 fps (829 mps) for the Bofor, which would have been much better, but only the Dutch, Swedish and Norwegian Navies had decided to buy the Bofor. However, the German 37 mm was not automatic in 1939 and France had only equipped one ship with an automatic 37 mm in 1940 France 37 mm/70 (1.46") Model 1935.



Actually, the 40mm HV pom-pom had a MV of 2400fps. I afraid you ran afoul of Navweaps dissing RN equipment again.


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## parsifal (Feb 13, 2013)

RCAFson said:


> Actually, the 40mm HV pom-pom had a MV of 2400fps. I afraid you ran afoul of Navweaps dissing RN equipment again.



Oh jeez here we go again, misquoting a highly reputable source for the purposes of an agenda.


The truth is the Mark VIII mount as designed had a muzzle velocity of 2300 as reported by NW. It was increased to 2400 after the introduction of a newly designed round, in 1938, which was not interchangeable (and I suspect one of the reasons behind the notorious unreliability of the 2pdr).

For the record, NW actually says this about the new round, and probably explains why they state the lower figure.....its because the lower figure MV ammunition remained in production and/or use thru-out the war concurrent to the higher velocity round. And whilst they dont say this, it may be that having two incompatible rounds for the same basic gun might explain the reliability issues that plagued the gun during the war. 

For the record, the relevant quote from NW is as follows

"A higher velocity projectile was introduced in 1938 and this required a different breech mechanism and other changes to the firing gear. However, guns firing only the older low-velocity projectiles were still manufactured throughout World War II. High velocity and low velocity ammunition was not interchangeable. There were also several other gun variations, as shown in the data tables below".

NW is reporting on the older mechanism and the lower powered round, which is still valid, and not disrespecting the gun or RN equipoment. 

Stop trying to put words into the mouth of such a great reference source as NW. It does your otherwise great knowledge on this subject no good at all.


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## RCAFson (Feb 13, 2013)

parsifal said:


> Incorrect on two counts
> 
> a)My problem was that in one of your earlier posts you calcuclated the weight of fire on the basis of a rate of fire below the minimum max rof for the 5/38, and at the max rof for the 4.7 mount. It looked as if you were calculating the oputput on the practical rof for the US gun and the max rof for the Brit gun.
> 
> ...



A)I used the practical rate of fire for both weapons, and actually reduced the 4.7in to 10 rpm from 12 and used 12 rpm for the early mods of the 5in/38. Again, I ask you to produce evidence that RN RoF was 1/2 of what navweaps and Campbell state. The data from HMS Basylisk ( 5 rounds in 17 seconds for a 4.7in single mount) and Scylla (16rpm), suggest that the RN maximum RoF was much higher then 10-12 rpm. 

b) Navweaps repeats (anecdotal?) evidence for very high RoF's with the later variants of the 5in/38 but doesn't do the same for RN weapons - clear evidence of bias. This bias extends to the AA FC systems where the USN is praised to high heaven, with no mention of the serious flaws and drawbacks of USN AA FC that have been scientifically documented while the RN system is condemned and every supposed flaw emphasized - another clear example of bias. In actual fact both systems were flawed, as you would expect from 1930s technology, but you'd never know that from the Navweaps site.

D) Here's what Captain Gatch had to say about the relative effectiveness of 5in/38 versus CIWS kill rates:


> The first enemy attack was concentrated against the Hornet. South Dakota operated near the Enterprise to provide her protective fire against the attacking aircraft. At 1045 Task Force 16 was attacked by a group of dive bombers. Approximately an hour later the task force was again attacked, this time by some 40 torpedo bombers. A third aerial assault was made with both dive bombers and torpedo bombers, coming in at 1230. South Dakota suffered a 550 lb (250 kg) bomb hit on top of her number one turret. When the action was broken off that evening, the American forces retired toward Nouméa, New Caledonia. The South Dakota was credited with downing 26 enemy planes. She had fired 890 rounds of 5 inch, 4,000 rounds of 40mm, 3,000 rounds of 1.1 inch and 52,000 rounds of 20mm ammunition during the action. *Captain Gatch made the following assessment of the relative effectiveness of each weapon type in bringing down enemy aircraft during the action: 5 inch: 5%, 40mm and 1.1 inch: 30% and 20mm: 65%.*[3]
> [3] United States Navy, AntiAircraft Action Summary, July 1942 to Dec 1942 (Information Bulletin No. 22), p111
> USS South Dakota (BB-57) - Wikipedia, the free encyclopedia


Now remember that it was RN Tribal-JKLMN destroyers that had the much heavier CIWS as built, and that is what they went to war with.

e)I'm sorry if I got a bit hot on this one. The problem is that there is clear evidence of bias on the Navweaps site against the RN with an editorial lead-in on virtually every RN weapon telling the reader how bad it was before he/she even gets to the actual data! I used 10rpm for the RN 4.7in (April 1940 twin mount)and 12rpm for the USN 5in/38 (April 1940 single mounts without integral hoists) and these RoFs are supported by actual combat data. If you read Crenshaw's account about USS Maury you will also read about the numerous problems that they had with their 5in FC, guns, and ammunition yet these kinds of cmments don't show up on Navweaps - and I ask you again why not?

f) No one, including me, is saying that 40deg elevation is perfect, but the RN report on Norway states quite clearly that the vast majority of attacks had to come within the envelope of a 40deg gun. Very high level attacks had very little probability of hiting anything anyways - witness Vian's 5knot convoy! and even the Stuka attacks achieved much of what they did beceause they were not engaged at all, not even by the CIWS, and having 5in/38 guns wouldn't change that. Additionally, the RN had a large number of sloops and cruisers that could fire above 70 degs and these were often in company with the 40deg destroyers.

g) Well Torpedo bombers are the one type that we all agree that the 40deg elevation guns would have no problem engaging.

h) The Stuka certainly did not operate at 5-6000m! Typically altitudes were 3000-4000m prior to their dive. 



i)

j) Illustrious's AA ammo was fired over many days, and the two Stuka kills were made during the first attack.



Gotta run - more later.


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## RCAFson (Feb 13, 2013)

parsifal said:


> Oh jeez here we go again, misquoting a highly reputable source for the purposes of an agenda.
> 
> 
> The truth is the Mark VIII mount as designed had a muzzle velocity of 2300 as reported by NW. It was increased to 2400 after the introduction of a newly designed round, in 1938, which was not interchangeable (and I suspect one of the reasons behind the notorious unreliability of the 2pdr).
> ...



Sorry, but that's not true. The pre 1938 LV 40mm pom-pom = 2040fps not 2300 fps. Campbell states 2400 fps for the HV round.


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## parsifal (Feb 13, 2013)

> A)I used the practical rate of fire for both weapons, and actually reduced the 4.7in to 10 rpm from 12 and used 12 rpm for the early mods of the 5in/38. Again, I ask you to produce evidence that RN RoF was 1/2 of what navweaps and Campbell state. The data from HMS Basylisk ( 5 rounds in 17 seconds for a 4.7in single mount) and Scylla (16rpm), suggest that the RN maximum RoF was much higher then 10-12 rpm.




No, you have not. according to Terry Giulan (In an essay dated 2009, entitled "The British High Angle Control System", reproduced in NW, but not where i found it), he provides a clue on the differencews between cyclic rate (or as I call it max rof), and max sustained rof (which I and some others refer to as practical rof). He says:

"_Almost all destroyers with 4.7-inch guns had the HE time fuzes set by hand. This affected the firing solution not only by the time setting itself, but also in that the fuze setter became the critical time factor. *No matter how fast the guns could fire or how quickly ammunition could be supplied to the mountings, even a well-trained fuze setter needed about 4 to 5 seconds to handle the round and set the fuze properly. * Faster speeds invariably resulted in improper fuze settings and loss of effectiveness. These factors encouraged the use of barrage firing as it meant that all fuzes were set the same, thus requiring less time by the manual fuze setters.11 Most larger ships used fuze setting machines, but all of these could only handle one round per barrel at a time, thus slowing the practical rate of fire. An interesting but unfortunate side effect of these fuze setting systems was that the “dead time” between the point that the shell left the fuze setting machine and the point it was fired out the gun needed to be calculated based upon the slowest gun crew on the ship. As the guns were fired by remote control, this effectively meant that all salvos had but a single time setting. Again, this slowed the practical rate of fire"_. 

On top of that, the redesignof the mounting itself wqas not conducive to fast loading. In a static situation, with the gun not moving, I have no problem in accepting 10-12 rpm. But in a real combat situation you have two major constraints that are not present for the 5/38. Firstly you have this manual fuze setting, which at minimum adds 4-5secs to the theoretical max rof. Then you have the poor design of the turret. relative to the gunner, the ammunition supply point was fixed, making it easy to become disoriented. For the single mounts you had a further complication, the hand ramming.

If the theoretical max rof was 12rpm, or 5 secs, you must then add 5 secs for the manual fuze setting and then some unknown time for the turret issues....say 2 secs per round. That reduces the practical rof for the 4.7 down to about 6 rpjm, or more approximately 4-8, which is a better way of describing it, gieven the variable human factors at work.

Now, neither of those constraints affects the Mk 30 5/38 turret. So its practical rof fire is going to be much closer to the max rof. The max rof is not 12rpm for the mk 30, as you are still saying....its 24 rpm. But the practical rof is somewhere between 15-22 rpm. I suspect the director issues you mentioned are the main cause for this downgrading in efficiency. but a more realistic comparison, if we want to use practical rofs, is to estimate the 4.7 at 4-8 rpm, and the 5/38 at 15-22 rpm. 




> Navweaps repeats (anecdotal?) evidence for very high RoF's with the later variants of the 5in/38 but doesn't do the same for RN weapons - clear evidence of bias.



no. Clear evidence that they have supporting material to inidicate lower standard of efficiency for the 4.7, in comparison to the 5/38. this is not a popularity or political excercise. i think it an excercise in trying to give an accurate assessment of true capabilities of each gun, taking into account various hidden factors. . 



> This bias extends to the AA FC systems where the USN is praised to high heaven, with no mention of the serious flaws and drawbacks of USN AA FC that have been scientifically documented while the RN system is condemned and every supposed flaw emphasized - another clear example of bias. In actual fact both systems were flawed, as you would expect from 1930s technology, but you'd never know that from the Navweaps site


.

The operational results that we have dont support that claim. US destroyers seem to have been more survivable and achieved overall more efficient standard of fleet and unit protection with their weapons than the RN was able to achieve. There may be good mitigating circumstances for that, but given the FC system is so critical to getting decent results I think it entirely reasonable for NW to take the position they do. Others can perhaps explain the technical side better than I, but the operational results speak to me better than any theoretical technical analysis. the USN destroyers did better than the RN destroyers. Its as simple as that. 




> Here's what Captain Gatch had to say about the relative effectiveness of 5in/38 versus CIWS kill rates:
> Now remember that it was RN Tribal-JKLMN destroyers that had the much heavier CIWS as built, and that is what they went to war with.



The higher standard of CIWs was theoretical rather than actual, but was more or less forced on the RN because of the failure of their 4.7s as a true DP weapon. I say the CIWs were theoretical because really if we are talking British CIWs we are talking 2 pounder guns. these lacked satisfactory performance to be really held up as good or efficient. No tracer, effective range of about 1700m (according to the RN) too many stoppages no relaiable explosive shell. All adds up to an inneffective CIW. So, whereas the USN entered the war with at least a good and true DP main, the RN went to war with neither a good DP main, or a decent CIW either. 




> I'm sorry if I got a bit hot on this one. The problem is that there is clear evidence of bias on the Navweaps site against the RN with an editorial lead-in on virtually every RN weapon telling the reader how bad it was before he/she even gets to the actual data! I used 10rpm for the RN 4.7in (April 1940 twin mount)and 12rpm for the USN 5in/38 (April 1940 single mounts without integral hoists) and these RoFs are supported by actual combat data. If you read Crenshaw's account about USS Maury you will also read about the numerous problems that they had with their 5in FC, guns, and ammunition yet these kinds of cmments don't show up on Navweaps - and I ask you again why not?



No need to apologise. its allo good. we are still rexchanging information and not insults. Dont agree that NW has much bias, for reasons already given. You are looking at the 5/38 without integral hoists, which makes a huge difference. Its pronbaly no exaggeration to say that more than 80% of 5/38 mounts built were mk 30 hoists with integral hoists. I think it far more relavant to the topic to look at the typical or prevalent type rather than pick an islated or minority failure. and as ive tried to show previously, 10 rpm for the 4.7 is not a realistic estimate of the real rof for this weapon 




> No one, including me, is saying that 40deg elevation is perfect, but the RN report on Norway states quite clearly that the vast majority of attacks had to come within the envelope of a 40deg gun. Very high level attacks had very little probability of hiting anything anyways - witness Vian's 5knot convoy! and even the Stuka attacks achieved much of what they did beceause they were not engaged at all, not even by the CIWS, and having 5in/38 guns wouldn't change that. Additionally, the RN had a large number of sloops and cruisers that could fire above 70 degs and these were often in company with the 40deg destroyers.



The report you posted does not say what you are claimimg for it. It say, essentially, that those types of attacks that fitted within the envelope they specified, could be countered. It goes on to say, virtually, that in other situations....panic, because you will not be able to hit anything with the equipment we have given you. You cannot make any claims about the 5/38 because it was not engaged in Norway. We need to keep opinion out of the way of known facts. 



> Well Torpedo bombers are the one type that we all agree that the 40deg elevation guns would have no problem engaging.




Nope, dont agree. Previously posted why, due to slow training rates and rofs, and the short range of the ciws, could not be effectively engaged in many situations. Lucky for the RN, the Germans were even more remiss in not having an effective air launched torp until later in the war. 




> The Stuka certainly did not operate at 5-6000m! Typically altitudes were 3000-4000m prior to their dive.


 
I dont know that we can nail a typical approach altide too well. Even at 3-4000 m there would be difficulties for the RN. but even if it was possible, the option was there for the LW simply to fly above the effective ceiling of the gun 


j


> Illustrious's AA ammo was fired over many days, and the two Stuka kills were made during the first attack.



Regardless, they exopended huge amounts of ammunition for virtually no gain. In any even, wiki suggests thats not the case.....they say that 30000 rounds were expended in the 1st attack. if youve got better, would be great to see it. 




Gotta run - more later.[/QUOTE]


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## fastmongrel (Feb 14, 2013)

Jeez will you two give it a break, about 7 pages ago this was an interesting thread.


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## Glider (Feb 14, 2013)

What I find interesting about this thread is how often the volume of the words hide the basic facts and avoid adressing the simple questions.

1) Tribals
RCAF believes that the twin 4.7 was a decent DP gun, so shy did the RN replace a turret with a twin 4in. We know that topweight issues were not the problem. It was done because they needed it. 
Generally speaking the RN had the SP 4.7 in destroyers a simple reliable average gun. It put 4in on ships designed to take on aircraft. The RN knew they were taking a chance with the detroyers and designed the DP 4.7 on the LM class. These were heavy, large, expensive and soon dropped. 
The JKN and Tribals had 4in installed because they needed it, to pretend otherwise flies in the face of all logic. A comment was made earlier that the RN could have rearmed the Tribals with 8 x 4in, no they couldn't demand far outstripped supply

2 US 5in how good was it.
RCAF believes that it was overated and nothing special. So the question is, why did the RN who first had experience of this weapon on HMS Delhi want to buy as many as they could to install on british Destroyers. It was the awnser to the problem highlighted in question 1

3 Rate of Fire
Much is made about the rof and was it this or that. That isn't the point, the British ships had manual fusing which took approx 4-5 seconds. However it probably had little impact on the rof, but, and this is the real point, it added 4-5 seconds in the cycle between the directions from the director and the gun being fired. An aircraft an go a long way in 4-5 seconds approx 1/3rd of a mile (at 240 mh) and that makes the difference between a hit and a miss.

4) Using a HAA gun to hit a dive bomber before proximity fuzes was almost pontless and it doesn't matter what gun your firing 

5) Firing Trials
If anyone believes that what was attained in trials of any weapon in the 1920's to the 1970's has any bearing on real life, needs to have their heads examined. Pick any weapon of any era and you be lucky to find that it does what is says on the tin in trials.

6) AA guns 
The first priority of any AA gun *Is not to shoot the aircraft down* its to stop them hitting you or the target you are defending. An attack where no one was shot down and no one hit is a huge win for the defenders

7) Elevation
The greater the elevation the long you can fire at the target and the better your chance of distrupting the bombers and if you are lucky shoot a couple down. 40 degrees isn't close to sufficient


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## vinnye (Feb 14, 2013)

Glider, I did not know that there was a supply / demand problem with the 4 inch.
Is it possible then that the RN were trying to buy any gun that had some potential as an AA weapon?


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## parsifal (Feb 14, 2013)

fastmongrel said:


> Jeez will you two give it a break, about 7 pages ago this was an interesting thread.




Your right. sorry about that. Will ease back a little and give you guys a go. Heated debate, no abuse, and for me some really intersting points. but I can fully understand your frustration. We did hijack things a bit.


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## RCAFson (Feb 14, 2013)

Glider said:


> What I find interesting about this thread is how often the volume of the words hide the basic facts and avoid adressing the simple questions.
> 
> 1) Tribals
> RCAF believes that the twin 4.7 was a decent DP gun, so shy did the RN replace a turret with a twin 4in. We know that topweight issues were not the problem. It was done because they needed it.
> ...



1) I have answered this several times and even produced and RN document to back up my case: 
_"9. It appears that enemy aircraft wait about overhead where they are impossible targets for destroyers and difficult for any ship. *Steps are being taken to strengthen the short range armament* of destroyers who have to operate within the range of dive bombers. It is to be recalled however that except for special aircraft for steep dive bombing and level bombing from considerable heights enemy aircraft must come within the envelope of a 40 degree gun when approaching for an attack."_

I think you should, rhetorically, speak to the Admiralty who wrote the above excerpt, and not to me. I have explained why they added a 4in twin - you can choose not to accept my explanation, or the Admiralty's explanation which is summarized above. You keep repeating that the twin 4.7in was a SP gun, even though I have very patiently produced reams of documentation to proof otherwise, including an Admiralty memo, which explicitly states that the 4.7in gun was intended for use against aircraft although the fact that the 4.7in twin had an on mount fuze setter which was directly linked to the AA FC computer should have ended any doubts that you might have had. The 4.7in/50 twin on the LM wasn't dropped, the UK simply couldn't build enough of these complex mounts fast enough to meet demand - heck they were arming some destroyers (OP class) with WW1 vintage 4in MK V single mounts, out of shear desperation and many others with the 40deg 4.7in single.

2) The RN had no intention of buying USN 5in guns or MK37 FC systems - they wanted to acquire them for free under lend-lease, for the simple reason that you yourself have pointed out: "demand outstripped supply" and the UK armaments industry, simply couldn't supply enough UK built guns and FC systems, forcing a request for US supply. Unfortunately, the USA would not build any weapon to UK specs unless it was approved for use by the the US Military (AFAIK only the 6pdr ever met this requirement) which is why Canada built RN spec weapons but not the USA - if the RN wanted to acquire DP naval guns in the USA they had to be USA spec weapons. See North American Supply by Hall for more information on this aspect of lend-lease. For example the RN wanted the USN to adopt the pom-pom so that both navies could have these weapons produced quickly in the USA, but this was turned down and the delay in producing the Bofors 40mm meant that very few USA built Bofors guns were provided to the RN, under lend-lease.


3) All Mk 33 class USN destroyers used a fuze setter (the shell was put in the fuze setter nose first and then had the timing set) which was very similar to that used on RN 4.7in twin mounts. It seems that you don't understand how AA fuze setting works; a shell is placed in the fuse setter, the FC computer predicts the time of flight needed to hit the target and sends this data to the fuze setter and the FC computer predicts far enough in advance to allow to shell to be fused, loaded and then fired according to the salvo interval selected. For an explantion of how RN AA worked, please read: The Gunnery Pocket Book - Part 4

5) Yes, and the practical RoF, as used in combat was 10-12rpm for the RN twin, 12-15 for the USN Mk 33 5in/38 and 15+ for the USN Mk 37. Robert Hughes, an RN gunnery officer gave a real life example of the RN 4.5in twin being fired at 16rpm in predicted fire where each shell had to be fuzed in the fuze setter, and Campbell quotes Illustrious' action report as stating that she fired 3000 4.5in rounds at an average of 12rounds per gun per minute. March reports that HMS Kimberly fired 180 salvos at Narvik, with most having a 5sec firing interval.

6) Vian accomplished just that with his Tribal class destroyers while defending a 5 knot convoy from a day long luftwaffe attack.

7) It all depends on the bomber's elevation. At very high altitudes they couldn't hit ships either.


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## RCAFson (Feb 14, 2013)

vinnye said:


> Glider, I did not know that there was a supply / demand problem with the 4 inch.
> Is it possible then that the RN were trying to buy any gun that had some potential as an AA weapon?



Exactly. The original proposal for Delhi, for example, was to arm her with 4.5in twin mounts and UK AA FC, but these couldn't be produced in the UK


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## cherry blossom (Feb 14, 2013)

RCAFson said:


> Actually, the 40mm HV pom-pom had a MV of 2400fps. I afraid you ran afoul of Navweaps dissing RN equipment again.


 
I was trying to be careful. I knew that NW gave the new gun velocity for American and the average gun velocity for British guns, so I gave the British average gun velocity for the Bofor as a comparison. If you look at the Bofor entry Sweden, Britain, USA, Germany and Japan Bofors 40 mm/56 (1.57") Model 1936, you find:

“One firm rule adopted early in the redesign process was that any new Allied munition for these weapons needed to be completely interchangeable with existing designs. This allowed ammunition produced by any American or British ordnance manufacturer to be used with any weapon produced by either country, thus greatly simplifying the logistics problems of a world-wide war.”

and 

“USA Marks 1 and 2: 2,890 fps (881 mps)
UK Mark NI: 2,720 fps (829 mps)”

Which illustrates how interchangable ammunition gives different velocity in USN and RN publications.


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## RCAFson (Feb 14, 2013)

Campbell: 

_"The gunnery report of Illustrious on the attacks of January 1941 is of interest...altogether about 30,000 rounds were expended."_ So the report covers the entire 13 day period of Jan 10 to 23 when she suffered numerous air attacks.


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## Glider (Feb 14, 2013)

RCAFson said:


> 1) I have answered this several times and even produced and RN document to back up my case:
> _"9. It appears that enemy aircraft wait about overhead where they are impossible targets for destroyers and difficult for any ship. *Steps are being taken to strengthen the short range armament* of destroyers who have to operate within the range of dive bombers. It is to be recalled however that except for special aircraft for steep dive bombing and level bombing from considerable heights enemy aircraft must come within the envelope of a 40 degree gun when approaching for an attack."_
> 
> I think you should, rhetorically, speak to the Admiralty who wrote the above excerpt, and not to me. I have explained why they added a 4in twin - you can choose not to accept my explanation, or the Admiralty's explanation which is summarized above. You keep repeating that the twin 4.7in was a SP gun, even though I have very patiently produced reams of documentation to proof otherwise, including an Admiralty memo, which explicitly states that the 4.7in gun was intended for use against aircraft although the fact that the 4.7in twin had an on mount fuze setter which was directly linked to the AA FC computer should have ended any doubts that you might have had. The 4.7in/50 twin on the LM wasn't dropped, the UK simply couldn't build enough of these complex mounts fast enough to meet demand - heck they were arming some destroyers (OP class) with WW1 vintage 4in MK V single mounts, out of shear desperation and many others with the 40deg 4.7in single.


It isn't that I don't accept solutions, what I do not accept are solutions that lack logic or support. You rightly say that the Admiralty took steps to improve short range weapons. But then ignore the fact that the 4in isn't a short range weapon. Its a long range weapon that would be of little use against a dive bomber. The first steps taken to improve short range defence was the swapping out of 0.5 mg and replacing them with 20mm. To say that installing a 4in helps short range defence is wrong, plain and simple.


> 2) The RN had no intention of buying USN 5in guns or MK37 FC systems - they wanted to acquire them for free under lend-lease, for the simple reason that you yourself have pointed out: "demand outstripped supply" and the UK armaments industry, simply couldn't supply enough UK built guns and FC systems, forcing a request for US supply. Unfortunately, the USA would not build any weapon to UK specs unless it was approved for use by the the US Military (AFAIK only the 6pdr ever met this requirement) which is why Canada built RN spec weapons but not the USA - if the RN wanted to acquire DP naval guns in the USA they had to be USA spec weapons. See North American Supply by Hall for more information on this aspect of lend-lease. For example the RN wanted the USN to adopt the pom-pom so that both navies could have these weapons produced quickly in the USA, but this was turned down and the delay in producing the Bofors 40mm meant that very few USA built Bofors guns were provided to the RN, under lend-lease.


Wrong. Lend lease was not free and nearly all US weapons were under lend lease and they had every intention of getting as many as they could.


> 3) All Mk 33 class USN destroyers used a fuze setter (the shell was put in the fuze setter nose first and then had the timing set) which was very similar to that used on RN 4.7in twin mounts. It seems that you don't understand how AA fuze setting works; a shell is placed in the fuse setter, the FC computer predicts the time of flight needed to hit the target and sends this data to the fuze setter and the FC computer predicts far enough in advance to allow to shell to be fused, loaded and then fired according to the salvo interval selected. For an explantion of how RN AA worked, please read: The Gunnery Pocket Book - Part 4


I will follow this up


> 5) Yes, and the practical RoF, as used in combat was 10-12rpm for the RN twin, 12-15 for the USN Mk 33 5in/38 and 15+ for the USN Mk 37. Robert Hughes, an RN gunnery officer gave a real life example of the RN 4.5in twin being fired at 16rpm in predicted fire where each shell had to be fuzed in the fuze setter, and Campbell quotes Illustrious' action report as stating that she fired 3000 4.5in rounds at an average of 12rounds per gun per minute. March reports that HMS Kimberly fired 180 salvos at Narvik, with most having a 5sec firing interval.
> 
> 6) Vian accomplished just that with his Tribal class destroyers while defending a 5 knot convoy from a day long luftwaffe attack.


Interesting


> 7) It all depends on the bomber's elevation. At very high altitudes they couldn't hit ships either.


Agreed it does depend on the bombers elevation but also on the guns elevation. If you look back at the chart you posted the 40 degree elevation gives you approx 40 seconds to fire at a level bomber before you can no longer fire at it. The 80 degree elevtation doubles that time. A destroyer is lucky to hit another ship within 40 seconds let alone a small aircraft. Equally important by ceasing fire you let the bomber concentrate for a precious 40 seconds and significantly improve their accuracy. Having an 80 degree elevation stops that happening. That is my undersanding is why the Tribals were given a twin 4in instead of the twin 4.7. It had nothing to do with improving the short range weapons.


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## RCAFson (Feb 14, 2013)

parsifal said:


> No, you have not. according to Terry Giulan (In an essay dated 2009, entitled "The British High Angle Control System", reproduced in NW, but not where i found it), he provides a clue on the differencews between cyclic rate (or as I call it max rof), and max sustained rof (which I and some others refer to as practical rof). He says:
> 
> "_Almost all destroyers with 4.7-inch guns had the HE time fuzes set by hand. This affected the firing solution not only by the time setting itself, but also in that the fuze setter became the critical time factor. *No matter how fast the guns could fire or how quickly ammunition could be supplied to the mountings, even a well-trained fuze setter needed about 4 to 5 seconds to handle the round and set the fuze properly. * Faster speeds invariably resulted in improper fuze settings and loss of effectiveness. These factors encouraged the use of barrage firing as it meant that all fuzes were set the same, thus requiring less time by the manual fuze setters.11 Most larger ships used fuze setting machines, but all of these could only handle one round per barrel at a time, thus slowing the practical rate of fire. An interesting but unfortunate side effect of these fuze setting systems was that the “dead time” between the point that the shell left the fuze setting machine and the point it was fired out the gun needed to be calculated based upon the slowest gun crew on the ship. As the guns were fired by remote control, this effectively meant that all salvos had but a single time setting. Again, this slowed the practical rate of fire"_.
> 
> ...


-You are verging on fantasy here. Please read:
http://www.admirals.org.uk/records/adm/adm186/adm186-339.pdf
starting at PDF page 142, for an explanation of maximum and usable RoFs for RN 4.7 and 4in HA mounts. *The deadtime is not additive to the cyclic rate of the gun, it is part of it*. Please if you don't understand this, then don't try to wing it, because it just confuses all concerned. I've done a lot of reading about this subject lately, and it takes some time to grasp the concepts involved.





> no. Clear evidence that they have supporting material to inidicate lower standard of efficiency for the 4.7, in comparison to the 5/38. this is not a popularity or political excercise. i think it an excercise in trying to give an accurate assessment of true capabilities of each gun, taking into account various hidden factors. .
> 
> .
> 
> ...


-I'm looking at the 5in without integral hoists because that was the only USN DP gun in service in April 1940 (Norway) and we know that Mk 37 had major teething troubles, so it would not have been a servicable weapon system for sometime after it's first introduction. 




> The report you posted does not say what you are claimimg for it. It say, essentially, that those types of attacks that fitted within the envelope they specified, could be countered. It goes on to say, virtually, that in other situations....panic, because you will not be able to hit anything with the equipment we have given you. You cannot make any claims about the 5/38 because it was not engaged in Norway. We need to keep opinion out of the way of known facts.



-The report is pretty clear in stating that most attacks would have to come within the envelope of a 40deg gun, and for dive bomber attacks, the pom-pom is always available.




> Nope, dont agree. Previously posted why, due to slow training rates and rofs, and the short range of the ciws, could not be effectively engaged in many situations. Lucky for the RN, the Germans were even more remiss in not having an effective air launched torp until later in the war.



- I used your own scenario to show how the RN would fire just as many rounds as the USN destroyers in the same time frame - the problem is that to make your argument work you have to cut the RoF of RN guns by half and you refuse to present any supporting data for this rather startling conclusion.




> I dont know that we can nail a typical approach altide too well. Even at 3-4000 m there would be difficulties for the RN. but even if it was possible, the option was there for the LW simply to fly above the effective ceiling of the gun



-The Stuka didn't have an unlimited ceiling except, apparently, against RN destroyers! The Stuka struggled to carry a 500kg bomb above 12000ft, and even then it meant a very short range. This has been gone over in the aircraft forum. Most IJN Val attacks were from 10-12 thousand ft. IJN level bomber attacks were typically flown at 9000ft.


j



> Regardless, they exopended huge amounts of ammunition for virtually no gain. In any even, wiki suggests thats not the case.....they say that 30000 rounds were expended in the 1st attack. if youve got better, would be great to see it.


- They "gained" the survival of their ship and after their first taste of RN AA, the Stukas never again attacked Illustrious with the same fervour.


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## RCAFson (Feb 14, 2013)

An appeal to all concerned: 

Please read:
HMS Scylla Story, 1942 - 1943

which is an excerpt from Robert Hughes' book, Flagship to Murmansk. It is a very good summary and intro to RN AA during WW2. Hughes was an RN gunnery officer on the AA cruiser Scylla and I guess he never read through the Navweaps site because he seems to have felt that RN AA was very effective and provides real life examples to prove it. Hughes was the man controlling Scylla's gunfire during this film clip showing the defence convoy of PQ 18, where RN AA fire cut the luftwaffe to ribbons:
CONVOY TO RUSSIA - British Pathé


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## RCAFson (Feb 14, 2013)

Glider said:


> It isn't that I don't accept solutions, what I do not accept are solutions that lack logic or support. You rightly say that the Admiralty took steps to improve short range weapons. But then ignore the fact that the 4in isn't a short range weapon. Its a long range weapon that would be of little use against a dive bomber. The first steps taken to improve short range defence was the swapping out of 0.5 mg and replacing them with 20mm. To say that installing a 4in helps short range defence is wrong, plain and simple.



I'm sorry but you're wrong. Most destroyers had 4in guns added in lieu of a set of TTs; these guns were aimed and fired over open sights, and thus they were additions to the CIWS. The Tribals were a happy exception as the 4in twin could be coupled to the AA FC system, but when countering dive bombers they were used with short range "barrage" fuze settings, and they probably engaged the DBs over open sights as well, and their effective range in that mode was hardly greater than a pom-pom. 



> Wrong. Lend lease was not free and nearly all US weapons were under lend lease and they had every intention of getting as many as they could.


Lendlease meant that the UK could acquire US hardware with no capital outlay - effectively free. There was some reciprocal obligations but these were not directly tied to UK acquisitions so if the USN released 500 5in/38 guns to the RN, it did not require a direct obligation for compensation in kind. All lend-lease required from the UK was the obligation to provide what ever it could, that was surplus to it own requirements. The RN never dreamed of purchasing 5in guns and USN FC because the UK simply didn't have the hard cash needed to do that. Acquiring 5in guns only became feasible after lend-lease. Nelson to Vanguard, p156 states that the original intention was to arm the D class cruisers with 4 x 4.5in twin mounts each but upon the outbreak of war in 1939 this was no longer possible, probably because of a lack of yard space. The two sets of 4.5in guns that were ordered went into Scylla and Charybdis, because of a shortage of 5.25in mounts. The UK naval armaments industry was badly overstretched during WW2 and many of the plants working on RN weapons and FC were bombed in 1940/41 further adding to the backlog. 

Nelson to Vanguard states further that the USN offered not only to release the guns and FC systems for HMS Delhi but also to do all the work, including a general refit and the addition of a UK supplied CIWS at the same time - all in a US yard!. The yard situation in the UK was so tight at that time (mid 1941) that even if the USN had delivered the guns directly to the UK, the work could not have been done, except at the expense of other vital repait work. The 5in/38+Mk37 would have had to have been pretty terrible for the UK to turn down this offer, but IMHO, Delhi with 4 x 4.5in twins and RN FC would have been a better AA cruiser. 

Delhi is often held up as a shining example of superior USN guns and AA FC, but AFAIK, Delhi was a bit of a bust in actual service and she was held back from the really critical Malta convoys in June and August 1942 , when the RN had no problem committing 4in armed C class AA cruisers to defend those convoys and 40 deg elevation destroyers...


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## Juha (Feb 14, 2013)

Hello RCAFSon
if RN thought that 40deg was enough why then the last 4.7" DD mount had 55deg max elevations as had the 4.5" mounts which were the main gun armaments of the late war RN DDs? And IMHO it was a sign of desperation to halve torpedo armament of Fleet DDs during early war years just to get one 12pdr/3" (on pre-Tribal DDs) or 4" (on J-M classes) HA gun capable only local control firing onboard.

Juha


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## RCAFson (Feb 14, 2013)

Juha said:


> Hello RCAFSon
> if RN thought that 40deg was enough why then the last 4.7" DD mount had 55deg max elevations as had the 4.5" mounts which were the main gun armaments of the late war RN DDs? And IMHO it was a sign of desperation to halve torpedo armament of Fleet DDs during early war years just to get one 12pdr/3" (on pre-Tribal DDs) or 4" (on J-M classes) HA gun capable only local control firing onboard.
> 
> Juha



I never said that the RN thought that 40 degs was enough! 

What I've been saying is that 40degs is not useless and that most air attacks could be engaged by destroyers with 40 deg guns - anyone who takes the time to read Lundstrom and First Team will know that in almost every case USN destroyers with 40 deg elevation could have provided the exact same AA support as they did in 1942. The problem is that most people seem to think that aircraft simply materialized directly over destroyers (but only RN destroyers), and they were helpless if they couldn't shoot straight up! Of course this is complete nonsense.

It certainly was a sign of desperation, to add single 3in or 4in guns - the problem being that the 20mm oerlikon was not yet in UK or Cdn production, nor was the Bofors 40mm in a naval mounting, and the quad pom-pom was in very tight supply, whereas these 3in and 4in guns were sitting around gathering dust...and so they were hauled out of storage and added to RN Fleet destroyers. Later in the war, most of these ships had the gun removed and replaced by TTs once again along with a greatly strengthened CIWS.


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## parsifal (Feb 14, 2013)

> You are verging on fantasy here. Please read:
> http://www.admirals.org.uk/records/a...adm186-339.pdf
> starting at PDF page 142, for an explanation of maximum and usable RoFs for RN 4.7 and 4in HA mounts. The deadtime is not additive to the cyclic rate of the gun, it is part of it. Please if you don't understand this, then don't try to wing it, because it just confuses all concerned. I've done a lot of reading about this subject lately, and it takes some time to grasp the concepts involved.



The link didnt work for me....


At 12 rpm the rof for the gun is 5 secs. Di Giulan says that fuze setting takes 5 secs. If that is part of the firing cycle, that leaves 1 second to traverse the turret, get instructions from the director, collect the shell, load the weapon, aim the weapon and then fire it. Some of the timesetting the time fuze can be done wholst other things are happening. But some things have to be done sequentially. Seting the fuze by hand, in the turret, is amajor constraint on the weapon system efficiency.

Glider made a better explanation than i 



> I used your own scenario to show how the RN would fire just as many rounds as the USN destroyers in the same time frame - the problem is that to make your argument work you have to cut the RoF of RN guns by half and you refuse to present any supporting data for this rather startling conclusion.



No, you made assumptions that are still being debated

I pretty much disagree with everything else that you are posting, but have made promises to other memebers not to hijack this thread any further. you might want to consider that as well. 

XXXXXXXX

Im not saying that RN AA was not effective. I am saying that ton for ton, it was not as effective as USN AA. I am not looking at an isloated time frame, but overall and not hypothersiing too much about what if scenarios. Dollar for dollar, maybe a different story compared to the US. The RN was very good at getting the absolute best out of equipment that was often second or even third rate. 

The criticism, and the topic, is about Destroyers, not the RN overall. It is not about a specific point in time, just the war overall. There are some pretty spectacular failures for the RN in terms of AA, but there are also some impressive victories as well. especially later in the war, just as the USN enjoyed its greatest successes later on. 

Glider hit the nail on the head by describing the primary mission of Naval AA as preventing ship losses, not inflicting aircraft losses. Aircraft losse are a bonus, unfortunately we are often forced to rely on loss rates as a surrogate measure for overall performance, because thats al we have to go on. In the case of PQ18, RN flak was not effective. according to the Luftwaffe in Norway website, as best as I can tell the LW suffered the following losses 

13.9.42
at about 16.00 hrs torpedo attack of I./KG26 - four He 111s were hit by naval flak and must be ditched. Two crews (He 111H-6 2./KG26 W.Nr.4727 and 1H+BK W.Nr.4535) were rescued by air sea rescue aircraft. 
The crew of 1H+NK W.Nr.7567 was rescued by U-457. The crew of 1H+DH W.Nr.7076 was not found. 
Next attack had been flown by 18 Ju 88s of III./KG26 - Ju 88A-4 W.Nr.142018 1H+KS was shot down by naval flak, crew posted MIA.
Two Ju 88s: W.Nr.2097 and 1536 were hit and damaged - they crashed on landing at Banak. 
At 16.15 hrs the convoy had been attacked by 9 He 115s of K.Fl.Gr.406. One Sea Hurricane of 802 Sqn FAA was forced down by German air gunners.
At 20.35 hrs 12 He 115s of 1./906 arrived. He 115 W.Nr.2247 8L+FH was brought down by naval flak as first. Three MIA.
At 21.00 hrs Ju 88As of I./KG30 bombed the convoy. All returned but two from 3./KG30 collided on landing at Petsamo: W.Nr.1007 written off and W.Nr.2064 45%.

I count 6 losses at the scene, and a further 2 crashing on landing due to flak damage. There were other non-combate related losses that i have not inlcuded.

In exchange for that the Lutwaffe torepedoed 8 ships, of which 7 sank. An eyewitness account by John Manners who was the First Lieutenant on HMS Eskimo i found interesting

"Then came September 13 when the Luftwaffe really went into action. There were continuous alarms starting with what we now know as diversionary attack by a number of high-level bombers. With misty conditions and a large amount of low cloud they had no success. Later at a crucial moment there were no Hurricanes airborne. With so few planes it was impossible to give air cover all the time.

Suddenly there was one of the most horrifying sights of the war. Along the whole horizon were aircraft flying just above the waves wing tip to wing tip and below radar cover. This was the German ‘Golden Comb’ attack in which all the planes released two torpedoes each at the same time. Records show there were forty-two Heinkel torpedo bombers and a number of Junkers 88′s. 

Everything was happening – as soon as they were seen the commodore of the convoy ordered an emergency turn away in order to comb the tracks of the torpedoes but unfortunately the two starboard columns did not comply. Like all the others Eskimo put the helm hard over and increased speed, which made the ship list and heel over. These frantic manoeuvres made it impossible for any accurate gunfire. However, every ship blasted off with everything and the air was thick with bullets. 

The Eskimo was in the starboard column of the screen and this menacing swarm passed a few feet overhead and as the aircraft were travelling at about 250 miles an hour they were gone before you could say ‘Jack Robinson’. We were not their prime target and shortly after passing us they released no less than a 110 torpedoes.

In no time eight ships were hit, some sank at once and in one case, there was a gigantic explosion sending a column of black smoke vertically upwards and the ship vanished completely. The barrage that was fired at the attackers was terrific, but according to German records only five planes were shot down though many more must have been damaged.

The situation was depressing with a fifth of the convoy having been lost and nobody in Eskimo saw any enemy planes destroyed. Two further desultory bomber attacks took place"

On the basis of the eye witness account RN flak was inneffective on this occasion. Certainly the Luftwaffe had not taken serious losses as a result of the attack, and their attacks had not been seriously disrupted. By either measure of success...a/c losses or protection of ships, the RN could not claim success for its Aa on that day. Strategically the convoy was a success. Tactically for its flak forces, it was a defeat. The Luftwaffe was not cut to pieces, on the basis of its own records. Sheer dogged courage by the RN and the merchant crews ensured continued allied control of the sea space, but it was not a resounding success for RN flak by any stretch


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## RCAFson (Feb 14, 2013)

parsifal said:


> At 12 rpm the rof for the gun is 5 secs. Di Giulan says that fuze setting takes 5 secs. If that is part of the firing cycle, that leaves 1 second to traverse the turret, get instructions from the director, collect the shell, load the weapon, aim the weapon and then fire it. Some of the timesetting the time fuze can be done wholst other things are happening. But some things have to be done sequentially. Seting the fuze by hand, in the turret, is amajor constraint on the weapon system efficiency.
> 
> Glider made a better explanation than i
> 
> ...


 
Fuze setting takes a fraction of a second with a machine fuze setter. By hand with the data transmitted by phone it takes:


> Dead Time
> 
> 6. Dead time is made up from:
> (a) Time to predict and transmit a new fuze by voice - say 1.5 seconds.
> ...


This is an RN document from 1935-36, which I had requested that you read, Progress in Naval Gunnery, 1914-36, p142.

With machine fuze setters and direct data transmission from the FC computer as in the RN 4.7in twin mount, fuze setting was done very quickly, probably on the order of a second. In AA fire the guns are, of course being directed by the FC computer continuously and the layer/trainer will stay on target by matching their pointers throughout the loading cycle. This is how Hughes was able to report 16rpm while engaging high level Luftwaffe bombers with predicted fire.

The above example is also for a hand rammed 4in gun, but the increase in loading difficulty is not applicable to guns like the 4.7in or 4.5in twin that had a loading tray and power ramming.


