Destroyers.....

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

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.

Glider · Feb 22, 2013

RCAFson said:
Here's bit of info I gleaned from Amazon:

View attachment 225534

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..

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.

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
extent that when she lost Athabaskan in 1944 she added an extra ship to her
own building plans as a replacement.
The first two ships, Micmac and Nootka launched in 1943 and 1944
respectively conformed pretty well to the second Tyne built pair. except that
they were given a lattice mast while on the stocks. Their three twin 4·7s were
the last to be fitted for service under the White Ensign and were specially
modified to take the Improved fuze-setting machines by then in plentiful supply.
Micmac shipped a quad pompom in the "Canadian' position, but
Nootka was better armed with 'sided' twin Bofors on the same site.
In the final pair, the armament was completely revised to take advantage of
late- and post.war developments. The ships could not accommodate the twin
4·5-inch Mk IV mounting of the RN 'Battle' class, so both ships were given the
best alternative the RPC version of the twin 4 inch-and had four such
weapons in the conventional positions. The (then) latest RN Destroyer Fire
Control system, employing a Mk 6 director. was adopted and the close-range
armament tidied-up to 40mm calibre.

Tribal Class Destroyers, p.61

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.

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....

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...

7. CONCLUSIONS AND RECOMMENDATIONS AS A RESULT OF THE ACTION.

(a) The 5" battery and close range weapons of surface ships are only partially effective in repelling a determined torpedo attack because of the low rate of fire of the 5" battery and fuze failures; short effective range of the 20 MM guns; and the failure of short range weapon gunners to lead the target sufficiently...
Battle of Midway: Commander Destroyer Squadron Six Action Report

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.

Complete power failures occurred on Groups I and II 5-inch. Partial power failure occurred on Group III. There were frequent rammer failures and electrical misfires on all guns.

The apparently unwieldy director firing system, augmented by numerous casualties which greatly slow the rate of fire, has made the 5-inch battery the least useful of the AA for all except high altitude horizontal bombing attacks. In local control, difficulty is experienced in getting both trainer and pointer on the same target. A new type of fuze, which it is understood will soon be available, may greatly increase the effectiveness of the 5-inch against dive bombing and torpedo attacks.

The performance of the 40mm in their first action was gratifying. Eventually these guns may prove to be our best defense against dive bombers. Several faults now exist, namely: empties jam in the chutes, local control is too sensitive, firing mechanism is not satisfactory, and our splinter shields are too high. Separate reports on these deficiencies will be forwarded.

The 20mm, in spite of its short range, was extremely effective and accounted for most of the enemy planes shot down by this ship. It can not always get the dive bombers before they release, but it can keep them high and reap fearful toll of those that press home their attacks.
Action Report: 26 October 1942

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.

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.

Click to expand...

I am dissapointed to note that you hadn't realised that the convoys to Russia and Malta had suffered very heavy losses to aircraft.

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.

Click to expand...

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.

Again this is altitude dependent. The pom-pom could achieve harrasing fire up to 10,000ft.

Click to expand...

Clearly the RN didn't believe it was 10,000 ft

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...

Click to expand...

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

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.

Click to expand...

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.

I've gone over the decision to mount a twin 4in on the Tribals and it is much more complex than you

Click to expand...

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.

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 and VT ammo made HA fire much more effective, but even so during the war the 4.7in twin was retained:

Click to expand...

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.

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.

Click to expand...

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.

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?

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

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.

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:
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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.

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.

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

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

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

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.

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.

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.

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

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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