# Was the Elektroboat really a "wonder weapon"?



## Jenisch (Apr 30, 2012)

Hello, 

So, this German submarine design is higly praised. But I ask: it was really "everything" told about it? I mean, the Allies didn't really have any answer or could develop one for it?


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## DonL (Apr 30, 2012)

What do you mean with wonder weapon Jenisch?

To every weapon you can develope an answer but at the introduction of the XXI submarine it was a very very advanced weapon and it was built to counter all anti submarine weapons.

-constructed to 300m maximum depth. At that depths weather hedgehogs nor waterbombs have a great impact because the water pressure is to high.

- 17kn-18kn underwaterspeed, also with the battery capacity to go around 30sm with full speed; 120sm with 8kn (highest speed of the Typ VII); Asdic had only a effictive range to 1,5-2sm and the destroyer must be on very slow speed.

- active sonar and a kind of passiv sonar (not in modern kind of way) Gruppenhorchgerät, with that "passiv sonar" you could detect large convoys at 80sm and small convoys at 40sm under water.

- first fire control computer that was interactive with the active and passive sonar and was able to shoot a torpedo at 50m depth with the numbers from the sonar arrays that feeded the computer.

- 3 different engines, Diesel engines with snorkel, E- machines and an extra silent E-machine. 
From Test at the USA a Typ XXI running with the extra silent E-engine couldn't be detected at 220m. 

- first aerodynamic underwater vessel for underwater highspeed.

The XXI was the real first true submarine, that was built to operate permanent under water.

Allied weapons against the XXI at introduction.
-The snorkel could be detected from aircrafts with radar under good conditions.

-Asdic and the MAD detection system if the XXI submarine was at slow speed or above 80m depths.

- The MK 24 FIDO or Mark 24 torpedo (12kn fast) and aircraft carried, which was self controled by hydrophones.

All this weapon could be very dangerous for a XXI submarine but against the Asdic and MAD and the MK 24 FIDO or Mark 24 torpedo it could escape with its high speed and possibility to dip very fast to 250-300m depths.

The XXI had much better chances to escape the allied anti submarine weapons or trick them out, these weapons were normally the sure death for the old submarines, but the XXI could match with them and had a good chance not to die!


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## Jenisch (Apr 30, 2012)

Thanks for the informations DonL. 

With "wonder weapon" I wanted to mean a system that didn't have effective answer.


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## tyrodtom (Apr 30, 2012)

Although 118 XXI's were built between 43-45, they had big quality control problems. Only 4 were ever brought up to combat ready status. Only 2 went on war patrols, and sank NOTHING.

More were taken as war prizes and served in foreign navies, than ever served in the Kriegsmarine.

Just another case of CSWBD.


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## fastmongrel (Apr 30, 2012)

The Royal Navy and US Navy would have struggled if large numbers had got to sea but countermeasures were on the way. The Loch class frigates with there sophisticated Action Information Centre, Squid mortar launched depth charges and a towed array sonar would probably have made things tough for the XXI class. Other countermeasures were on there way like heavier faster versions of the Mk24 torpedo. The RN was modifying S class subs as training targets with bigger motors, propellors and batteries plus streamlining to give them similar speed to the XXI. 

The main thing that would have beaten the XXI was the numbers game the Allies could build aircraft carriers, escorts and merchant ships twice as fast as 300 plus XXIs could sink them.


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## Jenisch (Apr 30, 2012)

Allied intelligence was aware of the XXI development?

A bigger air campaign against the U-Boat installations would not help in the case they were deployed in numbers? I think the Allies had resources to do this until measures against the submarine were developed.


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## DonL (Apr 30, 2012)

> Although 118 XXI's were built between 43-45, they had big quality control problems. Only 4 were ever brought up to combat ready status. Only 2 went on war patrols, and sank NOTHING.



No XXI submarine was on a real patrol station at WWII. You refering to myths.
No XXI were built at 1943! The submarines that were completely built till the end of 1944 were 61!

The XXI submarine typ was throught in production harum-scarum and yes they had quality problems but kindergarden issues were sorted out at the east sea at the end 1944 till march 1945.

U 2511, U 3008, U 3503,U 3523 had all incidents with allied hunt groups, aircrafts, allied submarines after the no attack order from Dönitz, no submarine could be hunted down by allieds, and all could escape!

No XXI submarine had ever driven a serious attack against allied ships or submarines!


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## tyrodtom (Apr 30, 2012)

So 4 XXI's had incidents with allied hunt groups, but even with their massive technological advances, sunk NOTHING.
Oh, wait, there was a "no attack" order from Donitz. That sounds like a convenient excuse/ myth.

If they had about 120 under constuction since 43, and only 4 were operational, it sounds like the quality control issues was well pass the kindergarden catagory.


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## DonL (Apr 30, 2012)

You should do some research!

Only 61 were ready at December 1944 and 28 out of 61 were produced and ready manufactored at *December 1944*!

With all new weapons you must train the crew! Read some books about the XXI but don't tell some myths or things that haven't anything to do with reality!

Also the manufaction program started August 1944! Again read some serious books about the XXI and don't tell any myths!


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## tyrodtom (Apr 30, 2012)

One thing that is not a myth, they sunk NOTHING.

Just like most of the wunderweapons, CSWBD.