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## RCAFson (Feb 14, 2013)

parsifal said:


> Luftwaffe in Norway website, as best as I can tell the LW suffered the following losses
> 
> 13.9.42
> at about 16.00 hrs torpedo attack of I./KG26 - four He 111s were hit by naval flak and must be ditched. Two crews (He 111H-6 2./KG26 W.Nr.4727 and 1H+BK W.Nr.4535) were rescued by air sea rescue aircraft.
> ...



That's the losses for one day. If you continue reading from the same source:
http://www.luftwaffe.no/SIG/Losses/tap422.html
you will see how the Lufwaffe suffered severe losses on further attacks (not that shooting down 8 aircraft is a bust!).


> Also on 13 September the convoy was again sighted by a reconnaissance aircraft, a BV 138 from Banak. The air forces at Banak mounted a full assault on the convoy, using a new anti-convoy tactic, called the "Golden Comb". This involved a mass torpedo attack by full group of torpedo bombers, and resulted in the sinking of eight ships from the convoy. Two more air attacks followed, but failed to score any hits. In all eight aircraft were shot down on this day.
> 
> The following day, 14 September, the attack was repeated; on this occasion, however, the escort force had developed counter-measures to the form of attack, and the massed AA fire from the convoy and fighter attacks, the result of aggressive handling by the carrier Avenger and the AA cruiser Ulster Queen, saw the attack broken up. Three air attacks saw one ship hit and sunk, while 21 aircraft were shot down. The 14th also saw further U-boat attacks. The tanker Atheltemplar was torpedoed by U-457; she was abandoned and sank later. In counter-attacks U-589 was destroyed by Onslow.
> 
> ...


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## Glider (Feb 14, 2013)

RCAFson said:


> I'm sorry but you're wrong. Most destroyers had 4in guns added in lieu of a set of TTs; these guns were aimed and fired over open sights, and thus they were additions to the CIWS. The Tribals were a happy exception as the 4in twin could be coupled to the AA FC system, but when countering dive bombers they were used with short range "barrage" fuze settings, and they probably engaged the DBs over open sights as well, and their effective range in that mode was hardly greater than a pom-pom.


Well we are going to have to differ. 
My definition of a short range AA gun is a fast firing HMG/20mm/40mm ect. My definition of a Heavy AA is a 3in upwards that fires shells
Your definition of a short range AA gun is something that fires over open sights. So a 4in linked to a fire control on an AA sloop/ Hunt is presumably a Long range heavy AA gun. The same gun fired over open sights is a short range AA gun.

Your definition is so wrong its untrue. Some of the RN AA sloops were originally armed with 8 x4in but had one taken out and replaced with a quad 2pd because it lacked short range defence. The JKN class had by the standards of the day quite effective short range weapons with a quad 2pd and the 0,5 replaced with 20mm but had a 4in added instead of the TT not because they needed short range defence but because they needed a HA heavy gun with a long range. When RN destroyers went to the Pacific they were given additional short range guns and you guessed it, they had 20mm/40mm/2pd added not 4in over open sights 




> Delhi is often held up as a shining example of superior USN guns and AA FC, but AFAIK, Delhi was a bit of a bust in actual service and she was held back from the really critical Malta convoys in June and August 1942 , when the RN had no problem committing 4in armed C class AA cruisers to defend those convoys and 40 deg elevation destroyers...


I think you will find tha the Delhi had her stern blown off in action which was why she was not available. Many ships were repaired and refitted in US shipping yards there was nothing special about the Delhi just that she was given US guns.


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## RCAFson (Feb 14, 2013)

Glider said:


> Well we are going to have to differ.
> My definition of a short range AA gun is a fast firing HMG/20mm/40mm ect. My definition of a Heavy AA is a 3in upwards that fires shells
> Your definition of a short range AA gun is something that fires over open sights. So a 4in linked to a fire control on an AA sloop/ Hunt is presumably a Long range heavy AA gun. The same gun fired over open sights is a short range AA gun.
> 
> ...



The RN didn't have pom-poms, 20mm and 40mm bofors guns gathering dust that could be used to quickly augment destroyer AA, but they did have lots of older 3in and 4in guns that were not being used - sorry but that is the way it was. A 3 or 4in gun fired over open sights against an aircraft is no more accurate than any other gun fired with the same method; a pom-pom or bofors would have a much better hit probability because of the high RoF.

Here's Delhi's service record:
HMS Delhi, British light cruiser, WW2

note how she was tucked away in the Irish Sea during HARPOON and PEDESTAL. Hardly what you'd expect if she was supposedly the best AA ship in the RN...


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## parsifal (Feb 14, 2013)

well, i think between the thee of us we have tried our very best to get some consensus but unfortunately just cannot reach agreement. Some believe RN AA was okay to good, others of us believe it was a weakness in their Destroyer designs. I think we need to move on now and let the other guys have a go and make their own minds up. 


With regard to the subsequent days of PQ18 , my sources are slightly different. In the early afternoon of the 14th the air battle around the convoy was renewed by a torpedo attack similar to that which had wrought such destruction the previous day, but smaller. This time the torpedo-bombers concentrated against the CVE Avenger and the escorting warships. This was significant to the air battle, because it allowed a concentrated defence to be mounted, and further, because the target was really just one ship (the Avenger), forced the LW to pass in close proximity of some defenders (ie a version of the "ideal scenario I posted) . However, despite at least 16 DDs being involved in the defence, the lions share of the defence was borne by the carrier and the A.A. ship Ulster Queen. these ships (and their escort) stood out from the convoy to gain freedom of manoeuvre, and the former flew off half a dozen Hurricanes. The fighters drove off some enemies which in turn assisted in their dedstruction , while the escorts' gunfire forced others to drop their torpedoes at long range. This was clearly a success for the AA, because the early release minimised convoy losses. However the actual aircraft losses does not seem to have had much to doo with the DDs efforts. At best we can say that the DD effects were inconclusive, at worst, that once again they were inneffective, at least in the kills they achieved (and this suggests inneffective LR DP armament) . No ships were hit and thirteen torpedo-bombers were shot down. 'It was a fine sight', wrote Admiral Burnett, 'to see [the] Avenger peeling off Hurricanes whilst streaking across the front of the convoy . . . Altogether a most gratifying action'.

Next came more bombing by Ju-88s. Though some ships, including the invaluable carrier, had narrow escapes, none was hit. Then more torpedo-bombers arrived, and again they made a dead set at the Avenger; but she was ready for them, and by clever organisation managed to get ten of her twelve Hurricanes in the air at the critical moment. They and the escorts' guns destroyed nine enemies. Once again the lions share of these credits were to the escorting cruiser and the carrier. several were credited to the CAP. I can find no special mention of DDs having much effect at all, but will stand corrected on this dayas action if you have specific information that credits them. I would say this days action is still inconclusive re the DDs effectivesness, but trending to support some effect. 

One merchantman-again in the ill-fated starboard wing column-was torpedoed and blew up, and three Hurricanes were lost when they most gallantly accepted the risk of flying through the ships' barrage. Note the use of the word "barrage" which suggests directed fire was inneffective or not available. All the pilots were rescued. The last event of the day was another ineffectual bombing attack.

Next day, the 15th, was comparatively quiet-if such an expression can ever be used to describe a day with a Russian convoy in the Barents Sea. desultory attacks by a few enemy a/c amounting just over 50 sorties attacked, and they were well harried by fighters and gunfire. No ships were hit, but they were also no aircraft losses. Probably a success i guess for the escorts, and probably including the DDs. A lull in the air battle followed. 

That same afternoon Admiral Burnett and the greater part of his force left PQ 18, to take over protection of the homeward convoy. PQ 18 received, however, a welcome reinforcement of four Russian destroyers by way of replacement. On the 18th, when at the entrance to the White Sea, the convoy was again attacked by a combination of bombers and torpedo-bombers. One ship was lost, but four enemies were destroyed-one of them by the Hurricane of the C.A.M. ship Empire Morn. The fighter pilot (Flying Officer A. H. Barr) then drove off other enemies by making dummy attacks, and finally flew 240 miles to an airfield near Archangel. He landed with four gallons of petrol left. A last enemy attempt was made on the 20th while the convoy, as though it had not already endured enough, was trying to shelter from a full gale which had blown up. Luckily no damage was done.

So, whilst losses were indeed heavy, there is no real evidence (as yet ) that such losses or defensive successes were attrributable to the DDs. so does nothing to support the notiuon that DD AA fits were satisfactory. probably the opposite in fact.


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## RCAFson (Feb 14, 2013)

parsifal said:


> The link didnt work for me....
> 
> 
> An eyewitness account by John Manners who was the First Lieutenant on HMS Eskimo i found interesting
> ...



Try this:
http://www.admirals.org.uk/records/adm/adm186/adm186-339.pdf

From the same account by John Manners:





> ...German aircraft destroyed, taken from their records were: 44, including 38 torpedo bombers and surely a large number more must have been damaged. Of their 12 submarines 3 were sunk, another 5 were damaged. They therefore suffered quite substantially...


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## RCAFson (Feb 14, 2013)

parsifal said:


> well, i think between the thee of us we have tried our very best to get some consensus but unfortunately just cannot reach agreement. Some believe RN AA was okay to good, others of us believe it was a weakness in their Destroyer designs. I think we need to move on now and let the other guys have a go and make their own minds up.
> 
> 
> With regard to the subsequent days of PQ18 , my sources are slightly different...



OK, I'll bow out for a while, but Avenger was given AA support by two Hunt class destroyers, WHEATLAND and WILTON. They had essentially the same AA FC as a Tribal or JKMN destroyer. Without reading all their action reports, it is impossible to draw any conclusions as to destroyer effectiveness however, it certainly was an overall victory for RN AA under rather trying conditions.


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## parsifal (Feb 14, 2013)

RCAFson said:


> Try this:
> http://www.admirals.org.uk/records/adm/adm186/adm186-339.pdf
> 
> From the same account by John Manners:




RCAF that is a great piece of information, and i see why you are saying what you are. I want to thank you for the trouble you have gone to in posting this stuff


In these situations there is always or invariably a "however" and I have several"howevers" on this document. Its clear that by 1936 at normal elevations a rof of 12 rpm for the 4.7 was expected, however, this was only at certain optimal elevations. The report specifically states "the rates of fire and dead times commented on in section 1 (which is what you have already posted) can only be adhered to between certain elevations....." the report does not further investigate this issue.

So at higher elevations, the rof was not 12 rpm. maybe at 40 degrees or below, though I am doubtful. For a gun like the 4.7 I would say the target had to be stationary and not changing position and the gun elevation below 30 degrees to achieve that optimum rof. 

The second "however" is that this report is still drawn up in peacetime conditions and assumes near perfectly trained crews. it says that repeatedly in the report. That means ships steaming at a leisurely pace, with no changes to elevation or traverse. Wartime conditions were very different. Moreover the amount of "deatime was for an aircraft travelling at 100knots. By 1940 this was greatly exceeded, meaning that dead times would also increase. The old perrennial problem of slow traverse and elevation times again begins to dog the 4.7. 

As a corollary to the second point, this report was prepreed at the time Chatfield was in charge, a time when the RN grossly over-estimated its AA abilities.Chatfield told Churchil that a single 4in gun would be suficient to protect most Destroyers from even the heaviest air attacks......

So this report, in my opinion, whilst certainly opening my eyes to some issues, does not prove your position. quite the opposite really...it shows that 12 rpm could only be achieved under ideal conditions. And warime conditions against aircraft were anything but ideal for the 4.7..... 

Its also clear why the 4in was favoured the main AA weapon....its much higher max elevation and rof...around 20 rpm and more like 55 deg elvation. still not enough to be fully effective, but better, much better.


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## RCAFson (Feb 15, 2013)

parsifal said:


> RCAF that is a great piece of information, and i see why you are saying what you are. I want to thank you for the trouble you have gone to in posting this stuff
> 
> 
> In these situations there is always or invariably a "however" and I have several"howevers" on this document. Its clear that by 1936 at normal elevations a rof of 12 rpm for the 4.7 was expected, however, this was only at certain optimal elevations. The report specifically states "the rates of fire and dead times commented on in section 1 (which is what you have already posted) can only be adhered to between certain elevations....." the report does not further investigate this issue.
> ...



*You will note that page 142, section two is dealing with the 4in gun*. This gun doesn't have a loading tray, therefore it gets more difficult to load at both low and high angles. *The power rammed 4.7in single and twin did not have this problem*. Dead time has nothing to do with target speed - it is solely a problem of setting the MT fuze and loading the gun. The other thing to remember is that when the target gets really close, the gunners switched over to "barrage fire" where the fuse was preset to ~2 seconds (typically a supply of prefused ready use ammo was kept handy) and the gunners loaded and fired as fast as they could. At longer ranges, (~6000 yards, for example) the target has relatively little apparent motion and the layer/trainer have a relatively easy time keeping on target, and there is very little movement of the gun - at 6000 yards a 270 knot crossing target would have an apparent motion of only 1.5 degrees/sec, and much less if the target is flying partly or directly towards the firing ship.

Chatfield was optimistic, but then so was the USN who made much the same assumptions, with similar results - the only problem is that we are told that the USN did much better than it really did and so we find the RN wanting, when it really wasn't, relatively speaking.

BTW, this is a very interesting website dealing with the RN in Norway:

http://www.royal-naval-reserve.co.uk/rutlandshire/default.htm

specifically the loss of the Rutlandshire, but it has some RN action reports and a report by the Norwegian pilot who creditted RN destroyers with effective AA, that greatly reduced the intensity of Luftwaffe attacks, and it also details the loss of the He-111 which bombed Rutlandshire (and was probably fatally damaged in return) - a loss which doesn't show up on the Luftwaffe Norwegian loss list.


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## parsifal (Feb 15, 2013)

> You will note that page 142, section two is dealing with the 4in gun. This gun doesn't have a loading tray, therefore it gets more difficult to load at both low and high angles. The power rammed 4.7in single and twin did not have this problem. Dead time has nothing to do with target speed - it is solely a problem of setting the MT fuze and loading the gun.



I was aware that section 2 does deal with the 4in gun, but this particular extract refers to all dead times, for both claibres, , not just not just the 4in. 


We dont know about the 4.7 twin, but it has the same published rof as the 1936 models. Power ramming still requires hand loading and can involve innefficiencies because of the poor placement of the shell hoppers, so I have to disagree with you. the power rammer might add or improve fireing cycle by 1-2 seconds over the older mounts but that still brings it in at somewhere below 12 rounds per minute. Given that 12 is already an indaequate number, the conclusion whether it be twin mounting or no, remains the same. 

If as I suspect the older models at non-optimal elvations can only fire at around 6 rpm, and power ramming improves that practical rof by say 1-2 secs, then you might get 8 rpm. still within the original estimate for practical rof of 4-8 rpm. 4 for the really old versions, 8 for the newer twins. 

Sorry, still dont agree with you. Far too rose coloured a view of the RN capabilities in my book.


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## RCAFson (Feb 15, 2013)

parsifal said:


> I was aware that section 2 does deal with the 4in gun, but this particular extract refers to all dead times, for both claibres, , not just not just the 4in.
> 
> 
> We dont know about the 4.7 twin, but it has the same published rof as the 1936 models. Power ramming still requires hand loading and can involve innefficiencies because of the poor placement of the shell hoppers, so I have to disagree with you. the power rammer might add or improve fireing cycle by 1-2 seconds over the older mounts but that still brings it in at somewhere below 12 rounds per minute. Given that 12 is already an indaequate number, the conclusion whether it be twin mounting or no, remains the same.
> ...



Look, I've provided abundant data regarding the RoF - *5 rounds in 17 sec for Basylisk in 1930* - 180 salvos from Kimberly at Narvik, *most with a 5 sec loading cycle* - *15rpm for the 4.7in Mk VIII*- 3000 rounds from Illustrious at an *average* of 12 RPM - *16 RPM from Scylla*...all these guns had essentially the same loading tray system, except that the last 4 all have power ramming. *It is time for you to get off this pot and accept the facts .* There is no rose coloured views here , just a lot of hard digging and research.

and another: 


> The day by day hum drum of her "working up" period, prior to her joining the Home Fleet at Scapa Flow, would make most uninteresting reading except the mention that she became, by virtue of her latest type radar, exceedingly rapid rate of gunfire (16 round per minute) and high speed, a very efficient ship. An efficiency that was to be a saving grace to her in her hectic times to come.
> http://www.naval-history.net/WW2Ships-Charybdis.htm


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## Glider (Feb 15, 2013)

RCAFson said:


> The RN didn't have pom-poms, 20mm and 40mm bofors guns gathering dust that could be used to quickly augment destroyer AA, but they did have lots of older 3in and 4in guns that were not being used - sorry but that is the way it was. A 3 or 4in gun fired over open sights against an aircraft is no more accurate than any other gun fired with the same method; a pom-pom or bofors would have a much better hit probability because of the high RoF.


A lot of truth in this but the 20mm were added pretty quickly, when would depend on the ship and availablity. I don't disagree with your description of the value of the effectiveness of the single 4in added in some destroyers.
What I disagree with, is your position that these were additions to the short range aa guns. All they were were are inaccurate longe range guns, useless against close range fast moving targets.

A slightly amusing aside. There was an obituary in the paper a few months ago. He had served in destroyers during the war and had to live with the somewhat embarrassing nickname 'Annie' all through his naval career. As a young officer he was put in charge of the 4in installed instead of the torpedoes and by absolute fluke shot down a Ju88 with the third shot. Everyone knew this was something close to a miracle and was given the nickname after Annie Oakley. He often said how much he regretted shooting down the Ju88


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## parsifal (Feb 15, 2013)

> Look, I've provided abundant data regarding the RoF



And all of it, for one reason or another has been misinterpreted. 




> 5 rounds in 17 sec for Basylisk in 1930




peacetime conditions, optimum elevation, no turret elevation or training to worry about. I bet they were a crack gun crew. 



> 180 salvos from Kimberly at Narvik, most with a 5 sec loading cycle



Not in an AA role. and against targets not really moving at least some of the time. Not relevant to what we are discussing 



> 15rpm for the 4.7in Mk VIII- 3000 rounds from Illustrious at an average of 12 RPM


Ilustrious was armed with 4.5 in guns. a completely differnt kettle of fish and not a destroyer anyway 12 rpm is still too slow to be effective



> 16 RPM from Scylla...all these guns had essentially the same loading tray system, except that the last 4 all have power ramming.



Scylla was armed with 4.5 inch guns. ive never questioned the rof of the 4.5 gun. Scylla was a cruiser. youve claimed repeatedly that the 4.7 gun had the same loading tray system, but wont recognize or acknowledge that at least one source does not agree with you. Even on the basis of max rof, the 4.5 is rated at 20rpm, whilst the best 4.7s are rated at 12 rpm. how can that be the same? 



> It is time for you to get off this pot and accept the facts .



Ive accepted the source material youve produced. what I have challenged, is your interpretation of those facts. When you get confronted by legitiamte questions and critiques you try every form of bluff bluster and bullying tactics you can think of. Wont work with me. You have not succeeded in convincing me. So what. I have questions you cant answer IMO. We can and should agree to disagree and leave it at that. its a difference of opinion, nothing more. I dont have to get off anything, and i dont have to move away, or accept anything. Im not losing my temper. Im enjoying the debate and the exchange of ideas to be honest. i am sorry if the discussion is upsetting you, seriously I am, but a tantrum is not reason for me to change my opinion. Ive happily conceded a number of points where I think you are are correct, and thats good. ive not denigrated in any way your source material. In fact im impressed with it. The one area where we have disagreed is in the interpretation of the data. get over it. its just a discussion, and opinions on the known data. 



> There is no rose coloured views here , just a lot of hard digging and research.




Yes, and I have and wil again commend you on the quality of the material you have produced. Well done. Thats not the issue. its the interpretation of the data. Me not accepting your opinion does not or should not affect how you view that material if you dont want to accept my point of view. 


Charybidis was a cruiser, armed with the 4.5 in gun which I have already commented on. a different gun, with a different published max rof, and specifically developed to address the known weaknesses of the 4.7 in weapon. Again, if anything just serves to underline or provide background evidence that the 4.7 was not a good DP weapon, in any of its forms.


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## RCAFson (Feb 15, 2013)

parsifal said:


> And all of it, for one reason or another has been misinterpreted.
> 
> peacetime conditions, optimum elevation, no turret elevation or training to worry about. I bet they were a crack gun crew.



5 rounds in 17 seconds = a cyclic rate of 17.6 rpm. OK, then an average crew should be able to do 10 - 12 rpm. 





> Not in an AA role. and against targets not really moving at least some of the time. Not relevant to what we are discussing


Kimberly certianly did engage moving targets and did so while moving rapidly herself, and again I reduced the AA rof to 10 rpm in my calculations



> Illustrious was armed with 4.5 in guns. a completely differnt kettle of fish and not a destroyer anyway 12 rpm is still too slow to be effective
> 
> Scylla was armed with 4.5 inch guns. ive never questioned the rof of the 4.5 gun. Scylla was a cruiser. youve claimed repeatedly that the 4.7 gun had the same loading tray system, but wont recognize or acknowledge that at least one source does not agree with you. Even on the basis of max rof, the 4.5 is rated at 20rpm, whilst the best 4.7s are rated at 12 rpm. how can that be the same?



Navweaps states: 


> Britain
> 4.5"/45 (11.4 cm) QF Marks I, III and IV
> (Marks 2, 3, 4 and 5)
> *Twin mountings of World War II: 12 rounds per minute per gun*


I've produced evidence that the gun could fire at an average of 12rpm for very long periods and up to 16rpm. 




> Ive accepted the source material youve produced. what I have challenged, is your interpretation of those facts...



While I'm challenging your interpretation of the facts and I supported my contentions with lots of data - I'm not bullying but you'll have to admit that trying to swim upstream against the bull that Navweaps would have us swallow is no easy task.





> Charybdis was a cruiser, armed with the 4.5 in gun which I have already commented on. a different gun, with a different published max rof, and specifically developed to address the known weaknesses of the 4.7 in weapon. Again, if anything just serves to underline or provide background evidence that the 4.7 was not a good DP weapon, in any of its forms.





I've produced evidence that the gun could fire at an average of 12rpm for very long periods and up to 16rpm maximum. The 4.7in twin and 4.5in twin gun mountings and loading facilities were almost identical:






4.7in twin - note the fuze setting pedestal located right beside the loading tray.




4.5in twin BD mount (Illustrious)- if the 4.5in BD housing was removing, you'd never be able to tell them apart. The actual loading tray and breech mechanisms are virtually the same, the only real difference is the higher trunnions (pivot point) on the 4.5in twin.


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## RCAFson (Feb 15, 2013)

USS Benham at Eastern Solomons:


> Benham opened fire with 5" anti-aircraft barrage"; initial range 5,000 yards (altitude 12,750 feet), and 20 m.m. fire.
> 
> 1714 -- Enterprise observed to be hit by bombs.
> 
> ...



Some comments - note they they used "barrage fire" A JKMN class could have engaged the same target, but would have had to open fire before 6000 yds and she would have been able to place a barrage over Enterprise (which is what happened) that the DBs would have to fly through. Note the small ammo expenditure. This is the same battle where Crenshaw of USS Maury stated that they were unable to engage the IJN aircraft because of the ineffectiveness of the Mk 33 GFCS.

Some more from the same report:


> Comment on material:
> 
> There were no material failures.
> The main feed pumps are in such a condition, that their reliability is uncertain. Early installation of new main feed pumps, already ordered by Bureau of Ships, is necessary for battle efficiency.
> ...



Note the very light CIWS for Aug 1942 - a JKMN would have a quad pom-pom and 2 - 4 20mm, and a HA 4in single in the same time frame, but even in 1939 the CIWS of a quad pom-pom and 2 x quad .5in was a superior CIWS.

27 AA claims were made, including 5 by the destroyers while the USNI summary states that maybe 15 were shot down by AA. Lundstrom estimates that about 5 IJNAF aircraft, in total, were shot down by AA. Again the clumsiness of the Mk 33 is pointed out.


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## Glider (Feb 15, 2013)

RCAFson said:


> USS Benham at Eastern Solomons:
> 
> 
> Some comments - note they they used "barrage fire" A JKMN class could have engaged the same target, but would have had to open fire before 6000 yds and she would have been able to place a barrage over Enterprise (which is what happened) that the DBs would have to fly through. Note the small ammo expenditure. This is the same battle where Crenshaw of USS Maury stated that they were unable to engage the IJN aircraft because of the ineffectiveness of the Mk 33 GFCS.


More interesting stuff from you, I wish I had a spare day or two to go through your books. One important observation, *the USS Benham opened fire at 5000 yards *at a target flying at approx 12,500 ft. Looking at the chart you included in posting 123, a JKN/Tribal using the twin 4.7 *would have had to cease firing **at about 7,500 yards *and could only open fire at about 11,000. In other words the chances of being damaged by the 4,7 would be very slim as the destroyer only had about 35 seconds to get the range, and at the point of bomb release the bomber would have been untroubled.


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## Glider (Feb 15, 2013)

An observation on the Twin 4.5 and the Twin 4.7 mountings. There was one significant difference between them, the twin 4.5 used a fixed shell and the twin 4.7 a seperate shell. This must have made fairly major changes in the loading arrangements


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## RCAFson (Feb 15, 2013)

Glider said:


> An observation on the Twin 4.5 and the Twin 4.7 mountings. There was one significant difference between them, the twin 4.5 used a fixed shell and the twin 4.7 a separate shell. This must have made fairly major changes in the loading arrangements


 
Not really. With the one piece shell, the entire round was placed into the loading tray. With the separate round the cartridge and then shell were placed in the loading tray. as you can see from the photos, the loading tray is much the same for both. Fuzing the separate round is probably easier.

BTW, I found the photos here: 

Vickers Photographic Archive


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## RCAFson (Feb 15, 2013)

Glider said:


> More interesting stuff from you, I wish I had a spare day or two to go through your books. One important observation, *the USS Benham opened fire at 5000 yards *at a target flying at approx 12,500 ft. Looking at the chart you included in posting 123, a JKN/Tribal using the twin 4.7 *would have had to cease firing **at about 7,500 yards *and could only open fire at about 11,000. In other words the chances of being damaged by the 4,7 would be very slim as the destroyer only had about 35 seconds to get the range, and at the point of bomb release the bomber would have been untroubled.



In this particular action, very few ships actually sighted the IJN aircraft prior to their dive (they were tracked on radar but lost as about 16000 yds) SOP for the RN would have been an "umbrella barrage" over the carrier, which seems to be what happened:


> The Enterprise radar lost track of the enemy group when it came within its minimum range, but, on the basis of previous tracking, radar plot reported at 1709 that "the enemy planes are directly overhead now!" In spite of this warning and the excellent visibility, the first plane was sighted after it already had entered its dive. Effective enemy plane camouflage and the fact that the first dives were made on the Enterprise from the port quarter, out of the sun, probably accounted for this belated visual contact. In the case of the Enterprise, the first plane was sighted at 12,000 feet by a 20-mm. battery officer. Although the target was well beyond effective range, he promptly opened fire with one gun, thus calling the ships' attention to the attacker and giving them a point of aim.
> HyperWar: The Battle of the Eastern Solomons [ONI Combat Narrative]




I checked the 4.7in engagement drawing carefully, and I get minimum range of about 6000 yds for 12750 ft altitude, but yes, potentially, there would be a few thousand yards where the destroyers would not be able to engage the aircraft with predicted fire, prior to the barrage.


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## parsifal (Feb 15, 2013)

I propose that we leave this sub debate about British and US DDs to one side. weve done it to death, and stil cannot reach agreement. I would like to discuss the destroyer techs of some of the lesser navies like the Russians and French

I dont know much about them, so would hope that other memebers step in and give us some insights. 

Fire away gentelemen


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## Glider (Feb 16, 2013)

RCAFson said:


> I checked the 4.7in engagement drawing carefully, and I get minimum range of about 6000 yds for 12750 ft altitude, but yes, potentially, there would be a few thousand yards where the destroyers would not be able to engage the aircraft with predicted fire, prior to the barrage.


I was allowing time fior the shell to arrive as the 6,000 yard is the last shell burst. However the chart is very clear in that the time between the earliest shell burt and the last shell burst is about 35 seconds. It would be the shortest and least effective barrage fire in history.


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## Glider (Feb 16, 2013)

All I kniow is that the italian destroyers had similar weapons as the British 4.7 (none DP) and the 20mm was quite well thought of. The French weapons looked quite modern even by todays standards but were very, very unreliable.


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## parsifal (Feb 16, 2013)

Soviet destroyers were based loosely on Italian Destroyers, but the Soviets upgunned themn to a 5" calibre. The first interwar design, the Leningrad class were a bad design, but thereafter there were gradual improvements, such that by 1945, they were considred quite good. The Soviet Destroyers did some good work in the Black Sea and in the far north. In the Baltic they suffered pretty heavily from mines mostly. They dis carry out a number of Dunkirk style evacuations, but with heavy losses. I vaguely recall they undertook the evacuation of the Hango peninsula in Dewcember 1941.


The Russians actually had two categories of Desytroyers, which we might classify as leaders and then destroyers. DD Tashkent was an example of a Leader, and was, by most accounts, an exceptionally well designed ship.


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## RCAFson (Feb 16, 2013)

In Which we Serve

This wartime film is a fictionalized account of HMS Kelly - but it was filmed on a J-K class destroyer and if you watch closely it shows how the 4.7 twin was loaded. The film also features very accurate naval terminology and is an invaluable introduction to understanding how Commonwealth destroyers were fought.

You can watch it online or download it here:
In Which We Serve : Noel Coward, Anthony Havelock-Allan, and Herbert Smith : Free Download Streaming : Internet Archive

"follow TBI" = follow target bearing indicator"


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## Glider (Feb 16, 2013)

Until laer in the war Russian ships lacked almost all modern electrical equipment, radar, sonar nearly all of it had to come from the USA or UK. Another problem was very poor training, a captain would get a a medal if his ship was at sea for three days and nights. One very telling statistic was that the Russian navy (excluding submarines and MTB's) didn't sink a single ship in the entire war including Merchant ships.

The Italian Navy had a similar problem but the ships were well designed and well manned. The problem with the Italian navy was poor senior officers, the crews on the ships often fought with considerable courage. Some of the ships had unusual but effective design features. The Gabbiano class of corvettes could switch to electric engines to assist when hunting submarines, as far as I am aware this was unique to the Italian Navy.


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## parsifal (Feb 16, 2013)

The opportunities for the Russians to sink ships were pretty restricted. There were plenty of RN ships that didnt sink a single ships either. And three days at sea in the baltic and/or the Baltic is a very long time.

I also know that not sinking a single ship is highly doubtful. For many years it was historical "fact" that not a single ship was lost to Soviet Submarines. But Of all places in the Kriegsmarines day by day war diaries (online and comppiled post war) I have found entries that quite a bit of Axis shipping was intersepted and sunk by Russian submarines in all three operational areas. Hayward, in wrinting his book about the Lw operations on the southern front, talks of how the LW was forced to divert resources to combatting Soviet Naval activities. He furthe mentions 9I think, that Soviet destroyers had sunk a number of small Axis (italian I think?) MAS boats based at makeshift bases trying to isolate Sevastopol. 

So whilst i too have seen such statements, and cant be 100% certain about thye actual truth, do have my doubts about the veracity of those claims. 

The italians make another interesting study. I think their overwhelming problem was the faulty leadership at the top,, followed closely by their lack of oil and the poor co-operation with the RA. I do not believe the italians particulalry needed a carrier, but they did need a dedicated naval co-operation unit to support naval operations. They lacked radar, or moree precisely a general fitout of radar and a doctrine on how to use it. Thay did have sonar, from the middle of 1941. They had some patchy equipment, some good, some not so good. Their chief naval guns for DDs were the 120/45 and 120/50 by Ansaldo and OTO, both based on Armstrong designs. The latter weapon came in a twin power mounting, with centralised hoists. The guns were fully enclosed, and spaced only 22 in apart which caused severe dispersion problems. The gun mounts were originally designed as hand cranked, but came in too heavy, so had to be electrically powered. They also started life as hand rammed, but were fitted with a mechanical loader from 1926, which was gradually imporoved over time. However the power rammers were a severe restriction on the operation of the turret, according to Campbell. Apparently the rammers would not operate above 30 degree elevation which meant that the guns (even though rated as elevating to 45 degrees, could not be loaded above 30 degrees. These guns (not the mounts) were a very close relative if somewhat lighter, to the british pattern 4.7in, but had a sustained rate of fire of 7 rounds per minute. hmmmm. 

Italian torpedoes were based on the whitehead pattern , and were reliable, on par designs. They has an aerial torp at the beginning of the war far supeior to that in use in Germany, so from 1941 the Germans began using the italian types over their own, until after 1942. 

Some accounts say the optics for the Italian guns was not good, but Im pretty sure that claim is bogus. What was missing for these guns were crews properly trained in nightime gunnery Wartime expereience also shows a marked reluctance for Italian destroyers to enter any smokescreen . This affected their performance during several battles.

Both the 120/50 and the larger 135 mm guns were meant to have a DP functionality, but operational experience showed that they could not fulfil that role. Hmmm again. The larger 5.3 in gun was eventually redesigned for the new carrier Aquila to have AA capability. manufacture AA ammuntion for it, but the gu was originally intended as a DP weapon.


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## Juha (Feb 16, 2013)

parsifal said:


> ... They dis carry out a number of Dunkirk style evacuations, but with heavy losses. I vaguely recall they undertook the evacuation of the Hango peninsula in Dewcember 1941.



Yes, KBF, Soviet Baltic Fleet, DDs participated the evacuation of the Hango peninsula




parsifal said:


> The Russians actually had two categories of Desytroyers, which we might classify as leaders and then destroyers. DD Tashkent was an example of a Leader, and was, by most accounts, an exceptionally well designed ship.



Taskent was built in Italy and was mostly Italian design


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## Juha (Feb 16, 2013)

RCAFson said:


> I never said that the RN thought that 40 degs was enough!
> 
> What I've been saying is that 40degs is not useless and that most air attacks could be engaged by destroyers with 40 deg guns - anyone who takes the time to read Lundstrom and First Team will know that in almost every case USN destroyers with 40 deg elevation could have provided the exact same AA support as they did in 1942. The problem is that most people seem to think that aircraft simply materialized directly over destroyers (but only RN destroyers), and they were helpless if they couldn't shoot straight up! Of course this is complete nonsense.
> 
> It certainly was a sign of desperation, to add single 3in or 4in guns - the problem being that the 20mm oerlikon was not yet in UK or Cdn production, nor was the Bofors 40mm in a naval mounting, and the quad pom-pom was in very tight supply, whereas these 3in and 4in guns were sitting around gathering dust...and so they were hauled out of storage and added to RN Fleet destroyers. Later in the war, most of these ships had the gun removed and replaced by TTs once again along with a greatly strengthened CIWS.



I agree that from Tribals onwards RN DDs had reasonable AA capacity against TBs and level bombers attacking at fairly low altitude but the problem was that the high level bombers, usually not dangerous but IJNAF bombers had fairly effective bombing tactic against ships, after flying through the zone inside which the British early war DDs could fire at them could made the final stage of their attack completely unhindered by fire from those DDs, same goes with the dive bombers. Even late war RN DDs had fairly weak CIWS when compared to USN Fleet DDs Allan M. Sumner and Gearing classes had 12 40mm Bofors and some 12 20mm Oerlikons, those which had landed a TT mounting had 16 Bofors. Even KM DDs after Barbara mods had heavier CIWS than late war RN DDs and as had the late war IJN DDs with 20-28 25mm AAA guns, even if IJN 25mm was fairly light AAA gun and the 3x25mm mount had its problems. Of course KM needed much more AA defence than RN in Europe in 44-45.

Juha


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## Juha (Feb 16, 2013)

RCAFson said:


> ...Here's Delhi's service record:
> HMS Delhi, British light cruiser, WW2
> 
> note how she was tucked away in the Irish Sea during HARPOON and PEDESTAL. Hardly what you'd expect if she was supposedly the best AA ship in the RN...



As you see, in June 42 Delhi was escorting QE, very high value ship which was probably in troop transport mission.
According to Roberts' British Cruisers of WW Two RN evaluaded gunnery trials of Delhi as highly successful.

Juha


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## RCAFson (Feb 17, 2013)

Juha said:


> I agree that from Tribals onwards RN DDs had reasonable AA capacity against TBs and level bombers attacking at fairly low altitude but the problem was that the high level bombers, usually not dangerous but IJNAF bombers had fairly effective bombing tactic against ships, after flying through the zone inside which the British early war DDs could fire at them could made the final stage of their attack completely unhindered by fire from those DDs, same goes with the dive bombers. Even late war RN DDs had fairly weak CIWS when compared to USN Fleet DDs Allan M. Sumner and Gearing classes had 12 40mm Bofors and some 12 20mm Oerlikons, those which had landed a TT mounting had 16 Bofors. Even KM DDs after Barbara mods had heavier CIWS than late war RN DDs and as had the late war IJN DDs with 20-28 25mm AAA guns, even if IJN 25mm was fairly light AAA gun and the 3x25mm mount had its problems. Of course KM needed much more AA defence than RN in Europe in 44-45.
> 
> Juha



Most of the time IJNAF carrier aircraft were engaged in attacking USN capital ships, mainly carriers, and a 40deg gun could still place a barrage over the ships being attacked. Of course there were several occasions when USN destroyers were caught alone and sunk by IJNAF DBs, 5in/38 HA guns not withstanding.

These late war USN DDs were quite a bit larger than equivalent RN destroyers as were the IJN and German Narvik class.


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## RCAFson (Feb 17, 2013)

Juha said:


> As you see, in June 42 Delhi was escorting QE, very high value ship which was probably in troop transport mission.
> According to Roberts' British Cruisers of WW Two RN evaluaded gunnery trials of Delhi as highly successful.
> 
> Juha



AFAIK, Delhi never saw an enemy aircraft during her entire time in UK waters. IMHO, Delhi must have been having problems with her MK37 system, especially after radar was added. Since she was one of the first ships equipped with it, it would have been very surprising if she had no problems.


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## vinnye (Feb 17, 2013)

I think these late USN destroyer losses were acting as radar pickets to give the fleet early warning of any raids.
In this situation, they were acting alone - like some RN destroyers that were sunk by the LW.
Even though they were built later and had more technology as standard and had the chance to learn lessons from others early experiences.

When acting in close fire support to capital ships, they were usually NOT the target, so the fact that THEY were not hit is not a reflection of their AA effectiveness.


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## Glider (Feb 17, 2013)

RCAFson said:


> Most of the time IJNAF carrier aircraft were engaged in attacking USN capital ships, mainly carriers, and a 40deg gun could still place a barrage over the ships being attacked. Of course there were several occasions when USN destroyers were caught alone and sunk by IJNAF DBs, 5in/38 HA guns not withstanding.


Having already supplied the evidence that the British 40 deg gun can only fire for approx 35 seconds at a bomber, how can you think that this would be any use at all?


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## Juha (Feb 17, 2013)

RCAFson said:


> ...These late war USN DDs were quite a bit larger than equivalent RN destroyers as were the IJN and German Narvik class.



Torpedoboot Type 39 (1297 tons standard/1752 full load) Barbara plan 10x37mm automatic (2x1+4x2) + 8 (4x2) 20mm but that wasn’t implemented. So Usually they had 4 (2x2) 37mm C/30 + 12 (3x4) 20mm plus sundry extra guns if lucky.
Hatsuharu and Shiratsuyu classes 1490 tons standard/1802 tons full load) landed one of their 5” gun in 1942/43 and got more AAA and after that had 4 (2x2) 5” DP + 13 – 21x25mm + 4x13mm
USN Bensons/Bristols (1839 tons standard /2395 tons full load) late war 4x5” DP + 4x40mm Bofors (2x2) and 4 – 6x20mm.


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## Glider (Feb 17, 2013)

RCAFson said:


> AFAIK, Delhi never saw an enemy aircraft during her entire time in UK waters. IMHO, Delhi must have been having problems with her MK37 system, especially after radar was added. Since she was one of the first ships equipped with it, it would have been very surprising if she had no problems.


You are of course entitled to your view, mine is that as she impressed in the AA trials that were undertaken, its both my view and reasionable to assume that she didn't have any issues with the 5in/mk 37 combination. 
As for your comment about the Delhi and her time in UK waters, it isn't her fault that the RN put a well equipped AA vessel on escort duties escorting high value ships. Many of the best equipped AA RN vessels were on similar duties and to imply that its a slight on the vessel and her equipment without evidence, is a little desperate.
This is only a guess but one reason which may have stopped HMS Delhi taking part in the Malta convoys were its 5in guns. She was one of the best equipped AA vessels in the RN, but she was the only vessel in the RN to have these weapons and the USN were not involved in the Med at that time. To stock and distribute a unique type of ammunition for one vessel which could go anywhere would have been an administrative nightmare. You don't know which base she might go to, so ammunition would have to be stored in a number of places around the Med. How you would have got supplies to Malta to restock the Delhi for the trip home, when every spare space was taken up with supplies to feed and maintain the island I do not know.


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## Juha (Feb 17, 2013)

RCAFson said:


> AFAIK, Delhi never saw an enemy aircraft during her entire time in UK waters. IMHO, Delhi must have been having problems with her MK37 system, especially after radar was added. Since she was one of the first ships equipped with it, it would have been very surprising if she had no problems.



And why then RN evaluaded gunnery trials of Delhi as highly successful?


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## RCAFson (Feb 17, 2013)

Glider said:


> Having already supplied the evidence that the British 40 deg gun can only fire for approx 35 seconds at a bomber, how can you think that this would be any use at all?



35 seconds by 6 destroyers ( a typical 1942 carrier TG escort) = 210 seconds = 210 rounds predicted rounds fired (if we assume a JKMN), plus an umbrella barrage, placed over the target ship as the aircraft begin their dive, for another 200 - 400 rounds.


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## RCAFson (Feb 17, 2013)

Juha said:


> And why then RN evaluaded gunnery trials of Delhi as highly successful?



They may have been successful within certain parameters, but do we have the full story? Until I began looking for info on the Mk37 and 5"/38 I was unaware that there were problems with both. Most accounts, such as Navweaps and Campbell are highly laudatory about the Mk 37 and neither mentioned the stability problems that occurred, nor the slowness of the Mk 1 computer, so until more info comes to light, I will remain skeptical about HMS Delhi, especially as RN deployment of her suggests a less than satisfactory performance. We know from well researched accounts (Lundstrom) of USN AA in the Pacific that the MK 37 wasn't terribly effective there, so why should it be any different for Delhi? In fact it would be amazing if the RN did better with Mk 37 than the USN itself!


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## RCAFson (Feb 17, 2013)

Glider said:


> You are of course entitled to your view, mine is that as she impressed in the AA trials that were undertaken, its both my view and reasionable to assume that she didn't have any issues with the 5in/mk 37 combination.
> As for your comment about the Delhi and her time in UK waters, it isn't her fault that the RN put a well equipped AA vessel on escort duties escorting high value ships. Many of the best equipped AA RN vessels were on similar duties and to imply that its a slight on the vessel and her equipment without evidence, is a little desperate.
> This is only a guess but one reason which may have stopped HMS Delhi taking part in the Malta convoys were its 5in guns. She was one of the best equipped AA vessels in the RN, but she was the only vessel in the RN to have these weapons and the USN were not involved in the Med at that time. To stock and distribute a unique type of ammunition for one vessel which could go anywhere would have been an administrative nightmare. You don't know which base she might go to, so ammunition would have to be stored in a number of places around the Med. How you would have got supplies to Malta to restock the Delhi for the trip home, when every spare space was taken up with supplies to feed and maintain the island I do not know.



Here's some more info on the Mk 37:



> Mk 37 (United States), Command and weapons control systems
> 
> Type
> Gun fire-control system.
> ...



Sorry, but I just don't buy the "Delhi was perfect" story as it doesn't fit the overall facts.

The great majority of HARPOON AND PEDESTAL Malta convoy escorts didn't make the trip all the way to Malta but turned back with the carriers.


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## Glider (Feb 17, 2013)

RCAFson said:


> 35 seconds by 6 destroyers ( a typical 1942 carrier TG escort) = 210 seconds = 210 rounds predicted rounds fired (if we assume a JKMN), plus an umbrella barrage, placed over the target ship as the aircraft begin their dive, for another 200 - 400 rounds.



I must repeat what I have posted before. A destroyer is lucky to hit a ship in 35 seconds against a small aircraft, its close to mission impossible. Just a thought but do you disagree with that statement?
If *a* ship had 210 seconds they would have a chance. All that would happen in your scenario is that all the ships are almost certain to miss. Also in your scenario there is the added confusion of the ships trying to work out which shell bursts are theirs and which are the the other destroyers. 
It was bad enough at sea targets, the French introuduced dyes to their shells so that each ship could concentrate their fire as they knew that they were firing Red and the ship behind Blue. 
Its also worth remembering that 35 seconds is the absolute maximum time and depends on the destroyer opening fire at exactly the right time.


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## Glider (Feb 17, 2013)

RCAFson said:


> Sorry, but I just don't buy the "Delhi was perfect" story as it doesn't fit the overall facts..


It isn't a case of Delhi was perfect, just that it was a lot better than anything else, that anybody else had. Its main problem with the combination was the problems at close range when the target was not flying straight, which isn't unexpected. Thats why navies had the short range fast firing guns. I am old enough to have served on HMS Tiger and even we had the 3in and Seacat for close range defence and our 6in was deadly against aircraft.


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## RCAFson (Feb 17, 2013)

Glider said:


> I must repeat what I have posted before. A destroyer is lucky to hit a ship in 35 seconds against a small aircraft, its close to mission impossible. If a ship had 210 seconds they would have a chance. All that would happen in your scenario is that all the ships are almost certain to miss. Also in your scenario there is the added confusion of the ships trying to work out which shell bursts are theirs and which are the the other destroyers.
> It was bad enough at sea targets, the French intouduced dyes to their shells so that each ship could concentrate their fire as they knew that they were firing Red and the ship behind Blue.
> Its also worth remembering that 35 seconsds is the absolute maximum time and depends on the destroyer opening fire at exactly the right time.



Yes, the odds of hitting are low, as the USN found out during 1942 - having HA guns didn't change things much, if at all, since even when targets were theoretically within range of HA guns, fire was still usually delayed for one reason or another.


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## RCAFson (Feb 17, 2013)

Glider said:


> It isn't a case of Delhi was perfect, just that it was a lot better than anything else, that anybody else had.



Please provide some proof for your statement.

BTW, how many aircraft did Delhi shoot down and how did she rank compared to other AA cruisers?


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## RCAFson (Feb 17, 2013)

Glider said:


> I am old enough to have served on HMS Tiger and even we had the 3in and Seacat for close range defence and our 6in was deadly against aircraft.



Did any of these weapons use Mk 37/Mk 1 computers? In fact, they used vastly more advanced computers.

We have all been fed a snow job about the MK37/Mk 1 - actual combat proved that it just wasn't very effective.


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## parsifal (Feb 17, 2013)

RCAFson said:


> 35 seconds by 6 destroyers ( a typical 1942 carrier TG escort) = 210 seconds = 210 rounds predicted rounds fired (if we assume a JKMN), plus an umbrella barrage, placed over the target ship as the aircraft begin their dive, for another 200 - 400 rounds.



Ammunition expenditures per kill did not remain static. As time progressed the number of rounds tended to drop, moreover the number of rounds required per kill was different for each nationality. A study by the USN is attached that gives the most accurate data that we have on USN AA performance.

I wonder if there is anything similar for the RN. Especially during the BPFs deployment off Japan and Okinawa in 1945. We have some snippets here and there like the performance of the Illustrious' gunners in January 1941, but I dont think that is a fair comparison, and unless we can get a campaign summary of some description, we get endless circular debate about repective AA performances, plus whether this or that piece of equipment works or doesnt work.

Antiaircraft Action Summary · World War II


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## RCAFson (Feb 17, 2013)

parsifal said:


> Ammunition expenditures per kill did not remain static. As time progressed the number of rounds tended to drop, moreover the number of rounds required per kill was different for each nationality. A study by the USN is attached that gives the most accurate data that we have on USN AA performance.
> 
> I wonder if there is anything similar for the RN. Especially during the BPFs deployment off Japan and Okinawa in 1945. We have some snippets here and there like the performance of the Illustrious' gunners in January 1941, but I dont think that is a fair comparison, and unless we can get a campaign summary of some description, we get endless circular debate about repective AA performances, plus whether this or that piece of equipment works or doesnt work.
> 
> Antiaircraft Action Summary · World War II



That and other USN AA studies are interesting, but these are based upon their own (USN) estimates of how many aircraft were shot down, rather than post war verfied accounts, so the AA effectiveness seems much better than it was. Similarly, Wikipedia gives this info regarding RN AA claims up to Dec 31 1942:


> The RN made the following claims for ship borne anti-aircraft fire against enemy aircraft, from September 1939 up to March 28, 1941:
> Certain kills: 234
> Probable kills: 116
> Damage claims: 134[41]
> ...


HACS - Wikipedia, the free encyclopedia is a must read - the footnotes and external links are invaluable.

The above USN study gives these figures:

totals for 1942:

_____5" Com__ 

Rounds_15,110- 
Kills__60
R.P.B.__252 

yet Lundstrom estimates about 90 AA kills for all of 1942 from all gun types (mainly CIWS). If we add actual AA kills at Pearl Harbour we get 100-110 AA kills where the USN AA study states 246 for kills by weapon type for 1942 and 228 for total kills from Dec 07 1941 to end 1942. It is very obvious that 5in kills are greatly overestimated in this study. 

We should remember Captain Gatch's estimate that 5in AA only accounted for 5% of the kills at Santa Cruz.


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## Juha (Feb 17, 2013)

RCAFson said:


> That and other USN AA studies are interesting, but these are based upon their own (USN) estimates of how many aircraft were shot down, rather than post war verfied accounts, so the AA effectiveness seems much better than it was. Similarly, Wikipedia gives this info regarding RN AA claims up to Dec 31 1942:
> 
> HACS - Wikipedia, the free encyclopedia is a must read - the footnotes and external links are invaluable.



Maybe you should try to get access to Edgar J. March's British Destroyers A History of Development 1892 - 1953 (1966) you would find out that A.C.N.S.(H) wrote in Sept. 40 "...4.7-in....40deg is good L.A., very bad H.A." Or that V.C.N.S. proposed 70deg or 80deg or more, that 55deg be pressed for Emergency Flotillas, if possible 60deg, "and ask U.S.A. if they can supply their new 5-in. guns and mountings, if not make details known to us"

Juha


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## RCAFson (Feb 17, 2013)

Juha said:


> Maybe you should try to get access to Edgar J. March's British Destroyers A History of Development 1892 - 1953 (1966) you would find out that A.C.N.S.(H) wrote in Sept. 40 "...4.7-in....40deg is good L.A., very bad H.A." Or that V.C.N.S. proposed 70deg or 80deg or more, that 55deg be pressed for Emergency Flotillas, if possible 60deg, "and ask U.S.A. if they can supply their new 5-in. guns and mountings, if not make details known to us"
> 
> Juha



I should be able to find copy in a local library but even used copies are selling for $250. We have to draw a clear distinction between the power operated 40deg 4.7in twin, with on-mount fuze setters and the previous (and post, in war emergency program destroyers) 4.7in single. However, and as I stated previously 40 degs is not, obviously, optimal for HA fire but neither is it useless or "very bad".


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## Juha (Feb 17, 2013)

RCAFson said:


> I should be able to find copy in a local library but even used copies are selling for $250. We have to draw a clear distinction between the power operated 40deg 4.7in twin, with on-mount fuze setters and the previous (and post, in war emergency program destroyers) 4.7in single. However, and as I stated previously 40 degs is not, obviously, optimal for HA fire but neither is it useless or "very bad".



Very bad was the professional oppinion of the RN's Assistant Chief of Naval Staff, he might have known something on the subject. And most probably wasn't an Anglophobe.

Juha


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## RCAFson (Feb 17, 2013)

Juha said:


> Very bad was the professional oppinion of the RN's Assistant Chief of Naval Staff, he might have known something on the subject. And most probably wasn't an Anglophobe.
> 
> Juha



As I stated, we have to draw a distinction between the twin and single 4.7in mount. Does the ACNS do that?


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## Juha (Feb 17, 2013)

RCAFson said:


> As I stated, we have to draw a distinction between the twin and single 4.7in mount. Does the ACNS do that?



Not in the quote, but probably meant single mount, because the discussion is under S-class.

Juha


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## RCAFson (Feb 17, 2013)

Juha said:


> Not in the quote, but probably meant single mount, because the discussion is under S-class.
> 
> Juha


 
I should be able to get a copy from a library tomorrow.


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## parsifal (Feb 17, 2013)

_The above USN study gives these figures:

totals for 1942:

_____5" Com__ 

Rounds_15,110- 
Kills__60
R.P.B.__252 

yet Lundstrom estimates about 90 AA kills for all of 1942 from all gun types (mainly CIWS). If we add actual AA kills at Pearl Harbour we get 100-110 AA kills where the USN AA study states 246 for kills by weapon type for 1942 and 228 for total kills from Dec 07 1941 to end 1942. It is very obvious that 5in kills are greatly overestimated in this study. 

We should remember Captain Gatch's estimate that 5in AA only accounted for 5% of the kills at Santa Cruz. _

its intersting that depending on who you talk to, how the revelations change.JoeB will tell you that at Santa Cruz, for example, the known kills of IJN aircraft were by far the result of AA fire, and of these, by far the result of 5/38 fire. Wildcats were effective, but fasr greater perentage was the reault of AA fire. 

I guess if we try to connect or fuse the two schools of thought, that in reality IJN losses were about 5% of the accepted numbers.

Seriously, I think we should look at sected actions in 1942, using main stream sources and determine the total losses suffereed by the Japanese and of that, the numbers destroyed by aircraft, the numbers destroyed by AA and the numbers lost to other non-combat related causes. That way, we should be able to determine the numbers of aircraft lost by each cause. 

Over Pearl either 9 or 11 a/c were shot down by AAC aircraft. That means either 18 or 20 aircraft were brought down by AA. The majority of these were by the navy, but not all. 

I would suggest that we try and use actions that are clearly all USN (which includes the Marine Corps) . We could look at Coral Sea, Midway, Eastern Solomons, Santa Cruz and the Battle of Guadacanal until releieved by US Army formations.

Overall during Guadacanal the Japanese reportedly lost over 1000 a/c. Its hard to visulaise the VMF squadrons shooting down over 900 a/c. Typically, non-combat related losses might run at 30-40% maximum, so we could realitically reduce combat related losses to say 500. Even so, visualising the Marine fighters shooting down more than 400 Japanese aircraft is still very hard. 

Provided the Marine Corps is considered part of the overall Navy tally, its very hard to accept Lundsstroms estimate as anything other than post war revisionism. One of the many reasons why Im not a fan of Lundstrom. If the Marines are not included, it becomes a bit of a false construct. 

Cannoit say too much about Gatch's comments, but the study I posted puts the 40mm as being the chief AA weapon, with 5/38 accounting for about 30% of kills. that seems a reasonable estimate to me. It states in that report that 20mm weapons, (or any weapons with an effective range below 2000m) were not much use in the latter part of the war, being overtaken by the 5/38 because it could literally tear an aircraft apart, whereas a 20mm could not. I would be very interested to see how the BPF, with its 2pounders (being replaced) fared against a similar enemy environment)


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## Glider (Feb 17, 2013)

If I can add to Juha statement, The 5in guns were in turrets which in itself is a significant improvement on the RN guns. They have a full DP ability when attacked by high level bombers and don't have 35 seconds to fire. They can fire at the aircraft until they start their dives. They have a higher rate of fire. They have modern fire control.
Now what advantages did the twin 4.7 have, err, umm, could it be, err no err sorry I will have to come back to you on that one. We know the Tribals have a turret replaced with a twin 4in, so thats not good. We know the AA ships were not fitted with them, so thats not good either. We know the RN's Assistant Chief of Naval Staff officially described them as very bad, which isn't promising.


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## parsifal (Feb 17, 2013)

According to John Webbs "The British Pacific Fleet - Experience and Legacy" "The RN had been developing its methods of defending vessels at sea under the particular circumstances of the med and the ETO. whereas in those circumstances heavy fire from 20mm weapopns could interfere badly enough with a pilots aim to make his chances of hitting with a bomb or torpedo more difficult, when faced with Japanese suicide planes the inability to actually destroy the aircraft was a problem. Kamikazes wouold not veer off or withdraw if damaged".

The book continues

"(The RN observed that) the USN had discovered that their 40mm and 5/38 fire was able to physically break up the attacking suicide aircraft, the british soon discovered their 2pdr and 20mm guns lacked the explosive power (and range) for a (similar result to be achieved)". 

Steps were taken to mount as many 40mm calibre weapons as possible and improve the standard of training in the BPF for AA defence. 

Fraser in commenting on the AA performance of his fleet in 1945 had this to say "The armament of our ships had been designed primarily for antisurface operations and generally speaking, as the Americans would say 'not able to look after themselves' . since 20mm weapons are not an ant-surface weapon, and 40mm guns not generally in service until the deployment of the BPF to the operational areas, Fraser was clearly referring to the main armament of his destroyers. 

Rawlings, who is also quoted, says in his final report "there were difficulties in providing effective area defences by our destroyers to the fleet generally " ...I think he was referring to the limits of the main armement being carried (destroyers included Q class and Tribal classes along with some N class manned by Australians. Some of the Q classes were also RAN) Rawlings continues"A new screening disposition was evolved in response, to increase the level of protection for the carriers, but it required careful and rigid station keeping on the part of the destroyers". I think he is again clearly referring to the 
limits of the main armament of his destroyers.

In July the british decided to adopt the radar picket duties undertaken by USN destroyers for their Task Forces. however the Directorate Of Air Warfare and Training considered the british destroyers to be incapable of effective self defence, so it was decided to fit and allocate cruisers each with 1-2 destroyers and four aircraft to this task. The directorate in its report stated that Destroyers were generally slow to open fire on attacking aircraft though it acknowledged that big improvements had been achieved in comparison to 1944. 

In mid may rawlings reported to fraser that the overall standard of AA defence had inproved considerably with the introduction of amnerican directors and 40mm guns, greater usage of Vt fusing, along with better AA fleet disppostiions and better standards of training. the BPF had always enjoyed better tactical organization with regard to airborne fleet defences, and it seems they were finally closing the gap in shipboard defences as well, which included adoption of better tactical usage of their destroyers. but their destroyers had in built disdvantages that had to be overcome by clever usage, not inbuilt advantages that could be exploited as advantages. 

There were also problems with the numbers of VT fuses available to the British guns. something less than 15% of british ammunition was VT fused, whereas the Americans by 1945 were expending fully 34% of their 5/38s with VT fuses.


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## RCAFson (Feb 17, 2013)

Glider said:


> If I can add to Juha statement, The 5in guns were in turrets which in itself is a significant improvement on the RN guns. They have a full DP ability when attacked by high level bombers and don't have 35 seconds to fire. They can fire at the aircraft until they start their dives. They have a higher rate of fire. They have modern fire control.
> Now what advantages did the twin 4.7 have, err, umm, could it be, err no err sorry I will have to come back to you on that one. We know the Tribals have a turret replaced with a twin 4in, so thats not good. We know the AA ships were not fitted with them, so thats not good either. We know the RN's Assistant Chief of Naval Staff officially described them as very bad, which isn't promising.



Your last sentence is not supported by what we know from March.

Not all 5in/38 destroyer guns were in turrets - the mk 33 destroyers generally had open mounts, with shields, much the same as RN destroyers. The twin 4.7 does have advantages over a 5"/38 single, the main one being that it is considerably lighter, thus allowing for a heavier CIWS. Not all attacking aircraft are divebombers (obviously), and 4.7in guns can place a barrage above the ship being attacked as easily as a HA gun.

The other big problem with your argument is that it lacks nuance; this is not a black and white argument, rather it is composed of many shades of grey...of design trades off regarding, weight, cost, complexity and the effectiveness of rapid fire CIWS versus medium calibre guns.

A rhetorical question:
Which plane is better; Hurricane or Spitfire? Obviously a 1944 Mk VIII Spit has is all over the Hurricane but in 1940, the Hurricane was cheaper, easier to mass produce, easier to repair and probably easier to land could be operated from rougher strips...in 1944 the choice between the two is easy, but not so in 1940.


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## RCAFson (Feb 17, 2013)

parsifal said:


> _The above USN study gives these figures:
> 
> totals for 1942:
> 
> ...



Lunstrom describes in detail all the actions where USN AA was involved and I used his numbers. No way was naval AA involved in large AA loses near Guadalcanal.

Captain Gatch was at Santa Cruz, and well placed to make his judgement call.



This was the officiak USN tally of AA kills as of the end of 1942:






So this is what the USN was reporting to the RN in 1942/43 (I found this on another board and reported it here - this is from the USN AA study number 20). Apparently, in 1944/5 the USN reduced the kill totals to those listed in the Oct 1945 study. 

It is not hard to see why the RN would have been impressed; too bad it just wasn't true.


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## Glider (Feb 18, 2013)

RCAFson said:


> Your last sentence is not supported by what we know from March.
> 
> Not all 5in/38 destroyer guns were in turrets - the mk 33 destroyers generally had open mounts, with shields, much the same as RN destroyers. The twin 4.7 does have advantages over a 5"/38 single, the main one being that it is considerably lighter, thus allowing for a heavier CIWS. Not all attacking aircraft are divebombers (obviously), and 4.7in guns can place a barrage above the ship being attacked as easily as a HA gun..


A couple of points
Twin 4.7in = 25.09 tons = 56,000 lb approx
Single 5in = 41,000 lb approx 

I make it 
Farragat and Mahan not in turrets 26 ships
Gridley, Dunlap, Bagley Benson and Sims some guns not in turrets 58 ships
All the rest in turrets and it should be noted that of the partial ships normally only one or two guns were in open shields, 

From this we know that there was no weight saved in the JKN/Tribal to allow for a heavier CIWS.

.


> The other big problem with your argument is that it lacks nuance; this is not a black and white argument, rather it is composed of many shades of grey...of design trades off regarding, weight, cost, complexity and the effectiveness of rapid fire CIWS versus medium calibre guns..


.[/QUOTE]
I agree that it is a trade off. The Bristol or Benson class were a similar size to the RN destroyers and were built in a similar timeframe so would make an interesting comparison. This should cover the last question you raised. 
The obvious trade off in simple terms was the RN emphasis on anti shipping with six guns vs four/five and the USN emphasising the AA capability with a true DP main battery. Apart from that the JKN and Bensons were pretty similar, even the close range weapons were broadly similar once the initial war updates were installed which generally were approx 6/8 20mm.


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## RCAFson (Feb 18, 2013)

RCAFson said:


> I should be able to get a copy from a library tomorrow.



I did find a copy of March and I'll have more on this tomorrow.


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## RCAFson (Feb 18, 2013)

parsifal said:


> According to John Webbs "The British Pacific Fleet - Experience and Legacy" "The RN had been developing its methods of defending vessels at sea under the particular circumstances of the med and the ETO. whereas in those circumstances heavy fire from 20mm weapopns could interfere badly enough with a pilots aim to make his chances of hitting with a bomb or torpedo more difficult, when faced with Japanese suicide planes the inability to actually destroy the aircraft was a problem. Kamikazes wouold not veer off or withdraw if damaged".
> 
> The book continues
> 
> ...



The RN also had a lot fewer destroyers per carrier than the USN, or so it seems to me. But I'll have more to say tomorrow.


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## parsifal (Feb 18, 2013)

At its peak, the BPF consisted of the following major units

5x CV, 4 x CVL, 4 x BB, 8 x CVE, 10 x Cruisers, 1 x AA Ship, 40 x DDs, and 30 Frigates and sloops. It was the equivalent of a USN TG, though somewhat stronger in numbers (ill check Morrison when I get home) . Not sure if the CVEs were used as front line units in the final offensives. They certainly were used in the 1944 operations. 

Roughly speaking the close escort for the Carriers (that might provide immediate closse AA coverage, taking into account TDs of the ships involved) might usually include 1 capital ship (either a cruiser or a BB...trouble is, a BB has a bigger TD therefore there are less DDs able to contribute in the inner ring defences). Typically you should have a TD of around 2-3000 yards, which meant the DDs could not provide effective AA cover over the Carriers. I think thats what Rawlings was talking about when he said that new tactical disppositions were found necessary. I think the brits were forced by the limitations in their weapons systems to close up to within 1000 yads or so, which would have meant running up signals "restricted in ability top manouvre". and that in turn would severely restrict the ability of the TG to use manouvre when presented with a threat.

The other possiblity is the reverse. if Rawlings decided that manouvre was their best defence, he would have pushed the TDs out. No cover over the Carriers, but more sea room to make violent changes of course and speed, possibly to take advantage of the poor pilot training in the IJN by that stage. That latter scenario would be consistent with the CAP dispositrions, which the british pushed out to above 35 miles (and out to 60 miles quite often). 

Either way, Rawlings was clearly reacting to improve the performance of the AA defences in his escorts. The BPF did not do well in January February, but following these changes, and some additional training, ramped up their effectiveness very quickly after that. 

As to numbers, well maybe, but there are definitie limits as to the number of escorts that can be effectively ringed around a carrier. Given that a BB needs roughly twice the TD of a DD, and there were 4 BBs and 5 carriers, you might have 1 BB and 4-6 DDs within the immediate escort of the carrier (it will depend where the BB is placed). US or British, thats about the limit of ship densities that you can achieve in a standard defensive AA circle around a single high value target like a carrier. You might want to add an outer screen for long range gunnery, but for the british this would of extremely limited value. 

So IMO the British were not short of escorts for the size of the fleet they committed. The limits of their weapon systems were coming home to roost however, because i dont think additional escorts would have helped them materially anyway in fleet air defence issues....

Edit

TF 57 which was the main battle force consisted of the following (for the Okinawa operation)

4 x CV, 2 x BB, 2 x CL 3 x CLAA, 11 x DDs.

Thats an average of 4.5 escorts per Carrier. about what I expected. 

By compartison, TGs 58.1, 58.2, 58.3 and 58.4 each had in their battle forces, the following (for the March 18 preliminary airstrikes) of the following

TG58.1: 3 x CV, 1 x CVL, 2 x BB, 3 x CL, 16 DDs; Average Escort to Carrier ratio 5.25
TG58.2: 2x CV, 2 x CVL, 2 x BB, 2 x CA, 1 x CLAA 17 DD; 5.5
TG58.3: 3 x cv, 1 CVL, 2 x BB, 1 x CA, 4 x CL, 17 x DD ; 5.75
TG58.4: 3 x CV, 3 x CVL, 2 x BB, 1 x CL, 2 x CLAA, 14 x DD; 3.3

The means the Escort to Carrier relationship for the American battle formations was 4.95. Given thats the majority of escorts were DDs for both nationalities, thats the equivalent of 0.5 DDs additional cover for each US ship. 

With regard to TDs, I dont have all of them, but at 30knots (or best max) the KGVs were 1025, the Illustrious class 1050, Essex classes were 765, the Iowas 814, and the Fletchers were 950 yds. somewhere I have the TDs for the battles and Daring Classes, but might take a bit more searching

Nothing to worry about in terms of numbers around each carrier


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## cherry blossom (Feb 18, 2013)

Here are some more little guys. I took most of the information from Wikipedia but changed the displacement of the Matsu class as the IJN did not calculate a standard displacement and added the range at 16 knots from Jentschura. I do not have ranges for the Ciclone class but Whitley gives 442 tons bunkerage, which was reduced from 520 tons in the earlier Orsa class to improve stability. Thus the displacement figures from Wikipedia and Whitley are odd because the difference between standard and full load should equal bunkerage plus spare boiler water.

*Matsu Class*
Displacement: 1,262 tons light 1,530 tons in battle condition
Length: 100.0 m (328 ft 1 in) overall, 92.15 m (302 ft 4 in) waterline
Beam: 9.35 m (30 ft 8 in)
Draft: 3.30 m (10 ft 10 in)
Propulsion: 2 × Kampon water tube boilers, 2 × Kampon impulse geared turbines, 19,000 shp 
Speed: 27.8 knots 
Range: 3,500 nmi (6,500 km) at 18 kn, 4,680 nmi at 16 kn. 
Complement: 211
Armament: (Matsu, April 1944)
3 × 127 mm (5.0 in) L/40 Type 89 AA guns 
24 × 25 mm (1") Type 96 AA guns (4×3, 12×1)
4 × Type 93 torpedoes
4 depth charge throwers and 36 × Type 2 depth charges

*Ciclone class*
Displacement: 910 long tons (920 t) standard, 1,625 long tons (1,651 t) full load
Length: 82.5 m (270 ft 8 in)
Beam: 9.9 m (32 ft 6 in)
Draught: 3.77 m (12 ft 4 in)
Propulsion: 2 shaft steam turbines, 2 Yarrow type boilers, 16,000 hp (11,900 kW)
Speed: 26 knots 
Complement: 154
Armament: 2 × 100 mm (3.9 in) guns (3 guns in some ships after refit)
8 × 20 mm (0.79 in) anti-aircraft guns, 8 × 13.2 mm (0.52 in) AA machine guns
4 × 450 mm (18 in) torpedo tubes
4 × depth charge throwers

*Rudderow class destroyer escort* (the generally similar later John C. Butler class might have been chosen because Samuel B. Roberts acted as a destroyer off Samar but that class had no torpedoes when they were needed)
Displacement: 1,740 tons (1,770 metric tons) (fully loaded)
Length: 306 ft (93.3 m) (overall)
Beam: 36 ft 6 in (11.1 m)
Draft: 11 ft (3.4 m) (fully loaded)
Propulsion: General Electric steam turbo-electric drive engine
Speed: 24 knots (most ships could attain 26/27 knots and Samuel B. Roberts reportedly reached 28 kn off Samar)
Range: 5,500 nautical miles at 15 knots
Armament: 2 x 5 inch /38 dual purpose mount, 4 x 40 mm Bofors, 10 x 20 mm
Three 21-inch (533 mm) torpedo tubes
Hedgehog
Eight depth charge throwers with approximately 200 depth charges



parsifal said:


> They certainly look impressive, but the first was not available until the beginning of 1942.
> 
> How do they compare to the Hunt Class? Type II appears to be the nearest equivalent with the following characterisitics
> 
> ...


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## stug3 (Feb 19, 2013)

The destroyer USS Peary on fire. At about 1045, Peary was attacked by Japanese dive bombers, and was struck by five bombs. The first bomb exploded on the fantail, the second, an incendiary, on the galley deck house; the third did not explode; the fourth hit forward and set off the forward ammunition magazines; the fifth, another incendiary, exploded in the after engine room. A .30 caliber machine gun on the after deck house and a .50 caliber machine gun on the galley deck house fired until the last enemy plane flew away. Peary suffered 88 men killed and 13 wounded; she sank stern first at about 1300 on 19 February 1942.


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## vinnye (Feb 19, 2013)

It seems to me that the USN lost a few destroyers that were on picket duty, so it does not look as though they could look after themselves?
This is not an attempt to belittle those who fought and too often died, but shows that if we wish, we can pick examples which prove our point.
The RN were far from perfect - as was some of their equipment. but they did quite a lot with what they had and sometimes even learned lessons.


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## RCAFson (Feb 19, 2013)

parsifal said:


> At its peak, the BPF consisted of the following major units



IIRC, the BPF suffered one of it's worst days for kamikaze hits on the CVs, when Vian took the 2 KGV class BBs along with several cruisers and destroyers away from the carrier escort, for a bombardment mission. In any event, the number of kamikaze attacks on the BPF is really insufficient to draw any conclusions. IMHO, we really have to compare the USN destroyers performance in 42/43 with the RN from 1939-43 if we want to draw any valid comparisons.


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## RCAFson (Feb 19, 2013)

Glider said:


> A couple of points
> Twin 4.7in = 25.09 tons = 56,000 lb approx
> Single 5in = 41,000 lb approx
> 
> ...



I disagree that no weight was saved. The Bensons were grossly top heavy in their original design format and soon had to surrender no.3 5in turret for a modest increase in their CIWS, but even so 5 x 5in = 205,000lb, 4 x 5in = 164000lb, while 6 x 4.7in (3 x 2) = 168000lb so the JKMs had a heavier main armament and a considerably heavier CIWS that weighed less than the 5 x 5in guns in a Benson.
Benson- and Gleaves-class destroyer armament in World War II
The other factor in the weight equation is the FC directors. The Mk37 director in the Bensons weighed about 12 tons, and this weight was carried very high in the ship while theDCT and 3 man rangefinder - AA director in the Tribal-JKMs weighed only 3.4 tons combined.


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## Glider (Feb 19, 2013)

RCAFson said:


> I disagree that no weight was saved. The Bensons were grossly top heavy in their original design format and soon had to surrender no.3 5in turret for a modest increase in their CIWS, but even so 5 x 5in = 205,000lb, 4 x 5in = 164000lb, while 6 x 4.7in (3 x 2) = 168000lb so the JKMs had a heavier main armament and a considerably heavier CIWS that weighed less than the 5 x 5in guns in a Benson.
> Benson- and Gleaves-class destroyer armament in World War II
> The other factor in the weight equation is the FC directors. The Mk37 director in the Bensons weighed about 12 tons, and this weight was carried very high in the ship while theDCT and 3 man rangefinder - AA director in the Tribal-JKMs weighed only 3.4 tons combined.


I would certainly agree that on average US destroyers (all classes) were top heavy when war broke out and the no 3 gun was soon removed. In the early days they sometimes lost a set of TT's and kept 5 x 5in, it varied a lot.


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## RCAFson (Feb 19, 2013)

Some notes from March (British Destroyers): 

There was intense debate over the armament of the new destroyer classes from the Tribals onward. The 40deg 4.7in twin was selected due to it's ability to provide long range HA fire

p338: The Tribal class were top-heavy and excessive rolling and a loss if stability was noted. It is not stated but the 4 ton reduction in topweight by replacing X twin 4.7 with a twin 4in must have helped considerably.

P.323:


> STAFF REQUIREMENTS
> 
> During 1934 the Naval Staff considered the preliminary investigations for "V" leaders, but the final requirements were to be formulated when it was clear how far they could be met. Differentiation was made between those characteristics fundamental to the design and those which, although important, need not be included to the detriment of the former.
> 
> ...



V class leaders = Tribal class.


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## Juha (Feb 19, 2013)

RCAFson said:


> I disagree that no weight was saved. The Bensons were grossly top heavy in their original design format and soon had to surrender no.3 5in turret for a modest increase in their CIWS, but even so 5 x 5in = 205,000lb, 4 x 5in = 164000lb, while 6 x 4.7in (3 x 2) = 168000lb so the JKMs had a heavier main armament and a considerably heavier CIWS that weighed less than the 5 x 5in guns in a Benson.
> Benson- and Gleaves-class destroyer armament in World War II
> The other factor in the weight equation is the FC directors. The Mk37 director in the Bensons weighed about 12 tons, and this weight was carried very high in the ship while theDCT and 3 man rangefinder - AA director in the Tribal-JKMs weighed only 3.4 tons combined.



Can you explain the "a considerably heavier CIWS" already in 43 Benson/Gleaves had 4x40mm Bofors (2x2) and 4 - 7x20mm, if one remember that even RN thought that twin Bofors was at least as good as quad pom-pom as AA weapon?

Juha


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## RCAFson (Feb 19, 2013)

Juha said:


> Can you explain the "a considerably heavier CIWS" already in 43 Benson/Gleaves had 4x40mm Bofors (2x2) and 4 - 7x20mm, if one remember that even RN thought that twin Bofors was at least as good as quad pom-pom as AA weapon?
> 
> Juha



And to do that the Bensons had to give up a set of TTs. However, as designed, it seems pretty obvious that the JKN CIWS of a quad pom-pom and two quad .5in was vastly superior to 6 x .5in on the Bensons.

The late war armament on an N class destroyer was 6 x 4.7in, 1 quad pom-pom, 2 twin power 20mm, 2 x single 20mm, 2 x quintuple TTs. Also, the the RN opinion of the value of a quad pom-pom varied as to the target type; against a kamikaze they felt it was almost as good per barrel as a Bofors. It seems obvious that by surrendering a set of TTs that the N class could have exceeded the Bensons in late war CIWS.


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## parsifal (Feb 19, 2013)

RCAFson said:


> IIRC, the BPF suffered one of it's worst days for kamikaze hits on the CVs, when Vian took the 2 KGV class BBs along with several cruisers and destroyers away from the carrier escort, for a bombardment mission. In any event, the number of kamikaze attacks on the BPF is really insufficient to draw any conclusions. IMHO, we really have to compare the USN destroyers performance in 42/43 with the RN from 1939-43 if we want to draw any valid comparisons.



Incorrect

The attacks on the carriers are described in some detail in various sources, notably David Browns book "Kamikaze" 


The BPF came in for repeated and sustained attacks from the Japanese from March through to the very end. This arose partly from the dispositions of the BPF.....it was placed in a critical sector of the campaign. There were over 1200 Kamikaze sorties flown against the BPF. The attacks against the carriers occurred over a 2 month period, with a summary I found as follws

"HMS Formidable 
1) 4 May 1945: Struck by a Zero carrying one 250 kg bomb which caused a 2 foot square hole and a 24 x 20 foot depression in the armored flight deck. Some structural damage was inflicted and three fragments penetrated the hanger deck with one going through a center boiler and into the double bottom. Speed was reduced to 18 knots and she was out of action for five hours. This attack killed eight men, wounded 51 and destroyed eleven aircraft.* 
2) 9 May 1945: Kamikaze strike into the after deck park killed one and wounded eight. Deck depressed 4.5 inches with a supporting beam distorted by 3 inches. Six Corsairs and one Avenger were destroyed on deck, and a blown out rivet allowed burning fuel to penetrate into the hanger, which together with the sprinkler system damaged a further eight Corsairs and three Avengers. Out of action for 25 minutes.* 

HMS Illustrious 
6 April 1945: A Judy (D4Y3) kamikaze struck a glancing blow to the island with the only apparent damage being a hole in the Type 272 radome forward of the bridge. However, after the plane skidded into the sea, its bomb exploded underwater close alongside. This inflicted severe structural damage, with the outer hull opened up and some of the frames cracked. The damage did not interrupt flight operations, but speed was limited to 19 knots. Sent home and arrived at Rosyth on 27 June 1945 for what was intended to be a four month repair and refit, but the end of the war slowed work and changed plans. She recommissioned in June 1946 as a trials and training carrier, replacing HMS Pretoria Castle. 

HMS Indefatigable 
1 April 1945: Struck by a Zero carrying one 250 kg bomb on the starboard side of island at the junction with the flight deck. Deck indented over 15 square feet by up to 3 inches but not penetrated. Much superficial damage inflicted by splinters and an intense fire started, but the fire was quickly brought under control and extinquished. Eight killed and sixteen wounded. Able to land Seafires about forty minutes after attack.* Repaired between 2 April and 1 May. 

HMS Indomitable 
4 May 1945: A Zero Kamikaze belly-landed next to the island but broke up and went over the side. Destroyed the radar arrays of the port midships directors but inflicted no serious damage to the ship. A bomb attached to the kamikaze exploded after the plane went into the water but this also inflicted no damage."

These were not the only attacks, but they are the successful attacks made against the carriers

So it is simply untrue to attribute the hits sustained to the alleged diversion of British escorts away from the battle line 9I havent checked this recently, but if my memory serves me, those detachments were made only after their positions in the AA defence rings were filled by other ships). 


Here we have an actual campaign, in which the operational results are fairly well known. Why on earth do we need to compare less well documented campaigns, in vastly different operational conditions? It makes no sense to do that.


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## Juha (Feb 19, 2013)

RCAFson said:


> And to do that the Bensons had to give up a set of TTs. However, as designed, it seems pretty obvious that the JKN CIWS of a quad pom-pom and two quad .5in was vastly superior to 4 x .5in on the Bensons.
> 
> The late war armament on an N class destroyer was 6 x 4.7in, 1 quad pom-pom, 2 twin power 20mm, 2 x single 20mm, 2 x quintuple TTs. Also, the the RN opinion of the value of a quad pom-pom varied as to the target type; against a kamikaze they felt it was almost as good per barrel as a Bofors. It seems obvious that by surrendering a set of TTs that the N class could have exceeded the Bensons in late war CIWS.



Hello RCAFSon, Thanks for the answer!
But situation wasn't that simple, Napier lost its after TTs by 23 Jun 45 and got 3 single Bofors Mk IIIs instead, it also lost 2xsingle 20mm, Nepal also lost its after TTs by Jun 45, but got only one Bofors Mk III instead. Same to Nizam. Norman kept its after TTs and didn't got Bofors. Those were only RN's Ns left at that time. That according to Appendix 3 on Langtree's The Kelly's (2002), but in the caption on p. 185 he writes that "...the number of Bofors carried by the ships of the BPF is an unclear question and Nepal and Nizam carried at least one and possibly up to three whilst Napier seems to have carried 3 or possibly 4... Installing Bofors meant the removal of the aft tubes again."

Juha


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## vinnye (Feb 19, 2013)

Found this on Wiki about the BPF, an exaggeration, but apt.
In March 1945, while supporting the invasion of Okinawa, the BPF had sole responsibility for operations in the Sakishima Islands. Its role was to suppress Japanese air activity, using gunfire and air attack, at potential Kamikaze staging airfields that would otherwise be a threat to U.S. Navy vessels operating at Okinawa. The carriers were subject to heavy and repeated kamikaze attacks, but because of their armoured flight decks, the British aircraft carriers proved highly resistant, and returned to action relatively quickly. The USN liaison officer on the Indefatigable commented: "When a kamikaze hits a U.S. carrier it means 6 months of repair at Pearl [Harbor]. When a kamikaze hits a Limey carrier it’s just a case of 'Sweepers, man your brooms.'


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## RCAFson (Feb 19, 2013)

Juha said:


> Maybe you should try to get access to Edgar J. March's British Destroyers A History of Development 1892 - 1953 (1966) you would find out that A.C.N.S.(H) wrote in Sept. 40 "...4.7-in....40deg is good L.A., very bad H.A." Or that V.C.N.S. proposed 70deg or 80deg or more, that 55deg be pressed for Emergency Flotillas, if possible 60deg, "and ask U.S.A. if they can supply their new 5-in. guns and mountings, if not make details known to us"
> 
> Juha



This is a full verbatim quote for page 402:


> 402
> 
> BRITISH DESTROYERS
> 
> ...



The ACNS was not stating that the 40deg 4.7in twin was a bad mounting, only that 40deg was insufficient to engage dive bombers. However on page 396 the value of 4in guns against divebombers was compared:


> A signal was sent to the C.s-in-C. "Theoretical investigation shows that the lethal value of a single F.K.C. controlled 4-in. gun in a destroyer against dive bombers is less that that of an Oerlikon up to 3000 ft. and considerably less than that of a 4-barrelled pompom up to 10,000 ft. Therefore propose to replace 4-in. H.A. in 'J' class and later and the 3-in. in 'E' to 'I' by the second set of T.T.s as opportunity occurs or by additional Oerlikons."



So the value of a DP 4in gun was less than one 20mm gun and much less than a quad pom-pom - so a 40deg armed ship with a heavy CIWS would be more effective against DBs than one which sacrifised the CIWS for a HA main armament.

Note also the RN tendency to credit their enemy opposite numbers with better weapons and technology than they actually had. No German destroyer was armed with HA FC and a DP gun in WW2, AFAIK, although some of the smaller DEs might have had 4.1 DP guns.


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## RCAFson (Feb 19, 2013)

parsifal said:


> Incorrect
> 
> The attacks on the carriers are described in some detail in various sources, notably David Browns book "Kamikaze"
> 
> ...



Vian took KGV and Howe on the bombardment mission on May 4th 1945:



> At 1000 hours in position 23-54N, 125-10E the bombarding force comprising KING GEORGE V, HOWE, SWIFTSURE, GAMBIA and UGANDA escorted by destroyers GRENVILLE (D5), UNDINE, URCHIN, URANIA, UNDAUNTED and URSA, and EURYALUS and BLACK PRINCE, detached from the carrier force and closed Miyako at 24 knots. The carriers provided an additional CAP for this force as well as aircraft for spotting.
> HMS King George V, British battleship, WW2



and your post shows that two carriers were hit that day, when deprived of the battleships' AA support along with their cruiser and destroyer escort. KGV and Howe were, by far, the most heavily AA armed carrier escorts, and no possible combination of cruisers and destroyers could adequately take their place.


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## RCAFson (Feb 19, 2013)

parsifal said:


> Here we have an actual campaign, in which the operational results are fairly well known. Why on earth do we need to compare less well documented campaigns, in vastly different operational conditions? It makes no sense to do that.



Because the overall number of kamikazes that attacked the BPF are too small to be statistically valid, but we have large numbers of attacks against the RN from 1939-42 that can be compared to attacks against the USN in 1942 and we have good summaries and analysis of these action as well.


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## Njaco (Feb 19, 2013)

can we keep things to one post.....


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## Juha (Feb 19, 2013)

RCAFson said:


> This is a full verbatim quote for page 402:
> 
> 
> The ACNS was not stating that the 40deg 4.7in twin was a bad mounting, only that 40deg was insufficient to engage dive bombers. However on page 396 the value of 4in guns against divebombers was compared:
> ...



My interpretion is that ACNS also thought that 4.7-in 40 deg was also inadequate against high level bombing.

Again my interpretion is that he thought that good CIWS is better than single HA gun. I was suprised ACNS's 4.7-in, 40°, one 4-in. H.A., 4 to 6 Oerlikons oppinion because already for Nelsons RN wanted that at least 4 HA guns should be able to engage any aerial targets and was disappointed when in Nelsons max 3 HA guns could engage an aerial target. Also in army/AF HAA batteries had minimum 4 HAA guns, that was considered minimum for effective controlled fire.

Juha


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## parsifal (Feb 19, 2013)

You just cannot draw the conclusions that you are inferring. There were also successful attacks on the carriers (that we know of) on the 1 April, 6 April and the 9 May. 