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## DonL (Apr 30, 2012)

> One thing that is not a myth, they sunk NOTHING.
> 
> Just like most of the wunderweapons, CSWBD.



This sentence shows your Kindergarden expert knowledge!

The XXI submarines were advanced weapons which influenced the USA GUPPY-Programm with the USS Albacore!
Also they influenced the UdSSR Whiskey-Class and Zulu-Class, the french Naval-Class and the british Oberon-Class!

Not bad for a s h i t weapon after your opinion!

*And again* no XXI submarine has ever driven a serious attack against allied ships or submarines, you should do some research Mr.....

Learn the facts and try to post again!


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## tyrodtom (Apr 30, 2012)

The XXI's were manufactored as subassemblies remote from the shipyards, usually construction on a conventionally assembled ship is when it is started at the shipyard itself,or laid down. The XXi's weren't considered laid down till the subassemblies reached the shipyard. Though construction of the subassemblies would have started earlier, of course.

The U-2511 subassemblies were started in Nov. 43, laid down at the shipyard Jul. 44.

The sad fact is the only thing they accomplished is to advance the Navys of other countries, they advanced the Nazi regime not one inch, not one second. All those tons of steel, and thousands of man-hours for not one allied ship sunk. That in anybodies estimation but yours is a abject failure.


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## DonL (Apr 30, 2012)

Rofl!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!



> The XXI's were manufactored as subassemblies remote from the shipyards, usually construction on a conventionally assembled ship is when it is started at the shipyard itself,or laid down. The XXi's weren't considered laid down till the subassemblies reached the shipyard. Though construction of the subassemblies would have started earlier, of course.
> 
> The U-2511 subassemblies were started in Nov. 43, laid down at the shipyard Jul. 44.
> 
> The sad fact is the only thing they accomplished is to advance the Navys of other countries, they advanced the Nazi regime not one inch, not one second. All those tons of steel, and thousands of man-hours for not one allied ship sunk. That in anybodies estimation but yours is a abject failure.



Yes you are right and it's true but what has this to do with the *weapon*?
Could you not abstract that this submarine (XXI) was state of the art as it's introduction? What has the XXI submarine to do with the nazis, other that it was developed in germany? Couldn't you abstract these things?

What is your agenda?


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## tyrodtom (Apr 30, 2012)

My agenda? What is your agenda? In my posts i've never got personal, can you say the same?

When a country puts millions of man-hours and steel into a weapon, it's expected to do some sevice for that country, if it doesn't then that weapon system is a failure, a waste of resources that could have been more productively used elsewhere.


I'm ROFL, because you can't see that this program and several others like it hastened the end of the war, sure it's a wunderweapon, but I wonder what Germany could have done with the same resources, more intelligently applied.

Can you actually elevate the XXI to the status of a weapon, since it was never used as such.


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## DonL (Apr 30, 2012)

> My agenda? What is your agenda? In my posts i've never got personal, can you say the same?
> 
> When a country puts millions of man-hours and steel into a weapon, it's expected to do some sevice for that country, if it doesn't then that weapon system is a failure, a waste of resources that could have been more productively used elsewhere.
> 
> ...



Yes you are ROFL!

Any german submarine mission from the middle of 1943 was a suicide comando! 35000 german submarine men died out of 46000 men!
The XXI submarine program was nothing else then a program to get again a *sharp* weapon other then the old suicide submarines.
Nobody of this program could imagine, when the war was over! The only goal was to counter the allied anty submarine weapons!

And the XXI submarine was a success to counter all anti allied submarine weapons, which was shown through allied tests after the war!

I can't understand your argumentation nor your agenda, because the supply way over the Atlantic to Britain was essential for the third reich!
So I can't understand the direction of your argumentation, only because the program was too late. Many weapon programs from *all* countrys were sometimes too late (example P51H). 
But this has *nothing* to do with the developed weapon and it's effective. Or do you want to tell us for example that the P51H or F7 F Tigercats were bad weapons because they weren't ready till the end of the war?

Sorry but I can't follow your agenda nor your argumentation and the fact is that the XXI submarines were very advanced weapons stated from all allieds!


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## tyrodtom (Apr 30, 2012)

The Allies had enough excess resources, they could afford a little wasted here and there, Germany couldn't.

If it could have been operational 6 months earlier, would it have changed the course of the war? Or just delayed the western allies so the Soviets would have overrun even more of Germany? Or delayed it enough that the atomic bombs would have been dropped on Germany?

So maybe Germany is actually lucky that a lot of the Wunderwaffe weapons were just nails in the 3rd. Reichs coffin.


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## DonL (Apr 30, 2012)

Again I think you don't understand what I'm refering to!

My agenda is the *weapon* abstract from any ideology or politics, the only interesting things to me is the technology and effectiveness of the weapons against it's weapon counterparts!

The facts of the XXI submarine and it's technology you can read at any good and serious book!


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## tyrodtom (Apr 30, 2012)

I agree the XXI was a advanced submarine, but as a weapon for the country that developed it, it was a failure, and actually contributed to it's defeat.


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## barney (May 1, 2012)

I will go a different direction here and say that what made the XXI a wonder weapon, and it was one, was the head slapping that occurred amongst the personnel of every other navy when they saw an XXI. 