Contrary to the popular belief, it was the CLAAs that were the most useful AA platforms rather than the BBs. The BBs needed far too big a TD to provide effective direct close support at a density. they were effective, and indeed essential for the british given the relative inneffectiveness of their DDs as AA platforms in the area defence role. They had had 6 years to correct that incidentally, and yet, according to the admirals that commanded them, were still inneffective at the role of protecting other ships, and indeed, too lightly armed with CIWs of indifferent quality to be considered effective. Only by adopting the most rigid of dispositions were they able to (partially) overcome these inherent design weaknesses.

The 4.5" guns went a long way to addressing at least some of these shortcomings. The other major advance in addressing the shortcomings of British fleet defence against a/c was the introduction of the 40mm Bofors. The same applies to the USN, but the USN had the advantage of already having an effective director control system in the Mk 37 and the 5/38, as well as having the pricless advantage of having a more widespread usage of VT fusing (about twice as much availability per ship)


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## RCAFson (Feb 19, 2013)

parsifal said:


> You just cannot draw the conclusions that you are inferring. There were also successful attacks on the carriers (that we know of) on the 1 April, 6 April and the 9 May.
> 
> Contrary to the popular belief, it was the CLAAs that were the most useful AA platforms rather than the BBs. The BBs needed far too big a TD to provide effective direct close support at a density. they were effective, and indeed essential for the british given the relative inneffectiveness of their DDs as AA platforms in the area defence role. They had had 6 years to correct that incidentally, and yet, according to the admirals that commanded them, were still inneffective at the role of protecting other ships, and indeed, too lightly armed with CIWs of indifferent quality to be considered effective. Only by adopting the most rigid of dispositions were they able to (partially) overcome these inherent design weaknesses.
> 
> The 4.5" guns went a long way to addressing at least some of these shortcomings. The other major advance in addressing the shortcomings of British fleet defence against a/c was the introduction of the 40mm Bofors. The same applies to the USN, but the USN had the advantage of already having an effective director control system in the Mk 37 and the 5/38, as well as having the pricless advantage of having a more widespread usage of VT fusing (about twice as much availability per ship)



Two of the 4 kamikaze strikes that you detailed, occurred when the AA escort was weakened considerably.

Please provide some hard evidence for your statements of RN DD ineffectiveness. The problem with small scale attacks, is that the aircraft are free to radically manoeuvre, so that no system of AA FC in existence in WW2, could hit them, except by chance and/or sheer volume of fire so this tells us nothing.


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## RCAFson (Feb 19, 2013)

This was the official USN tally of AA kills as of the end of 1942:







From the above:

USN AA kill claims / Lundstrom verified AA kills at:

Bougainville 6 / 1 ( 2 shared AA/fighter kills)

Coral Sea = 49 / 9 (5 to Crace's RAN and USN TG, 1 to Neosho and Sims rest to carrier TG) 

Midway = 20 / 3 (1 = two shared AA and fighter kills)

Solomons
Aug 7-8 = 59 / 15 (2 on Aug 7, 13 on Aug 8 mostly CIWS)

Eastern Solomons = 30 / 4

Santa Cruz = 127 / 25 (Gatch: 5% 5in, rest CIWS)

Solomons
Nov 11-12 = 32 / 11 (approx, most CIWS)

Total = 323 / 67 

I'm sure that the USN and RN staff were impressed by the above AA claims, and doubtless many in the RN must have felt that USN AA FC and weaponry was vastly superior to RN AA FC and weaponry. I suspect that the truth would have made a huge difference in how both Navies looked at their AA situation.


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## parsifal (Feb 19, 2013)

> Two of the 4 kamikaze strikes that you detailed, occurred when the AA escort was weakened considerably.



You cannot claim that the Aa defences were weakened. though I have yet to confirm, it may well be that CLAas were used to replce the BBs, or that the BBs were in fact replaced by the other 2 BBs attached to TF 57 (there were a total of 4 BBs under Frasers Command. 

BBs were not that good as AA escorts, at5 least in the RN. with a TD of over 1000 yards, and the carriers also having a TD of over 1000 yds, they could not place effective LAA over the Carriers and could not provide effective area defence with those weapons (2pdrs and 20mm). The 5.25" were good, but were no substitute for effective LAA which they lacked. The RN rated the max effective range of the 2pdr at 1700 yds, which meant that two large ships could not provide mutually supportive fire for each other. The Americans, with their 40mm Bofors (with an effective range of over 4000 yds) could provide such mutually supportive fire. that, plus the fact that they were firing twice as many HAA with VT at roughly twice the rof (oh know here we go again....) gave them a telling advanatage, as is reported by the British Admirals on the scene at the time. they saw what was happening and reported accordingly. 


In any event, if RN DDs had been effective at AA, as you claim, they should have been able to provide area defence in place of the DDs. USN DDs were considered good enough to undertake picket duties independantly (RN DDs were not), so there in itself is evidenmce of a systemic failure by the RN. 



> Please provide some hard evidence for your statements of RN DD ineffectiveness. The problem with small scale attacks, is that the aircraft are free to radically manoeuvre, so that no system of AA FC in existence in WW2, could hit them, except by chance and/or sheer volume of fire so this tells us nothing.



But there is hard evicdence already. Read the reports by Rawlings and Fraser. These reports by these British Admirals are very clear that AA defence in the BPF was left wanting (and by my reading mostly because the DDs were incapable of fulfilling an aeffective AA role) and that this could only addressed by re-equipoment and new fleet dispositions (which were very rigid and limiting in their arrangements) . Fraser contrasted RN AA inneffectiveness to the USN effectiveness, which he includes in his report. Its all in the book I recommended. Its the operational results that were achieved with all those gizmos you parade as so effective. the admirals that actually had to use them, once confronted with a competing and contemporary US system, in the same environment were unequivocal. They were of the opinion that the US AA defences were vastly superior. Proof enough for me


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## RCAFson (Feb 19, 2013)

parsifal said:


> You cannot claim that the Aa defences were weakened. though I have yet to confirm, it may well be that CLAas were used to replce the BBs, or that the BBs were in fact replaced by the other 2 BBs attached to TF 57 (there were a total of 4 BBs under Frasers Command.
> 
> BBs were not that good as AA escorts, at5 least in the RN. with a TD of over 1000 yards, and the carriers also having a TD of over 1000 yds, they could not place effective LAA over the Carriers and could not provide effective area defence with those weapons (2pdrs and 20mm). The 5.25" were good, but were no substitute for effective LAA which they lacked. The RN rated the max effective range of the 2pdr at 1700 yds, which meant that two large ships could not provide mutually supportive fire for each other. The Americans, with their 40mm Bofors (with an effective range of over 4000 yds) could provide such mutually supportive fire. that, plus the fact that they were firing twice as many HAA with VT at roughly twice the rof (oh know here we go again....) gave them a telling advanatage, as is reported by the British Admirals on the scene at the time. they saw what was happening and reported accordingly.
> 
> ...



I'm afraid that I have to strongly disagree.


> 1st May.
> Task Force 57- sailed from Leyte in -groups at
> 0630 and consisted .of the following ships: —
> 1st Battle Squadron
> ...



so 4 CVs, 2 BBs, 5CLs, and 14 DDs.





> At 1000 hours in position 23-54N, 125-10E the bombarding force comprising KING GEORGE V, HOWE, SWIFTSURE, GAMBIA and UGANDA escorted by destroyers GRENVILLE (D5), UNDINE, URCHIN, URANIA, UNDAUNTED and URSA, and EURYALUS and BLACK PRINCE, detached from the carrier force and closed Miyako at 24 knots. The carriers provided an additional CAP for this force as well as aircraft for spotting.



So 2 BBs, 5 CLs, and 6 DDs detached themselves for the bombardment mission and no additional ships replaced them; *the remaining escort was reduced to 8 destroyers*, to try and screen 4 fleet carriers! No wonder that Vian was criticized, as taking the CLs was a truly boneheaded decision.

The *effective range of the pom-pom and 40mm bofors in eyeshooting was estimated to be 1700 yards*, but by this time many RN destroyers had gyro guns sights for their pom-poms and some may have had the Simple Tachymetric Director for them as well, but the plain fact is that the BPF was tragically weakened by Vians move. The BPF was simply too weak in supporting CLs and DDs to be compared to USN Task Groups.

Effective range of director controlled pom-poms and bofors was about the same - 3500-4000 yards (the range limit of self destructing ammo).


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## parsifal (Feb 20, 2013)

As of the 1st May 4 N class were added to the force temporarily increasing the Escort ratio to 5.25. I dont have much detail on this attack, just that one kamikaze broke through out of about 20 attackers and hit Indomitbale (I think)


For the attack on the 4th, you are right, there were only 8 DDs present for defence, but this really highlights their weknesses if anything. granted on that occasion the Escort ratio fell through the floor to just 2. but the DDs were ideally placed to protect the carriers, having closed right up as I suspected (I am referring to the Flag Officers reports to the Admiralty 6 June'45, of which I have copies....they are fairly easy to come by). Though these reports make repeated references to this type of gun opening fire and this destroyer being here or there, NOWHERE does it mention the 4.7s ever having ANY effect on the Kamikazes attacking. For example

"At about 1100 three small groups of bogeys were detected to the westward, and were soon followed up by a fourth. Probably 16 to 20 enemy aircraft were employed with some acting as decoys. Fighters engaged one group working round to the southward, but one Kamikaze group penetrated to the carriers and was first detected when a plane was seen diving on the Force. Analysis shows that this group escaped detection either because, in the absence of the Bombarding Force, too many of the reduced number of radar sets were fully engaged-tracking the diversionary planes and too few acting as warning sets, or else because they made a very low approach followed by a very high climb at about 15 miles range.

There were no bandits on the screen within 20 miles when at 1131 a Zeke was seen diving from a great height on to H.M.S. 
FORMIDABLE and engaged by gunfire. A.C.1 there upon manoeuvred his Force under wheel at high speed by successive emergency turns. Though reported hit by close range weapons from his target, the (single) Kamikaze crashed into the flight deck of H.M.S. FORMIDABLE near the island structure arid started a large fire in the deck park of aircraft. A.C.1 manoeuvred the formation to keep in close touch with the damaged ship, whose speed was temporarily reduced to 18 knots.

At 1134 a Zeke flying from forward to aft off the starboard bow of H.M.S. INDOMITABLE was engaged by 4.5 in. guns and temporarily disappeared in cloud. It soon reappeared diving at the ship as steeply as about 60° from the starboard beam. The Force was turning to starboard at the time and H.M.S. INDOMITABLE's wheel was increased to hard over. As the plane approached it was heavily engaged by close range weapons from the ship and set on fire; it flattened out at the last moment, deck landed on the flight deck, and bounded over the side, taking the radar arrays of the port midships directors with it. The bomb appeared to explode shortly after the plane submerged.

At 1142 another Zeke dived steeply on H.M.S. INDOMITABLE whose close range weapons and those of HiM.S.. QUALITY hit him hard and often. The aircraft burst into flames and crashed into the sea about 10 yards off the starboard bow of the ship'

If you wanted to summarize these attacks, there is absolutely no mention of the 4.7s engaging, here or elsewhere in the report. The 4.5s are mentioned as engaging, but inneffective. The CIWs of the Carrier and one DD were mentioned, and appear to have been successful againt two out the three attackers, but hese attackers were pressing home their attacks singly. this is not a good look for the vaunted claim of the 4.7 being an effective AA weapon, and is also pretty clear evidence that the 2pdr was also not good at stopping Kamikazes if massed attacks had been employed

Elsewhere in this report to the Admiralty Rawlings reports 

"At 1945 CTF 57 assumed tactical command. A total of 14 enemy aircraft, all airborne, were destroyed during the day by fighters, 2 shot down by gunfire"

2 shot down is not a great score, neither were the attackers thrown off their missions by the RN fire. The Brits were lucky they had armoured flight decks, otherwise they may well have lost two carriers that day. This too was noted by the admirals report. 

In his book Carriers in Combat: The Air War at Sea, Chester G. Hearn notes the failings of RN AA as well. He notes the total ineffectiveness of the 4.7 as an AA weapon, and furthe the inability of the Pom Poms and the 20mm guns to act effectively against determined attackers like the Kamikazes.

T


> he effective range of the pom-pom and 40mm bofors in eyeshooting was estimated to be 1700 yards, but by this time many RN destroyers had gyro guns sights for their pom-poms and some may have had the Simple Tachymetric Director for them as well, but the plain fact is that the BPF was tragically weakened by Vians move.



I agree with the last bit, and dont disagree with the 1st bit relating to the technological improvements. Still wasnt enough, even when the fleet was operating with an excess of escorts, such as on March 27, when the first attacks on Sakushima were launched, and Illustrious was hit by a Kamikaze. that failure led to the changes that saw the RN DDs ideally placed on 1 May. However Rawlings on both occasions commented on the inadequacy of the RN CIWs, gizmos or no. Both he and fraser knew they needed the 40mm bofors, and actively lobbied for US methods and Directors to be installed in their ships.


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## RCAFson (Feb 20, 2013)

parsifal said:


> As of the 1st May 4 N class were added to the force temporarily increasing the Escort ratio to 5.25. I dont have much detail on this attack, just that one kamikaze broke through out of about 20 attackers and hit Indomitbale (I think)
> 
> 
> For the attack on the 4th, you are right, there were only 8 DDs present for defence, but this really highlights their weknesses if anything. granted on that occasion the Escort ratio fell through the floor to just 2. but the DDs were ideally placed to protect the carriers, having closed right up as I suspected (I am referring to the Flag Officers reports to the Admiralty 6 June'45, of which I have copies....they are fairly easy to come by). Though these reports make repeated references to this type of gun opening fire and this destroyer being here or there, NOWHERE does it mention the 4.7s ever having ANY effect on the Kamikazes attacking. For example
> ...



C'mon...you can't seriously argue that if an kamikaze aircraft makes it through the screen, that it means the destroyers have ineffective AA because that same argument would be also damn Mk 37 and the 5in/38 because hundreds of kamikazes were able to hit USN ships despite the destroyer screens. As I said before, an aircraft flying an erratic course was an impossible target for WW2 AA FC systems, and a single aircraft can be very hard to spot, and if you can't see it you can't engage it.


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## parsifal (Feb 20, 2013)

> C'mon...you can't seriously argue that if an kamikaze aircraft makes it through the screen, that it means the destroyers have ineffective AA because that same argument would be also damn Mk 37 and the 5in/38 because hundreds of kamikazes were able to hit USN ships despite the destroyer screens. As I said before, an aircraft flying an erratic course was an impossible target for WW2 AA FC systems, and a single aircraft can be very hard to spot, and if you can't see it you can't engage it.


.

I dont say that, the commanders on the spot on the receiving end of those attacks say it in their reports to the Admiralty. 

These are not my words. they are the words of the commanders on the spot (not the exact words, but Ive previously quoted him in preceding posts, but I am faithfully paraphrasing him). They run contrary to the case youve made i know, but that is what it is. The 4.7, the Pom, the 20mm and the british HACs system fire may be effective against a less resolute enemy (Fraser says that too), but against a ruthless, determined (if by 1945 a somewhat illtrained) enemy like the Japanese simply not up to par (Fraser recognizes that as well). 

Fraser in particular in his report says that the destroyers had been designed and built for surface action, and then during the war years had been developed around the 2pdr and 20mm CIWs for close in defence. He does not mention the 4.7, but his inferences are very clear....the long range DP and its directors were inneffective in that role

As for your claims about US DDs, again I rely on the advice of Rawlings and Fraser. They thought they were very effective, so they dont agree with you assessment of inneffectiveness either. They dont agree with your summation. Paraphrasing again, but these men essentially observed the higher levels of success by the US and advocated the adoption of their methods, and technology in shipboard air defence matters. That basically meant using the Mk37 and 5/38, greater usage of the VT fuses along with the Bofors to break up the determined Japanese attacks, and tighter tactical dispositions around the high value targets. Allowed a much more highly integrated defence than had previously been the case for the RN, or even the USN in its formative stages of the doctrine. 

Unpalatable as these observations are (for me as well), they are not my opinions, though I agree with them. they are the opinions of the men leading the british forces in the Pacific.

Not exactly on topic, but while these men called a spade a spade when it came to the AA defences of their fleet, and were in a position to know, they also did point out the far more advanced airborne air defence methods. The RN got a lot out of their airborne air defences. Not so their ship based air defencess (but in particular the destroyers used in that capacity). 

As the war drew to a close the British upgraded their equipment and modified their procedures. according to the commanders, in their subsequent reports, things did get better as time progressed. but it had taken a while (since the outbreak of hostilities in '39).

I dont see your opinions as completely at odds with the fleet commanders of 1945. British AA defence was made adequate for the ETO, but initially was found lacking in the PTO. It staged a partial recovery, after adopting US methods and equipment (as far as possible) in a fairly short space of time.


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## RCAFson (Feb 20, 2013)

parsifal said:


> As for your claims about US DDs, again I rely on the advice of Rawlings and Fraser. They thought they were very effective, so they dont agree with you assessment of inneffectiveness either. They dont agree with your summation. Paraphrasing again, but these men essentially observed the higher levels of success by the US and advocated the adoption of their methods, and technology in shipboard air defence matters. That basically meant using the Mk37 and 5/38, greater usage of the VT fuses along with the Bofors to break up the determined Japanese attacks, and tighter tactical dispositions around the high value targets. Allowed a much more highly integrated defence than had previously been the case for the RN, or even the USN in its formative stages of the doctrine.



The RN thought USN destroyers were effective because the USN said they were effective:

***

This was the official USN tally of AA kills as of the end of 1942:






From the above:

USN AA kill claims / Lundstrom verified AA kills at:

Bougainville 6 / 1 ( 2 shared AA/fighter kills)

Coral Sea = 49 / 9 (5 to Crace's RAN and USN TG, 1 to Neosho and Sims rest to carrier TG) 

Midway = 20 / 3 (1 = two shared AA and fighter kills)

Solomons
Aug 7-8 = 59 / 15 (2 on Aug 7, 13 on Aug 8 mostly CIWS)

Eastern Solomons = 30 / 4

Santa Cruz = 127 / 25 (Gatch: 5% 5in, rest CIWS)

Solomons
Nov 11-12 = 32 / 11 (approx, most CIWS)

Total = 323 / 67 

I'm sure that the USN and RN staff were impressed by the above AA claims, and doubtless many in the RN must have felt that USN AA FC and weaponry was vastly superior to RN AA FC and weaponry. I suspect that the truth would have made a huge difference in how both Navies looked at their AA situation.

***

The problem is that the historical record says otherwise. This is the big stumbling block that completely trashes MK 37-5in/38; in actual combat it just couldn't destroy aircraft in large numbers despite the incredible claims of the USN to the contrary. Look at the carrier versus carrier actions; Coral Sea, Midway, Eastern Solomons, where the USN relied on the MK 37 as their CIWS was very weak (yet still claimed the lions share of kills) prior to the Bofors becoming available, and the AA results were pathetic - only 10 AA kills in all 3 actions yet the USN claimed ~90 AA kills in these 3 clashes. Yet in all three actions the USN carrier TGs were well screened with their latest destroyer models and at Eastern Solomons they had the last word in Mk37 AA defence via a battleship (North Carolina) and a CLAA (Atlanta) and they still couldn't generate an effective AA defence.


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## parsifal (Feb 20, 2013)

The final report by the HQ Naval headquarters CinC does not make those claims. The report is dated October 1945, so in reality was being collated from known fleet data for at least two years before that. The report makes the following conclusions regarding their AA effectiveness

"Of these, an estimated 2,773, or 36 percent, were shot down by naval and merchant ships. In addition to these, the enemy expended 314 planes and pilots in suicide crashes on ships.

AA. successes for the war by 6-month periods follow:

Period: Assessed kills 
Pearl Harbor 26 
First half 1942 56 
Second half 1942 146 
First half 1943 72 
Second half 1943 300 
First half 1944 171 
Second half 1944 310 
First half 1945 964 
July and August 1945 11 
Total 2,056 
Armed Guard total 200 
Grand total 2,256 

The "kills" listed in the foregoing table occurred within sight of the ships being attacked. The 5,500 planes not shot down immediately were so harassed by antiaircraft gunfire that comparatively few were able to carry out their missions successfully. Damage to ships caused by enemy planes is outlined later in this chapter.

It has been the experience of our own aircraft with enemy AA. that 70 percent of them fell at or in the vicinity of the target. The remaining 30 percent either crashed en route back to their bases or were so badly damaged that they had to be stricken after arriving at their bases. It appears justified to conclude, therefore, that except for suicide planes, which by their nature are committed to destruction, those enemy planes which...."


I would think it highly likley that Fraser and Rawlings as foreign components of the 5th Fleet, would have seen preliminary or interim estimates of those figures at some point in 1945.

The figures contained in the final report dont look too far from the truth to me. For example, it lists 26 losses to AA over Pearl in December. That pretty much accords to other figures Ive seen. It lists 56 losses for the first half of 1942, and 146 losses for the second half. I dont know if they are correct, but they seem to accord to some other sources, including some that are Japanese (such as the tramslated book on operations in the SWPacific through to June 1943). Its hard to know how accurate these figures are, but they seem okay to me. By comparison, Ive seen RN estimates of the numbers of a/c they shot down as about 2-300. Admittedly, you have to make allowance for the vastly smaller size of the RN, and also that these figures are all very rubbery, but if even half right, it shows starkly the difference in AA performance and efficiency of the two navies.

Oveclaimimng by AA was common to both Navies, and could generally only be corrected only long after the battle
In the naval battles around Crete in May 1941, for example, attacks by German planes, mainly Ju-87 and Ju-88, destroyed three British cruisers (Gloucester, Fiji and Calcutta) and six destroyers (Kelly, Greyhound, Kashmir, Hereward, Imperial and Juno). Damage to the aircraft carrier Formidable, battleships Warspite and Barham, destroyers Kelvin and Nubian, and cruisers Ajax, Dido, Orion, and Perth kept these ships out of action for months. By 1 June the effective eastern Mediterranean strength of the Royal Navy had been reduced to two battleships and three cruisers to oppose the four battleships and eleven cruisers of the Italian Navy.

This has to be considered a major action by any standard, and in fighting that fight, the RN shipborne AA claimed for the period of 15–27 May Twenty enemy aircraft...shot down for certain, with 11 probables. At least 15 aircraft appeared to have been damaged..."; from 28 May – 1 June, another two aircraft were claimed shot shot down and six more damaged, for a total of 22 claimed destroyed, 11 probably destroyed and 21 damaged, during the entire campaign. In fact in that period, Axis admitted losses to AA were just 10 aircraft, with a lot more damaged. If the RN was influenced by USN overclaiming, why wouldnt they be similalry swayed by RN overclaimimg. it cuts both ways. 



However, even thats not the point. Rawlings and Fraser were not influenced by those written estimates, at least Ive not found them mentioning them. But Webb doioes say that they observed first hand the effectiveness of USS AA, and could see straiaght away, from first hand observation that it was superior to anything they had in the BPF at that time. They dont actually say that in their reports, but in Hearns book, he says that they did press for changes to American Weaponary and tactical methods before the launching of Olympic (which of course never happened). I am convinced that fraser and rawlings formed the opinions that they did, on the basis of what they saw, and not what they were told. There is simply no evidence to support that notion. and what they saw was their own DDs not performaing that well in the fleet defence role, and US DDs sufficiently capable at AA defence as to be entrusted with the extraordinarily difficult radar picket duties independant of any real support. The British could not entrust their DDs to undertake that task on their own. 

Final


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## RCAFson (Feb 20, 2013)

parsifal said:


> The final report by the HQ Naval headquarters CinC does not make those claims. The report is dated October 1945, so in reality was being collated from known fleet data for at least two years before that. The report makes the following conclusions regarding their AA effectiveness
> 
> "Of these, an estimated 2,773, or 36 percent, were shot down by naval and merchant ships. In addition to these, the enemy expended 314 planes and pilots in suicide crashes on ships.
> 
> ...



Even these numbers are a considerable overestimate, but it was the claims made by the USN in the earlier time frames that probably did the damage, in terms of creating an unjustified reputation for the MK 37, a reputation we now know is just plain false.



> I would think it highly likley that Fraser and Rawlings as foreign components of the 5th Fleet, would have seen preliminary or interim estimates of those figures at some point in 1945.
> 
> The figures contained in the final report dont look too far from the truth to me. For example, it lists 26 losses to AA over Pearl in December. That pretty much accords to other figures Ive seen. It lists 56 losses for the first half of 1942, and 146 losses for the second half. I dont know if they are correct, but they seem to accord to some other sources, including some that are Japanese (such as the tramslated book on operations in the SWPacific through to June 1943). Its hard to know how accurate these figures are, but they seem okay to me. By comparison, Ive seen RN estimates of the numbers of a/c they shot down as about 2-300. Admittedly, you have to make allowance for the vastly smaller size of the RN, and also that these figures are all very rubbery, but if even half right, it shows starkly the difference in AA performance and efficiency of the two navies.



Naval AA success over Pearl Harbor were in the range of 15 aircraft. I've enumerated the USN losses for the major battles of 1942 and they fall far short of the numbers listed.



> Oveclaimimng by AA was common to both Navies, and could generally only be corrected only long after the battle
> In the naval battles around Crete in May 1941, for example, attacks by German planes, mainly Ju-87 and Ju-88, destroyed three British cruisers (Gloucester, Fiji and Calcutta) and six destroyers (Kelly, Greyhound, Kashmir, Hereward, Imperial and Juno). Damage to the aircraft carrier Formidable, battleships Warspite and Barham, destroyers Kelvin and Nubian, and cruisers Ajax, Dido, Orion, and Perth kept these ships out of action for months. By 1 June the effective eastern Mediterranean strength of the Royal Navy had been reduced to two battleships and three cruisers to oppose the four battleships and eleven cruisers of the Italian Navy.
> 
> This has to be considered a major action by any standard, and in fighting that fight, the RN shipborne AA claimed for the period of 15–27 May Twenty enemy aircraft...shot down for certain, with 11 probables. At least 15 aircraft appeared to have been damaged..."; from 28 May – 1 June, another two aircraft were claimed shot shot down and six more damaged, for a total of 22 claimed destroyed, 11 probably destroyed and 21 damaged, during the entire campaign. In fact in that period, Axis admitted losses to AA were just 10 aircraft, with a lot more damaged. If the RN was influenced by USN overclaiming, why wouldnt they be similalry swayed by RN overclaimimg. it cuts both ways.


 
Those numbers appear to come from the wikipedia article on Crete:
Battle of Crete - Wikipedia, the free encyclopedia
and you will note that the article states:


> In total, Royal Navy AA gunners shot down 10 Luftwaffe aircraft and damaged 16 more, some of which crash-landed upon return to base, *on 21/22 May*.[55]
> [55]Shores 1987, pp. 357–9. 5 Ju-87 and 5 Ju-88 aircraft were lost.



So Shores states 10 kills on May 21/22 alone. AFAIK, the article doesn't detail Luftwaffe losses from RN AA for the rest of the battle, but we can safely assume that there was losses on other days as well, so the RN estimate seems extremely accurate, especially by way of comparison with the USN in 1942. RN losses were amplified and AA successes minimized by the need to disperse the fleet, thus allowing the Luftwaffe to attack and overwhelm small numbers of ships, many of whom, such as Gloucester and Fiji, were critically short of AA ammo even before they were detached from the main body. Several ships, such as Fiji had AA FC radar during the battle, but it was still not fitted in any numbers to RN destroyers.




> However, even thats not the point. Rawlings and Fraser were not influenced by those written estimates, at least Ive not found them mentioning them. But Webb doioes say that they observed first hand the effectiveness of USS AA, and could see straiaght away, from first hand observation that it was superior to anything they had in the BPF at that time. They dont actually say that in their reports, but in Hearns book, he says that they did press for changes to American Weaponary and tactical methods before the launching of Olympic (which of course never happened). I am convinced that fraser and rawlings formed the opinions that they did, on the basis of what they saw, and not what they were told. There is simply no evidence to support that notion. and what they saw was their own DDs not performaing that well in the fleet defence role, and US DDs sufficiently capable at AA defence as to be entrusted with the extraordinarily difficult radar picket duties independant of any real support. The British could not entrust their DDs to undertake that task on their own.
> 
> Final



I'm afraid that is a very narrow base upon which to rest your case. Observers of USN target practise were mislead as 5"/38 efficiency:



> Heavy AA. Gun Batteries
> 
> *The most outstanding deficiency in Fleet AA. in suicide actions to date has been the performance of heavy AA. batteries*. Previously (1 January to 1 July 1944) accounting for 39 percent of the kills credited to AA., the performance of 5-inch batteries against suicide planes has dropped to 18 percent. This is due to two factors namely:
> 
> ...


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## Glider (Feb 20, 2013)

The question is Was the 5in DP gun better for AA defence compared to the twin 4.7in RN destroyers gun. There is no doubt that all the RN officers who observed both in action believe that the result is yes, the 5in was a much better weapon. No one has even tried to quote an RN officer who believed that the twin 4.7 was even close to being as good as the 5in. We have opinions, theories but no quote from anyone at the time.

To base the defence against this on observations that the USN believed that the 5in wasn't as good as they liked is a different answer to a different question. I am very confident that the RN would have been absolutely delighted if their Heavy AA guns had shot down 18 percent of the suicide aircraft. To claim 39% of all kills in the period Jan - July is a remarkable achievement.


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## RCAFson (Feb 20, 2013)

Glider said:


> The question is Was the 5in DP gun better for AA defence compared to the twin 4.7in RN destroyers gun. There is no doubt that all the RN officers who observed both in action believe that the result is yes, the 5in was a much better weapon. No one has even tried to quote an RN officer who believed that the twin 4.7 was even close to being as good as the 5in. We have opinions, theories but no quote from anyone at the time.
> 
> To base the defence against this on observations that the USN believed that the 5in wasn't as good as they liked is a different answer to a different question. I am very confident that the RN would have been absolutely delighted if their Heavy AA guns had shot down 18 percent of the suicide aircraft. To claim 39% of all kills in the period Jan - July is a remarkable achievement.



There's a huge difference between claims and actual kills. My look at USN AA kills as stated by Lundstrom leads me to believe that the actual 5in kill rate during 1942 was around 5 to 10%, at most, of total AA kills. After 1943 the USN began using VT ammo in large quantities, so one would expect an increase in 5in AA efficiency, but it seems to me that the decline from 1944 to 1945 was mainly due to increased accuracy of reporting and that the 39% claim for 1944 was greatly overstated.

However, if 5in AA was ineffective (and it was) in 1942 and if RN 4.7in AA was similary ineffective, then there would be a greater reliance on the CIWS, and thus the RN policy of of saving weight via lower elevation main armament but ensuring a heavy CIWS was justified, and that total RN AA efficiency and kill rates would actually decline if RN destroyers were equipped with MK37+5in/38 at the expense of their CIWS. This trade off is not something that anyone in the RN could have known, given how greatly inflated and misleading USN AA stats were during WW2 - especially given that RN AA kills seems to have been much more conservatively stated.


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## Glider (Feb 21, 2013)

RCAFson said:


> There's a huge difference between claims and actual kills. My look at USN AA kills as stated by Lundstrom leads me to believe that the actual 5in kill rate during 1942 was around 5 to 10%, at most, of total AA kills. After 1943 the USN began using VT ammo in large quantities, so one would expect an increase in 5in AA efficiency, but it seems to me that the decline from 1944 to 1945 was mainly due to increased accuracy of reporting and that the 39% claim for 1944 was greatly overstated.
> 
> However, if 5in AA was ineffective (and it was) in 1942 and if RN 4.7in AA was similary ineffective, then there would be a greater reliance on the CIWS, and thus the RN policy of of saving weight via lower elevation main armament but ensuring a heavy CIWS was justified, and that total RN AA efficiency and kill rates would actually decline if RN destroyers were equipped with MK37+5in/38 at the expense of their CIWS. This trade off is not something that anyone in the RN could have known, given how greatly inflated and misleading USN AA stats were during WW2 - especially given that RN AA kills seems to have been much more conservatively stated.


I don't disagree that there is a huge difference between claims and kills a difference that applies to all the armed forces of all the nations in the conflict.
The key point is that and I repeat myself here _All the RN officers who observed both in action believe that the result is yes, the 5in was a much better weapon. No one has even tried to quote an RN officer who believed that the twin 4.7 was even close to being as good as the 5in. We have opinions, theories but no quote from anyone at the time_.

I can see where you are coming from re the 1942/43 time period but you still have no quote from anyone to support you. You have your theory but nothing more. Few would deny that 4-6 20mm and a quad 2pd is better than 4-6 20mm normally carried by the USN by late 42.
Even in your papers when describing the air battles in 1942 there were a number of examples of the attacking aircraft turning away in the face of 5in fire. There were examples where the reccomendation was that the 5in should be retained for putting barrage fire up over the carriers. However I can find no examples of any RN report saying that the 4.7in helped in turning away Japanese air attacks (I do know of one where his happened using the 5.25). I find no examples of reports saying that the 4.7in actually helped when firing barrage fire over the carriers. Plenty saying that it should be able to, but none saying that it did. 

What we do have is a lot of reports from RN officers saying that they wanted the 5in as its a lot better than what they had. 

A key thing to remember is the effectiveness of the fire against the Japanese. In 1942 I am sure most will agree that they had the best trained and equipped naval airforces in the world.


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## parsifal (Feb 21, 2013)

> What we do have is a lot of reports from RN officers saying that they wanted the 5in as its a lot better than what they had.



And some of those officers said that after first hand observation of the 5/38 as opposed to their own 4.7s.

Ive seen some officers sing the praises of the 4.5, Ive seen some more or less say the 4in was good enough. Some officers are supportive of the 2 pounder, though less so than the 4.5. Ive never seen any officer say the 4.7 was okay. even Vians report on operations in Norway isnt glowing about the weapon. 

And there are quite a few comments from RN officers that suggest they really liked the 5/38. Are all these officers wrong or idiots. It just beggars belief. 

I think we need unequivocal evidence that officers though the British AA suites as superior to anything around. I would accept that there is evidence that the Brits had a workable system, but I simply dont think many people saw it as a great system, or that the US system operationally was a dud. Its true I think that there were teething problems, but that is a long way from proving or showing the system was a failure....


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## RCAFson (Feb 21, 2013)

parsifal said:


> And some of those officers said that after first hand observation of the 5/38 as opposed to their own 4.7s.
> 
> Ive seen some officers sing the praises of the 4.5, Ive seen some more or less say the 4in was good enough. Some officers are supportive of the 2 pounder, though less so than the 4.5. Ive never seen any officer say the 4.7 was okay. even Vians report on operations in Norway isnt glowing about the weapon.
> 
> ...



RN contact with the 5in/38 was very limited.

I don't really care what officers thought - it is the results that they obtained that matters. One of the huge problems is that the USN was reporting great things about the 5in/38 that simply weren't true and this must have swayed opinion in both navies; something along the lines of: "...Gee we got hammered in Norway and Crete yet the USN appears to be shooting the Japanese out of the Pacific skies...their system must be better..." The other problem is that if a staff study states that a 40deg gun and a heavy CIWS is better than a 80deg gun and a light CIWS, it doesn't mean that line officers will agree, *even if the study is correct.* The average RN destroyer officer probably thought his weaponry was inadequate to the task, and he was right, but that doesn't mean that an alternate FC system and a reliance on a HA 5in gun as in MK33 or Mk 37 USN destroyers would have produced better results - and there is no evidence that USN destroyers were doing better than RN destroyers in 1942.


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## RCAFson (Feb 21, 2013)

Glider said:


> I can see where you are coming from re the 1942/43 time period but you still have no quote from anyone to support you. You have your theory but nothing more. Few would deny that 4-6 20mm and a quad 2pd is better than 4-6 20mm normally carried by the USN by late 42.
> Even in your papers when describing the air battles in 1942 there were a number of examples of the attacking aircraft turning away in the face of 5in fire. There were examples where the reccomendation was that the 5in should be retained for putting barrage fire up over the carriers. However I can find no examples of any RN report saying that the 4.7in helped in turning away Japanese air attacks (I do know of one where his happened using the 5.25). I find no examples of reports saying that the 4.7in actually helped when firing barrage fire over the carriers. Plenty saying that it should be able to, but none saying that it did.
> 
> .



There are numerous examples here:
http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38377.pdf
of Luftwaffe and IAF aircraft refusing to come through the gunfire put up by the destroyer screens.


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## parsifal (Feb 21, 2013)

RCAFson said:


> There are numerous examples here:
> http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38377.pdf
> of Luftwaffe and IAF aircraft refusing to come through the gunfire put up by the destroyer screens.




The heavy losses for Destroyers to air attack dont support what you are suggesting here, in my opinion.. Just comparing the RN fleet destroyers to the USN Fleet destroyers would suggest the Axis were less frightened of penetrating of British screen than they were the USNs....granted the RN was in action for longer and fighting with their backs to the wall for longer. We dont know the numbers of enemy a/c that entered RN combat zones, but we do have some figures for the USN. They say more than 7000 enemy aircraft entered their battle zones.. These enemy aircraft intrusions managed to sink 24 US Destroyers (along with other ships).

We dont know the numbers of enemy aircraft that entered British screens. We do know that about 1200 sorties entered BPF airspace in 1945, comparedf to over 10000 faced by the USN. In both cases, the majority of aircraft never entered the flak zones of the two fleetsbut that iis still a heck of a lot of aircraft. Not all of these were kamikazes, and not all were able to enter the defensive screens of the two forces.

However, for the entire war (1939-45, the British lost 56 DDs to air attack, according to Janes war loss section in the 44-45 edition (published after the war). By comparison the USN suffered the loss of 24 DDs to air attack. The RN was much smaller, and suffered on the defensive for a lot longer than the USN, however, on the other hand, unlike the germans, the Japanese continued to pour vast proportions of their air strength into anti shipping operations until the very end. Over 12000 sorties against allied shipping in 1945 alone, involving well over 6000 aircraft. And thats in 1945 only. In terms of total DDs (fleet DDs) the USN had about twice as many as the RN during the war, roughly speaking.

It cannot be said that the axis were hesitant to penetrate RN controlled airspace with those losses. im sure that it happened , but as a general trend, naa, not possible. There may be reasons for it, but it is simply misconstruing the true picture to suggest that the RN could cuccessfully deny or scare off German attacks to a greater extent than anybody else.


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## parsifal (Feb 21, 2013)

> RN contact with the 5in/38 was very limited.



Not in the Pacific, where it was observed first hamd over a very long period of time. Im not in a position to say too much about Europe, but would be surprised if it was true there either 



> I don't really care what officers thought - it is the results that they obtained that matters.



Really. Apart from demonstrating incredible disrespect and breathtaking arrogance, I would simply suggest that these men were in a better position to observe what was happening than you are. Or me for that matter.




> One of the huge problems is that the USN was reporting great things about the 5in/38 that simply weren't true and this must have swayed opinion in both navies; something along the lines of: "...Gee we got hammered in Norway and Crete yet the USN appears to be shooting the Japanese out of the Pacific skies...their system must be better..."




USN misreporting was no worse or better than the RN. Both made errors in overclaiming. However even allowing for that, the USN was shooting down many times the number of aircraft than the RN ever even claimed.....In 1945 they shot down at least 900 enemy aircraft which is about 3 times the entire wartime tally for the RN. They suffered losses in Destroyers about half that suffered by the RN, despite being subjected to what I thin is obviously a much higher number of enemy sorties. I dont think the men making these observations were swayed by what they read so much as what they saw. And in that regard they have an immeasurably better understanding of the real situation than you or i can ever hope to achieve. 




> The other problem is that if a staff study states that a 40deg gun and a heavy CIWS is better than a 80deg gun and a light CIWS, it doesn't mean that line officers will agree, *even if the study is correct.*



But those same line officers observed the relative success of the USN, the relative lack of success of their own AA, and realized the truth. Then they wrote it down, and told their bosses. their bosses believed them and started to make changes as the line officers had recommended. that isnt the disgruntled rumblings of a couple of junior officers or chairbound admirals who dont know what they are talking about. Its the mark of a couple of highly respected commanders, who observed what was happening and passed that information up the chain as they should. the command structure responded to their advice and began to make changes....being to adopt US methodss and techs. Thats not anything like what you are now trying to argue. thats a command system working as it should......the support commands listening to what the frontline is sayin and passing experience gained to the planners for appropriate action. in this case steps were being made to respond and rectify the obvious waknesses in the British defences. 

I just cannot fathom why you are seriously attempting to argue along these lines. its a nonsense, and deep down I think you know it.... 



> The average RN destroyer officer probably thought his weaponry was inadequate to the task, and he was right, but that doesn't mean that an alternate FC system and a reliance on a HA 5in gun as in MK33 or Mk 37 USN destroyers would have produced better results - and there is no evidence that USN destroyers were doing better than RN destroyers in 1942


.

These were not a couple of disgruntled 2 ringers , they were flag officers observing for themselves the far more efficient US systems at work for themselves. They couldnt comment on the 1942 situation, but they could see for themselves what the results were in 1945. It wasnt a case of being disgruntled. Rawlings and frasers reports heaped great praise on certain weapons and told it like it was for others. They highlighted the great success of the airborne deterrent, they mentioned the ability of the 4.5s to engage (whilst the 4.7s remained silent, or had no effect) , they knew they needed the Bofors because of what they had seen in TF58. Package this how you like, the facts are the people in a position to know do not support your rather extreme views on this subject.


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## Glider (Feb 21, 2013)

RCAFson said:


> There are numerous examples here:
> http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38377.pdf
> of Luftwaffe and IAF aircraft refusing to come through the gunfire put up by the destroyer screens.



First of all do you seriously expect the Gazette to say our AA guns were not up to the job. Secondly can you tell me where there is an example of the attacking aircraft turning away. I have seen a number of comments such as theenemy pressed home their attack, one where the Beaufighters withdrew but the enemy bombers dropped their bombs, but so far none that have turned away.


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## Glider (Feb 21, 2013)

If I can give a few examples

29 A very heavy determined and skilfull dive bombing attack enveloped the fleet

32 a second attack developed on the Illustrious

39 dive bombers attaked Southampton

48 Three of the aircraft pressed on through the barrage of the destroyers (note these were TB)

50 Another TB dropped his torpedo 500 - 1000 yards off the bow of the Nelson one of this unit was shot down by the destroyers, claimed by the Laforey a destroyer armed with DP guns

54 A TB attack deflected by the destroyers fire

55 Three of those that turned away came back one of which was shot down by the Ark Royal and Nelson

85 Some enemy aircraft turned away when fire was opens, probably CR 42 (can you blame them)

108 Zulu heard four aircraft buit only saw one that was so close the guns could not track fast enough

26 page 4496 High Level bombers attacked. As uual the bombers were not seen until they reached bombing position and gunfire was ineffective

31 page 4496 the only success I can find. The gunnery of the fleet failed to score any known kills but did much to break up the attack
However this was a fleet and we do not know which HAA were involved.


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## RCAFson (Feb 21, 2013)

Glider said:


> First of all do you seriously expect the Gazette to say our AA guns were not up to the job. Secondly can you tell me where there is an example of the attacking aircraft turning away. I have seen a number of comments such as theenemy pressed home their attack, one where the Beaufighters withdrew but the enemy bombers dropped their bombs, but so far none that have turned away.



Yes, I absolutely expect Admirals, such as Cunningham and Somerville to speak their mind. 




> 8. The remarks of the Commanding Officer,
> H.M.S. JAGUAR are of considerable interest,
> in particular his practice of firing 4.7-mch barrage
> over the stern of a ship attacked by
> ...



Anytime a TB attacked a destroyer it was a success for the destroyer screen since it had less chance of hitting a destroyer than a merchant ship, and indicated that the fire from the destroyers deterred the attackers from pressing through.


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## RCAFson (Feb 21, 2013)

parsifal said:


> Not in the Pacific, where it was observed first hamd over a very long period of time. Im not in a position to say too much about Europe, but would be surprised if it was true there either



There were instances of RN and RAN destroyers working with USN ships, but by and large the USN and RN worked independently.





> Really. Apart from demonstrating incredible disrespect and breathtaking arrogance, I would simply suggest that these men were in a better position to observe what was happening than you are. Or me for that matter.



Sorry, but from 70 years on we have access to far more information about the "big picture" than those on the spot. The other fact is that there was a great divergence of opinion within the RN (and USN) regarding the value of HA guns and destroyer armament, as the excerpts from March and USN Action Reports show. There is a general belief prevalent now that those RN officers who advocated 40deg guns along with an AA FC system were wrong, but in the main I believe that this stems from the highly inaccurate reports being issued by the USN in 1942 regarding the efficacy of their 5in/38 guns and destroyer FC systems - the reality appears to be that they were no more successful or accurate than their RN counterparts.







> USN misreporting was no worse or better than the RN. Both made errors in overclaiming. However even allowing for that, the USN was shooting down many times the number of aircraft than the RN ever even claimed.....In 1945 they shot down at least 900 enemy aircraft which is about 3 times the entire wartime tally for the RN. They suffered losses in Destroyers about half that suffered by the RN, despite being subjected to what I thin is obviously a much higher number of enemy sorties. I dont think the men making these observations were swayed by what they read so much as what they saw. And in that regard they have an immeasurably better understanding of the real situation than you or i can ever hope to achieve.



Sorry, but USN overclaiming was much worse than RN overclaiming, and USN overclaims were staggeringly inaccurate and optimistic:

At Coral Sea they claimed 49 AA kills of which about 37 were claimed by the USN carrier TG and they got 3. DDs in the CV screen claimed 11.
At Midway they claimed 20 AA kills and got 3. DDs claimed 8.
At Eastern Solomons they claimed 30 and got 4. DDs claimed 5.
At Santa Cruz they claimed 127 and got ~25. DDs claimed 22.
Yet the actuality is that USN destroyers probably shot down no aircraft in the first 3 actions and only a handful at Santa Cruz.

The RN claimed 740 AA kills by Dec 31 1942 - I don't know the number for the entire war. But the number of attacking sorties was much higher against the RN than the USN:
HyperWar: HyperWar: War at Sea 1939-1945, Vol. II: The Period of Balance (UK--History of the Second World War)
HyperWar: HyperWar: War at Sea 1939-1945, Vol. II: The Period of Balance (UK--History of the Second World War)
HyperWar: HyperWar: War at Sea 1939-1945, Vol. II: The Period of Balance (UK--History of the Second World War)
The above three tables show ~10,000 sorties against shipping around the UK alone, and when we add in the number of sorties flown against the RN in the Med and Arctic, the number would grow much higher.




> But those same line officers observed the relative success of the USN, the relative lack of success of their own AA, and realized the truth. Then they wrote it down, and told their bosses. their bosses believed them and started to make changes as the line officers had recommended. that isnt the disgruntled rumblings of a couple of junior officers or chairbound admirals who dont know what they are talking about. Its the mark of a couple of highly respected commanders, who observed what was happening and passed that information up the chain as they should. the command structure responded to their advice and began to make changes....being to adopt US methodss and techs. Thats not anything like what you are now trying to argue. thats a command system working as it should......the support commands listening to what the frontline is sayin and passing experience gained to the planners for appropriate action. in this case steps were being made to respond and rectify the obvious waknesses in the British defences.
> 
> I just cannot fathom why you are seriously attempting to argue along these lines. its a nonsense, and deep down I think you know it....


 IMHO they observed the number of AA kill claims made by the USN, and then they drew the wrong conclusions:















> These were not a couple of disgruntled 2 ringers , they were flag officers observing for themselves the far more efficient US systems at work for themselves. They couldnt comment on the 1942 situation, but they could see for themselves what the results were in 1945. It wasnt a case of being disgruntled. Rawlings and frasers reports heaped great praise on certain weapons and told it like it was for others. They highlighted the great success of the airborne deterrent, they mentioned the ability of the 4.5s to engage (whilst the 4.7s remained silent, or had no effect) , they knew they needed the Bofors because of what they had seen in TF58. Package this how you like, the facts are the people in a position to know do not support your rather extreme views on this subject.



The only way to make a valid comparison in 1945 would have been to assemble an RN fleet of equivalent size to the USN fleet, equip it with weapons and FC of comparable vintage and then subject it to comparable levels of attack. There is no way to do that, except theoretically. Without access to RN action reports we can't say what the 4.7in guns were doing. RAN Tribal class were using their 4.7in guns to engage IJ aircraft in the Pacific.


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## vinnye (Feb 21, 2013)

The Crete missions were near suicide missions to recover troops that should not have been sent there in the first place, but never mind - just my opinion.
Given the total air supremacy of the LW - who were pretty good at their job, having had a bit of practice, I am surprised that any RN ship got out! From Wiki :
Force C met up with Rear Admiral Rawling's Force A1 at the Kithera Channel where more air attacks inflicted damage on both forces. A bomb struck HMS Warspite and then the destroyer Greyhound was sunk. King sent HMS Kandahar and HMS Kingston (F64) to pick up survivors while the cruisers Gloucester and Fiji provided anti-aircraft support. "The Rear Admiral Commanding, 15th Cruiser Squadron was, however, not aware of the shortage of antiaircraft ammunition in Gloucester and Fiji...", which were down to 18 and 30 percent of their AA ammunition, respectively, four hours before they were detached to support the destroyers.[52] Gloucester was hit by several bombs at 15:50, several hours after being detached, and had to be left behind due to the intense air attacks. The ship was sunk with 700 ratings and 22 officers losing their lives.

It was a mistake sending the cruisers back to cover the rescue of the survivors of Greyhound. If I remember correctly, the usual procedure was to send a destroyer at night to pick up survivors.
Admiral Cunningham criticized King's decision making during these actions.


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## RCAFson (Feb 21, 2013)

HMAS Arunta:


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## parsifal (Feb 21, 2013)

Good find. I note that the Aruntas report says she fired 60 rounds of 4.7 from 1641 to 1642. i wouldnt read too much into the times....having filled out these very after action reports myself, you tend to just put any duration that kind of fits. She might have been firing for 3 minutes, or 2 minutes, or 1 minute. Its usually a guesstimate that number. The number of rounds is more accurate, and i note that the two 4in HA threw out as much lead as the 4 x 4.7s, in the same time.

According to this report, the Arunta by this time (January 1945) had 6 x 40mm guns. Thats what i understoodas as well (which makes wiki wrong....it says they were not fitted until September 1945). It also says this intruder was brought down by the combined fire of the entire TG. Acoupe of things to note here. Arunta had been working with the Americans since 1942, and had by January 1945, been fully converted to their methods. They had partially re-equipped with US equipment (the Bofors) and did not claim this shoot down as entirely theiur own. It was brought down by the combined fire of the entire TG. Thats an American TG incidentally. 

These were exactly the recommendations that had been made by Rawlings and Fraser, incidentally....people whom you think dont know what they are doing.

As for "by and large the RN and USN worked independantly". Are you serious? Operations by cruisers Australia, Canberra, hobart, Perth, Shropshire, Leandertroopships Kanimbla, Manoora, the operations off palembandg and Sumatra. Look at the strikes into Java, the battles of Coral Sea, Overlord, Husky gosh the list goes on and on. this statement is so staggeringly incorrect I am genuinely shocked


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## RCAFson (Feb 21, 2013)

parsifal said:


> Good find. I note that the Aruntas report says she fired 60 rounds of 4.7 from 1641 to 1642. i wouldnt read too much into the times....having filled out these very after action reports myself, you tend to just put any duration that kind of fits. She might have been firing for 3 minutes, or 2 minutes, or 1 minute. Its usually a guesstimate that number. The number of rounds is more accurate, and i note that the two 4in HA threw out as much lead as the 4 x 4.7s, in the same time.



In terms of weight of metal the 6 x 4.7in fired 3000lb and the 2 x 4in 1050lb but the lethal radius of each 50lb 4.7in burst would have been considerably greater than a 35lb 4in burst. 



> According to this report, the Arunta by this time (January 1945) had 6 x 40mm guns. Thats what i understoodas as well (which makes wiki wrong....it says they were not fitted until September 1945). It also says this intruder was brought down by the combined fire of the entire TG. Acoupe of things to note here. Arunta had been working with the Americans since 1942, and had by January 1945, been fully converted to their methods. They had partially re-equipped with US equipment (the Bofors) and did not claim this shoot down as entirely theiur own. It was brought down by the combined fire of the entire TG. Thats an American TG incidentally.



Yes, it was the combined fire of the TG, and we would have to read the Action Reports of all the engaged ships, to see how many kill claims this one aircraft engendered...not every skipper might have been as modest as Arunta's. The Bofors were probably power worked UK designed Mk VII single mounts of UK or Cdn origin. The Bofors was not originally US in design and most Commonwealth Bofors were built in the Commonwealth. In any event, I think we can all agree that Arunta had a very considerable CIWS. This appears to be Arunta in 44/45 and the Mk VII (actually theymight be Mk V Bofin mounts)Bofors are plainly visible:
http://upload.wikimedia.org/wikipedia/commons/f/f5/HMAS_Arunta_SLV_AllanGreen_1.jpg

The sponson mounted Bofors have superior arcs of fire yet the quad pom-pom fired 192 rounds or 48/barrel. The 3 Bofors fired 131 rounds or 43.7/barrel. Total weight of metal = 346-326lb (HV shell weight = 1.7 or 1.8lb) for the pom-pom and 262lb for the Bofors.



> These were exactly the recommendations that had been made by Rawlings and Fraser, incidentally....people whom you think dont know what they are doing.



I don't want to put words into people's mouths, that they might not have said or whose comments might be taken out of context. In any event, their opinions were shaped by the reports that they read as well as by what they saw.



> As for "by and large the RN and USN worked independantly". Are you serious? Operations by cruisers Australia, Canberra, hobart, Perth, Shropshire, Leandertroopships Kanimbla, Manoora, the operations off palembandg and Sumatra. Look at the strikes into Java, the battles of Coral Sea, Overlord, Husky gosh the list goes on and on. this statement is so staggeringly incorrect I am genuinely shocked



If we consider the total number of destroyer sorties conducted by the RN and USN, we would find that the number of sorties where they operated in company with one another would be exceedingly small.


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## RCAFson (Feb 21, 2013)

Actual average rate of fire for a Mk 37 equipped Gleaves class destroyer, USS Edison:




> A total of 362 rounds were fired, 74 at the shore battery, 20 in the first engagement, and 268 in the second destroyer engagement, of which it is estimated that 200 rounds were fired at the first destroyer and 68 at the second. All firing was director-controlled, rapid, continuous fire. The average gun range for the first firing was 9,500 yards, for the second 14,000 yards, and for the third 12,500 yards... ...It is particulary pleasing that the guns maintained a sustained rapid fire of 268 rounds (average 68 rounds per gun) at an estimated rate of at least 12 shots per gun per minute without casualty.[1]
> [1]United States Navy, AntiAircraft Action Summary, July 1942 to Dec 1942 (Information Bulletin No. 22), p.161-163
> USS Edison (DD-439) - Wikipedia, the free encyclopedia



and here's the quote from HMS Kimberly's action report at Narvik from March:

_"Salvos fired about 180 in all...drill to guns very good, great part of the action a loading interval of about 5 seconds was achieved..." _

The actual quote is somewhat longer and details minor problems with ejected casings and problems with communications, as would be expected from such an intensive amount of gunfire. The report also states that _"...the loading numbers were fairly exhausted at the end but no loading delays occurred...D.C.T. firing was used..."_


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## parsifal (Feb 21, 2013)

The key here are twofold. Edisons report says "at least" which means they never went lower than. it does not mean that the average sustained raof was 12 rpm. By definition, because it never dropped beloiw 12rpm, will be higher, over a sustained period. Fedhala incidentally was open water, and the conditions were rough. from memory also the types of targets at the beachead kep changing....were there not surface targets, land targets and airborne targets all present. if so, it may well be that Edison was changing from AA to HE to SAP at various intervals, and this may well have affected the rof. maybe not....would have to look more closely 

Before I make any comment about Kimberley, would need to see the Action Report. And once again, entirely irrelevant, because it is an engagement in the hoirizontal plane....low angle gunfire against a surface target. No argument about sustained rof against surface target and could use contact fusing. In the vertical, its an entirely different matter, wher there were problems with the rammers above 30 degrees and fusing still had to be by hand fusing, because of the timers to be set. Also problems of slow turret traverse and elevation not a factor in a statis shoot, or against a relatively static surface target. The snippet you did provide, suggest s a certain relief that there werent any stoppages, which in fact suggest that they expected stoppages but they didnt happen.


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## Glider (Feb 21, 2013)

RCAFson said:


> Yes, I absolutely expect Admirals, such as Cunningham and Somerville to speak their mind.
> 
> 
> 
> ...



We all indicated that the RN DD would be of some use against torpedo bombers, I couldn't find any high level, medium level or Dive bomber attack that was turned back by the fire of the destroyers. All the examples you gave were torpedo bombers. As I said I am aware of one report when the 5.25 guns forced high level bombers to turn away but that is an exception.

It is of course against these targets that the HA gun is of assistance


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## RCAFson (Feb 21, 2013)

parsifal said:


> The key here are twofold. Edisons report says "at least" which means they never went lower than. it does not mean that the average sustained raof was 12 rpm. By definition, because it never dropped beloiw 12rpm, will be higher, over a sustained period. Fedhala incidentally was open water, and the conditions were rough. from memory also the types of targets at the beachead kep changing....were there not surface targets, land targets and airborne targets all present. if so, it may well be that Edison was changing from AA to HE to SAP at various intervals, and this may well have affected the rof. maybe not....would have to look more closely
> 
> Before I make any comment about Kimberley, would need to see the Action Report. And once again, entirely irrelevant, because it is an engagement in the hoirizontal plane....low angle gunfire against a surface target. No argument about sustained rof against surface target and could use contact fusing. In the vertical, its an entirely different matter, wher there were problems with the rammers above 30 degrees and fusing still had to be by hand fusing, because of the timers to be set. Also problems of slow turret traverse and elevation not a factor in a statis shoot, or against a relatively static surface target. The snippet you did provide, suggest s a certain relief that there werent any stoppages, which in fact suggest that they expected stoppages but they didnt happen.



Edison was firing at surface targets, just as Kimberly was. Again there are no additional difficulties in loading either the 5in/38 or the power rammed 4.7in twin at higher angles and both mounts had machine fuze setters, although the integral hoist-fuzesetters on Edison were theoretically more efficient. Conditions at Casablanca were quite calm.

The other key factor is that in surface fire, Kimberly would have 50% more firepower than Edison, and equal or greater AA firepower up to 40deg elevation depending on the rates of fire:
RPM-Kimberly / RPM-Edison / totals K-E

12 / 12 / 72-48 (50% advantage to Kimberly)
10 / 12 / 60-48 (25% advantage to Kimberly)
12 / 15 / 72-60 (20% advantage to Kimberly)
10 / 15 / 60-60 (tie)

and I have discounted Kimberly's 4in entirely, but it would certainly break any ties...


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## RCAFson (Feb 21, 2013)

Glider said:


> We all indicated that the RN DD would be of some use against torpedo bombers, I couldn't find any high level, medium level or Dive bomber attack that was turned back by the fire of the destroyers. All the examples you gave were torpedo bombers. As I said I am aware of one report when the 5.25 guns forced high level bombers to turn away but that is an exception.
> 
> It is of course against these targets that the HA gun is of assistance



Here's bit of info I gleaned from Amazon:






Note that Jaguar used controlled fire against the DBs prior to their attack on Illustrious. This is an extract from Jaguar's Action Report, and is from The Royal Navy and the Mediterranean Convoys.

The fact that Luftwaffe DBs were not turned back on this occasion (or any other) doesn't mean that the 4.7in fire was ineffective, since for all we know it might have been worse without it. The big problem was that Illustrious was not at the centre of a T.G. as per the USN carriers in the Pacific, rather she was detached with a relatively small screen. The larger part of the RN destroyers were covering the convoy itself, which reached Malta with no losses, IIRC, on this occasion. If Illustrious was screened by a flotilla of destroyers as per the USN CVs, a whole lot more firepower would have been concentrated on the DBs, prior, during and after their attacks.


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## parsifal (Feb 21, 2013)

RCAFson said:


> Edison was firing at surface targets, just as Kimberly was. Again there are no additional difficulties in loading either the 5in/38 or the 4.7in twin at higher angles. Condition at Casablanca were quite calm.



Sorry, but a total distortion of facts. I will not comment directly on the Kimberley action until the full details come to light. However for the edison, the preconditions you describe were simply not there. Firstly, the actions in Narvik were all undertaken withiin sheltered waters, whereas for the Edison, the conditions were sea state 3 and rising. not much to worry about, but thye are not the same. 

For the Kimberley, I do not know which days action you are referring to (I will tonite though). The Edison however was attempting to deal with multiple threats, some airborne, some under the ocean, some stationary and some underway. The crew, to say the least would have been extremely busy as they chased the French Commandant Delage and La Gracieuse back into the harbour. then they were confronted with fire from the Jean Bart and the shore batteries....and attempts by the submarines Tonnant, Meduse and Antiope, against the capital ships Edison was escorting. These submarines were vigorously counterattacked by USN forces, including Edison, which again would affect her gunfire....you cannot maintain a good rof whilst manouvering to sink a sub....(which was achieved incidentally).

But then why am i bothering. if information doesnt suit your purposes you will simply reject it. And it doesnt matter who, I still cannot get over your rejection of the official reports to the Admiralty given by the men on the spot, who just happen to be the best and most competent carrier commanders from the RN at that time, and your stated preference to book learnt theory over any operational or practical experience. I think I can say on behalf of those of us that do have operational experience, including some expereince on some of the equipment you are quoting academically from, its a little unbelievable your dismissal of these mens expertise. 

As to your claim about the 4.7 having no problems at higher elevations...well if true (which it isnt) that means that it was better than the 4.5 (which replaced it, because it was a true DP weapon) , which Ive seen and used. The 4.5 did have some difficulties when firing at higher altitudes. If the RN had no difficulties at higher altitudes with the 4.7, and the 4.7 could fire at 16-20 rpm at those altitudes as you claim why on earth did they bother changing to the 4.5, which from my expereience had a max rof at elevation of just under 20 rpm, with VT fusing . . Never saw the 5/38, but did see the auto loaded version of it....had no problems at those altitudes at a high rof (about 60 rpm in the automated version) .

This is really getting ridiculous. You are not really debating, or discussing. you are lecturing, as am i now. We really should change the subject and move on


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## RCAFson (Feb 21, 2013)

parsifal said:


> As to your claim about the 4.7 having no problems at higher elevations...well if true (which it isnt) that means that it was better than the 4.5 (which replaced it, because it was a true DP weapon) , which Ive seen and used. The 4.5 did have some difficulties when firing at higher altitudes. If the RN had no difficulties at higher altitudes with the 4.7, and the 4.7 could fire at 16-20 rpm at those altitudes as you claim why on earth did they bother changing to the 4.5, which from my expereience had a max rof at elevation of just under 20 rpm, with VT fusing . . Never saw the 5/38, but did see the auto loaded version of it....had no problems at those altitudes at a high rof (about 60 rpm in the automated version) .
> 
> This is really getting ridiculous. You are not really debating, or discussing. you are lecturing, as am i now. We really should change the subject and move on



The 4.5in used a far superior shell design which gave better range and barrel life but the actual guns were much the same and almost identical externally and, of course, the 4.7in was limited to 40degs. 

As March indicates there was an intense debate in the RN over destroyer armament - the big problem is that no one has bothered to present both sides of the debate; only the side that considered that the USN was correct has recieved any serious consideration yet the argument was, by no means, cut and dried.


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## Glider (Feb 22, 2013)

RCAFson said:


> Here's bit of info I gleaned from Amazon:
> 
> View attachment 225534
> 
> ...



So to sum up
We agree that there are no examples of German, Italian or Japanese level or dive bombers being turned back by the fire of the RN 4.7in guns. We agree that there are examples of Japanese aircraft being turned back by the fire of the USN 5in.

We have an example of the tactics being developed as the war progressed which worked for the USN but none of those tactics actually working for the RN.

We agree that the RN using longer range 4.7in fire might help the ships they are covering but are very exposed themselves to aircraft attacking them as they only have 35 seconds in which they have a chance to defend themselves. 

We agree that the twin 4.7 could be used with some effect against torpedo bombers

We agree that in this situation the RN using twin 4.7 are unable to even open harrasing fire against bombers trying to bomb them as they released their bombs.

We agree that had the RN destroyers been equipped with HA 5in they would have been able to fire at aircraft attacking them up until bomb release and had twice as long to fire at the target.

Finally we agree that the RN went to DP guns just as fast as they could 

I think we are getting somewhere

Re this statement of yours


> As March indicates there was an intense debate in the RN over destroyer armament - the big problem is that no one has bothered to present both sides of the debate; only the side that considered that the USN was correct has recieved any serious consideration yet the argument was, by no means, cut and dried.


The fact that the Tribals were equipped with a twin 4in gun, that the last two Tribals were built with 8 x 4in and that ALL navies went with DP guns as a result of war experience proves that the the USN approach was correct. Its also worth remembering that the IJN also went the same route as the USN. Their guns were not as good as the USN but they continued with the Akizuki Class which seem to be highly regarded by all.


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## RCAFson (Feb 22, 2013)

Glider said:


> So to sum up
> We agree that there are no examples of German, Italian or Japanese level or dive bombers being turned back by the fire of the RN 4.7in guns. We agree that there are examples of Japanese aircraft being turned back by the fire of the USN 5in.



I don't know of any examples of IJN DBs being turned back by 5in/38 destroyer fire. 



> We have an example of the tactics being developed as the war progressed which worked for the USN but none of those tactics actually working for the RN.



Huh? I guess the RN escorted convoys to Malta and the USSR were all sunk...not! RN weapons and tactics evolved and improved during the war and generally were able to defeat Luftwaffe/IAF attacks as long as the fleet stayed together so that it could develop sufficient AA firepower...the USN, in their first years of the war generally fought in tight, compact CV centered TGs, which allow for a good concentration of fire while destroyers were seldom targeted. I have argued that the combination of the ineffective MK33 GFCS and the 5in/38 would have been worse than what the RN had in 1940, while the Mk 37-5in/38 (on a treaty hull) also meant a drastic reduction in armament and CIWS, to the point where it would have been less effective than RN designs with the 4.7in twin mount and heavy CIWS.



> We agree that the RN using longer range 4.7in fire might help the ships they are covering but are very exposed themselves to aircraft attacking them as they only have 35 seconds in which they have a chance to defend themselves.


I don't know where you get 35 seconds from - I have taken some pains to demonstrate that the length of the predicted fire engagement varies with target speed and altitude, but in any event RN 4.7in twin mount destroyers had an exceptionally heavy CIWS by design so they were never in a position where they couldn't defend themselves. USN destroyers were fortunate that, by and large, they were not singled out for attack by IJN DBs but on those few occasions when they were, they seemed to get sunk despite their 5in HA guns.



> We agree that the twin 4.7 could be used with some effect against torpedo bombers



and low level glide bombing, which was a favorite Luftwaffe tactic.



> We agree that in this situation the RN using twin 4.7 are unable to even open harrasing fire against bombers trying to bomb them as they released their bombs.


 Again this is altitude dependent. The pom-pom could achieve harrasing fire up to 10,000ft.



> We agree that had the RN destroyers been equipped with HA 5in they would have been able to fire at aircraft attacking them up until bomb release and had twice as long to fire at the target.



Again, this is altitude dependent. The problem being that HA 5in mounts weren't truly compatible with treaty displacement limited destroyer designs. The USN was forced to remove the 5th mounting on almost all their pre Fletcher designs and had to severely limit their CIWS as well. Trade-offs, tradeoffs...



> Finally we agree that the RN went to DP guns just as fast as they could



Yes, the RN introduced the 4.7in DP twin mount with the Tribal class, but they did not agree that ~80deg mountings were necessary until much later. I would argue, that the optimal destroyer mount would have been a 4.7in/4.5in 55 deg twin mount. IMHO, elevations above 55degs were not worth the added weight and complexity, which inevitability meant a reduction in the CIWS and/or the number of main armament guns carried. 





> The fact that the Tribals were equipped with a twin 4in gun, that the last two Tribals were built with 8 x 4in and that ALL navies went with DP guns as a result of war experience proves that the the USN approach was correct. Its also worth remembering that the IJN also went the same route as the USN. Their guns were not as good as the USN but they continued with the Akizuki Class which seem to be highly regarded by all.



I've gone over the decision to mount a twin 4in on the Tribals and it is much more complex than you seem to want to accept. The last (post war) Tribals went with 8 x 4in but again this was not a straightforward decision to adopt purely HA mountings, the addition of increasing amounts of topweight (the Mk VI was very heavy) probably played a role in going to the much lighter 4in twin, that and the outdated 4.7in ammo and the lack of an RPC mounting. The other factor is that late war and post improvements in FC (specifically the USN MK 56 GFCS and the apparently similar RN Flyplane GFCS) and VT ammo made HA fire much more effective, but even so during the war the 4.7in twin was retained:


> THE Halifax TRIBALS
> The original intention of the two Dominions had been to equip themselves
> with a flotilla 'Tribals' each, as counterparts to the first RN order. In the event
> Australia cancelled all save three but Canada persisted with her ideas to the
> ...



The IJN HA 5in mountings did not have loading trays - this meant that the guns could not be loaded at all angles which drastically cut their rate of fire at higher elevations. The 3.9in gunned Akizukis had no more firepower than some RN sloops and this on a 3000 ton design. Overall IJN destroyer design shows very little emphasis on HA firepower.


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## parsifal (Feb 22, 2013)

> So to sum up
> We agree that there are no examples of German, Italian or Japanese level or dive bombers being turned back by the fire of the RN 4.7in guns. We agree that there are examples of Japanese aircraft being turned back by the fire of the USN 5in.


Yes, agree



> We have an example of the tactics being developed as the war progressed which worked for the USN but none of those tactics actually working for the RN.



Not sure. In the pacific we have examples of the british Commanders observing the releively far greater effciency of USN equipment, and tehniques,and more or less adopting those techniques, whereupon RN performance in AA defence showed a marked improvement. In the ETO I would say RN methods worked, but at a heavy cost, that cost would probably have been reduced if the RN had adopted US methods and technologies earlier. 



> We agree that the RN using longer range 4.7in fire might help the ships they are covering but are very exposed themselves to aircraft attacking them as they only have 35 seconds in which they have a chance to defend themselves.



Im not even sure I agree with that. I dont nelieve the 4.7 was an effective AA weapon at all. It had a theoretical capability, and occasionally might have a success here or there, but had too many limits to be effective against any type of airborne target. 



> We agree that the twin 4.7 could be used with some effect against torpedo bombers



To a dgree , yes, but only to the extent that they could be pointed in the general direction of the target. there were too many other limits to the wepon for it to be ever considered "effective". If youve been deliberate in choosing your words as "some effect", I could agree with that. if your intent was to suggest "effective, then no, not really



> We agree that in this situation the RN using twin 4.7 are unable to even open harrasing fire against bombers trying to bomb them as they released their bombs.



I substantially agree with this. Theoretically against bombers below 3000 feet they and at long range they could bring fire to bear. in reality in most situations they were helpless. 



> We agree that had the RN destroyers been equipped with HA 5in they would have been able to fire at aircraft attacking them up until bomb release and had twice as long to fire at the target.



Absolutely, agree completely 



> Finally we agree that the RN went to DP guns just as fast as they could



Yep, but just to clarify, the 4.7 was not a true or effective DP weapon. And the RN paid a heavy price for that prewar error of judgement. They also made a mistake in their choice of HACS 



> I think we are getting somewhere



With me, yes.



> The fact that the Tribals were equipped with a twin 4in gun, that the last two Tribals were built with 8 x 4in and that ALL navies went with DP guns as a result of war experience proves that the the USN approach was correct. Its also worth remembering that the IJN also went the same route as the USN. Their guns were not as good as the USN but they continued with the Akizuki Class which seem to be highly regarded by all.



Agree completely. well put....


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## RCAFson (Feb 22, 2013)

Some more info on 5in/38 rates of and Mk33/37 effectiveness:


> 3. At 1641 a group of five enemy planes (later identified at TB) were sighted in line abreast or in a broad Vee formation on bearing 350° (T), distance about 10 miles, position angle 10° heading toward port beam of Yorktown. Shortly thereafter at least four planes, believed enemy, shot down by our fighters, were sighted falling in flames bearing about 10° to left of above planes. Vincennes and Benham opened fire on enemy planes with 5" A.A. battery. Immediately thereafter ships on attack side of formation (port flank) commenced firing with A.A. weapons, medium and close range. Our fighters followed torpedo planes in to the screening circle of cruisers and destroyers and then sheered off to pick them up after torpedo release. One friendly fighter was seen to crash in a vertical dive and one additional Jap plane was brought down in flames before the first torpedo bomber reached the screening circle. The Jap planes at this point were converging singly toward the carrier over an arc of about 45° in a shallow glide and a slow zigzag course at a speed approaching 200 knots. *While A.A. fire was heavy, no plane was observed brought down by surface ship fire prior to reaching the torpedo release point*...
> 
> 5. Of the estimated four Jap planes which reached the carrier, three were observed shot down during retirement: one by own VF, *one by Balch short range weapon fire (1.1 and 20 MM battery), and one by Balch 5" battery firing a 2.0 second barrage* using A.A. common projectile fitted with the Mark XVIII time fuze...
> 
> ...



So the only IJN planes observed shot down, were those hit by USS Balch, (Porter class)which didn't have any AA FC system, but had a heavy CIWS similar to the quad pom-pom found on RN twin 4.7in Tribal-JKN class destroyers. I suspect that the slow computing speeds of the Mk33/37 were partially responsible for the slow rate of fire.

Enterprise's comments on the Mk 33 GFCS after Santa Cruz:



> DEFENSE BY ANTI-AIRCRAFT BATTERIES
> Again fire control radar did not pick up any target. At no time since its installation has it been useful. Previously submitted recommendations relative to its modification are again stressed. The precision requirements necessary to put this equipment on an aerial target apparently cannot be met in action.
> Neither 5-inch director picked up targets, although the rangefinder in Sky Forward was able to do so.
> 
> ...



Enterprise's "official bag" ( see post 271) was 30 AA kills at Santa Cruz, the real number being substantially less and so the number of 5in kills must have been far fewer still.


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## Glider (Feb 22, 2013)

RCAFson said:


> > Huh? I guess the RN escorted convoys to Malta and the USSR were all sunk...not! RN weapons and tactics evolved and improved during the war and generally were able to defeat Luftwaffe/IAF attacks as long as the fleet stayed together so that it could develop sufficient AA firepower...the USN, in their first years of the war generally fought in tight, compact CV centered TGs, which allow for a good concentration of fire while destroyers were seldom targeted. I have argued that the combination of the ineffective MK33 GFCS and the 5in/38 would have been worse than what the RN had in 1940, while the Mk 37-5in/38 (on a treaty hull) also meant a drastic reduction in armament and CIWS, to the point where it would have been less effective than RN designs with the 4.7in twin mount and heavy CIWS.
> 
> 
> I am dissapointed to note that you hadn't realised that the convoys to Russia and Malta had suffered very heavy losses to aircraft.
> ...


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## RCAFson (Feb 22, 2013)

Glider said:


> I am dissapointed to note that you hadn't realised that the convoys to Russia and Malta had suffered very heavy losses to aircraft.



So the USN losses to IJN aircraft in 1942 indicate that everything was perfect? - seems like you have a double standard. 





> The 35 seconds comes from the diagram you posted showing the AA coverage of a Tribal class destroyer. Its my misake it actually says 37 seconds. It also shows that the effeective range of the 2pd was a lt less than th 10,000 ft you now claim.



37 seconds is for one specific example of aircraft speed and altitude. 



> Clearly the RN didn't believe it was 10,000 ft


 
Remember this?:


> A signal was sent to the C.s-in-C. "Theoretical investigation shows that the lethal value of a single F.K.C. controlled 4-in. gun in a destroyer against dive bombers is less that that of an Oerlikon up to 3000 ft. and considerably less than that of a *4-barrelled pompom up to 10,000 ft*. Therefore propose to replace 4-in. H.A. in 'J' class and later and the 3-in. in 'E' to 'I' by the second set of T.T.s as opportunity occurs or by additional Oerlikons."


 From Navweaps:
2pdr: _AA Ceiling with HV shells	13,300 ft. (3,960 m)_ which is basically the limit imposed by the self destructing ammo.



> Clearly this is rubbish. A treaty displacement destroyer could carry 4 x 5in for the same weight as the 6 x 4.7 in a JKN


*Exactly; The 5in/38 + Mk37 = a 50% reduction in firepower and a lighter CIWS.*




> Again this is rubbish. The people invovled in the development and design did all they can to increase the elevation. They wouldn't have done that unless they thought it worth the effort.
> 
> Your stories and theories keep changing. One arguement you used was that the RN wanted to increase the short range weapons and decided to install the 4in. This would be akin to tryng to go clay shooting with a rifle, it was totally without logic. Then you switched to the weight issue, ignoring the act that the tribals never had a problem with weight. As we have seen at the end of the war they had 6 x 40mm added without any reduction of any kind.
> 
> It was a very straightforward decision, the 8 x 4in was a better all round weapons suite than the mixed LA and DP 4in. You are going on about weight again but it wasn't a problem for the Tribal.



Again, this is not the case. The RN, RCN and RAN all the option to outfit the tribals with an all 4in HA armament from day one, yet they never did so, but retained the 4.7in twin throughout the war and even increased it's AA capability. Post war the decision to go with an all 4in had a multifaceted origin, but in any event the topweight imposed by the Mk6 would have meant that reductions in topweight had to be found in other areas:





Here's the effect of moving from the K DCT to the MK VI:


> D.G. and A.A.W. asked fitting Mk. IV Bofors provided sutffcient compensation to retain Mk. VI director, but the D.N.C. said "no, the 3 tons excess weight at 54 ft. above the keel is equivalent to topweight additional 20 tons upper deck".
> March p.426


so adding 6 or 7 tons by going from the original Tribal DCT and RFD would require ~50 tons of topweight compensation - this practically necessitated removal of the 4.7in twins. It also shows the penalty paid by the USN for the MK37 DCT which was 2-4 tons heavier than the MK VI and the need to reduce topweight on the original Tribals via the substitution of a 4in for a 4.7in...



> I am afraid I was expecting better from you than this. If the Japanese didn't have any emphasis on HA firepower why did they have destroyer 5in with an elevation of 75 degrees.
> If they didn't have any emphasis on HA firepower why did they build the Akizukis 90 degree elevation and a very fast rate of fire.



I was expecting a bit more understanding of the requirements needed for a useful RoF at high angles, from you. Every time the IJN 5in needed to be reloaded it had to be brought to 10deg elevation, loaded and then elevated to the required angle. This simply doesn't show an emphasis on HA fire and if the RN had done something similar you'd probably be using it as proof of their incompetence. The IJN built a handful of destroyers that emphasized AA (less than 5% of construction) and then you hold this out as proof of IJN concern about destroyer AA?


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## Juha (Feb 22, 2013)

RCAFson said:


> ...I was expecting a bit more understanding of the requirements needed for a useful RoF at high angles, from you. Every time the IJN 5in needed to be reloaded it had to be brought to 10deg elevation, loaded and then elevated to the required angle. This simply doesn't show an emphasis on HA fire and if the RN had done something similar you'd probably be using it as proof of their incompetence. The IJN built a handful of destroyers that emphasized AA (less than 5% of construction) and then you hold this out as proof of IJN concern about destroyer AA?



you have clearly forget Matsu/Tachibana class smaller DDs. 

Juha


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## RCAFson (Feb 22, 2013)

Juha said:


> you have clearly forget Matsu/Tachibana class smaller DDs.
> 
> Juha



I didn't consider these to be destroyers, but rather destroyer escorts, as per the Hunt class. Only 32 were built, most in the last year of the war. Even if we consider them destroyers and add them to the Akizuki class, it only comes to ~20% of IJN destroyers.

Also, the Matsu class doesn't appear to have any AA FC system.


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## Glider (Feb 23, 2013)

RCAFson said:


> So the USN losses to IJN aircraft in 1942 indicate that everything was perfect? - seems like you have a double standard.


In 1942 the IJN had without question the best trained and equipped anti shipping aircraft in the world bar none. The USN were fresh into the war, the CIWS relied on 20mm and 0.5mg which lacked the range and the punch. Of course there would be losses, but they were kept managable and the USN took quite a toll of the attcking aircraft.


> 37 seconds is for one specific example of aircraft speed and altitude.


Correct but if you pick a different height you willsee it makes little difference. I repeat whay I have said a number of times. A ww2 destroyer is lucky to hit a ship in 35 seconds, to pretend that you can hit an aircraft, particualy at the long ranges demended by having a 40 deg elevation is a pipe dream.


> Remember this?:


Yes, but I was quoting from the evidence that you supplied to support your argument, nothing more and nothing less. I also note that he is more than happy to replace 1 x 4in gun which is light, with 5 x TT which weigh heaven only knows what, plus additional 20mm and no one raises a comment about weight.



> From Navweaps:
> 2pdr: _AA Ceiling with HV shells	13,300 ft. (3,960 m)_ which is basically the limit imposed by the self destructing ammo.


I note a) that you are now quoting from Navweaps and b) you ommited the second part of the entry where is states that the British considered the 2pd HV to have an effective range of 1,700 yards



> *Exactly; The 5in/38 + Mk37 = a 50% reduction in firepower and a lighter CIWS.*


50% reduction infirepower against ships and a significant increase in firepower against aircraft


> Again, this is not the case. The RN, RCN and RAN all the option to outfit the tribals with an all 4in HA armament from day one, yet they never did so, but retained the 4.7in twin throughout the war and even increased it's AA capability.


The RN did have the chance pre war to equip the Tribals with 8 x 4in but didn't because they wanted to preserve its anti shipping ability and no navy really understood the AA requirement. The RN believed with good reason that the quad 2pd and 8 x 0.5 was a good AA defence as pre war this was about the best in the world. You yourself pointed out that once the war started the RN more or less had to arm the destroyers with what was available, hence the O class being given four second hand ex 1920's 4in probably taken off the cruisers who had these replaced with the more modern twin 4in just before the war. The RN didn't have loads of twin 4in lying around to replace whatever they wanted. New production was sent where possible to new ships.


> Post war the decision to go with an all 4in had a multifaceted origin, but in any event the topweight imposed by the Mk6 would have meant that reductions in topweight had to be found in other areas:
> View attachment 225676


I have read your quote and notice a number of things which you must have missed. In particular the fact that at the end of the day they didn't lose any topweight and only added 20 tons of ballast. When you think of the changes made to the destroyers of almost ALL the other navies this was tiny.



> Here's the effect of moving from the K DCT to the MK VI:
> 
> so adding 6 or 7 tons by going from the original Tribal DCT and RFD would require ~50 tons of topweight compensation - this practically necessitated removal of the 4.7in twins. It also shows the penalty paid by the USN for the MK37 DCT which was 2-4 tons heavier than the MK VI and the need to reduce topweight on the original Tribals via the substitution of a 4in for a 4.7in...


Once again you are getting wrapped up in theory and ignoring what happened. You provided evidence that in 1945 one of the vessels had 1 quad 2pd and 6 x 40 mm. I don't know what the mounting was but its safe to assume that they weighed a lot more than 6 tons between them and we also know that they didn't lose any guns, torpedos, radars or anything else.


> I was expecting a bit more understanding of the requirements needed for a useful RoF at high angles, from you. Every time the IJN 5in needed to be reloaded it had to be brought to 10deg elevation, loaded and then elevated to the required angle. This simply doesn't show an emphasis on HA fire and if the RN had done something similar you'd probably be using it as proof of their incompetence.


I totally agree that the IJN didn't get the design right for the loading of the guns but you cannot deny that they did at et least try for a DP gun and once they realised the problem design a destroyer with AA ability to escort carriers and other high value ships


> The IJN built a handful of destroyers that emphasized AA (less than 5% of construction) and then you hold this out as proof of IJN concern about destroyer AA?


Yes they built a number of AA vessels escort type destroyers as did the RN with the Hunt class. I aslo believe that the RN took the air threat very seriously but made a mistake sticking to the 4.7in LA gun.


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## RCAFson (Feb 23, 2013)

Glider said:


> In 1942 the IJN had without question the best trained and equipped anti shipping aircraft in the world bar none. The USN were fresh into the war, the CIWS relied on 20mm and 0.5mg which lacked the range and the punch. Of course there would be losses, but they were kept managable and the USN took quite a toll of the attcking aircraft.



I bet the boys from Fliegerkorps X would dispute your claim, *but why did the USN need an effective CIWS when they had the mighty 5in/38* directed by the incomparable Mk33 and Mk 37? As for taking quite a toll that's not the case, as I have shown via Lundstrom.




> Correct but if you pick a different height you willsee it makes little difference. I repeat whay I have said a number of times. A ww2 destroyer is lucky to hit a ship in 35 seconds, to pretend that you can hit an aircraft, particualy at the long ranges demended by having a 40 deg elevation is a pipe dream.


There's several things to consider; some aircraft flew lower and slower increasing the engagement envelope and, the RN introduced MT fuzes with longer time settings (45 versus 25 seconds) which combined with type 285 radar to push maximum range out several thousand yards and greatly increased accuracy of the resulting gunfire. As the altitude of the aircraft decreases, so does the differential between a 40deg gun and an ~80 deg gun and at higher elevations the accuracy of both the aircraft and the defensive gunfire decreases.



> Yes, but I was quoting from the evidence that you supplied to support your argument, nothing more and nothing less. I also note that he is more than happy to replace 1 x 4in gun which is light, with 5 x TT which weigh heaven only knows what, plus additional 20mm and no one raises a comment about weight.



Last sentence above : _Therefore propose to replace 4-in. H.A. in 'J' class and later and the 3-in. in 'E' to 'I' by the second set of T.T.s as opportunity occurs *or* by additional Oerlikons."_ The ships were designed with 2 x quintuple tubes so removing the 4in and replacing the tubes gets them back to their design configuration. The RN was always very cautious in terms of weight compensation to ensure adequate stability for their destroyers which had to operate in the bad weather prevalent in the Atlantic and Arctic oceans, along with the possibility of ice formation on the weather decks.