The advancements of the XXI, any sailor could have told you then, were what any submarine needed but until the XXI, it never happened. You needed to dive deeper, any submariner who had been depth charged knew that. You needed more underwater speed and endurance. That is why zig zagging proved to be such an important protection scheme for surface units. 

So, take off the forest of railings, guns and cable cutters. A submarine shouldn't be rigged like a clipper ship. Hey, the conning tower goes underwater too, should it be shaped like an office building? Shape the hull so that the fastest speed occurs submerged. Hadn't any sailor seen a whale? And, was there a treaty that limited the capacity of the batteries? 

So what Germany was forced to do was build the submarine that every navy should have had all along. None of these advances when viewed separately is revolutionary. What was amazing was that they all occurred and came together in one boat. Meanwhile, everyone else was building boats that wouldn't have looked out of place in WWI. 

For a Guppy Class conversion, take an American Fleet Class Submarine, torch off all the junk on the deck, put some streamlined plating around the conning tower, add a snorkel and you have two thirds of an XXI. It still needs more batteries and a better hull.


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## Juha (May 1, 2012)

Even if Type XXI didn't participate actively to WWII its "coastal cousin/half-brother" Type XXIII did. IIRC usually the first incling to Allied that a XXIII operated in certain area was an attack. Because it operated in coastal areas, British could move their assets fast to the area but none were sunk in British waters by RN. They were far more difficult enemies than earlier snorkel equipped boats which also participated those last attacks around GB.

XXI/XXIII were not a new in idea, but had better intergrated systems than their predessors. The RN WWI R-Class hunter-killer subs were the first nearly real subs, but really had too high max underwater speed for their control system. IJN had also in late 30s a high speed sub, was that I-71 or I-91 or something, but they didn't pursue that route and went to big subs with recon plane. Only very late in WWII they produced I-201 type steamlined high speed sub.

Juha


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## davebender (May 1, 2012)

The Type XXI submarine was a great advance over 1930s designs but it was not invulnerable. 

By 1945 there were so many Allied DEs and ASW aircraft that no enemy submarine could operate effectively in the North Atlantic. How could they when Germany couldn't even maintain air superiority over submarine bases and the surrounding coastal waters?


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## barney (May 1, 2012)

If you wish to see the American version of the XXIII here is the link.

USS MARLIN

I had occasion to visit this vessel when first on display in Omaha. What a blast. I found that the boat's blueprints and operating manuals were still in lockers in the wardroom. Back toward the stern, the aisles around machinery were were tiled and they were one tile wide - back when they made 9 inch floor tiles. Everything still worked so you had to be careful to not elbow switches.

It is funny to think that nobody seemed to realize that the upper half of a submarine needed to be streamlined like the hull until they finally did. But then I remember viewing the Marlin, perched as she was out of the water and there, in the middle of each prop blade was a Navy applied zinc brick about the size of a cinder block. What did that do for performance?


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## Matt308 (May 1, 2012)

Gentlemen, please keep this thread civil, tone it down and do not levy veiled insults to other members. You will not be warned twice.


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## davebender (May 1, 2012)

Probably part of the cathodic protection system used by ships in mothballs.


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## barney (May 1, 2012)

davebender said:


> Probably part of the cathodic protection system used by ships in mothballs.



Yeah, that makes perfect sense.


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## psteel (May 13, 2012)

Prior to WW-I a German air independent propulsion system was experimented with that looked promising, but the war prevented further development. The British did have a high underwater WW-I sub able to make 14 kts submerged for about 15nm endurance ….again good, but somewhat limited tactically.

British R class submarine - Wikipedia, the free encyclopedia

The German Type XXIII apparently went on a few cruises with new crews and were able to sink 5-6 merchants without any losses, when the yearly average was about two subs for every merchant sunk.

looking at this site we have pre war Go-71 which could make 21knts underwater but only had endurance of 30nm @ 7knts. So it could not really use its dash speed realistically. 

71-go experimental submarine (1938) - Imperial Japanese Navy (Japan)

About the same time the Germans were working on the Walters V-80 experimental fish submarine. This was tested [100 sortie] and made [email protected] 28knts.Given that the best the service subs could make was [email protected] 4knts and about 15nm @7kts; one can see the potential, but to be fair that was Walters infamous peroxide drive turbines. It’s not just a high underwater speed, but high endurance that’s part of the evolution of the threat from ‘submersibles’ into ‘genuine submarines’. Dr Walters who designed the boat in the mid 1930s, also included a complicated retractable Schnorkel system. Weaponizing this into the V-300 and follow on designs during wartime; proved to be much more difficult due to the politics of Hitler’s armaments programs , but did result in 200 additional sortie with only one accident incident leading to one death. The system seemed to be robust enough to work in put into mass production.

When the process closed in on the Type XVIII Walter design, the amount of fuel per sortie [~ 200tons] would be an enormous challenge to overcome, since annual production was merely 12000 tons and the missile programs took the bulk of that. German naval designers pointed out that the space eked out for the Peroxide fuel, was more than enough room to triple the battery capacity increasing potential from 80-60 nm to [email protected] 4 knots. New more powerful creep motors were designed that allowed underwater endurance to increase to 300-225nm @ 5kts.