> I note a) that you are now quoting from Navweaps and b) you ommited the second part of the entry where is states that the British considered the 2pd HV to have an effective range of 1,700 yards


 1700 yards = 5100 ft (they considered the Bofors to have the same effective range), but your point was about "harrassing fire" and this could be accomplished up to much higher altitudes - the engagement diagram actually shows a max altitude of ~7500 ft for the pom-pom but in any event at 2300fps (a typical MV of a worn gun in service) the max altitude was well above 10,000ft.



> 50% reduction infirepower against ships and a significant increase in firepower against aircraft


I would say that it amounted to a very minor increase in firepower against aircraft - see your first point, above.



> The RN did have the chance pre war to equip the Tribals with 8 x 4in but didn't because they wanted to preserve its anti shipping ability and no navy really understood the AA requirement. The RN believed with good reason that the quad 2pd and 8 x 0.5 was a good AA defence.


That argument holds water up to April 1940 and then falls apart, as *all the wartime Commonwealth Tribals commissioned with 6 x 4.7in and 2 x 4in.*


> I have read your quote and notice a number of things which you must have missed. In particular the fact that at the end of the day they didn't lose any topweight and only added 20 tons of ballast. When you think of the changes made to the destroyers of almost ALL the other navies this was tiny.


The fact is that ballast was required even with the original design configuration.




> Once again you are getting wrapped up in theory and ignoring what happened. You provided evidence that in 1945 one of the vessels had 1 quad 2pd and 6 x 40 mm. I don't know what the mounting was but its safe to assume that they weighed a lot more than 6 tons between them and we also know that they didn't lose any guns, torpedos, radars or anything else.


If you look at the weight saved by replacing a 4.7in twin with a 4in twin and then removing the quad .5in mounts, it almost exactly balances the weight added by the 6 x 40mm mounts and the additional radar equipment.



> I totally agree that the IJN didn't get the design right for the loading of the guns but you cannot deny that they did at et least try for a DP gun and once they realised the problem design a destroyer with AA ability to escort carriers and other high value ships


The Akizukis were more akin to an RN C class light cruiser than a destroyer but if the IJN had placed an emphasis on destroyer AA firepower they could have fitted the 5in/40 twin onto their fleet destroyers - but they didn't.


> Yes they built a number of AA vessels escort type destroyers as did the RN with the Hunt class.



It looks to me that the Matsus didn't have an AA FC system which the Hunt class did. 



> I also believe that the RN took the air threat very seriously but made a mistake sticking to the 4.7in LA gun.



I have been arguing that the treaty limited RN destroyers with the 4.7in twin represented a compromise between topweight, AA firepower and surface firepower and the lower weight of the twin allowed for a heavy CIWS -which appeared to have produced a destroyer with better all round firepower and AA capability than their USN treaty limited counterparts - and I believe that I have proved my case.


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## Juha (Feb 23, 2013)

N vs Bensons: in mid 45 RN Ns with Bofors had 6 x 4.7in, 1 quad pom-pom, 1-3 single 40mm Bofors, 2 twin power 20mm, 0-2 x single 20mm, 1 x 5 TTs vs in 44 Benson/Gleaves had 4x5”, 4x40mm Bofors (2x2) and 7x20mm (7x1) plus 5x21”TTs. So CIWS nearly same, not that RN DD had clearly more heavy CIWS, only slightly better if at all.
And IMHO 4 5” guns firing slightly heavier shells with slightly higher rof didn’t have 50% less firepower than 6 4.7” guns, nearer 25% less firepower.

Juha


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## Juha (Feb 23, 2013)

RCAFson said:


> ...*but why did the USN need an effective CIWS when they had the mighty 5in/38* directed by the incomparable Mk33 and Mk 37? ...



Because multi layer system is a key of effective AA.





RCAFson said:


> ...I have been arguing that the treaty limited RN destroyers with the 4.7in twin represented a compromise between topweight, AA firepower and surface firepower and the lower weight of the twin allowed for a heavy CIWS -which appeared to have produced a destroyer with better all round firepower and AA capability than their USN treaty limited counterparts - and I believe that I have proved my case.



See above, IMHO RN DDs didn't have especially heavy CIWS when compared to same sized late war USN DDs and bigger USN DDs had clearly heavier CIWS.

Juha


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## Juha (Feb 23, 2013)

RCAFson said:


> I didn't consider these to be destroyers, but rather destroyer escorts, as per the Hunt class. Only 32 were built, most in the last year of the war. Even if we consider them destroyers and add them to the Akizuki class, it only comes to ~20% of IJN destroyers.
> 
> Also, the Matsu class doesn't appear to have any AA FC system.



Yes they were much like Hunts but with TTs, which most Hunts didn't have, less HAA but much more CIWS (24-39x25mm). Hunts and Matsus also showed how excellent 5"/38 was, it was really a DP gun, suitted well both LA and HA work, so USN didn't need 2 different guns, one optimised to LA like RN 4.7"/45 or IJN 5"/50 and another optimised to HA like RN 4" or IJN 5"/40.

Juha


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## RCAFson (Feb 23, 2013)

Juha said:


> N vs Bensons: in mid 45 RN Ns with Bofors had 6 x 4.7in, 1 quad pom-pom, 1-3 single 40mm Bofors, 2 twin power 20mm, 0-2 x single 20mm, 1 x 5 TTs vs in 44 Benson/Gleaves had 4x5”, 4x40mm Bofors (2x2) and 7x20mm (7x1) plus 5x21”TTs. So CIWS nearly same, not that RN DD had clearly more heavy CIWS, only slightly better if at all.
> And IMHO 4 5” guns firing slightly heavier shells with slightly higher rof didn’t have 50% less firepower than 6 4.7” guns, nearer 25% less firepower.
> 
> Juha



The fact remains that the N class had a heavier main armament and at least equal if not superior CIWS.

Also the N class were able to fire 2 x 40mm bofors and the quad pom-pom to either side giving them a far superior weight of fire to a Benson since her CIWS broadside was limited to 2 x 40mm bofors and 3-4 20mm.


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## RCAFson (Feb 23, 2013)

Juha said:


> Yes they were much like Hunts but with TTs, which most Hunts didn't have, less HAA but much more CIWS (24-39x25mm). Hunts and Matsus also showed how excellent 5"/38 was, it was really a DP gun, suitted well both LA and HA work, so USN didn't need 2 different guns, one optimised to LA like RN 4.7"/45 or IJN 5"/50 and another optimised to HA like RN 4" or IJN 5"/40.
> 
> Juha



The Matsus were somewhat larger than the Hunt class.

The USN found to it's dismay that the 5in/38 was too heavy for its DEs when combined with MK33 or Mk 37. Most USN DEs had no effective long range surface or AA FC system, while the Hunts had both.


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## Shortround6 (Feb 23, 2013)

Pre war and early war there were 4 different threats to ships. 

1. High level bombers (actually 8-15,000ft or so) 
2. Dive bombers.
3. Strafers
4. Torpedo bombers.

Not all weapons worked against all threats. The DP 4-5in guns worked against the High level bombers and to some extent against torpedo bombers. Dive bombers changed altitude (range) too fast for the 4-5 in guns fire control and fuse setting to keep up. Even a good gun director has to allow for several seconds between when the fuse is set and the round fired let alone the time of flight for the shell. No bodies director/fire control computer was fast enough to deal with dive bombers. 
To deter strafers it was thought that a few guns of equal size the what the strafer carried would do the job. two to six .5 in machine guns or a few 20-25mm guns depending on navy. 
5in/38s were never intended to be effective against dive bombers or strafers.

As the war went on low level bombers became more dangerous and the coming of guided missiles ( and Kamakazes were guided missiles from a defense stand point) change the threat mix considerably. The over estimation of the effectiveness of the early AA weapons suite also called for a rethink. Strafers also had become much more dangerous in just a few years. When the 5in/38 was being developed a "strafer" was something like a Grumman F3F-2 or -3. No armor, no self sealing tanks. One .50 cal gun and one .30 cal gun. Many other navy's had strafers with two .30 cal guns in 1936-38. By 1941-42 Several heavy MGs were common and 20mm cannon were starting to appear in multiples on aircraft with light armor and protected fuel tanks. 

While a few tripod mounted .50s might be able to deal with a handful of Biplane fighters attempting to strafe they were woefully inadequate against more numerous, more heavily armed mono-plane fighters. 
The US was working on the 1.1in quad AA Mount for use against dive bombers from about 1928. It had a number of problems of it's own but it shows that the US Navy was NOT depending on the 5in/38 to counter ALL of the air threats it faced. 

The plain truth is that NO SINGLE gun could counter all 4 threats no matter how wonderful it was.


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## Juha (Feb 23, 2013)

RCAFson said:


> ... Most USN DEs had no effective long range surface or AA FC system, while the Hunts had both.



A good catch.

Juha


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## Juha (Feb 23, 2013)

RCAFson said:


> The fact remains that the N class had a heavier main armament and at least equal if not superior CIWS.
> 
> Also the N class were able to fire 2 x 40mm bofors and the quad pom-pom to either side giving them a far superior weight of fire to a Benson since her CIWS broadside was limited to 2 x 40mm bofors and 3-4 20mm.



And against attack from ahead Bensons could use 4-5 x 20mm singles and usually one of the twin 40mm mount on the other hand Nizam only 3-5 x 20mm because its quad pom-pom and the only Bofors would have been wooded. One always can play with firing sectors.

Juha


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## RCAFson (Feb 23, 2013)

Juha said:


> And against attack from ahead Bensons could use 4-5 x 20mm singles and usually one of the twin 40mm mount on the other hand Nizam only 3-5 x 20mm because its quad pom-pom and the only Bofors would have been wooded. One always can play with firing sectors.
> 
> Juha



Destroyers are quite maneuverable and SOP was turn ASAP to present the maximum amount of firepower to attacking aircraft.


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## Glider (Feb 23, 2013)

RCAFson said:


> I bet the boys from Fliegerkorps X would dispute your claim, *but why did the USN need an effective CIWS when they had the mighty 5in/38* directed by the incomparable Mk33 and Mk 37? As for taking quite a toll that's not the case, as I have shown via Lundstrom.


Do you not understand that you need layered defence. Did the example of HMS Tiger whose 6in were deadly against aircraft but still needed 3in and Seact missiles not show this. That the USN with the 40mm and the 5in had the best combination going.


> There's several things to consider; some aircraft flew lower and slower increasing the engagement envelope and, the RN introduced MT fuzes with longer time settings (45 versus 25 seconds) which combined with type 285 radar to push maximum range out several thousand yards and greatly increased accuracy of the resulting gunfire. As the altitude of the aircraft decreases, so does the differential between a 40deg gun and an ~80 deg gun and at higher elevations the accuracy of both the aircraft and the defensive gunfire decreases.


And at the end the 4.7 stops firing and is useless against divebombers whatever you say this is the final fact.


> Last sentence above : _Therefore propose to replace 4-in. H.A. in 'J' class and later and the 3-in. in 'E' to 'I' by the second set of T.T.s as opportunity occurs *or* by additional Oerlikons."_ The ships were designed with 2 x quintuple tubes so removing the 4in and replacing the tubes gets them back to their design configuration. The RN was always very cautious in terms of weight compensation to ensure adequate stability for their destroyers which had to operate in the bad weather prevalent in the Atlantic and Arctic oceans, along with the possibility of ice formation on the weather decks.


The first changes made were the replacement of the 0.5 with 20mm guns initially 4 then normally increased to 8 with twin mounts replacng singles. The TT were removed for the 4in, then replaced. Later the TT's were removed again and replaced with the 40mm.
On Tribals the 0.5 were replaced with 20mm, then the twin 4in replaced a twin 4.7, then as we have seen 6 x 40mm were added. You cannot make any assumptions about weight unless you know the mounting.



> 1700 yards = 5100 ft (they considered the Bofors to have the same effective range), but your point was about "harrassing fire" and this could be accomplished up to much higher altitudes - the engagement diagram actually shows a max altitude of ~7500 ft for the pom-pom but in any event at 2300fps (a typical MV of a worn gun in service) the max altitude was well above 10,000ft.


Where on earth did you get the RN saying the 40mm had the same effectve range of 1,700 yards. 



> The fact is that ballast was required even with the original design configuration.


 Which was nothing compared to other navies




> If you look at the weight saved by replacing a 4.7in twin with a 4in twin and then removing the quad .5in mounts, it almost exactly balances the weight added by the 6 x 40mm mounts and the additional radar equipment.


 see above re 20mm being added



> The Akizukis were more akin to an RN C class light cruiser than a destroyer but if the IJN had placed an emphasis on destroyer AA firepower they could have fitted the 5in/40 twin onto their fleet destroyers - but they didn't.


I admit I don't get this statement can you explain


> It looks to me that the Matsus didn't have an AA FC system which the Hunt class did.


I have no idea but would assume they had a basic system similar to the US DE's



> I have been arguing that the treaty limited RN destroyers with the 4.7in twin represented a compromise between topweight, AA firepower and surface firepower and the lower weight of the twin allowed for a heavy CIWS -which appeared to have produced a destroyer with better all round firepower and AA capability than their USN treaty limited counterparts - and I believe that I have proved my case.


 Well you have failed to convince anyone.


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## Glider (Feb 23, 2013)

RCAFson said:


> Destroyers are quite maneuverable and SOP was turn ASAP to present the maximum amount of firepower to attacking aircraft.


In the Med one standard tactic (there were others) against dive bombers was to turn under them to try and make them go past the vertical.


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## RCAFson (Feb 23, 2013)

Glider said:


> Do you not understand that you need layered defence. Did the example of HMS Tiger whose 6in were deadly against aircraft but still needed 3in and Seact missiles not show this. That the USN with the 40mm and the 5in had the best combination going.
> And at the end the 4.7 stops firing and is useless against divebombers whatever you say this is the final fact.


Yes, and the inner layer is the most important of all, and is far more likely to score hits against DBs than HA medium calibre guns. The RN recognized this and developed the quad pom-pom to fill that need.



> The first changes made were the replacement of the 0.5 with 20mm guns initially 4 then normally increased to 8 with twin mounts replacng singles. The TT were removed for the 4in, then replaced. Later the TT's were removed again and replaced with the 40mm.
> On Tribals the 0.5 were replaced with 20mm, then the twin 4in replaced a twin 4.7, then as we have seen 6 x 40mm were added. You cannot make any assumptions about weight unless you know the mounting.



The simple fact is that topweight compensation was required to fit increased CIWS and the post war Mk VI director.



> Where on earth did you get the RN saying the 40mm had the same effectve range of 1,700 yards.



From the RN:



> The "Maximum Effective Ranges" of close range weapons are as follows:-
> 
> 2-pdr. multiple Pom-Pom *and Bofors* in local control	1,700 yards.
> Oerlikon 20 mm. single gun	1,000 yards.
> ...











> I admit I don't get this statement can you explain



IJN fleet destroyers used a twin mount that required fixed angle loading above 10 degrees. They could have used the 5"/40 twin mount as on the Matsu's which had loading trays for all angle loading.



> I have no idea but would assume they had a basic system similar to the US DE's



The US DEs had no centralized FC until late ~43/44 when the Mk 51 director (similar to the RN Simple Tachymetric Director) was adapted to give some measure of close range AA firecontrol but this was pretty useless against longer range air and surface targets. Most USN DEs used the 3in/50, BTW.



> Well you have failed to convince anyone.



I've never subscribed to "group think" and I doubt you do either.


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## Glider (Feb 23, 2013)

RCAFson said:


> Yes, and the inner layer is the most important of all, and is far more likely to score hits against DBs than HA medium calibre guns. The RN recognized this and developed the quad pom-pom to fill that need.


Unfortunately that left them stuck unable to fire anything at a bomber bout to drop its load.


> The simple fact is that topweight compensation was required to fit increased CIWS and the post war Mk VI director.


No you are wrong. No changes were made for the addition of 20mm guns and the Tribals were later able take the 40mm without any reductions in weapons. Unless you can support your statement that when the 40mm were added someting was removed from the tribals to compensate.


> From the RN:


Good find, but can I ask if you knew the effective range under local non directed control was 1,700 ish yards, why were you claiming 10,000ft?


> IJN fleet destroyers used a twin mount that required fixed angle loading above 10 degrees. They could have used the 5"/40 twin mount as on the Matsu's which had loading trays for all angle loading.


Good question and I don't know the reason. A guess is that pre war they decided like the UK and USN that fixed one piece shell was unsuitable for a destroyer. By the time 1944 came around they were not in a position to be so fussy.


> The US DEs had no centralized FC until late ~43/44 when the Mk 51 director (similar to the RN Simple Tachymetric Director) was adapted to give some measure of close range AA firecontrol but this was pretty useless against longer range air and surface targets. Most USN DEs used the 3in/50, BTW.


good info


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## Juha (Feb 23, 2013)

RCAFson said:


> Destroyers are quite maneuverable and SOP was turn ASAP to present the maximum amount of firepower to attacking aircraft.



Also US DDs had rudders and sometimes tactical situation limited the freedom of manoeuvre of individual ships.

Juha


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## RCAFson (Feb 23, 2013)

Glider said:


> Unfortunately that left them stuck unable to fire anything at a bomber bout to drop its load.


You keep forgetting about the pom-pom.



> No you are wrong. No changes were made for the addition of 20mm guns and the Tribals were later able take the 40mm without any reductions in weapons. Unless you can support your statement that when the 40mm were added someting was removed from the tribals to compensate.


The 4in twin was added immediately after Norway and the 20mm came after that, and then came the 40mm Bofors - it is pretty easy to see how the topweight progressed.



> Good find, but can I ask if you knew the effective range under local non directed control was 1,700 ish yards, why were you claiming 10,000ft?



effective range is synonymous with a reasonable probability of getting hits (IE a well trained crew should hit within that range). It doesn't mean that hits are not possible beyond that range and your average Stuka pilot knew that a single pom-pom hit was likely to ruin his day. Also I provided a quote from March showing that the RN thought it theoretically accurate to 10,000ft.

THE USN's opinion on the Luftwaffe versus the IJNAF:


> ENEMY TACTICS AND EQUIPMENT
> 
> German
> 
> ...



[/QUOTE]


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## parsifal (Feb 24, 2013)

We can always find instances where a weapon system has suffered unusual failures or successes. Thats what historical records tend to record....the highs and the lows of something. But that does not mean that an exception makes for the rule.

I have no doubts there were many instances where the 5/38 achieved poor results, including poor rofs in a particular action. i have no doubts that the 4.7 at times achieved outstanding rofs. thats stands to reason. Neither gun was a perfect or complete wepon system.

But the exceptions dont establish the norm for that weapon. The extremes that we can find documentation on will simply show the depths and the highs that a particular weapon system will achieve. Sort of anecdotal snap shots of the statisitcal spread for the weapon.

In my opnion the published max rofs for these weapons are probably the way to start. Ive tried to point out that max rof is different from pracxtical rof, and still believe that to be a factor, but simply to avoid having to go through the pain and suffering of yet another propaganda lecture, lets just agree to use the published max rofs. That puts the 4.7 published figures at 12 rpm for me, and the 5/38 at 15-24 rpm. I do not accept that the British DCT was any faster than the Mk 37 directors, so dont even try to argue that, your just wasting your breath with me. Lets compromise and settle for the middle ground with the 5/38, and say that it had an average rof of 19 rpm. That means on average the 5/38 will be 50% faster than the 4.7, so 4 x 5/38 is the same in terms of output as 6x 4.7. 

We also know that the rate of traverse and max elevation rate of the 4.7 twin was slower than the Mk30 turret....roughly half the speed in both planes. Thats been discounted as not being important except at close range, but that is not the case. Even at long range corrections have to be made by both mounts for the changing position of the target, and if that takes longer because of slower traverse rates, thats going to affect the number of times that target can be fired at before the a/c releases its ordinance. Basically, the theory is the same for all directed fire....the course and speed of the target is calculated, the gun moves to a position in the sky where the aircraft is predicted to be be, a shell(s) is/are fused, with time fused shells (either in the turret or in the shell handling areas) , or automatically (in the case of VT), and at the direction of the DCT the gun is fired. If the aircraft position is within the kill radius of the shell, it will be hit, if not, it continues. It should be obvious that AA gunnery is heavily dependant on how many shells can be fired, which is the main reasoining for HAA (the other being it is better suited to providing cover fire for high value targets....the entire screen can be directed to protect critical targets). For the British, one of the disadvantages they suffered was a somewhat lower rof, but also a slower rate of traverse and elevation. There were other issues, that have been argued, but remain unresolved at this point. With a slower rof, and a slower turret, there will be less points that the 4.7 can fire at, and hence less chances for that gun system to hit. 

But it is worse than that. Because the 4.7 could only fire at 40 degrees. it could not even fire at targets that approached above a certain altitude and could not fire at targets that remained fairly high and closed the range. If an a/c was at 6000 feet, it cannot be fired on at any closer than 4000m range, whereas a turret with say an 85 deg elevation (what most 5/38 mounts were capable of) can fire until the target is only 500 m horizontal range. Effectively, the 4.7 has a fire opportunity of 4500m, compared to the fire opportunity of 7500, if effective max range is assumed to be 8000m for both weapons. That gives the 5/38 nearly twice the firing time, during which time they will sustain ahigher rate of fire, on the baasis of their quicker training and elevation capabilities. Nothing else can really be argued, because up to now we have been unable to agree on basically anything. 

So, in my opinion, its a fiction to argue that the 4.7 was comparable to the 5/38 as a HAA weapon. Moreover, as a fleet scrfeeing unit it was also severely limited. If a Brit destroyer wanted to use its 4.7s to provide cover fire over a high value target, it had to place itself outside the range of its CIWs that could only provide cover fire out to a certain range.

For the USN with its combination of 5/38 and 40mm Bofors, it could provide cover fire from both its main armament and its CIWs as part of a fleet units. I think this was a priceless advantage, and it is relfeceted in the much lower loss rates to air attack for USN Destroyers. British Destroyers had to choose between one or the other. They could move their relative position to the target ship out, so that they could continue to provide 4. 7 fire over the target (and sustaining fire was the issue, even if nothing was hit, disrupting the attack was the important event), or they could forego their 4.7 fire and close right up and rely on their CIWs. But its just not a valid comparison to try and compare the 2 pounder pom pom to the 40mm Bofors, or even the 20mm Oerlikon in my opinion. It was a severely restricted piece of equipment. It suffered from frequent jams, it lack an effective incendiary capability, it certainly did not have an effective celining of 1000feet for all types. It had a max ceiling with the high velocity round (about half the ships in the fleet at a guess) 13000 feet, but max celining is not max effective celing, for the lower powered round, this might be as low as 6000 feet max effective ceiling. But over open sights, the chances of a hit at those ranges.....not good.

These shortcomings in the British Destroyer AA capabilities were painfully brought home throughout the war, and were confirmed in the last campaigns in the pacific, when the British Admirals forced to endure the terrible ordeals of the Kamikaze attacks on their fleet, saw first hand the limitations for the AA screens, and could only compare and lament the relatively poor performance of their own ships to the relatively outstanding performance of the US ships, with their vastly superior combinations of 5/38, 40mm Bofors and Mk 37 directors. They immediately took steps, as best they could to rectify what they could and emulate, as far as they could, the tremdous success that they observed first hand in the US fleet. both Fraser and Rawlings specnt some time on US ships observing for themselves the tremendous effectives of the US systems.


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## Glider (Feb 24, 2013)

RCAFson said:


> You keep forgetting about the pom-pom.


You mean the pom pom, the weapon wth an effective range of approx 5,100 ft, the pom pom you claim can fire effectively up to 10,000 ft? The pom pom that the RN said was only half as effective as the 40mm against targets apart from suicide aircraft. The pom pom that even the chart you produced showing the arc of fire of an RN destroyer gave a range of approx 7,000ft, that pom pom.


> The 4in twin was added immediately after Norway and the 20mm came after that, and then came the 40mm Bofors - it is pretty easy to see how the topweight progressed.


So we agree that the Tribals had the 4in and the 20mm before they received the 40mm guns. Which brings us back to the question you keep avoiding. Of course the toweight increased, the question is, was this a problem for the Tribal class destroyers.
My case is no it wasn't. I support this by the simple fact that the guns were added and no guns were removed to cater for it.
Your case is yes it was a problem but your evidence is -----------? what exactly

Adding a bit of ballast doesn't count as a problem as the ship still functioned in the front line with all her weapons.



> effective range is synonymous with a reasonable probability of getting hits (IE a well trained crew should hit within that range). It doesn't mean that hits are not possible beyond that range and your average Stuka pilot knew that a single pom-pom hit was likely to ruin his day. Also I provided a quote from March showing that the RN thought it theoretically accurate to 10,000ft.


There you go again, getting wrapped up in the theory, not the what happened. In Vietnam in theory the F4 didn't need a gun as the Sparrow and Sidewinder were so effective, in the real world they paid a high price for that theory. In WW2 the RN had a theory that their destroyers didn't need a HA gun, in the real world they also paid a price for that theory. In WW2 in theory Enigma was unbreakable, but the germans paid a very high price for that theory. On HMS Tiger in theory we didn't need the Seacat as we had the 3in, in the real world for various reasons we needed the Seacat, at least that was a lesson learnt in peacetime. Do I need to go on, if you wish we could cover the introduction of the M16, the SA80, the decision taken in 1938 that the RN didn't need a single seat fighter, that the Seafire didn't need additional fuel tanks, the list is endless.
I take it you never served in the armed forces. I promise you that what counts at the end of the day is the real world, not the theoretical.



> THE USN's opinion on the Luftwaffe versus the IJNAF:


Maybe this had something to do with it
_During the 8 months of 1945, when approximately half of the war's kills were made, rounds per bird dropped off. Except for those attacking the fast carrier force, many enemy planes were outmoded types, comparatively slow and operated by unskilled pilots. Gunners had improved in accuracy as a result of increased experience in action and increased training_


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## Shortround6 (Feb 24, 2013)

If 40 degrees of elevation was considered sufficient for AA work in the late 20s and early 30s _why_ the British spend so much time, money and tonnage getting 8in cruiser guns to elevate to 70 degrees and 6in cruiser guns (twin turrets) to elevate to 60 degrees? Practice fell far short of theory as the loading angle was down around 10 degrees and the elevation and training speeds were too slow to follow any but the slowest of aircraft. Of course at the time of design the standard RAF bomber was the Vickers Virginia. 







Top speed 103mph. 

As far as strafers go the standard RN fighter in 1930 was the Fairey Flycatcher. The "E" class Destroyers were under construction in 1931 so design and characteristics (armament) had already been decided by 1931. 






These were soon replaced by the Hawker Nimrod. 






Max speed (not at sea level) under 200mph. Not until 1937 does the RN search for a replacement, well after the Tribal class is in the works. 

The Fairey Swordfish doesn't enter service until mid 1936. 

What constituted "effective" air defense against such aircraft ( and even that is debatable) was woefully inadequate by 1941/41. 


on another point, effective range/altitude is much shorter than max range/altitude. The chances of hitting dropping almost exponentially with range/altitude. When fired straight up the last few hundred ( or even 1000) feet are covered at a comparative crawl. The last 1000ft can take the shell about 8 seconds to cover. That is just due to gravity and not counting air resistance. Even a 200mph airplane is covering about 330ft per second. To have a deterrent effect the pilot needs to know that he is being shot at and that the shells are at least close. This means either tracers or shells that explode close by or in his flight path. Time fuses or shells with self destruct fuses. Self destruct fuses limit the max effective range to the fuse limit regardless of what the theoretical range/altitude is. The Gunner, to be effective needs to know where the shells are going in relation to the plane aimed at. Again tracers or exploding shells provide a reference for the gunner/s. But many shells run out of trace at a distance much shorter than their max range/altitude. at a point a bit longer than the tracer burn out the gunner is no longer aiming at an aircraft but simply filling a portion of the sky with junk and hoping a plane runs into it. Hardly "effective" fire. 
Many light AA guns used ring and bead or cartwheel sights that relied on the gunners _estimation_ of both course and speed. Combined with tracer this did work fairly well, tracers (shell bursts) telling you were you _should_ have been aiming several ( or 10-15 seconds for long ranges) seconds ago but they do allow for a correction of fire.


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## RCAFson (Feb 24, 2013)

From Navweaps:


> 2) The guns installed on HMS Delhi had originally been destined for USS Edison (DD-439). *These guns had been hand-picked by Edison's first commanding officer*, Lt. Cmdr. Albert C. Murdaugh, who had just previously been assigned to the Naval Gun Factory at Washington, D.C. Much to Lt. Cmdr. Murdaugh's distress, President Roosevelt ordered these guns diverted to Delhi and as a result Edison did not receive her replacement guns until after she had been commissioned and had completed her preliminary trials. Perhaps as a result of having these hand-picked weapons, the gunnery officer on Delhi reported that during gunnery trials in February and March 1942 that these guns were able to fire 25 rounds per minute with the ready-use ammunition stored in the handling rooms and *15 rounds per minute with the normal supply from the magazines.*


It seems very likely that these are the maximum cyclic rates possible under static (ideal) conditions and normally the gun would use the ammunition hoists (use of the hoists was mandatory during predicted AA fire) and so with handpicked guns the max RoF is 15 rpm. 

Coincidentally we know what Edison (for whom Delhi's guns were originally intended) could do in actual combat conditions:




> A total of 362 rounds were fired, 74 at the shore battery, 20 in the first engagement, and 268 in the second destroyer engagement, of which it is estimated that 200 rounds were fired at the first destroyer and 68 at the second. All firing was director-controlled, rapid, continuous fire. The average gun range for the first firing was 9,500 yards, for the second 14,000 yards, and for the third 12,500 yards... ...It is particulary pleasing that the guns maintained a sustained rapid fire of 268 rounds (average 68 rounds per gun) at an estimated rate of at least 12 shots per gun per minute without casualty.[1]
> [1] United States Navy, AntiAircraft Action Summary, July 1942 to Dec 1942 (Information Bulletin No. 22), p.161-163


We have info from USS Maury:


> The sharp tang of Smokeless Powder filled the air as succeeding Salvoes roared out at five-second intervals...
> 
> The ammunition passers, mostly the new volunteers from the states, were trying so hard to keep the gun firing at its maximum rate that some of them started “saving time” by handing the projectiles directly to the shellman instead of tilting them into the fuzesetters. They had maintained a great rate of fire, but the fuzes weren’t set!
> http://destroyerhistory.org/goldplater/ussmaury/index.asp?r=40130&pid=40133


So 15RPM was the maximum and 12 RPM the actual RoF. Maury also report that two of her 4 guns became unserviceable after this action due to excessive bore enlargement. 

We know that the RN 4.5in twin could fire at 12 RPM per gun for long periods of time in actual combat and on occasion up 16 RPM.
We know that the RN 4.7in twin could fire with a 5sec cyclic rate per gun for long periods of time in actual combat - which is no surprise since the loading tray arrangement of both RN twins was very similar.
We know that the handworked RN 4.7in single could fire at a cyclic rate of 17.6 rpm for at least 5 rounds.

The inescapable conclusion is that the actual combat RoFs were the much the same for the 4.7in twin and the USN 5in/38 single.


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## Shortround6 (Feb 24, 2013)

RCAFson said:


> We know that the handworked RN 4.7in single could fire at a cyclic rate of 17.6 rpm for at least 5 rounds.



No we don't. 
you are confusing burst fire with cycle rate. 

5 rounds in XX seconds is not equal to the cycle rate because you have left out one loading/ramming cycle. You started the watch with a loaded gun going bang and ended with a loaded gun going bang. The time to load the first round is not counted and time for the gun to recoil and run out from the 5th shot is not counted. 

It is an impressive performance but only includes 4 loading cycles. 

Using action reports is informative but will always be lower than "theoretical" rates of fire. Guns in action are only fired by director control when on target and when either ALL guns are ready or the majority of guns are. Many directors had "ready lights" showing which guns/turrets were loaded and ready to fire and the director crew would wait for all lights/indicators before firing so the cycle rate for the ship was governed by the slowest crew/mount. Guns were also often fired only at a certain point in the ships roll. So there may be a certain delay in firing until that point is reached. The 5in/38s (and darn few other destroyer main guns) not being stabilized. Trying to fire on the roll means the guns are chasing the target/indicators in elevation constantly making loading a bit slower.


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## RCAFson (Feb 24, 2013)

Shortround6 said:


> No we don't.
> you are confusing burst fire with cycle rate.
> 
> The 5in/38s (and darn few other destroyer main guns) not being stabilized.



You don't know that the gun was loaded prior to the first round being fired - in fact why would it be, since the gun was undergoing firing trials?

I assume that you mean that the 5in guns were stabilized. RN destroyer guns were fired via stabilzed sights (as per the USN, albeit using a gyro in the director, rather than a below decks gyro) and the firing was continuous except in very heavy seas where firing at some point in the roll might be used instead.


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## RCAFson (Feb 24, 2013)

Some of my earlier posts regarding 40 deg elevation:



> The Tribals, JKN and L-M class destroyers had DP 4.7in guns with on-mount AA fuze setters, that were controlled with the FKC HA FC system. It is true that elevation was limited to 40 or 50 degs, but they were not SP guns, as per the 5"/38 guns on the USN Porter and Somer class, which had no capability for predicted fire against aircraft. The overall AA power of a Tribal or JKLMN class was probably better than the early USN destroyers with 4 or 5 x 5"/38 DP guns, because the RN destroyers had a CIWS of a quad pom-pom and 2 quad .5in mounts versus only 4 x.5in mgs on the USN destroyers.
> 
> As for 40 degs not being enough, well that's not true; it all depends on the altitude of the attacking aircraft, obviously against a torpedo bomber or a low altitude level bomber, 40degs is plently, and against dive bombers attacking other ships, the same gun could place a barrage over the ship being attacked. If you read the accounts of the IJNAF attacks on the USN carrier task forces in 1942, you will see that the destroyers could have performed as AA escorts even with 40deg elevation. The key factor is that the guns be controlled in AA mode by a computer that can predict the movement of the target and direct the gun to the correct elevation and deflection while also providing fuze timing, and every RN destroyer from the Tribal class onward could do this. Here's the firecontrol schematic of the Tribal class (this also shows type 285 radar which was being fitted to RN destroyers from mid 1941):
> Attachment 224237
> The big problem for RN destroyers and 40 deg elevation guns, came when they had to operate alone or where they became the target of attacking aircraft, and then really only when they faced dive bombers. High altitude level bombing was not very effective against ships anyways, and the RN would have preferred to add an extra quad pom-pom when the dive bombing threat was realized in 1940, but these simply didn't exist so they added (spare) 3in and 4in single HA mount guns on some destroyers to allow for engaging high altitude and divebombers and a twin 4in in lieu of the after upper 4.7in mount on the Tribal class..



We know from actual combat that when USN destroyers were singled out by divebombers that they seemed to sink just like RN destroyers - what saved USN destroyers from suffering losses at the same rate as RN destroyers was the generally weaker opposition that they faced and the fact that they most often met IJNAF aircraft while performing escort duties for other higher value targets mainly carriers. I've tried to show the trade-offs made by both the RN and USN in selecting 4.7in/5in gun elevation and how a lower gun elevation creates less topweight, thus allowing for a heavier CIWS.


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## vinnye (Feb 24, 2013)

I agree that any destroyer on its own was in grave danger from air attack.
The RN lost many destroyers that were acting on their own or in loose cooperation with other ships, usually withdrawing troops without air cover.
They were attacked by very professional bomber crews who had a lot of experience and were well motivated.
I do not think that USN destroyers in the same position would have fared any better.


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## Shortround6 (Feb 24, 2013)

RCAFson said:


> You don't know that the gun was loaded prior to the first round being fired - in fact why would it be, since the gun was undergoing firing trials?



And you don't know the gun was unloaded at the start. 

Your quote "During gunnery trials in 1930, HMS Basilisk'' was able to fire "...five rounds in 17 seconds."

If it started loaded that is a cycle of rate of about 4 seconds or 15 round per minute which is quite good. it is also believable considering later performance. A cycle rate of 3.4 seconds or 17.6 rpm is just a bit too good considering the later performance. 

The HMS Basilisk also used the 30 degree elevation mount. We also do not know the conditions of the trials. Speed and sea conditions affected the destroyer or type, speed (if any) of the target. Was the destroyer in calm water doing 12-15kts firing at a stationary/moored target at close ( under 3000yds) range that required little or no change in elevation and only minor changes in train? Where was the gun in relation to the ammunition hoist/feed or for 5 rounds was that even a consideration?

The L&Ms with the big 4.7s suffered a drop in rate of fire with the turrets rotated 90 degrees from the center line because the ammunition hoists did not turn with turret calling for a longer, more confused pathway for the ammunition numbers to follow. 
With the Ls part of the 1937 Naval estimates ( budget?) and Ms part of the 1939 it can be seen that at least some in the RN were not satisfied with the twin 4.7 as used in the Tribal and J&K classes. The Mark XX twin hada few problems of it's own and shows the problem of trying to combine both good surface gunfire with a DP mount. The Americans sacrificed some surface capability ( muzzle velocity/range) for the DP capability. 

You can find "burst fire" ratings for a number of land artillery pieces. Vickers offered a SP 155 gun that could fire 2 rounds in 8 seconds, 3 rounds in 13 seconds or an "intense" rate of 6 rounds per minute. Sustained of 2 rounds per minute for one hour. The last two firing rates may have more to do with barrel cooling and barrel life than the loading arrangements. The last certainly does. There is no way a gun using 100lb shells and bagged charges "cycles" at 4 seconds. 
I did not make up "burst fire", it exists and can be found. It is perhaps more useful for advertising or press releases than evaluating combat performance. 

The US 5in/38 guns were not stabilized. Heavy seas is subject to interpretation and heavy seas slow the rates of fire by throwing the loading numbers (crew) around slowing the work at the guns. Even before WW I most knowledgeable gunnery officers figured that the rate of fire "in combat" for medium sized guns on cruisers would be 1/2 to 1/3 what was achieved during the summer annual "shoots". Destroyer guns using lighter ammunition ( and cased charges rather than bagged) would show less of a fall off until the weather got really bad.


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## Shortround6 (Feb 24, 2013)

vinnye said:


> I agree that any destroyer on its own was in grave danger from air attack.
> The RN lost many destroyers that were acting on their own or in loose cooperation with other ships, usually withdrawing troops without air cover.
> They were attacked by very professional bomber crews who had a lot of experience and were well motivated.
> I do not think that USN destroyers in the same position would have fared any better.




It depends on the type of attack. EVERYBODY's destroyers were woefully ill prepared for dive bomber attacks in 1939-42. The Americans could do much better against level bombers attacking at 8-15,000ft but since attacks from that height, even by formations of several squadrons, seldom hit anything anyway it is a bit hard to prove. 

Torpedo bombers could be engaged by just about anybodies destroyer guns. Fire control may change from navy to navy.

The 5in/38 may be over rated in the early part of the war but since it was on hand and in wide use when the proximity fuse (VT) showed up it's ability took a sudden leap upward (subject to ammo availability). Navy's with limited ability ( in elevation limits, loading limits, training speed limits) needed now guns/mounts to take full advantage of VT fuses even if they could make them.


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## vinnye (Feb 24, 2013)

Totally agree, everyone was ill prepared upto 1942 - lessons being learned the hard way!
Also agree hitting a moving ship from 8,000 + feet was difficult, even if it was an aircraft carrier - Illustrious dodged a lot!!!
There are some examples of medium level bombing success eg Tirpitz was hit several times by Lancasters, but she was atationary.


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## RCAFson (Feb 24, 2013)

Shortround6 said:


> And you don't know the gun was unloaded at the start.
> 
> Your quote "During gunnery trials in 1930, HMS Basilisk'' was able to fire "...five rounds in 17 seconds."
> 
> ...



I don't know that it was unloaded but I doubt the trials were conducted to mislead anyone, but by the same token we don't know the conditions under which Delhi's handpicked guns achieved their stated ROFs either, or for how long.

Actually the LM class guns appear to be optimized for fire on the beams with loading becoming less efficient towards the centreline.

If the director sights are stabilized, the guns are effectively stabilized as well.


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## Shortround6 (Feb 24, 2013)

I am not saying the trials were to mislead anyone at the time. If the writer knew what he saying and assumed the reader understood his term or phrase there is no misleading. If someone 70 years later wants to read something more than is stated based on a short excerpt? 

The L&M guns, at least according to a drawing in "Destroyer Weapons of World War II" British section by Peter Hodges, show four tubes in the ammunition hoist. The "front" two are the shell hoists and the rear two are the cartridge hoists. Pretty well laid out for firing along the axis of the ship. (no mention of how X turret was laid out but perhaps mirror image? shell hoists towards muzzle with guns pointed aft?) Since the ammunition hoist/trunk does not rotate when the guns are pointed 90 degrees to the broadside, say to starboard, the two shell hoists are next to the left hand gun and the two cartridge hoists are next to the right hand gun. The hoists being between the guns. This requires extra movement (distance) to get the right components to correct loading trays and a bit of interference as the left hand gun cartridge handler in order to place the cartridge in the loading tray has to stand in or very near where the left hand gun shell handler has to stand to get the shell out of the hoist. A similar dance has to be performed by the loaders of the right hand gun with the shell handlers dealing with 62lb shells. How this is "optimized for fire on the beams" is beyond me. 

"If the director sights are stabilized, the guns are effectively stabilized as well"

If this was true a lot of navy's spent a lot of money on stabilized gun mounts that they didn't need to. The director sight may be stabilized and stay pointed at fixed point in space as the ship rolls, pitches and yaws beneath it but the gun barrels are going to be waving all over the place. You can rig the firing circuits to fire when the barrels are aligned with the sight and get sort of the effect of a stabilized gun but that plays merry h**l with the rate of fire as it may take a number of seconds for the natural motion of the ship to bring the guns into alignment with the sight.


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## RCAFson (Feb 24, 2013)

vinnye said:


> I agree that any destroyer on its own was in grave danger from air attack.
> The RN lost many destroyers that were acting on their own or in loose cooperation with other ships, usually withdrawing troops without air cover.
> They were attacked by very professional bomber crews who had a lot of experience and were well motivated.
> I do not think that USN destroyers in the same position would have fared any better.



Just to provide some more data:
Coral Sea:2CV, 5 CA, 9DD.
At Coral Sea they claimed 49 AA kills of which about 37 were claimed by the USN carrier TG and they got 3. DDs in the CV screen claimed 11.

Midway first attack: 1CV, 2 CA, 5 DD
2nd attack: 1CV, 4 CA, 7DD
At Midway they claimed 20 AA kills and got 3. DDs claimed 8.

Eastern Solomons: 1 CV, 1 BB, 1CA, 1 CLAA, 6 DD
At Eastern Solomons they claimed 30 and got 4. DDs claimed 5.

Santa Cruz:
two forces:
1Cv, 1BB, 1 CA, 1 CLAA, 8 DDs
1CV, 2 CA, 2 CLAA, 6 DDs
Total: 2CV, 1BB, 3CA, 3CLAA, 14DD
At Santa Cruz they claimed 127 and got ~25. DDs claimed 22.

Yet the actuality is that USN destroyers probably shot down no aircraft in the first 3 actions and only a handful at Santa Cruz. All USN ships had progressively augmented CIWS by Coral Sea and none fought with their pre-war (design) CIWS. most had AA FC radar at Coral Sea and all by Eastern Solomons.

The first large scale air attack on the RN was on April 09 1940:

Two forces:

2 BBs 5 cruisers, 7 DDs
4 cruisers 7 destroyers
total: 2 BB, 9 cruisers, 14 destroyers (all ships had their pre-war AA/CIWS armament)

Attackers: 47 Ju 88 and 41 He111

Losses: DD Gurkha, several ships suffer minor damage; 4 Ju-88s shot down. Several He111s might have been lost as well, but this is unclear.



The RN forces were not concentrated and the only loss was Gurkha, and this occurred when she detached herself from her flotilla. At the time the RN was under the impression that only one Luftwaffe Ju-88 was shot down - another example of the RN being very conservative in its AA kill claims. None of the RN ships had AA FC radar but the BBs had air warning radars. The weather conditions were quite severe which greatly hampered destroyer gunnery, in sharp contrast to the Pacific actions where in each case the weather was quite calm.


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## parsifal (Feb 24, 2013)

Ship trials are notoriously undertaken for political or propaganda reasons. Particulalry the french and Italians, whi would undetake speed trials under the most artificial of conditions......forced machinery, ultra light loads, hand picked sea conditions. Thats why Italian cruisers so often paraded as being much faster than the RN, were found to be about the same under wartime conditions. 

I dont think the RN was as afflicted by that disease of fudgung trials results, but neither do i think it beyond possibility that they would not still frame the trials results in the best possible light. There were often peacetime gunnery competitions and the like that many ships would go to extraordinary lengths to win. I can easily see a gunnery trial being fudged for that reason....the gun set at the best elevation and traverse angle, the ship and sea state close to stationary as was allowed, the crews handpicked, extra gunnery hands on deck....who knows. 

All I know is that results under wartime conditions are going to not as efficient as trials results, as a general rule. The only eception to that might be where the trials show up some problem.


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## RCAFson (Feb 24, 2013)

Shortround6 said:


> I am not saying the trials were to mislead anyone at the time. If the writer knew what he saying and assumed the reader understood his term or phrase there is no misleading. If someone 70 years later wants to read something more than is stated based on a short excerpt?
> 
> The L&M guns, at least according to a drawing in "Destroyer Weapons of World War II" British section by Peter Hodges, show four tubes in the ammunition hoist. The "front" two are the shell hoists and the rear two are the cartridge hoists. Pretty well laid out for firing along the axis of the ship. (no mention of how X turret was laid out but perhaps mirror image? shell hoists towards muzzle with guns pointed aft?) Since the ammunition hoist/trunk does not rotate when the guns are pointed 90 degrees to the broadside, say to starboard, the two shell hoists are next to the left hand gun and the two cartridge hoists are next to the right hand gun. The hoists being between the guns. This requires extra movement (distance) to get the right components to correct loading trays and a bit of interference as the left hand gun cartridge handler in order to place the cartridge in the loading tray has to stand in or very near where the left hand gun shell handler has to stand to get the shell out of the hoist. A similar dance has to be performed by the loaders of the right hand gun with the shell handlers dealing with 62lb shells. How this is "optimized for fire on the beams" is beyond me.
> 
> ...



The statement in March is "5 rounds in 17 seconds". If the gun is is loaded prior to firing it would be a misleading statement, but it doesn't say that.

I took another look at Destroyer Weapons and you're correct. At first glance it appears as though the drawings are opposite of their actual positions.

The whole point of stabilized sights is to allow continuous aim and fire from unstabilzed gun moutings; as long the layer and trainer follow their pointers the gun is effectively stabilized. AFAIK, only the RN Hazemeyer 40mm mounting and the German 4.1in twin mount used actual stabilzed (gimballed) moutings during WW2.


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## Shortround6 (Feb 24, 2013)

"5 rounds in 17 seconds" isn't really misleading. That is what it did. They are not claiming that is the firing cycle or that they can fire 10 rounds in 34 seconds or 17.6 rounds per minute. Your original quote was "..........5 rounds in 17 seconds" which rather makes it look like _something_ got left out. It may have been totally unimportant. 

As far as "as long the layer and trainer follow their pointers the gun is effectively stabilized" goes that is a might tough condition and actually darn near impossible even with a power worked mounting. For one thing elevation and train are only two axis of movement while most stabilized mountings or sights are stabilized in 3 axis. The Germans started with a bi axial mounting in 1929 and progressed though several mounts and systems (changing to a triaxial mounting real quick) using at least 3 guns starting with 8.8 cm guns. There was also a traxial stabilized twin mount for the 3.7cm LC/30 gun. 
The Italians had a Quadraxial 90mm/50 gun mounted in the Littorio and Duilio classes but it ran into a number of problems.
The British were working on stabilized 40mm mountings beside the Hazemeyer during the war but none made it. The post war STAAG MK II went 15-17 tons for a pair of 40mm barrels which both shows the problem of good stabilized mounts performance wise ( reliability excepted) and the price they were willing to pay to get it, weight wise. Granted it carried it's own radar on the mount. 

With enough electronic trickery one can get a stabilized gun sight to function with non-stabilized guns but it is going to take a lot more than a follow the pointer system. RPC (remote power control) is needed at a minimum. 

Some estimates on how well the British pre war guns/mounts met requirements can be worked out by looking at some of the late war/post war guns/mounts like the twin 4.5in. Apparently it took almost 50 tons to provide 80 degrees of elevation for a pair of guns that that didn't perform much better than the late 1920s 4.7in and didn't fire any faster to boot? 12-14rpm hand worked (loaded) and 18rpm burst fire. 

Either the US MK 37 did something the British directors didn't do or the British were sold a bill of goods because the last Battle class Destroyers (the 1943 group) were to be given US MK 37 directors or a system using MK 37 components if not the actual directors, but fitted with British radar. Of course by this time the VT fuse was coming into wide spread use and the bigger guns (4in and above) had some hope of engaging a dive bomber with it.


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## parsifal (Feb 24, 2013)

> Either the US MK 37 did something the British directors didn't do or the British were sold a bill of goods because the last Battle class Destroyers (the 1943 group) were to be given US MK 37 directors or a system using MK 37 components if not the actual directors, but fitted with British radar. Of course by this time the VT fuse was coming into wide spread use and the bigger guns (4in and above) had some hope of engaging a dive bomber with it


. 

Thats one of RCAFs central points. He claims that USN overclaimed by at least 5:1, and then used that propaganda to sell their systems to everyone else. He claims the Mk 37 to be an overall liability and the 5/38 to be an overrated gun.

Im not saying that i agree with any of this. in fact I think it quite laughable that anyone might take the claims seriusly. But thats what he believes, and nothing will sway him from his opinion. 

Good luck trying to convince hime otherwise


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## RCAFson (Feb 24, 2013)

parsifal said:


> . Thats one of RCAFs central points. He claims that USN overclaimed by at least 5:1, and then used that propaganda to sell their systems to everyone else. He claims the Mk 37 to be an overall liability and the 5/38 to be an overrated gun.


I used the USN's own kill claim data (and I provided the hard numbers from USN sources), and Lundstrom's data on actual USN AA kills - *so this is not my opinion!* The truth of the matter is literally staring you in the face. Any reasonable person will accept the facts as they stand.



The USN didn't "sell" their systems to the RN, they gave them away via LL- March makes it clear that the UK could not produce enough FC equipment to meet RN needs and so they ordered USN equipment in the USA. Lendlease regulations prevented USA manufacturers from producing UK spec guns and equipment so the RN had no choice but to order USN spec equipment - I've already discussed this and provided a source to verify this; North American Supply.


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## parsifal (Feb 25, 2013)

sorry, but they ARE your opinions. youve taken selected opinions and reports, ignored the opinions of others,, including some highly qualified officers in far better position to know than you or I, used questionable basic data, skewed data or even incorect data, and reached a highly biased and innaccurate conclusion, simply because thats the conclusion you wanted in the first place. i think it safe to claim, that no-one else participating in our discussion agrees with your conclusions. your entitled to your opinions, but claimimg they are not your opinions (which infers they are facts) is just further evidence of your incredible arrogance and bias in this matter. Dont get me wrong, you have produced some amazing pieces of information that has certainly changed my view on particular details. But the conclusion YOU draw from the data you present is somewhere bewtween amusing and alarming for me. 

If you want to get on better and avoid being hounded every time you open your mouth, try a few things from someone who has made every possible mistake in this place.

1) Dont try to claim your opinions as facts. Even if they are wll supported, with the level of disagreement you are facing right now, you cant claim any of your thesis as anything but opinion at this point. 
2) Dont openly say you are goiong to ignore some sources and then parade other sources as fact, just because they accord to your preconseptions. In particualr, give due respect to front line soldiers who have enjoyed success doing things and following procedures you might not agree with. 
3) Try going into discussions with an open mind for a change. its very refreshing once you try it. I speak from personal expoereience ther, so dont think for a moment that I consider myself superior to you. 
4) Stop lecturing the rest of us
5) Try listening rather than talking down at us
6) Learn to respect the viewpoits of others, even if you dont agree with them.
7) Dont instantly get onto the forum if you see statements that you dont agree with. Allow the debate to mature a bit. You might be surprised, we may even reach a point that we will agree with you on something.


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## RCAFson (Feb 25, 2013)

parsifal said:


> sorry, but they ARE your opinions. .


 
Sorry, but I've produced hard data to back up the fact that the USN claimed 87 AA kills from Coral Sea to Eastern Solomons and yet only got 10 AA kills. That's not my opinion.


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## cherry blossom (Feb 25, 2013)

I suspect that RCAFson is correct that RN heavy anti-aircraft fire was more effective than USN anti-aircraft fire over 1941-2. This is because the HACS system (much criticized on the internet) had been improved by adding the Gyro Rate Unit Box (GRUB) and integrated radar ranging. Thus in December 1941, the RN probably led the World in AA capacity. Unfortunately, Force Z suffered because the critical radars did not work in the very humid Gulf of Siam. They did normally work in the Mediterranean or off Norway and might have worked for Force Z if there had been time to make adjustments for the local conditions. 

The problem is that from late 1942, the USN also added radar ranging and soon proximity fuses. Thus by 1944, the USN heavy AA was probably much more effective than that of the RN who lacked proximity fuses. Similarly, the USN was able to equip its ships with Bofors much faster than the RN although both navies were equally desperate to fit those guns.


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## Njaco (Feb 25, 2013)

We're watching......


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## parsifal (Feb 25, 2013)

we are trying. 

Ive had a bit of a look at Lundstrom and, judging from his explanation of sources, I think he is simply publishing known or confirmed losses when it comes to AA. He relies on Japanese accounts of losses as well as the observations of the fliers themselves. Yet I dont think the japanese are in much better position to know the cause of losses than the Americans were. They would certainly know the total losses but would not be in much better position to know the cause of those losses. It may also well be the case that an aircraft hit but not destroyed on the spot may not make it home. For major battles like Midway and Coral Sea, the overall losses are pretty well documented, whats at issue are the causes for those losses. 

So it may be that the differences between the final USN estimates and Lundstrom relate to how the losses are being collated. I dont think there is any argument now that the original claims by the USN especially for 1942 are pretty badly inflated. I am less convinced about the end of war report. The Americans had three years in which to revise and collate that report. They would have good knowledge of the pilots claims, and because they were reading about 70% of enemy signal traffic, would also have pretty complete knowledge of enemy total losses. We dont know how many of the Japanese losses were due to non-combat related issues. Some of the aircraft listed as missing in the japanese loss records may well have gone down due to battle damage, and some of that battle damage may well have been due to flak damage.

For that reason, whilst Lundstrom is held in near deity like reverenace around here, I am inclined to think that the final US estimates are as reliable as his figures. If we want to be honest about this, the facts are there are alot of unexplained losses, and losses that would be misreported. It may be the case that Lundstroms tallying methods are not comparable to the tallying system used by the USN. 

Finally I note that in the 1942, the tables refer to "bags" and not kills. What exactly is a "bag". Given the huge discrepancy in the kill tallies of this claim sheet, one has to at least wionder what it is they were recording.


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## Juha (Feb 26, 2013)

RCAFson said:


> Sorry, but I've produced hard data to back up the fact that the USN claimed 87 AA kills from Coral Sea to Eastern Solomons and yet only got 10 AA kills. That's not my opinion.



IMHO not the fact but Lundstrom's interperation of limited facts and oppinions available. While Lundstrom's books are very good one must remember that his books are on USN fighter pilots and IMHO at least on the first one, The First TEam, had biased towards fighter claims against AA claims when they were in conflict as they many times were, because overclaiming was fairly bad problem in early part of the Pacific War.

Juha


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## RCAFson (Feb 26, 2013)

Juha said:


> IMHO not the fact but Lundstrom's interperation of limited facts and oppinions available. While Lundstrom's books are very good one must remember that his books are on USN fighter pilots and IMHO at least on the first one, The First TEam, had biased towards fighter claims against AA claims when they were in conflict as they many times were, because overclaiming was fairly bad problem in early part of the Pacific War.
> 
> Juha



Lundstrom may be biased towards awarding kills to fighter pilots rather than AA, but by the same token Shores and Co. are probably guilty of the same when assessing RN AA and FAA fighter kill claims in the Med. However, it seems to me that Lundstrom has closely examined all the sources and we can be fairly certain that he is in the ball park - even if we increase AA kills by 50%, it still leaves the USN over claiming AA kills by a factor of 6. 

Again, IMHO, a typical RN officer who read the USN AA claim reports probably assumed that there was some over-claiming, perhaps by a factor of two, however since they knew that USN CIWS were far weaker than in the RN, they could then only assume that the USN's 5" MK33/37 GFCS were responsible for the still impressive (albeit false) number of AA kills. I have to wonder, though, that if the USN assessed their AA kills as severely as the RN did if we would be having such heated discussions about the relative efficacy of RN and USN naval AA?


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## RCAFson (Feb 26, 2013)

parsifal said:


> Finally I note that in the 1942, the tables refer to "bags" and not kills. What exactly is a "bag". Given the huge discrepancy in the kill tallies of this claim sheet, one has to at least wonder what it is they were recording.



I think my reply to Juha covers the first part of your post.

The USN used bird hunting terminology for some reason, and if you look at their AA kill tables by gun type they refer to "rounds per bird" rather than aircraft.


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## Juha (Feb 26, 2013)

RCAFson said:


> Lundstrom may be biased towards awarding kills to fighter pilots rather than AA,... However, it seems to me that Lundstrom has closely examined all the sources and we can be fairly certain that he is in the ball park - even if we increase AA kills by 50%, it still leaves the USN over claiming AA kills by a factor of 6...



I agree with that, IMHO he was less biased, at least the possible bias was less obvious, in his second book, The First Team and The Guadalcanal Campaign.



RCAFson said:


> but by the same token Shores and Co. are probably guilty of the same when assessing RN AA and FAA fighter kill claims in the Med...



Entirely possible but the fighting in Europe was a bit different from that in the Pacific where intense carrier war was common, so maybe that bias isn't so important. When there was no fighters around AA was clearly the obvious killer.

Juha


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## RCAFson (Feb 26, 2013)

Juha said:


> Entirely possible but the fighting in Europe was a bit different from that in the Pacific where intense carrier war was common, so maybe that bias isn't so important. When there was no fighters around AA was clearly the obvious killer.
> 
> Juha



All of the Malta Convoys had some carrier or shore-based fighter support.


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## Juha (Feb 26, 2013)

Every USN CV carried 20-27 Wildcats during the timeframe we are talking about, so they had more and generally better fighters available at that time than RN so in the Pacific fighters had greater impact.

Juha


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## Glider (Feb 26, 2013)

RCAFson said:


> Sorry, but I've produced hard data to back up the fact that the USN claimed 87 AA kills from Coral Sea to Eastern Solomons and yet only got 10 AA kills. That's not my opinion.



However you have ignored the other part of the posting where Parsifal said
_sorry, but they ARE your opinions. youve taken selected opinions and reports, ignored the opinions of others,, including some highly qualified officers in far better position to know than you or I,_ 

There can be no doubt that you have ignored these officers statments, people who were both experienced in combat and had seen both RN and USN at first hand.

There is also no doubt that you tend to make statments as if they were facts e.g _The RN wanted the 5in because they were free_. Nope the RN already had weapons lined up for the war built destroyers (the ones they were built with) and wanted the 5in because:-
a) we had seen an example on HMS Delhi and it had impressed
b) The officers whose opinions you have ignored were impressed
c) Because they were better than anything the RN had at the time

There is also no doubt that when faced with a question you cannot answer you just leave it and hope it goes away:-
_So we agree that the Tribals had the 4in and the 20mm before they received the 40mm guns. Which brings us back to the question you keep avoiding. Of course the toweight increased, the question is, was this a problem for the Tribal class destroyers.
My case is no it wasn't. I support this by the simple fact that the guns were added and no guns were removed to cater for it.
Your case is yes it was a problem but your evidence is -----------? what exactly

Adding a bit of ballast doesn't count as a problem as the ship still functioned in the front line with all her weapons_.

I also believe , that was well as the additional 40mm the Surviving Tribals also had a lattice mast added to hold the heavy radars. What they weigh I have no idea but they would have weighed something all without losing any weapons.

On attached photo I see 6 x 4.7, 2 x 4in, 4 x TT, 4 x 2pd, 6 x 40mm (single Mount), heavy mast and radars high up

http://www.google.co.uk/imgres?imgu...v=2&tbm=isch&um=1&itbs=1&sa=X&ved=0CC4QrQMwAg


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## parsifal (Feb 26, 2013)

Im happy, if for no other reason than we are getting some great images of the Arunta. Youd have to agree.....a fantastic looking ship if nothing else.


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## RCAFson (Feb 26, 2013)

Glider said:


> However you have ignored the other part of the posting where Parsifal said
> _sorry, but they ARE your opinions. youve taken selected opinions and reports, ignored the opinions of others,, including some highly qualified officers in far better position to know than you or I,_
> 
> There can be no doubt that you have ignored these officers statments, people who were both experienced in combat and had seen both RN and USN at first hand.
> ...



I haven't ignored anything- but at some point I simply stop repeating myself...I have stated repeatedly, that IMHO, the RN was swayed and misled by the extreme degree of AA kill overclaiming by the USN - something they were not in a position to know was happening at the time but something that I have proved conclusively did happen. If Delhi "impressed" it was during gunnery trials, in early 1942 yet the USN itself stated:


> Existing primary fire control systems in combatant vessels (Mark 37 or 33) are designed for dual purpose functions. Their efficiency in handling a critical AA. problem accordingly suffers. *Unfortunately this deficiency does not become apparent as a result of training because the towed sleeve, with which the bulk of training is of necessity performed, lends itself well to the shortcomings of the system*...
> HyperWar: Antiaircraft Action Summary--Suicide Attacks [Chapter ]


It is a fact that Delhi never saw combat during the critical Malta convoy battles of 1942 and when she did enter combat she had a less than stellar record; much less stellar than other AA cruisers equipped with RN equipment, and that Delhi was originally slated to have RN AA guns and FC installed. I have produced numerous quotes showing that the USN itself became disenchanted with Mk37 because of it's sluggish processing speeds and that they considered the MK33 to be an outright failure. The RN never attempted to purchase USN guns and firecontrol and what they did get, they got via lend-lease, effectively for free! They ordered USN firecontrol (via Lend-lease and according to USA LL policy they could not order RN spec equipment) because the UK could not produce enough to meet it's own needs.



> There is also no doubt that when faced with a question you cannot answer you just leave it and hope it goes away:-
> _So we agree that the Tribals had the 4in and the 20mm before they received the 40mm guns. Which brings us back to the question you keep avoiding. Of course the toweight increased, the question is, was this a problem for the Tribal class destroyers.
> My case is no it wasn't. I support this by the simple fact that the guns were added and no guns were removed to cater for it.
> Your case is yes it was a problem but your evidence is -----------? what exactly_


The Tribals deleted the 56000 lb 4.7in twin at "X" position (one deck above the weather deck), then added a 4in twin in it's place saving 19000lb. They then added 4 - 6 20mm guns which weight about 1500lb for the single mount and about 2900lb for the power operated twin mount, so this weight is more than compensated by the removal of the 4.7in twin mount, plus at some point they also deleted the two .5in quad mounts at 2600lb each, so they reduced weight by 19000 + 5200lb = 24000lb and added a maximum of 12000lb for 3 twin 20mm and several tons for radar etc. They then deleted all the 20mm guns and added 6 x single 40mm bofors in either Mk V power mountings (the Boffin mounting) or MK VII power single mount- both of these mounts weighed about 1.4-1.5 tons according to Campbell and Friedman.

so to sum up the RAN deleted 24000lb in the twin 4.7in and the two quad .5in and added about 18000lb for the 6 x 40mm single mounts, leaving 6000lbs for other additions.



> _Adding a bit of ballast doesn't count as a problem as the ship still functioned in the front line with all her weapons ._



The ship wouldn't have functioned properly without the ballast - March makes that clear! (note that this appears to be your opinion...  )



> I also believe , that was well as the additional 40mm the Surviving Tribals also had a lattice mast added to hold the heavy radars. What they weigh I have no idea but they would have weighed something all without losing any weapons.
> 
> On attached photo I see 6 x 4.7, 2 x 4in, 4 x TT, 4 x 2pd, 6 x 40mm (single Mount), heavy mast and radars high up



Yes, the lattice mast was required for the radars, which is why they weighed so much.


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## RCAFson (Feb 26, 2013)

A general summary of lenlease and USA restrictions on weaon and equipment types:



> But in the summer of 940 the hard facts were that the decision as to the standardization on British designs lay with the Americans and that in the main the decision was adverse. The British had therefore to decide whether, notwithstanding all the objections to such a course, they should agree to place orders for American types or whether they should persist in the attempt to secure a separate niche, within the general framework of American munitions production, for the manufacture of at least some weapons of purely British type. Against the latter policy there were two arguments so obvious and decisive that to invoke them seemed almost superfluous. One was that it would mean foregoing the chance of American capital assistance for British orders. On 24th August there was an important meeting between British and United States representatives, the theme of which was 'the adoption of common types so as to create one productive capacity'. Here was renewed Morgenthau's offer to consider financing the manufacture for British orders so long as the United States were satisfied that the type of weapon manufactured for England was the same as the United States Army and Navy had adopted. If the United Kingdom pressed its own types, it did so at the risk of having to pay the whole capital cost as well as purchase the output and with no prospect of later American assistance. The other argument was the Administration's control over priorities and shipments. British supply representatives in America united in underlining the folly of trying to start separate British programmes which would be bound to take second place to production for the United States Services. For example, the better-known aircraft firms would -be unlikely to accept British orders in preference to American. It might, therefore, be necessary to fall back on untried and inexperienced firms. This would hardly be practicable unless the United Kingdom could provide fully equipped production teams, as well as much larger capital assistance. *Moreover the United States Government was always in a position to bar British access to American firms, which it did temporarily in August I940 pending a settlement of the question of types.* Purvis summed up the whole position as he saw it in a very important cable of 24th August. 'We believe that it is only if (as in the last resort will be inevitable) we agree promptly with the Americans on common types of weapons, so achieving complementary programmer, that we can hope to take advantage of the plan . . . whereby the American Administration finances our capital expenditure . . . or obtain United States consent to . . . priorities on deliveries.' The point about priorities was that the Administration would allow 'British' plants to be built and equipped more quickly than its own if, but only if, the material produced thereby could be diverted in case of need to its own use; also that it might sometimes release to the British material produced under its own contracts if it knew that there would be identical material coming along later on British contracts, from which it could be recouped
> Overseas Supply, Hall, p.97-98.​



So at one point the US government called a halt to UK orders, if the UK would not agree to ordering US designs and this was when the UK was paying cash...the situation only got worse when lend-lease formally started. So the USN was in a position to veto the production of any RN spec weapons and FC equipment. WE have seen how USN DEs went to sea with no AA or surface FC equipment, even though the UK was outfitting all UK built Hunt class DEs with lightweight and effective FC equipment right from the start. Similarly the RN 4in twin was, IMHO, a better DE weapon than any built in the USA (3in/50 was too light and the 5in/38 too heavy) but while it was produced in Canada it was never built in the USA.


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## Shortround6 (Feb 26, 2013)

The US got "burned" in the First World War with too many of it's factories tooled up for French and British weapons/ammo that the US didn't want or couldn't use when it did declare war 1917. Granted the US 75mm field gun of 1916 was often called the "crime of 1916" but what the US "standardized" on was the British 18pdr field gun chambered/lined for French 75mm ammo. The US majority of US troops went to war not with the 1903 Springfield but with the 1917 Enfield ( a 30-06 version of the British .303 Pattern 1914) and so on through a variety of weapons. Or weeks/months were lost as factories re-tooled. The US was determined that that would not happen again. 

Mistakes were made and the British 4in twin was a better DE weapon than the US 5in but making large numbers means something else not being made and complicating the ammo supply even more than it was.


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## parsifal (Feb 26, 2013)

yes, standardization was very important from a logistic point of view. Having a single calibre for main armament for destroyers and smaller made a lot of sense. If the 5/38 was the best that was available, but didnt quite suit the Escot Destroyers because of its size, it would have been even less satisfactory to have some ships using 4" and some the 5/38. It would still work, but it would place strains on the logistics system, not just in terms of ammo, but also in terms of a whole range of things....training, spare parts, capability. Putting the 5/38 on the DEs was a case of "good enough".


I dont have any problem in stating British Hunt Class Escort Destroyers were generally superior to the USN classes of DEs.

The problem for the RN was quite narrow. It lies with its "Fleet Destroyers". They were supposed to provide muti level defence for high level targets, and that meant being able to counterr threats from the surface, above the surface and below the surface. For a long time British Destroyers had a hard time providing effective fleet defences against air attack. They could defend themselves, and they could defens against other threats, but providing area air defence seems to have been a difficult task for them. Now, whether the USN could do it any better is in disopute, but for me, it seems clear that the USN filled that role better than the RN.


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## vinnye (Feb 27, 2013)

The USN destroyers had a hard time defending themselves off Okinawa - 5 sunk and 16 badly damaged.
Multiple attacks against any ship without aircover or mutual support are going to have a bad day.


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## Shortround6 (Feb 27, 2013)

That is part of the trouble with using combat results as a comparison. The "opposition" is not consistent. For that matter even the AA defense is not consistent. 

The US Navy off of Okinawa was facing what were in effect, primitive guided missiles capable of different attack profiles. A much different threat than conventional aircraft (goal of the pilot was to get home).

Helping the US was the VT fuse which made the 5in/38 up to seven times more effective than using regular time fuses. 

The 5in/38 might be remembered a bit differently without VT fuses. However it had the elevation, training and elevating speed (mostly) and rate of fire to make good use of them. Please note that is was more of a happy coincident than good planning, the VT fuse being little more than vague ideas when the 5in/38 was adopted.


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## parsifal (Feb 27, 2013)

Many Of the DD losses occurred because the USN were using radar pickets, some posted as far out as 60 miles from the main body, to provide advance warning of incoming attacks. The Japanese were using their suicide strikes very intelligentlyand were generally approaching from multiple directions and very ow in Altitude. The CAP was not being given enough warning of the approaching strikes, and as a consequence, whilst they were geneerally vectoring to intercept, were simply not given enough time to break up the incoing strikes. Placing radar pickets around the TGs allowed the CAP longer time to deal with the suicide attacks. 

Unfortunatly, the down side of this initiative was that the picket destroyers whilst operating in pairs could not generate enough fire to prptect themselves fully. As the Japanese became increasingly desperate, many attacks targetted the Picket ships. Losses amongst these ships was heavy, amounting to about 20% of total USN DD losses for the entire war. However, for the work they were doing, this was judged a reasonable price to pay. 

Fraser Rawling spent some time aboard a US Task Force flagship in 1945. I forget which one. What they saw for themselves changed the way they organized the defences of the BPF. The USN Carrier TGs were organized so as to maximize AA defences against high value targets, and theiir CAP was given a lot of time to intercept and engage the incoming strikes. Once within the flak zone they also witnessed the USc DDs providing effective and concentrated cover fire simulataneously from both the DDs main batteries and the 40mm CIWs. The smaller TDs of the USN heavy units meant that USN TGs could be more densely packed than the BPF (around 20% more tightly).....if you attacked a carrier in a USN TG, all the wepons in the support screen of that carrier could fire at you. The result was a very effective defence screen, in which the Destroyer screens played a critical part. 

Fraser and Rawlings compared this very tight and effective defence to the efforts of the BPF. The BPF had a generally, man for man, more effective CAP, but it too was not being given enough time to react. The Brits generally used their LIII Sefires for the intercepts down low (and with its heavy firepower, high low level manouverability and climb rates it was probably the best a/c in the pacific for this purpose) whilst stacking their Hellcats and Corsairs further out and higher. But intercpets were still not happening quick enough. generally at the 30 mile range, this was just not enough to break up the typical suicide strike of 20-30 a/c. 


Once the attackers did break through, the British admirals noted the inability of their own DD screens to operate as effectively as the US DDs in the area air defence role. There were a number of reasons for this. The low elevation of their main armament, the slow traverse and elevating speed, the unreliability and relative short range of their CIWs, the lack of effective incendiary rounds for them, the inability of the DDs to use both their Main HA armmanet and CIWs together, the inability of DD CIWs to always and uniformly provide cover fire over the core ships. Time and agin in March -April-May, the Kamikazes had broken through the British defences and caused damage to the precious carriers.

Fraser and Rawlings came up with solutions for these problems, and they followed closely the US pattern (but taking into account the limits of their own wepons) . The TD limits of the Capital ships were ignored to allow the 2 pounders of the escorts to get cover over the carriers, the inability of the 4.7s to fire at those close ranges was accepted. The British admirals pushed for the installation of 40mm Bofors to replace the 2 pounders which by then was all but an obsolete weapon ( wthe replacement of the 2 pounder with the 40mm Bofors was happening progressivley by wars end),. But it was also acknowledged that the BPFs best defences against the Kamikazes were the airborne CAPs, and in the current situation they were not being given enough time or space to have full effect. It was very quickly realized that pickets similar to the US sytem were needed. However, unlike the Americans, who saw their better armed DDs as having some chance at self defence the british never considered placing unprotectd DDs alone in the picket screen. Instead they intended (or may have actually done it) to form two picket screens, each centred around a cruiser and 2 x DDs with 2-4 fighters flying constant air patrols over them


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## RCAFson (Feb 27, 2013)

The 20mm gun was being replaced progressively by the Bofors but the pom-pom was also being used in the new power single mounts on many new built destroyers. Given equal firecontrol to the Bofors, the pom-pom was an effective weapon against Kamikazes and much better than the 20mm.

USN picket destroyers were generally their later classes, which being much larger than RN destroyers had no equivalent in the BPF, especially as the Battle class were delayed in entering service. In any event using DDs as pickets was a bad idea, that the USN could get away with because they had so many destroyers by 1945. 

Without seeing their action reports, I cannot comment of the performance of RN destroyers during the Kamikaze attacks, but Kamikazes certainly did penetrate the dense screens to hit USN CVs, often with disastrous results.


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## Glider (Feb 27, 2013)

I think you will find that some of the USN DE's were used as picket ships, it wasn't just the latest Fletcher and later classes of destroyers. 

The USN got away with it as you put it, because their ships had a good chance of surviving. Its also worth remembering that the USN were not just protecting the CVN but often very vulnerable CVL and invasion fleets. The pickets detected the incoming attackers and directed the fighters to intercept. Often the attacking aircraft picked on the destroyers because they couldn't get to the main targets the fleet and knocking out the radar pickets was a valid tactic. 

Re
_In any event using DDs as pickets was a bad idea,_
Clearly if you are going to withdraw the pickets then the defending forces are are going to have less time to respond to the threat. The less time you have to react, the attacks will be closer before being intercepted. The more concentrated and organised the attack, the more attacking aircraft are going to get through and the higher the losses. 

What would be a good idea?


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## RCAFson (Feb 27, 2013)

Glider said:


> I think you will find that some of the USN DE's were used as picket ships, it wasn't just the latest Fletcher and later classes of destroyers.
> 
> The USN got away with it as you put it, because their ships had a good chance of surviving. Its also worth remembering that the USN were not just protecting the CVN but often very vulnerable CVL and invasion fleets. The pickets detected the incoming attackers and directed the fighters to intercept. Often the attacking aircraft picked on the destroyers because they couldn't get to the main targets the fleet and knocking out the radar pickets was a valid tactic.
> 
> ...


 
I think the ideal would be a CLAA such as Dido or Atlanta class as even lightly armoured ships were nearly impossible to sink via kamikaze strikes. The other possibility would be old BBs outfitted with a very heavy CIWS. However, the USN really "got away with it" because they considered their DDs expendable, much as the RN did in Norway and the Med. For the USN Okinawa was "the tip of the spear" where they concentrated the bulk of their fleet, whereas for the RN it was a secondary theatre until after the German surrender, and by then the RN had shot it's bolt, militarily speaking, since they had been at war for 2 1/2 years longer than the USN. Although if the bulk of the 1945 RN had been concentrated around Okinawa they would have had the ships to expend as well.


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## vinnye (Feb 27, 2013)

The pickets were used as a way of detecting air raids - conventional and Kamikaze at a distance from the main fleet. 
I would suggest that some of the pilots given their lack of training would attack the first target they found - the pickets.
If they tried to attack a carrier of any sort or troop ships etc, they would have to try to evade the CAP and an intense AA barrage - giving them less chance of success.
I believe the USN had in its plans to build radar stations on land so that the pickets could be moved back to a safer location?
Also, a change in top brass made a shift in emphasis from detecting aircraft to laterly destroying them.
This change in emphasis would probably put the destroyers at greater risk?


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## RCAFson (Feb 27, 2013)

Part of the problem with many books dealing with WW2 destroyers is that they praise the USN for developing a HA 5in gun, and damn the RN for not doing so, but then in the same breath admit that the HA 5in guns were useless against dive-bombers or other close range attacks:



> On the other hand, US pre-war destroyer designs did not include provision for many automatic AA weapons, partly because the slow development of the 1.1in machine gun made this a moot point for many years. *The 5in gun was considered useful for breaking up horizontal bombing formations, and perhaps for dealing with torpedo bombers flying at low level (eg by firing into the water to create splashes); but it was useless as a counter to the two other major airborne threats, the dive bomber and the strafer.* Against the latter, most pre war destroyers were armed with the .5in warer-cooled machine gun. The l.lin weapon was intended to deal with dive bombers, but pre-war destroyers generally limited by treaty to 1500 tons could not accommodate it, the only exceptions being the 1850-ton destroyer'Leaders'. By 1937 many people in the feet wanted the 1.1in gun aboard destroyers, but that appeared impossible until the design of the large Fletchers. 'Impossible' turned out by 1941 to mean rather 'impossible unless some other weapons were sacrificed', and much of the story recounted here is the story of the variety of 'trade offs' made between traditional destroyer weapons and the weapons required for close range air defence.
> Destroyer Weapons of WW2, Hodges, Friedman, p106.



So the RN developed the Tribal and JKN class DDs with DP 4.7in guns to engage level bombers and torpedo bombers and equipped their destroyers with an extremely heavy CIWS (by pre-war standards) of 8 .5in MGs and 4 x 40mm pom-poms (which the USN considered superior to the 1.1in) and then receive very faint praise for their efforts.


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## parsifal (Feb 27, 2013)

> The 20mm gun was being replaced progressively by the Bofors but the pom-pom was also being used in the new power single mounts on many new built destroyers. Given equal firecontrol to the Bofors, the pom-pom was an effective weapon against Kamikazes and much better than the 20mm.



This is in direct contrast to the recommendations of Fraser and rawlings. They found the Pom Pom to be severely limited on the DDs attached to the BPF. It lacked effective range, lacked effective Tracer capability and was too prone to james. They wanted the Bofors AND the POM PoMs replaced with the bofors. they were provided 



> USN picket destroyers were generally their later classes, which being much larger than RN destroyers had no equivalent in the BPF, especially as the Battle class were delayed in entering service. In any event using DDs as pickets was a bad idea, that the USN could get away with because they had so many destroyers by 1945.



They were only "generally the later classes" because the later classes greatly outnimbered everthing else. Tough break for the BPF, but the ships in the British Fleet, such as the Q classes were only as old, or even newer than some of the Fletchers serving in the Picket lines. 



> Without seeing their action reports, I cannot comment of the performance of RN destroyers during the Kamikaze attacks, but Kamikazes certainly did penetrate the dense screens to hit USN CVs, often with disastrous results.



Youve got the reports submitted by Rawlings and Fraser, which give a detailed ccount of their performance to the Admiralty. And we know from the results of those attacks in that time period the level of success they enjoyed (time and again Kamikazes broke through....so too did the Americans, but they appear to be suffereing much heavier levels of attack). Against even single attackers, the BPF destroyers were unable to bring 4.7 fire to bear, could not use their CIWs at all times, and were unable to bring mutually supporting combined fire to bear over the Carriers. Saying you need to see the actual battle reports is a cop out in my opinion. Their commanding admirals already submitted some good details of their performance, you just choose not to take any notice of them.


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## Glider (Feb 27, 2013)

RCAFson said:


> Part of the problem with many books dealing with WW2 destroyers is that they praise the USN for developing a HA 5in gun, and damn the RN for not doing so, but then in the same breath admit that the HA 5in guns were useless against dive-bombers or other close range attacks:


Remembering that all HAA was useless against dive bombers before the proximity fuse.


> So the RN developed the Tribal and JKN class DDs with DP 4.7in guns to engage level bombers


Remembering that the RN only had approx 35-40 seconds to engage the level bombers and couldn't touch them when they dropped their bombs
This is worth considering when the proximity fuse arrives. The RN 4.7 still only has 35-40 ish seconds to fire whereas the US 5in can give now effective fire down to the last second.


> and equipped their destroyers with an extremely heavy CIWS (by pre-war standards) of 8 .5in MGs and 4 x 40mm pom-poms (which the USN considered superior to the 1.1in) and then receive very faint praise for their efforts.


This bit I do agree with

Note to one and all. The advantage of destroyers is that they were considered expendable by all navies.


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## RCAFson (Feb 27, 2013)

parsifal said:


> This is in direct contrast to the recommendations of Fraser and rawlings. They found the Pom Pom to be severely limited on the DDs attached to the BPF. It lacked effective range, lacked effective Tracer capability and was too prone to james. They wanted the Bofors AND the POM PoMs replaced with the bofors. they were provided
> 
> 
> They were only "generally the later classes" because the later classes greatly outnimbered everthing else. Tough break for the BPF, but the ships in the British Fleet, such as the Q classes were only as old, or even newer than some of the Fletchers serving in the Picket lines.
> ...



Here's the Despatch from Fraser and Rawlings:
http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38308.pdf

I can't find any real criticism of RN AA or weaponry. Here's a few pertinent excerpts:




> *One Judy and another unidentified enemy
> plane flying low were engaged by destroyers of
> 4th Destroyer Flotilla on the screen, one being
> hit by gunfire*. Corsairs and Hellcats closed the
> ...



In fact the BPF did use pickets, and they generally used a CL and DD together.

That USN picket destroyers were larger than their RN counterparts is a fact, but the main point is that a larger hull always allows for a much more capable CIWS and it is difficult to make valid comparisons between ships of greatly different displacement and dimensions. I have no doubt that, in terms of treaty limited designs, RN destroyers were superior to their USN counterparts in terms of overall balance between AA and surface fire.


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## RCAFson (Feb 27, 2013)

Glider said:


> Remembering that all HAA was useless against dive bombers before the proximity fuse. Remembering that the RN only had approx 35-40 seconds to engage the level bombers and couldn't touch them when they dropped their bombs
> This is worth considering when the proximity fuse arrives. The RN 4.7 still only has 35-40 ish seconds to fire whereas the US 5in can give now effective fire down to the last second.
> This bit I do agree with
> 
> Note to one and all. The advantage of destroyers is that they were considered expendable by all navies.


At 9000ft ( at which altitude, and at a speed of 150 knots (172mph),IIRC, IJN level bombers scored hits on PoW, Repulse and Hornet ) a 240mph bomber could be engaged for about 50 seconds with a 40deg 4.7in and about 65 seconds at 6000ft so, as the altitude of the level bomber decreases to increase it's accuracy, so to does the time under fire. 
Remembering that high altitude level bombers posed little threat to manoeuvring ships at sea, it doesn't make sense to optimize a destroyer for that threat alone, at the expense of a large reduction in surface firepower and a strong CIWS which was the only counter to divebombers. I have argued that the optimal compromise between gun elevation and weight increases occurs at around 55degs, which the RN adopted for the last variants of the 4.7in single and first version of the 4.5in single but IMHO 40degs with a heavy CIWS is better than 85degs with a handful of HMGs for a CIWS and a 50% reduction in main armament.


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## parsifal (Feb 27, 2013)

Your looking and quoting the wrong report.

I refer you to JR Webb – The British Pacific Fleet Experience and Legacy 1944-50 In the Chapter titled "Air Defence" for the period March to May he says the following 

"British AA defence procedures had grown out of the RNs pre- war experience and it operations in European waters. Before the outbreak of war the RN had doubted defensive fighters could be directed to successful interception due to the speed at which air attacks could develop, and this led to little attention being given to this role. The development of RDF and its potential to assist a fleet in dealing with air attacks was clearly demonstrated in the fleet exercises of 1939 and the fighting instructions issued shortly after included fleet dispositions to optimise its effect. 

The RN had developed its method of defending vessels at sea from air attack under the particular circumstances of the (ETO). But whereas AA fire from 2 pdr and 20mm guns could interfere badlly enough with a pilots aim to make his chances of hitting with a bomb or torpedo more difficult in that TO, in the PTO, when faced with suicide planes these weapons showed a marked inability to actually destroy the aircraft. This was seen as a major problem by the commanders on the scene. Kamikazes would approach at high speed and would not veer off if damaged. The Americans had found that their 40mm guns could break up attacking planes and the british discovered for themselves that (their weapons) could not. The british discovered that they had a desperate need for (the Bofors) to replace their inadequate and underpowered LAA. Fraser wrote 

"_The armament of our Destroyers has been designed primarily from an anti-ship point of view and generally speaking they are as the Americans would say 'not able to look after themselves_" 

Indeed, when Fraser came to write his report on the lessons learned by the BPF in the Okinawa campaign he said

"_The standard of AA gunnery by our destroyers was low which could be offset by training and requipment _….."

Webb again

"Although armoured decks had saved the BPFs carriers, it was abundantly clear that Kamikaze attacks required a change in tactical thinking. Rawlings acknowledged that the kamikaze attacks had placed a premium on fighter interceptions being carried out at maximum possible range…..he wrote in his report

"_Operations were revealing that US pattern defensive dispositions were superior to our own, but a conventional US pattern AA screen (was difficult for us)….there were difficulties in providing fire support over the main body _(by our Destroyers). " 


Webb
"Rawlings partially addressed this by adopting a new screen disposition, which was more densely packed (to attempt to allow the escort to place supporting fire over the main body). Speaking after the actions of 9 May, Rawlings stated "The object of these new dispositions were in evolved in response to our experiences and had the object of giving better protection to the carriers during suicide attacks." But these new dispositions led to station keeping and manoeuvre inflexibility and led to Rawlings advocating the re-equipment with 40mm Bofors as the chief LAA as well. Secondly". 