Furthermore new HP generators were nearly completion that could effectively triple the power to weight ratio of these Submersibles. Given existing Submersible design; that should lead to a top underwater speed of ~11-12 knots. As it was submersibles designs relied on large flooding slits in the hull to allow rapid crash dives of 30-40 seconds. In WW-I before these appeared, the crash diving took up to 2 minutes, but there was a draw back since it reduced top underwater speed by about 10-12%. If on the other hand the sub was to remain mostly underwater using Schnorkel these numerous flooding slits were not needed and increased top speed could be achieved brining that to 13 kts. Further the “Winter garden” explosion of railings and flak guns the Germans added along with inefficient conning tower design added at least one knot to the top speed [14kts]. The rest of the increase to speed to ~ 18knts for the Type XXI was in the actual streamlining of that submarine design.

At this time some German leaders pointed out that many of these same ideas could be back fitted to the existing fleet of 400-500 Type VII/IX submersibles. Tripling the battery power sealing up the flooding slits, should allow the top underwater speed . Historically this would have delayed the XXI/XXIII program by months and this was considered unacceptable. But in truth all this could have been done 1942-44 transforming the ‘Submersible fleet’ into a ‘submarine fleet’. 

The initiative to add the Flak “winter gardens” could have instead been used to adopt a small streamlined weaponless conning tower with a tractable Schnorkel and clear out the internal ammo plus 4 reserve torpedoes to make space for the triple battery capacity.Combined this would have allowed these subs to reach ~11 knots submerged [Type XXIII reached 12knots] with an endurance of about [email protected] knots [Type XXIII could reach 175nm @ 4knts].


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## davebender (May 13, 2012)

For some reason the German Navy was slow to adopt this device. In fact at least one Dutch submarine captured during 1940 had the Schnorkel removed before being placed into German service.


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## psteel (May 14, 2012)

From an operational point of view the wolfpack had to work on surface to hunt for enemy shipping since the LW failed to integrate into operations. Even schnorkeling reduces radius to 3/4 of the surface endurance and makes actual detection alot harder. That is until the GHG gets developed and allied airpower forces the Germans below the water. Trouble is this was all forseen before the war began. The recommended solution was to make better use the LW in an integrated strategy, but Adm Dontiz solution was instead to rigg the Uboats to out fight the allied airpower and install some ultra light gyro copters for extended vision. Standing and fighting in enemy airsuperiorty was a poor second choice to exploiting the best quality of UBoat, to disappear below the surface.


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## davebender (May 14, 2012)

I agree. That's not what snorkels are for.

Snorkels allow a submarine to transit to their patrol area in relative safety. Expecially important in the Bay of Biscay as you are almost immune to dectection by WWII era aircraft. Snorkels also allow you to recharge batteries in relative safety before resuming attacks on enemy shipping.


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## delcyros (Jun 3, 2012)

If I can offer my 2 cents worth thinking on the subject...

The XXI wasn´t the first high underwater performing submarine. The ROYAL NAVY R-class submarines of 1918 vintage had very comparable performances at least on the paper.

The XXI (and XXIII) suffered some issues, which is true, too.
You may name f.e.
[+] poor workmanship compared to earlier boats. Some had to underwent repairs to be servicable and capable of diving
[+] the Walter 8 hullform was untried and is statically difficult to calculate. They made design mistakes here. That is crush depth has been varied between 280m and 305m in british and US trials, that was somehow less than earlier type VIIc/41 boats and somehow short of design expectations
[+] initial design speed was 18.0 kts submerged at the one hour rating. However, such a speed was found to be impossible. The batteries could not produce the high currents required to max out the electric motors. At full current, the power delivered by the batteries dropped and max power was unattainable. A change of the flooding slits increased the hydrodynamic drag but a compromis between diving time and top speed eventually was found. Realistic top speed was slightly faster than 16 kts (17.1 kts if You accept longer diving times) and the endurance was 1.20 hours instead of the intended 1.40 hours at this rating.
[+] The boat was silent by period standarts but the offensive firecontroll wasn´t yet fully developed to the high underwater speed. Designers of the GHG weren´t informed about XXI´s speed capabilities and correspondingly, the GHG passive detection arrey initially had problems at any speed faster than 8 kts and quit working at speeds faster than 11kts. A change in fairing over the GHG balcony was required to fix the issue after which the GHG worked out to 15.5 kts in trials. This happened in february 1945 and at wars end not all XXI were yet modified to the new standart
[+] Readers familar with the XXI perhaps know that the boat had been designed with excess battery reserve capacities. However, the recharging took considerable time. To the first battery stage (60% level) it took 2.6 hours, then 2.5 hours more to the 90% level and a last 2.4 hours to the 100%. However, this is at best conditions, in normal conditions when snorting, the recharging to 6.2 hours to the 90% level.
[+] There were considerable problems with H2 generation by the batteries, creating a dagerous gas mixture. The H2 vents and filters didn´t statisfied and at least two serious accidents are reported with XXI H2 explosions in post war services.