Webb then comments on the BPFs efforts to develop effective picket forces. 

"The USN had utilised radar to a greater extent in their light forces than the RN. Radar equipped ships were utilised as advanced warning pickets. These pickets were seen as central to the BPFs overall air defence response to Kamikaze attacks. Each picket was initially to contain 4 DDs and 4 Fighters was stationed 40-60 miles from the fleet to cover an arc of 180 degrees in the most likely direction of attack. These DDs were specially equipped with radar and fighter direction equipment, but the BPFs response was technologically inferior to that of the USN. The Directorate of air warfare and flying training decided in July to fit out cruisers to perform the same function and provide similar levels of defence to the picket line. Cruisers were considered better able to protect themselves and the existing fleet destroyers radar was not efficient enough in his assessment. The Director Of radio Equipment at the time commented that the number of aircraft involved was swamping the Action Information Organization (AIO) and radar identification . despite the fact that the RN had assisted earlier in the war, in the introduction of AIOs (CICs in the US parlance) the clear superiority of US C&C in this field was another example of the Americans being able to bring to bear more resources to develop an idea faster and better than the RN could ever hope to achieve".

In commenting on the improvements to air defence Webb states that the BPF still lagged behind the USN, but the improvements that had been achieved were cause for some satisfaction. "The AA defence of the TF had also seen important improvements. In mid-May Rawlings reported to Fraser, advising that the BPF had been devoting much of its exercise time and resources to the introduction of new air defence technologies, techniques and procedures, with pleasing results. In particular he drew attention to the new VT fuses. He wrote

"_We do depend on this VT fuse now. All our recent training has been centred around them. The improvements in equipment, radar, fighter direction (have achieved astounding improvements_)" 

Webb
"The British had been developing VT fuses for use in bombs and rockets , but had convinced themselves the technical problems in making such fuses rugged enough to be fired from a gun were at that time (too difficult)


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## RCAFson (Feb 27, 2013)

parsifal said:


> Your looking and quoting the wrong report.
> 
> I refer you to JR Webb – The British Pacific Fleet Experience and Legacy 1944-50 In the Chapter titled "Air Defence" for the period March to May he says the following...



I see Webb stating his opinion of the pom-pom, but with no supporting evidence for that statement, which runs counter to Campbell and to commonsense; multiple pom-pom hits would tear apart any IJN aircraft just as Bofors hits would, albeit the Bofors would require fewer hits but then a quad pom-pom has a greater volume and density of fire, than a twin bofors MK V, which weighed about the same. The USN's own experience showed that the Bofors could not be relied upon to stop kamikaze aircraft, and we've all seen film footage of kamikaze's penetrating USN screens to hit their carriers even after being hit by 5in and 40mm fire. Fraser's and Rawlings statements regarding the nature of kamikaze attacks and their ability to evade detection seems to indicate that the armament of RN destroyers was not the problem, and if the USN had superior radar or CIC, this is not a reflection on RN destroyers.

Webb is wrong about UK development of the VT fuze - UK development of VT fuzes to fit AA guns proceeded before and after turning over their technology to the USA via the Tizard mission, but part of the quid pro quo of giving VT technology to the USA was that the development and output of north american VT fuze production would be shared with the UK, with the RN receiving 2nd place in priority after the USN. Consequently, the development of VT fuzes received lower priority in the UK than previously, since two full development programs in the UK and USA would have been a huge duplication of effort. The Deadly Fuze has a good summation of the UK effort.


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## parsifal (Feb 27, 2013)

Its not just webbs opinion. he is fleshing out and reaffirming those held by Rawlings and Fraser, and quote them to support his statements . And campbell does not say what you are claiming he does. In fact whilst Campbell does say alot about the technological operation of the weapon, he is pretty silent about its value (the 2pounder) . 

He does say, however that the type had serious problems with relatively low muzzle velocity, though some mountings and later gun types in the family did addresse this at least partially. As to common sense, well, thats a matter of opinion really, but a genuinely friendly piece of advice, I would not start running around spriuiking that this or that source lacks common sense. What do you think the other contributors would say if they were asked who was lacking common sense (and experience) in this debate....... for what it worth I think I am lacking in common sense and judgement for even getting mixed up in this debate..... .

The Pom Pom could not operate as effectively as the bofors because of the limits of the gun. It was not a good area defence weapon at all really, which is why is was obsolete by wars end. It was shorter ranged and the loadout of the ammunition more restricted. It had some serious relaibility issues. Pom Poms, whilst better able to provide some cover fire over high value targets than a 0.5 or 20mm cannon, , were still too restricted in their effective range (at least in the DD fit outs) to do this job as effectively as the longer ranged and more lethal Bofors. 

no-one is saying that the 5/38-bofors combinination was completely effective. The USN thought it needed a heavier punch than either could deliver,m which is why they spent so much time and effort working on a 6" DP weapon. Determined Kamikazes could still penetrate the screens even with Bofors and 5/38 blazing away as hard as they could. But the british Admirals at the scene thought they had greater capability than their own equipment, which they saw as part of the problem, along with, as you say, the shortcomings in their DD radar fitouts.


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## cherry blossom (Feb 28, 2013)

There is some information on the philosophy of RN DD design with respect to anti-aircraft guns at http://www.royalnavalmuseum.org/documents/SB45_Autumn2012.pdf. It is too short but seems interesting.


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## parsifal (Feb 28, 2013)

A great find IMO

Dosent confirm that either side of this debate is completely correct. My opjnion on its key points.....the RN was correct and adequately armed in the pre-radar age, though its choice of weapons was poor. It relevantly quotes Friedman...."Norman Friedman, in ‘British Destroyers and Frigates’ (2006) writes ‘Once war broke out, it became painfully obvious that the 40˚ 4.7” gun, was an inadequate AA weapon’ (p34). Yet later (p113) Friedman acknowledges that wartime experience tended to confirm the pre-war view that arming destroyers with ‘High Angle’ main armament imposed a significant weight penalty for no real benefit".

This commentary would suggest that by 1945, the USN and the theory of air defence had bypassed the RN and its oudated equipment.


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## RCAFson (Feb 28, 2013)

parsifal said:


> Its not just webbs opinion. he is fleshing out and reaffirming those held by Rawlings and Fraser, and quote them to support his statements . And campbell does not say what you are claiming he does. In fact whilst Campbell does say alot about the technological operation of the weapon, he is pretty silent about its value (the 2pounder) . He does say, however that the type had serious problems with relatively low muzzle velocity, though some mountings and later gun types in the family did addresse this at least partially. As to common sense, well, thats a matter of opinion really, but a genuinely friendly piece of advice, I would not start running around spriuiking that this or that source lacks common sense. What do you think the other contributors would say if they were asked who was lacking common sense (and experience) in this debate....... for what it worth I think I am lacking in common sense and judgement for even getting mixed up in this debate..... .


Campbell, Naval Weapons of WW2, p. 67: "_...if control and mountings were of equal efficiency, the Bofors was reckoned to be twice as effective as the pom-pom against torpedo planes *but not much better against very close range targets such as Kamikazes.*"_

The comparative service MVs of the Bofors/Pom-pom are 2720/2300fps - The Bofors will be more accurate and hit harder, but if a 40mm 2lb explosive shell can tear apart an airframe so can a 40mm 1.8lb explosive projectile as Campbell implies.



> The Pom Pom could not operate as effectively as the bofors because of the limits of the gun. It was not a good area defence weapon at all really, which is why is was obsolete by wars end. It was shorter ranged and the loadout of the ammunition more restricted. It had some serious relaibility issues. Pom Poms, whilst better able to provide some cover fire over high value targets than a 0.5 or 20mm cannon, , were still too restricted in their effective range (at least in the DD fit outs) to do this job as effectively as the longer ranged and more lethal Bofors.



With self destructing ammo, the Bofors and pom-pom had roughly the same effective range. A well maintained quad pom-pom was also quite reliable and had the advantage of a large on-mount ammo supply, that could fire without reloading for over a minute. One could fit a quad pom-pom into the same weight of mounting, occupying the same deck area, as a twin Bofors.



> no-one is saying that the 5/38-bofors combinination was completely effective. The USN thought it needed a heavier punch than either could deliver,m which is why they spent so much time and effort working on a 6" DP weapon. Determined Kamikazes could still penetrate the screens even with Bofors and 5/38 blazing away as hard as they could. But the british Admirals at the scene thought they had greater capability than their own equipment, which they saw as part of the problem, along with, as you say, the shortcomings in their DD radar fitouts.


Of course the larger and better armed late war USN destroyers had greater capability than existing BPF destroyers. The latest classes of RN destroyers were still working up in Europe as the war ended.


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## RCAFson (Feb 28, 2013)

parsifal said:


> This commentary would suggest that by 1945, the USN and the theory of air defence had bypassed the RN and its oudated equipment.



I don't think that comparing 1945 designs with 1939 designs is very helpful. The last classes of wartime RN destroyers the C, Ch and Battle classes had improved FC with better radar, a modern CIWS outfit and RPC 4.5in guns - but they arrived just too late to make a useful contribution to the BPF.


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## RCAFson (Feb 28, 2013)

cherry blossom said:


> There is some information on the philosophy of RN DD design with respect to anti-aircraft guns at http://www.royalnavalmuseum.org/documents/SB45_Autumn2012.pdf. It is too short but seems interesting.



Yes, an interesting and informative article by an RN officer:
_Museum Model Series – Part 2: HMS Eskimo (Mark Brady) p.24_


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## parsifal (Feb 28, 2013)

> Campbell, Naval Weapons of WW2, p. 67: "_...if control and mountings were of equal efficiency, the Bofors was reckoned to be twice as effective as the pom-pom against torpedo planes *but not much better against very close range targets such as Kamikazes.*"_The comparative service MVs of the Bofors/Pom-pom are 2720/2300fps - The Bofors will be more accurate and hit harder, but if a 40mm 2lb explosive shell can tear apart an airframe so can a 40mm 1.8lb explosive projectile as Campbell implies.




I did see that quote, but only after Id made my original post. An omission on my part, but doesnt change much. Campbell is being very kind to the 2 pdr here. The problem is this. Kamikazes like all aircraft start out as long range targets. Unlike other forms of attack, they close at very high speed, and reduce the range to zero. They tend to attack so as to reduce the effects of centrally located weapon systems....for example, if the main defences are located aft, they will attack from ahead. This is probably why in those reports I posted earlier, the British ceased firing at critical moments. And unlike the Bofors, the 2 pounder mountings tended to be concentrated at one point on the ship. Kamikazes had an easier time blocking fire from 2 pounder mountings than they did against the Bofors mountings....poorrer fields of fire I guess.

However thats not the point. Whilst both the Bofors and the 2pounder had the same sized explosive shell, both had difficulty in destroying Kamikazes at close range. It usually took multiple hits to stop a kamikaze, and that required successful engagement from long range. Once a Kamikaze got to within several hundred metres of the target, unless it just missed, it was too late. For either of the 40mm mounts to actually stop a kamikaze, they really had to do it several thousand metres from the target. 2 pounder fire was much less effective at that, as Campbell points out. In other words, he was trying to be charitable to the 2 pounders. Again,i would point you in the direction of the commanders on the spot. they were clamouring for the Bofors to replace the 2 pounders for precisely this reason.

By way of comment, the USN even considered the 5/38 as lacking effective stopping power for a kamikaze, which is one reason they were working on a 6in DP weappon at the end of the war. 




> With self destructing ammo, the Bofors and pom-pom had roughly the same effective range. A well maintained quad pom-pom was also quite reliable and had the advantage of a large on-mount ammo supply, that could fire without reloading for over a minute. One could fit a quad pom-pom into the same weight of mounting, occupying the same deck area, as a twin Bofors.




I dont know about the self destruct ammo. but its just untrue that the Bofors and 2 pounders had the same range. again I refer you to the commanders on the spot. They simply dont back up the claims you make for the 2 pounder. And as you are so fond of quoting max ranges all the time, the max horizontal range of 10750m and a vertical range of 23000 ft, compared to the 2pounders maxs of 6800 and 13k vertical. They are not similar at all. If we want to be realistic and look at max effective range, the Bofors was about 4000 yards horizontal, and about 6000 vertical, the pom was about 2000 horizontal ( in the DD mounts that were deployed) and about 1800 vertiical. Again not comparable at all. Thats why the BPF wanted to ditch their 2 pounders and replace them with Bofors. 



> Of course the larger and better armed late war USN destroyers had greater capability than existing BPF destroyers. The latest classes of RN destroyers were still working up in Europe as the war ended.




In your following posts you mention Battle classes and various of the C classes. We have talked a lot about the Tribals and the JKN classes, and that I dont mind in the case of the tribals and the JKN, because these classes are within the spec of the original topic. Just to remind you, Luckys original list did not include any of the super exotic late war types, including the battle class or the Gearing classes for that matter. The best you could do would be to compare the Fletchers to the L M clases. Incidentally, all your rants about prewar US DDs are completely off topic because they too are not mentioned. Stay inside the specs of the original topic, or at least within the spirit of those specs. 


This i would be happy to say. The USN, after developing truly war winning designs across the board in 1940-41 pretty much resisted further changes,, because at some point they rightly recognized the need for numbers. In the case of DDs the designs were so good, they really didnt go too wrong with that policy. With cruisers it was a different story. The Clevelands are the case in point. A workable design, but badly affected by topweight disease, in my opinion they should have brought forward the Worcesters and the DesMoines. These two designs give some indication of the vastly superior designs that could have eminated from the US if the need in the destroyer area had arisen. The British, with their Battles and C classes were simply playing catch up to the US DD designs. You have to go to the darings before you start to get a superior British design, and these really were true post war designs, and in any event were outdated before they were even commissioned.


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## Shortround6 (Feb 28, 2013)

The problem with shooting at a Kamikaze, as Parsifal says, is once it gets within several hundred yds it is too late, even with the pilot dead and large chunks of the plane missing it stands a good chance of hitting the ship _someplace._ It has gone "ballistic". This is why the 20mm, which was a fairly effective gun ( at least much better than .5in MG) in the beginning and middle of the war was considered almost useless against the Kamikaze. It could not inflict enough structural damage to the attackers to cause them to miss in the time/distance available. While the 2pdr shell may have been fairly effective once it hit the _effective_ range was much shorter than the effective range of the Bofors, a combination of lower velocity and shell shape.

What would help is if any body has the time of flight to a given distance for both guns or the distance covered in, say 3 or 4 seconds of flight?


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## parsifal (Mar 1, 2013)

I dont have that, but just to give some perspective to this, most common kamikaze was the A6M5. Kamikazes approached the tartget at the maximum possible speed in the final run.....for the A6M thats around 300-350 mph or about 12000 m per min. Thats 160m per sec.

The dedicated Japanese Kamikaze wasa the baka. This craft had a max level speed of 534 mph at sea level. Thats about 270 m/sec. 


The known operational history of the Baka is intersting. The BPF fortunately never was targetted by this weppon. The US was hit , or targetted quite a number of times

"On 21 March 1945, 16 Ohka-carrying "Betty" bombers were to be escorted by 55 Zeros to attack Task Group 58.1 (Hornet, Bennington, Wasp, and Belleau Wood). Another two "Bettys" were to escort and provide navigation and observation. Due to technical problems, 25 Zeros had to turn back or could not take off. The Ohka attack force was intercepted by 16 US Navy Grumman F6F Hellcat fighters and the Ohkas were immediately jettisoned by the "Bettys," some 113 km (70 mi) from the target. None of the "Bettys" returned, no ships were attacked and 16 of the Jinrai Butai were killed, with only 15 damaged Zeros making it back to their base.

Attacks intensified in April 1945. On 1 April 1945, six "Bettys" attacked the U.S. Fleet off Okinawa. At least one made a successful attack, with its Ohka thought to hit one of the 406 mm (16 in) turrets on the battleship West Virginia, causing moderate damage. Postwar analysis indicated that no hits were recorded and that a near-miss took place. The transports Alpine, Achernar, and Tyrrell were also hit by kamikaze aircraft, but it is unclear whether any of these were Ohkas from the other "Bettys". None of the "Bettys" returned.

The American military quickly realized the danger and concentrated on extending their "defensive rings" outward to intercept the "Betty"/Ohka combination aircraft before the suicide mission could be launched. On 12 April 1945, nine "Bettys" attacked the U.S. Fleet off Okinawa. The destroyer Mannert L. Abele was hit, broke in two, and sank, witnessed by LSMR-189 CO James M. Stewart. Jeffers destroyed an Ohka with AA fire 45 m (50 yd) from the ship, but the resulting explosion was still powerful enough to cause extensive damage, forcing Jeffers to withdraw. The destroyer Stanly was attacked by two Ohkas. One struck just above the waterline just behind the ship's bow, with the charge punching completely through the other side of the hull before splashing into the sea and detonating like a depth charge, causing little damage to the ship, and the other Ohka narrowly missed (likely due to the pilot being killed by anti-aircraft fire) and crashed into the sea, knocking off the Stanly's ensign in the process. One Betty returned. On 14 April 1945, seven "Bettys" attacked the U.S. Fleet off Okinawa. None returned. None of the Ohkas appeared to have been launched. Two days later, six "Bettys" attacked the U.S. Fleet off Okinawa. Two returned, but no Ohkas hit their targets. Later, on 28 April 1945, four "Bettys" attacked the U.S. Fleet off Okinawa at night. One returned. No hits were recorded.

May 1945 saw another series of attacks. On 4 May 1945, seven "Bettys" attacked the U.S. Fleet off Okinawa. One Ohka hit the bridge of a minesweeper, Shea, causing extensive damage and casualties. Gayety was also damaged by a near-miss by an Ohka. One "Betty" returned. On 11 May 1945, four "Bettys" attacked the U.S. Fleet off Okinawa. The destroyer Hugh W. Hadley was hit and suffered extensive damage and flooding. The vessel was judged beyond repair. On 25 May 1945, 11 "Bettys" attacked the US Fleet off Okinawa. Bad weather forced most of the aircraft to turn back, and none of the others scored hits.

On 22 June 1945, six "Bettys" attacked the U.S. Fleet off Okinawa. Two returned, but no hits were scored. Postwar analysis concluded that the Ohka's impact was negligible with no US Navy capital ships actually hit during their attacks due to an extremely effective set of defensive tactics that were employed."


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## RCAFson (Mar 1, 2013)

The range of a pom-pom at 2400fps = ? (~7200 yards?)
The range of a pom-pom at 2300fps = 6800 yds (Campbell)
The range of a Bofors at 2890fps = 11000 yds (USN range table)
The range of a Bofors at 2800fps =?

Bofors data: http://www.eugeneleeslover.com/USN-GUNS-AND-RANGE-TABLES/1956-4-1-0.jpg
Bofors range table: http://www.eugeneleeslover.com/ENGINEERING/OP1188/OP1188_Abridged_Range_Tables_1944.pdf (page 2)
Note that the above 40mm range table states that it is for 2800fps, but this is incorrect; it is actually computed for some other MV and this is easy to see since at 500 yards the SV = 2800fps, so the IV must be ~3200fps (V drop from 500 yds to 1000yds = 356fps). This is rather frustrating.
*US Army data:*


> Ammunition: (for complete data, refer to TM 9-251 or TM 9-252)
> Muzzle velocity:
> AP-T shot and HE-T shell	2,870 fps.
> Range (maximum):
> ...



This RN manual states that Bofors effective range = 2500 yds and 1200 yds depending on director type:
http://www.hnsa.org/doc/pdf/br1919.pdf (see introduction). Rounds SD at 3500 yds.


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## RCAFson (Mar 1, 2013)

USN claimed kills in 1945: 40mm = 476.5. 
5in = 380
20mm = 297.5 



> Credit for approximately 80 percent of all plane kills in suicide actions goes to the automatic weapons (50 percent to 40mm. and 27 percent to 20mm.), leaving 20 percent to 5-inch batteries, which fired disappointingly small quantities of ammunition at the many targets presented...
> 
> *Although many ships have criticized the 20mm. as a defensive weapon against suicide planes, Tables V and VI indicate that it still is an effective AA. weapon* both against suicide and non-suicide attacks. However, the 40mm. was by far the most effective weapon against suicide planes.
> HyperWar: Antiaircraft Action Summary--Suicide Attacks [Chapter 2]



So if the 20mm was still effective, I guess the pom-pom was too.


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## parsifal (Mar 1, 2013)

Not according to Webb, Rawlings , Fraser and a whole bunch of Allied Seaman that had to endure the japanese assault. But then, they havent written books that can be misused and misquoted 70 years later.


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## Shortround6 (Mar 1, 2013)

RCAFson said:


> So if the 20mm was still effective, I guess the pom-pom was too.



Try reading the whole thing and look at the tables ( aside from a misprint or two, the table for 1.1 ammunition expenditures against non-suicide planes seems more than a little suspect). 

"191	or 61 percent were shot down or deflected, but of these 53 or 17 percent, crashed close enough to ships to damage them"

That doesn't count ( and perhaps they didn't count) planes that were hit/damaged and actually hit the ships. 

By the time a plane was close enough to "crash close enough to ships to damage them" the 5in was pretty much useless as was the 3in/50 so what was shooting down those 53 planes that crashed close enough to damage the ships? 

40mm and under guns. While the 20mm can score a "Kill" for the chart if the ship is damaged by a near miss crash the 20mm has _FAILED_ to protect the ship and so can be considered ineffective. 

Having a 20mm battery that allows you to trade one destroyer out of commission for months for one or two attacking aircraft is hardly the way to win a war of attrition. 

Maximum ranges mean very little because changes in projectile shape can have enormous differences in max range but a smaller difference in "practical" range. 

Also please look at the materials you have presented. Some of the answers can be found there, it just takes a bit of digging and interpretation. Army and Navy 40mm shells were the same. Self destruct on those shells with it was about 5000yds which rather limits the "practical" AA range to that as a MAXIMUM. 
However look at the navy range tables. Time of flight to 5000yds is 11.27 seconds and speed is down to 915fps. a 300mph airplane is doing 440fps so for the 40mm to "HIT" at that range the gun had to aimed and fired at point in space 4958ft ahead of where the plane was when the gun went off. When our valiant gunners see the puff of smoke from the self destruct burst it tells them where they should have been aiming 11.27 seconds ago. 5000yds is hardy a "practical" range for the 40mm gun.Also please note that 1/2 that distance (2500yds) the time of flight is 3.92 sec 35% of the time of flight to 5000yds. This is a much more "effective" range for the 40mm. 
Please note that the 20mm has a time of flight of 7.27 seconds to 2500yds or about 85% longer. 

The extra 500fps or so of the 40mm Bofors may be good for an extra 500yds _practical range_ while a difference in the projectile shape may be good for another 500yds or so. You can change the "Max range" of a WW I/II military rifle by close to 2000 yds just by changing the shape of the bullet. The change in "practiacl" or "effective" range is much less but you cannot assume all projectiles are created equal.


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## tomo pauk (Mar 1, 2013)

The maximum slant range really tells nothing about the effective range. The 30 mm AAA I've served on were to have some 9600m max range, but the self-destruct mechanism was igniting the shell after some 4,5 sec (ie. the max range was only applicable for the AP round). The effective slant range was 4000 m, effective altitude was 3000 m. That's a projectile of 430g fired at 1000 m/s (3280 ft). We were told by instructors that 3 shells are sufficient to kill a mid-sized jet, like MiG-21 or F-16.

The 20mm in the JNA was far less powerful, the practical range of only 1500m, for shell of 130-140 g fired at 830-850 m/s. (here, the 20mm).


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## stug3 (Mar 1, 2013)

HMS Encounter sunk along with HMS Exeter and USS Pope on 1st March 1942, her crew were stranded in the waters of the Java Sea for almost 24 hours until rescued by the Japanese Navy.







U.S. Navy Clemson-class destroyer USS Pope (DD-225) in January 1924, sunk by Japanese dive bombers on the 1st March 1942.


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## RCAFson (Mar 1, 2013)

Shortround6 said:


> Try reading the whole thing and look at the tables ( aside from a misprint or two, the table for 1.1 ammunition expenditures against non-suicide planes seems
> Also please look at the materials you have presented. Some of the answers can be found there, it just takes a bit of digging and interpretation. Army and Navy 40mm shells were the same. Self destruct on those shells with it was about 5000yds which rather limits the "practical" AA range to that as a MAXIMUM.
> However look at the navy range tables. Time of flight to 5000yds is 11.27 seconds and speed is down to 915fps. a 300mph airplane is doing 440fps so for the 40mm to "HIT" at that range the gun had to aimed and fired at point in space 4958ft ahead of where the plane was when the gun went off. When our valiant gunners see the puff of smoke from the self destruct burst it tells them where they should have been aiming 11.27 seconds ago. 5000yds is hardy a "practical" range for the 40mm gun.Also please note that 1/2 that distance (2500yds) the time of flight is 3.92 sec 35% of the time of flight to 5000yds. This is a much more "effective" range for the 40mm.
> Please note that the 20mm has a time of flight of 7.27 seconds to 2500yds or about 85% longer.


 
I explained, in my post above, how the USN 40mm range table was incorrect, so the data in it is useless. I presented a Royal Navy manual showing that 40mm SD range = 3500 yds and Campbell states the same. 

The point is that the effective ranges of a Bofors and Pom-pom are identical, and the pom-pom has a longer effective range than the 20mm.


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## Shortround6 (Mar 1, 2013)

RCAFson said:


> I explained, in my post above, how the USN 40mm range table was incorrect, so the data in it is useless. I presented a Royal Navy manual showing that 40mm SD range = 3500 yds and Campbell states the same.



No, what you showed was that initial entry in the striking velocity column was wrong. This may mean that some or all of the entries in the rest of the column is wrong or displaced by one line. Could be a simple typo. It does not follow that all of the rest of the data is wrong. 

Time of flight to 500yds for the 20mm in the same publication. 0.66 seconds. Times of flight to *600*yds for .30-06 M2 ball = 0.88 seconds, for .30-06 M1 BT =0.86 seconds, for .50 ball 0.72 seconds and for 20mm ammo 0.84 seconds. This last is a little off from the range tables shown but fairly close. 
Time of flight to 500yds for the 40mm Bofors. 0.57 seconds. 
Time of flight to 500yds for the 1.1in AA gun = 0.61 seconds. 
Time of flight to _1000_yds for the 40mm Bofors is 1.23 seconds
Time of flight to _1000_yds for the 3in/50 mv 2700fps is is 1.18 seconds

Times of flight given for the 40mm Bofors are quite consistent with other rounds. 

Going back to the British manual for the 40mm there is a dramatic difference in effective range depending on the type of fire control provided. This relates to the time of flight and difficulty in aiming (predicting) were the target aircraft will be several seconds after the gun is fired. The better your fire control the longer into the future you can predict the targets path (mainly because you have been tracking it's previous path more accurately).

Picture from Anthony Williams excellent website. 






and 






and








RCAFson said:


> The point is that the effective ranges of a Bofors and Pom-pom are identical, and the pom-pom has a longer effective range than the 20mm.



Unless you repeal the laws of physics there is no way a slower, blunter shell has the same time of flight to a given distance or the same effective range as the faster, more streamline shell given the same level of fire control.


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## RCAFson (Mar 1, 2013)

Shortround6 said:


> No, what you showed was that initial entry in the striking velocity column was wrong. This may mean that some or all of the entries in the rest of the column is wrong or displaced by one line. Could be a simple typo. It does not follow that all of the rest of the data is wrong.
> 
> Time of flight to 500yds for the 20mm in the same publication. 0.66 seconds. Times of flight to *600*yds for .30-06 M2 ball = 0.88 seconds, for .30-06 M1 BT =0.86 seconds, for .50 ball 0.72 seconds and for 20mm ammo 0.84 seconds. This last is a little off from the range tables shown but fairly close.
> Time of flight to 500yds for the 40mm Bofors. 0.57 seconds.
> ...



The SV data is completely wrong for the whole table, which is easy to see since the first entry, at 500 yds, should be ~2400fps so each subsequent entry is considerably in error, and while TOF might be correct, it also might not be.

No one is claiming the same range for each gun. Max range for the pom-pom at 2300fps = 6800 yds. Max range for the Bofors at 2800fps is probably ~9-10,000 yds. However, max range is limited in both guns by the SD ammo to 3500 yds. The Bofors will be more accurate within that 3500 yd range but there are other factors as well. A quad pom-pom has a higher effective rate of fire than a twin bofors and thus there are more shells in the air to compensate for lower accuracy. In terms of TOF to 3500 yds, we have:

Bofors: 6.5 seconds (which may be incorrect)
1.1in: 8.1 seconds
20mm:13.3 seconds
pom-pom: ~8.5-9 seconds (my estimate for MV = 2300fps)


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## Shortround6 (Mar 1, 2013)

RCAFson said:


> The SV data is completely wrong for the whole table, which is easy to see since the first entry, at 500 yds, should be ~2400fps so each subsequent entry is considerably in error, and while TOF might be correct, it also might not be.



And if you delete the 2800 fps entry and slide the rest of column up one line you get 2444fps. Not that far off your estimate is it? 

That would make remaining velocity at 1000yds 2116fps compared to the 3in/50s 1000yd remaining velocity 2,345 fps. At least is sounds close. 



RCAFson said:


> No one is claiming the same range for each gun. Max range for the pom-pom at 2300fps = 6800 yds. Max range for the Bofors at 2800fps is probably ~9-10,000 yds. However, max range is limited in both guns by the SD ammo to 3500 yds.


 I didn't say any one was claiming the same MAX range. And while you can adjust the tracer burn/self destruct to the same range it doesn't do anything for the time of flight. 




RCAFson said:


> The Bofors will be more accurate within that 3500 yd range but there are other factors as well. A quad pom-pom has a higher effective rate of fire than a twin bofors and thus there are more shells in the air to compensate for lower accuracy.



Ah, no. we have two aspects of accuracy here. More shells help with group dispersion, they help with the exact range estimation and the curve of the trajectory, they do not help if the mount is pointed several hundred feet away from where the target is. 



RCAFson said:


> In terms of TOF to 3500 yds, we have:
> 
> Bofors: 6.5 seconds (which may be incorrect)
> 1.1in: 8.1 seconds
> ...



Even going by your estimate the target 300mph airplane is going to be 880ft _further_ along it's flight path when the 2pdr shell gets there. It makes range measurement, speed measurement and course estimation much more critical. target is moving about 33% further at the same range. If you want comparable effectiveness you need the range the 2pdr can reach in 6.5 seconds. 

With simple fire control the 40mm may have an effective range of only 1200yds which means the 2pdr is even shorter.


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## RCAFson (Mar 1, 2013)

Shortround6 said:


> Ah, no. we have two aspects of accuracy here. More shells help with group dispersion, they help with the exact range estimation and the curve of the trajectory, they do not help if the mount is pointed several hundred feet away from where the target is.
> 
> 
> 
> ...



Neither of these weapons have precision fire control (except the Hazemeyer Bofors and cruiser,BB, or CV mounted pom-poms with MK IV/type 282 radar control), and they rely on hitting by "hosing down" the target, so more rounds = better chance of hitting. If we accept a 33% reduction in accuracy for the pom-pom, it still means that a quad pom-pom will have about the same hit probability as a twin Bofors, at 3500 yds. 

880ft = a crossing target on a perfect parallel course, but this number will decline as the target's path moves closer to an intercept course.

at 1200 yds the difference in TOF will be be very small, and here 4 barrells will certainly make a difference. The RN Pocket Gunnery book gives both an effective range of 1700 yds with "eye shooting".


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## Glider (Mar 2, 2013)

Can anyone confirm that the US Destroyers did have directors for their 40mm guns, whereas the RN didn't?


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## Wavelength (Mar 2, 2013)

^^USN light Flak had the excellent Stark Draper computing (optical) gun sight. This was an exclusive feature as far as I know. 



> Neither of these weapons have precision fire control (except the Hazemeyer Bofors and cruiser,BB, or CV mounted pom-poms with MK IV/type 282 radar control),



Type 282 radar wasn't very accurate or effective in practice, so it’s not really a big plus having it over optical methods. 

Much of problems of the BPF in dealing with Kamikaze had to do with their radar rather than guns. The British radar during this period was in state of disarray. The Skyatron system was a fiasco and the new centimetric radar system (277/293) supporting it demonstrated poor performance well into the 1950s. By using more primitive methods of command and control the old 3.3 meter Type 281 and particularly 7.5 meter Type 279 did prove valuable in the Pacific by virtue of their long range and pronounced vertical lobes structure. 

The new 10cm firecontrol radars, Type 274 and Type 275, were having teething problems. Type 275 for Flak direction featured conical scan but proved very difficult to use in action. 50cm Type 285 was usually limited to ranging. Type 285M (which still predominated) had lobe switching but only on one axis so it had to be combined with optics. 

Advanced light flak radar Type 262 was years away from operational deployment. 

The Allied IFF system was a complete mess with only 40% of warships even equipped with IFF interrogators or transponders. 

The USN was also having problems with radar, although this didn't affect their light flak. The Mk4 (FD) and its derivatives were demonstrating an inability to cope with Kamikaze and on destroyers especially were still hampered by being tied to an obsolete director with slow mechanical predictor. Naval equivalents to SCR-584 conical scan radar were not deployed because it was too big of a job to refit all the ships. The advanced Mk56 directors were not deployed and the make shift Mk57s did not reach the fleet until into 1945.


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## RCAFson (Mar 2, 2013)

Wavelength said:


> ^^USN light Flak had the excellent Stark Draper computing (optical) gun sight. This was an exclusive feature as far as I know.
> 
> 
> 
> Type 282 radar wasn't very accurate or effective in practice, so it’s not really a big plus having it over optical methods.



The Mk51/MK14 director was supplied to the RN, according to Campbell, and the RN developed an equivalent in the Simple Tachymetric Director, according to Campbell, however both these systems used a simple range estimation system, and could hardly be called precision systems - they only worked OK when there was a large volume of fire.

Regardless of how well Type 282/MK IV worked in practice, it was, theoretically, a precision system, where Mk 51 was not.


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## RCAFson (Mar 2, 2013)

Glider said:


> Can anyone confirm that the US Destroyers did have directors for their 40mm guns, whereas the RN didn't?



My understanding is that any RN DD with a twin bofors Mk V or USN LL supplied equivalent, had an associated MK51 director, as did USN destroyers. Theoretically, power worked Bofors/pom-pom singles or quad pom-poms would have an on-mount Mk14 or equivalent gyro gunsight.


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## stug3 (Apr 14, 2013)

U.S. Navy Wickes class destroyer USS Roper (DD-147) escorting a convoy, out of Hampton Roads, Virginia (USA) in 1942. Ships of the convoy are visible on the horizon. Roper is wearing Measure 12 (Modified) camouflage.


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## parsifal (Apr 15, 2013)

The Allies got really good value out of theior old DDs. For me, proves the man is as important as the hardware. Thinking of the Scrap Iron Flotilla here


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## vinnye (Apr 15, 2013)

Those old WWI 4 stackers certainly got their moneys worth - same as RN WWI BBs !


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## Glider (Apr 15, 2013)

Can I put a vote in for the old RN WW1 Destroyers. My Grandfather was an engineer on the SS Norfolk that was sunk by U552 on 18th June 1941. He and nearly all the crew were picked up by HMS Skate three days later. Being launched in Jan 1917 she must have been one of the oldests destroyers in the RN, but my Grandfather thought she was the most beautiful ship he had ever seen.

We have a letter of thanks from the captain, after the crew of the Norfolk sent a donation to the destroyers comfort fund. He had already been sunk once in WW2 and once in WW1.


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## stug3 (May 6, 2013)

The Flower class corvette HMS Snowflake


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## stug3 (May 7, 2013)

The USS Lamson was a 1919 vintage Clemson class destroyer.


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## stug3 (Jul 7, 2013)

HMS Keppel was the lead destroyer for Convoy PQ17 escort group


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## stug3 (Aug 6, 2013)

USS Sterett (DD-407) aft portion of the ship, photographed from a crane at the Mare Island Navy Yard, California, 6 February 1943, at the end of an overhaul. Circles mark recent alterations, including the installation of 40mm guns on her after deckhouse. Note the photographer’s shoes in lower left. Photograph from the Bureau of Ships Collection in the U.S. National Archives.






USS Dunlap






Imperial Japanese Navy destroyer Arashi, photographed in 1940.


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## stug3 (Aug 6, 2013)

Juno Beach Centre - HMCS Assiniboine and the destruction of U-210

Completed in 1932, River class destroyer HMCS Assiniboine first served with the Royal Navy as HMS Kempenfelt. She was transferred to the Royal Canadian Navy on October 19, 1939 and participated in numerous escort missions.






U-210 seen from HMCS Assiniboine, 6 August 1942






On the starboard side of HMCS Assiniboine, a fire caused by guns of U-210 threatens the bridge.






Damages inflicted to “A” Gun by enemy fire. One gunner was killed at his post and three others wounded during the attack.






At one point U-210 came so close that it was impossible for the Canadian destroyer to depress her guns low enough to target her.






U-210 was rammed by HMCS ASSINIBOINE as she dived and again as she resurfaced.






There were 37 survivors out of 43 crew members. Survivors from U-210 are escorted on board Assiniboine.


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## parsifal (Aug 6, 2013)

bloody marvellous


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## swampyankee (Aug 6, 2013)

ToughOmbre said:


> The "Fletchers" are to DDs what the "Iowas" are to BBs.
> 
> And good looking ships to boot!
> 
> TO



Not quite. They kept building destroyers after the Fletchers; I think most people here would accept that, say, the next eight classes of USN destroyers had some improvements over the Fletchers. They stopped building battleships after the Iowas, for the same reason they stopped building biplane fighters after the F3F.


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## stug3 (Aug 12, 2013)

12 August, 1942: Operation Pedestal- HMS ITHURIEL coming in to ram the Italian submarine COBALTO. 






Photograph taken from HMS ITHURIEL showing the COBALTO from the destroyer’s port side after ramming it.


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## stug3 (Aug 14, 2013)

The damaged tanker OHIO, supported by Royal Navy destroyers HMS PENN (left) and HMS LEDBURY (right), approaches Malta after an epic voyage across the Mediterranean as part of convoy WS21S (Operation Pedestal) to deliver fuel and other vital supplies to the besieged island. OHIO’s back was broken and her engines failed during earlier German and Italian attacks. Because of the vital importance of her cargo (10,000 tons of fuel which would enable the aircraft and submarines based at Malta to return to the offensive), she could not be abandoned. In a highly unusual manoeuvre, the two destroyers supported her to provide buoyancy and power for the remainder of the voyage.






The damaged tanker OHIO finally enters Valletta on the morning of the 15th August, 1942 supported by Royal Navy destroyers, after an epic voyage across the Mediterranean as part of convoy WS21S.


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## parsifal (Aug 14, 2013)

Ive seen those photos before, but i still get a lump in the throat when i see them. What an epic story. I never get tired of it.


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## vinnye (Aug 14, 2013)

The Ohio episode shows the best traditions of both the RN and the Merchant Navy. 
Unbelievable tenacity and courage!


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## stug3 (Aug 19, 2013)

A destroyer makes a smoke screen to cover the landing during the Combined Operations daylight raid on Dieppe. 






HMS BERKELEY settling down in the water after being bombed during the Combined Operations daylight raid on Dieppe. One of the destroyers boats is still alongside, empty but still attached to its davits. BERKELEY was torpedoed shortly afterwards by British forces.






HMS BERKELEY being torpedoed by RN after being bombed during the raid on Dieppe.






Wounded soldiers being helped on board the destroyer HMS ALBRIGHTON 






Canadian troops on board a destroyer after the raid.






A wounded Canadian soldier being disembarked from the Polish Navy destroyer ORP at Portsmouth on return from Dieppe. 






A naval motor-launch seen with four of the landing craft used during the raid on Dieppe.


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## stug3 (Aug 28, 2013)

HMS CELADINE, British corvette, arrives at Algiers Harbour as part of a troop convoy, 1943


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## stug3 (Sep 14, 2013)

Convoy PQ 18 at sea, 9/42. An underwater detonation erupts next to HMS ASHANTI. The destroyer HMS ESKIMO is seen in the foreground. Merchant ships are in the background.






Sailors placing a depth charge into position in a rack on the stern of the destroyer HMS ESKIMO, just out of harbour (possibly Hvalfjord)






A look-out and machine gunner on board HMS ESKIMO in northern waters.


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## stug3 (Sep 20, 2013)

HMCS St Croix (ex-USS McCook, DD-252) underway circa 1942. Sunk by U Boats 9/20/43 while escorting convoys ONS 202 and ONS 18, headed west from Britain. 67 men of its 147 crew were lost.(NavSource)






A ship of the same class, USS Mason which became HMS Broadwater.


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## stug3 (Sep 24, 2013)

Royal Navy destroyer HMS Express. She was transferred to the Royal Canadian Navy as HMCS Gatineau in 1943.







HMS KEPPEL (D 84) – Shakespeare-class Flotilla Leader


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## stug3 (Feb 18, 2019)

5 Inch 38 Caliber Enclosed Gun Mount & Handling Room

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## Wurger (Feb 19, 2019)



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## fliger747 (Apr 13, 2019)

I served for a while as a hot case man on a 5"38 single mount as shown above. The rate of fire that these were capable of (up to 20 rounds/min) depended entirely on a very fit crew and lots of practice. Manual loading, it's why a practice loader was installed on the quarterdeck! The Mk 37 fire control system was unparalleled in it's capability, at least for WWII era aircraft.

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## Sid327 (Aug 31, 2019)

The Fletcher and Tribal class were great ships.


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## fastmongrel (Sep 3, 2019)

HMS Skate an Admiralty R class Destroyer laid down in 1916 by John Browns Clydebank launched 11th Jauary 1917. She was the oldest destroyer in the RN during WWII and the only 3 funnelled ship. Pictured in Liverpool 1942 between Atlantic Convoy duties.






HMS Skate (1917) - Wikipedia


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## Wurger (Sep 3, 2019)




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## nuuumannn (Sep 3, 2019)

The Ca Class destroyer HMS Cavalier, the Royal Navy's last surviving WW2 vintage destroyer. She is preserved at Chatham Historic Dockyard.




Cavalier i 




Cavalier ii




Cavalier iii


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## Sid327 (Sep 4, 2019)

stug3 said:


> 5 Inch 38 Caliber Enclosed Gun Mount & Handling Room
> View attachment 529581




Probably one of the finest naval guns ever made. Nice.

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## Snautzer01 (Oct 8, 2022)

stug3 said:


> 12 August, 1942: Operation Pedestal- HMS ITHURIEL coming in to ram the Italian submarine COBALTO.
> View attachment 438667
> 
> 
> ...





















Large Original WW2 Press Photo Royal Navy sink Italian U-Boat "Cobalto" 21x15cm | eBay


<p dir="ltr" style="margin-top:0; margin-bottom:0;">Large Original WW2 Press Photo Royal Navy sinking of Italian U-Boat "Cobalto" by HMS Ithuriel</p> <br> <p dir="ltr" style="margin-top:0; margin-bottom:0;">Size is 21 x 15 cm</p> <br> <p dir="ltr" style="margin-top:0; margin-bottom:0;">Agency...



www.ebay.com

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## Wurger (Oct 8, 2022)




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