--------------
Despite these limitations, the XXI was a highly developed underwater attack platform. The much improved GUPPY refits of USN fleet boats in the period 1946 to 1954 had comparable top speed performance (up to 16 kts) but despite battery enlargements and improved battery types, the speed could only be hold for 30 minutes as compared to 1 hour and 20 minutes in type XXI. The GUPPY´s also were much noisier than U-2513 and U-3008 trialed by the USN off Key West after the war. The GUPPY´s also neither enjoied a passive acoustic detection arrey, nor the much superior S(U) active / passive sonar device of XXI (later adopted to USN services). Also, they had to be at periscope depth to fire a torpedo and fielded no homing or pattern running torpedoes. Still, in trials against DE´s with 1948 ASDIC equipment, GUPPY´s had a chance to avoid beeing damaged by a hunter group of 5 DE which varied between 70 and 85% after contact. Agressively handled, a GUPPY once torpedoed all five DE and then engaged the protected convoi in these trials. These trials were very alarming but little could be done at this point. If the submarine increased speed to 12 kts or faster the success rate of the 5 DE dropped suddenly to 0% in all trials. GUPPY´s could be heard at speeds faster than 5 kts, though U-2513 couldn´t be detected even from a stationary HE listening platform moving at max speed of the creep motors (6.2 kts), at 16 kts top speed it was as noisy as a GUPPY at 11 kts and at 10 kts it was barely detectable at best conditions with a 10 kts moving platform and close range. ASDIC wasn´t effective at depth´s larger than 400ft and it´s range varied with conditions between 800 and 1500 yard. The mk24 FIDO homing torpedo/mine didn´t worked at depths larger than 300ft maximum diving depth and with 12 kts top speed hadn´t the required speed to effectively hunt down such a fast submarine.
The first submarine type which approached XXI performance after end of ww2 was the US TANG-class after the troublesome radial 8 zylinder pancake diesels were removed by normal 6 cylinder Diesel units in 1952.


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## Milosh (Jun 3, 2012)

If anyone is interested,


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## davebender (Jun 3, 2012)

Many things constructed in 1945 Germany were poor quality. How could it be otherwise? Component manufacturers were destroyed by bombing or over run by enemy ground forces. So late war German equipment was bound to include a multitude of substandard components that wouldn't meet normal safety standards.


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## delcyros (Jun 4, 2012)

That´s correct, Dave.

Still, it needs to be outlined. The XXI was demanding in mastering all the advanced technologies implemented. That means a lot of issues to work out and additional training for crews to complete the tactical courses, the principal reason why so few boats were attached to flotilla 11 in Bergen/Norway at wars end. 
Initially, the XXI was intended to carry a close range SUBROC defensive missiles in it´s stern compartement. Altough the weapons and it´s targeting device were developed and tested, mass production didn´t stated and the compartement was shipped empty in all operational boats.
Similarely, the torpedo tubes were of a new design and could have allowed wire guided and active homing torpedoes ("Lerche" in german torpedo terminology) and shots from a depth of up to 100m (OT-II). Though neither the Lerche nor OT-II was operational and these boats carried pattern running LuT and OT-I which was servicable down to 40/50m.

This platform, despite it´s numerous limitations was advanced but it could not have stopped the soviets from advancing into Germany. So it´s not what the period propaganda made out of it.


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## psteel (Jun 5, 2012)

Delcros this is very interesting information and I would like to read more on the subject of the Guppy and the post war sources. Can you share with us your sources on these matters?



delcyros said:


> If I can offer my 2 cents worth thinking on the subject...
> 
> The XXI wasn´t the first high underwater performing submarine. The ROYAL NAVY R-class submarines of 1918 vintage had very comparable performances at least on the paper.
> 
> ...


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## delcyros (Jun 6, 2012)

Psteel,

You may consider 
J. Roberts article about Guppy conversions interesting in that matter, published in Warship International 1989. It´s interesting but a bit aged now.
I also relied heavily on 
Palmer, Origins of the Maritime Strategy: The Development of American Naval Strategy, 1945-1955 (Washington 1988);
Polmar/Moore, Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines (Washington 2004);
Denny, Blip, Ping Buzz: Making Sense of Radar and Sonar (Baltimore 2007);
Friedman, U.S. Submarines Since 1945: An Illustrated Design History (Annapolis 1994);
Friedman, British Destroyers Frigates: The Second World War and After (London 2006); 
Friedman, U.S. Destroyers: An Illustrated Design History (Annapolis 2004);
Harding, The Royal Navy, 1930-2000: Innovation and Defence (Abingdon 2005);
O´Brian, Technology and Naval Combat in the Twentieth Century and Beyond (London 2001);
O´Connel, Submarine Operational Effectiveness in the 20th Century: 1939 - 1945 (Bloomington 2011);
Rössler, U-Boottyp XXI. 7th Ed., Bernard Graefe Verlag (Bonn 2005);
Rössler, Die Sonaranlagen der deutschen U-Boote. (Bonn 2006)

Friedman and Harding, along with Polmar/Moore are extremely important sources published recently.

Harding (p.150ff) goes into some details as with regard to sequential trials conducted 1948 to 1949 off Key West with GUPPY modified USS TRUMPETFISH and the 4th EF as a preparation followed by tactical trials with USS AMBERJECK and the 6th DF in summer 1948, followed by trials with USS SCOTSMAN and USS DOGFISH november´48 to march 1949. During the last trials the 6th DF was enforced by two more DE´s, BROADSOWRD and SCORPION.
These trials were triggered by examination and trials of U-2513 and U-3008 off Key West, which caused some excitement in US submariner circles (eventually leading to the US submariners rejection of BuShip´s proposal for a US postwar submarine 1946) but also raised questions as to ASW efforts necessary to overwhelm these fast types of submarines.

At least in one case USS TRUMPETFISH aggressively handled would have sunk all four DE´s and proceeded further to the convoi. Probability to achieve a damage with type 144 ASDIC and Squid ranged between 13.0% (mean against USS SCOTSMAN) and 32.3% (USS DOGFISH) but the trials were kind of skewed for peacetime (in wartime the submarines would fire anti escort homing torpedoes, which the escorts didn´t minded here). It was also questioned whether or not four to six escort vessels would be aviable at any time to deal with a single fast submarine. Also, it was pointed out, that the probability to achieve a damage suddenly dropped to 0% in all trials when the submarine increased speed to 12 kts or faster or slower than 4 kts.


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## psteel (Jun 7, 2012)

Hi Delcryos 


Just so I'm getting this clear, your recommending these following titles to explore the trails mentioned in the previous posts?

Harding; The Royal Navy 1930-2000 (Naval Policy and History)
Polmar/Moore, Cold War Submarines: The Design and Construction of U.S. and Soviet Submarines (Washington 2004);
Friedman, U.S. Submarines Since 1945: An Illustrated Design History (Annapolis 1994);

Is that right?


hummm I can get "Palmer, Origins of the Maritime Strategy: The Development of American Naval Strategy, 1945-1955" at the library.
Also; Cold War submarines : the design and construction of U.S. and Soviet submarines / Norman Polmar and Kenneth J. Moore.


btw you wrote...



> Also, it was pointed out, that the probability to achieve a damage suddenly dropped to 0% in all trials when the submarine increased speed to 12 kts or faster or slower than 4 kts.



This is refering to the chance the ASW weapon has on the Sub at those speeds?


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## parsifal (Jun 7, 2012)

havent read all the posts guys, so my apologies in advance. 

Type XXI were a generational change in sub techs, and casualty rates would have dropped substantially if introduced in 1945 and the fighting continued in that year. Moreover offensively the high speed endurance and torpedo auto loading system would have made them very dangerous. I have also read the hull was coated in a rubber like compound to reduce sonar effectiveness, and the engines designed for better silent running. They still emitted quite a bit of noise at 10 knots+ but less than the 1930s clunkers equipping the KM at that time.

With all those advantages there would bound to be some improvement in submarine operations for the germans, but the allied countermeasures, numbers and training would still win the day in my opinion. We trained with subs at least as good as tghe Type 21s and had no difficulty in tracking them down and sinking them (well, in simulation at least) on a more or less regular basis. The key to defating them were carriers....lots of them, and the US was building or had built 140 of them by 1945, whilst the Brits were completing a further 20 or so "trade protection carriers"...colossus class etc, in 1945. The western approaches would have been a very busy and hectic place in 1945, and I have serious doubts that the type XXis could have made much of a dent against that level of defence.


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## delcyros (Jun 7, 2012)

psteel said:


> btw you wrote...
> 
> 
> 
> This is refering to the chance the ASW weapon has on the Sub at those speeds?


 
No, it´s a function of attaining a fix on the boat in the first place. If the GUPPY went slower than 4 kts it was practically not discriminable by background noises by methods of HE. If it went faster than 12 kts, the ASDIC gear failed, or, in case another DE went slower and forwarded the ASDIC data by wireless to the faster hunter ship, the probable error was larger than 400 yard with type 144 ASDIC.

A GUPPY is not quite a XXI but it represents a reasonable match.



> We trained with subs at least as good as tghe Type 21s and had no difficulty in tracking them down and sinking them (well, in simulation at least) on a more or less regular basis.



Would You mind to share Your experiences Parsifal?

thanks in advance,
delc


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## parsifal (Jun 7, 2012)

> Would You mind to share Your experiences Parsifal?



I participated in naval excercises known as RIMPAC in the late 70s and early 80s (ther were also some other excercises, including training with the five power defence pact). I served on the carrier and the DDG HMAS Brisbane. 

Airpower back then was critical to the ASW counterstrategy. We used Grumman Trackers for distant early warning and Wessex and Sea King Choppers for detection close in. We used Barra Sonar bouys and the mulloka sonars. Principal weapons were the homing torpedoes and the Ikara launch sytem, which had an effective range of 10NM, until the arrival of the NCDS which effectively doubled that range, because the missile could be guided onto the target using the fixes obtained by the heos dropping the dunking sonars. An ASW detachment could vary in size, but a ty[ical detachment might be 3 Frigates and 2 or 3 helos and about the same numbers of fixed wing A/C. 

We exercised with both nuclear attack subs and conventional diesel electrics. The most dangerous were by far the Oberon class when fitted with Harpoon sub launched anti shipping missiles (which unfortunately were only ever simulated....we never fif get those misiles) or Mark 48 wire guided torpedoes (which they did get, and became deadly with). Oberons were slow, but they were extremely quiet, and had this very nasty habit of being able to use ocean thermocline and salinity layers to get into position undetected. If they were equipped with Mk 46 torps, the nearest equivalent to the armament that was carried by a Type XXI they had no hope against the modern ASW defences that we could breeing to bear. Even our ancient Darings, by then using Limbo mortars and WWII era sonars could hunt them down and "sink" an Oberon, if it had assistance from airborne assets.

SSBN and SSN subs were much faster, but were noisy. They were expensive, so were seldom used for shipping attacks, but because of their noisy characteristics we could generally take steps to deal with them. Because of their speed, it was usually best to attack them from the air rather than try and run them down with ships. 

Even 1970s sonars still had problemes performing well at high speed. Before NCDS we would usually have two relatively slow moving ship[s undertaking the search patterns, assisted by aircraft , and one attacker. After NCDS all threee DDs would undertake the attacks....they could use the helos detection system to guide their weapons onto the target. 

Subs in 1945 against a well defended convoy with good aircover needed effective standoff weaponary. I am not aware that the KM possessed that capability in 1945. They had acoustic torps did they not, but I dont think lr guided torps existed at that time


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## psteel (Jun 7, 2012)

The Daring class had the type 170 /174 177 sonars which were designed for the Limbo and were much better than the Type 144 era systems. Friedman reports the type 177 ASDIC was capable of scanning at up to 18,000 yards, against 15kt subs in sea states of 2-3. Type 144 would have been only about 1/3 of that range. SeaKing helicoter with dipping sonar was a hugh advantage and would have had detection ranges in the 10-12ky region although half that in realistic sea conditions. 

Most WW-II active sonars were about 1-2 miles or 2-4ky. Looking at weapons effectiveness most WW-II Ballistic weapons were about 15% effective under realistic conditions, while DC attacks would have been maybe 5% against WW-II submarines. Even 1970s ASW torps should be in the 50-70% region against 15 knots submarine.

Thats an order of magnitude increase in effective ASW over the WW-II systems.


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## parsifal (Jun 7, 2012)

All agreed, but what isnt being considered are the improvements to sub weapons systems and silent running gear. Mark 48s had a range of about 50000 yards, whilst a sub launched sea skimming missile had a range of about 40-50 miles. Post WWII era subs were also far more difficult to detect because their acoustics were superior and because they could dive much deeper....typically to over 1000 feet. The equivalent of the Type XXI was the whiskey class diesel electric, and this boat was far more detectable than an Oberon or even an SSN. 

Mulloka was a superior sonar designed to achieve a higher power output and cope better with inversion phenomenon. 

In my opinion, whilst there had been great strides in undersea detection and attack systems 1950-70, there had also been great strides in submarine techs and weapon systems. My opinion is that relative to each other, submarines had widened the technology advantage, rather than lose ground. that is of course a value judgement, and open to alternative opinion.


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## psteel (Jun 7, 2012)

I don't agree with your comparison between old and new relative capability. The newer systems had much better software search programmes and much better air component. I think helicopter dipping sonars revolutionized ASW missions. 

http://www.uboataces.com/uboat-type-xxi.shtml

Whiskey was not comparable to the XXI, it was originally designed to counter the Type VII and was modified when Type XXI were captured . It could only manage 13 knots underwater .

STMMain

Project 651 Romeo/Julliet was a better comparion with XXI it could manage 17knots submerged and 300nm @ 3 knots. The Type XXI could manage 285 @ 6 knots and if Delycros reporting is accurate it was undetectable at that speed using the creep motors.

http://www.russianwarrior.com/STMMain.htm?1947vehicle_Whiskeyhist.htm1


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## N4521U (Jun 7, 2012)

I think I've got the bends!


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## parsifal (Jun 7, 2012)

Oberons have creep motors as well, and they certainly were detectable even whilst stationary. It simply is a matter from combat to combat as to how detectable your sub is, and no sub, however good it is technologically waas ever completely undetectable in all situation. For that matter no ship, of any description or nationality was ever unsinkable. 

The earlier WWII sonars (eg type 144) are essentially as discriminating as those of the later Type 164s and 170s introduced 1950 and 1955, but simply with less power. What makes the problem difficult is the speed. Asdic wont work at speed, which means you need more escorts to track travelling at low speed, others positioning themselves to continue the tracking ahead of the sub, and others being directed onto the target to deliver the attacks. if the effective range of the Asdic is limited to 2500 yards as was the case with a type 144, you need more "stationary" trackers in your hunting group to maintain your search pattern. It doesnt mean the sub is undetectable. It means its more difficult to track and combat, and you need thickened up defences to beat it. 

There is no such thing as an undetecbale target...at least no such thing that can have a blanket statement applied to it. There will be occasions when a sub is undetectable....thats what they rely on to deliver their attacks. Conversely ASW forces rely on detection to sink those subs. There is no such thing as a fullproof defence either, though that does not seem to be in contention here, since the germans were not manning the ASW forces.... They (the ASW forces) dont rely on detection to supress the target. If a sub is forced to submerge, it has a much harder task achieving a good firing solution. A submerged WWII sub, even a Type XXI is a relatively immobile target. Get him to submerge and you have the opportunity to re-route your convoy away from him. The problem with the Type XXI attack is that they could sustain high speed submerged for a relatively long time, but not indefinately, and not much greater than the speed of the a typical convoy. Suppressing a type XXI (ie forcing it to submerge and turn away) isnt as effective as it was against a type VII, but it was still effective, as it is against any conventional diesel electric boat. Only SSNs, with their relatively limiltless suibmerged speeds and power, can sustain a continual underwater attack . 

The prize against conventional subs is of course to force the target to submerge in the first instance (thereby greatly increasing the survivability of your shipping because the sub loses its range and mobility advantages. In the second instance, the golden prize is to detect that submerged sub, achieve a firing solution and sink him. No submarine, at any time in history has ever been able to achieve that outcome every time. A type XXI as a piece of high tech kit was more likley than a Type VII, but not immune to detection and the density of the defences in 1945 would have meant its losses would still have been heavy. 

To deliver an effective attack, a Type XXI equipped with unguided weaponary has to close to about 1000 yards to be effective. With a heavy amount of aircover, and the density of defences available to the allies in 1945, that a very tall ask. The germans hoped to counter that problem by attacking submerged using massed broadsides of Gnats. i have serious doubts that those tactics would have been all that effective. gnat was a weapon system more or less easily countered using towed arrays 



> I don't agree with your comparison between old and new relative capability. The newer systems had much better software search programmes and much better air component. I think helicopter dipping sonars revolutionized ASW missions.



You are making the same error again. What about the enhanced techs acquired by the submarine arm in that time. Sub detection and tracking systems exploded exponentially in the post war period, they also acquired weapons 10, 20 or 50 times as accuarate, and/or with greatly increased ranges. they acquired the ability to fired sub-launched SLAMs. 



> Whiskey was not comparable to the XXI, it was originally designed to counter the Type VII and was modified when Type XXI were captured . It could only manage 13 knots underwater .



I agree, but basing ideaas of overall capability on the basis of submerged speed alone is a poor way of determining the types overall capability. Speed is just one capability. The Ws could dive deeper, stay submerged longer and later had better weapons and electronics and detection gear fitted

The Type XXI was designed to have a design depth of 135 meters, which gives a crush depth of 340 meters and a maximum safe depth of 225 meters. However, when the finished product was tested, there was a minor problem in the design which reduced the design depth to 120 meters, so we get a crush depth of 300 meters and a maximum safe depth of 200 meters, rather similar to the VIIC. The deepest test dive was to 220 meters. 

A W class had a design depth of over 200 meters, giving it a max design depth of about 350m. I do not know its maximum crush depth. 

"During the five years following the end of World War II, Soviet exploitation of the Type XXI lagged significantly behind American fears. US intelligence initially foresaw in 1946 a force of 300 Soviet Type XXI equivalents by 1950. But it was not until 1949 that the first postwar Soviet submarine designs -- the Whiskey and the Zulu -- put to sea. While the Zulu was a true Type XXI, the Whiskey was a smaller, less capable, shorter range boat, designed more with an eye toward coastal defense and European littoral operations. It was not until the mid-1950s that Whiskeys were even given snorkels.

Early post-war construction focused on small submarines, the vast majority of which were Whiskey-class boats. Between 1949 and 1958 a total of 236 Whiskeys were commissioned. A shore targeting station would direct these vessels in their defense of the sea approaches to the Soviet Union. The larger Zulu-class and smaller Quebec-class submarines augmented the Whiskey-class. The thirty-two Zulu-class submarines operated further out at sea and coordinated with shore-based aircraft to provide targeting information to the shore centers. The approximately thirty Quebec-class submarines operated in the coastal waters. 

During the 1950s there were efforts to convert Whiskeys into cruise missile submarines (SSGs). As the Soviet navy's mission expanded to combating the US Navy on the open ocean. The Echo I and Whiskey Long Bin class submarines deployed with anti-ship cruise missiles to fulfill this role." 


They could dive


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## psteel (Jun 7, 2012)

According to the site I linked the maximum safe depth of the Whiskey class was only 200m, which is similar to the XXI and was cleared in trails down to 220m before the war ended more testing. Likewise the endurance of the Whiskey underwater was not as good as XXI . Whiskey got [email protected] 2knots while XXI got [email protected] 6knots or 340nm @ 5knots. In other cases of German U-boats; if you half the speed from 4-2 knots, you almost double the endurance. Going on that; suggests XXI could be able to do about 590 @ 2.5knots [160 hours vs 230 hours].

Its quite clear from the samples Delcyros shared with us, the post war Destroyer Escorts had little or no chance of stopping modified American Guppy subs from attacking. These subs were less capable than the Type XXI in most respects [underwater speed and endurance plus quietness]. Given the ease with which they attacked, I would suggest your comparison is doubtful. I was reading a piece on NATO Canadian carrier ASW missions and it seemed even a single SSK Sub was a very difficult enemy to defeat in most of the exercises they conducted through the 1950s and 60s. Perhaps by the late 1970s Sonar technology and ASW surveillance in general, had improved dramatically? I suggest you read his piece.


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## parsifal (Jun 8, 2012)

> According to the site I linked the maximum safe depth of the Whiskey class was only 200m, which is similar to the XXI and was cleared in trails down to 220m before the war ended more testing.




You need to be careful when quoting max safe and max crush depth. The figures I relied upon for the Type XXI was the Uboat net site. plus i have a book at home. its max safe dive limit was 135 m, but due to some production issues (i dont know what, that was downrated to 120m. Max depth (ie with safety standards exceeded was 220 and crush depth slightly above that. The max depth they ever dived to was 225m. by comparison the W class has a max safe diving limit of 200m, which means they have a max dive limit of about 350m. I dont know the crush depth and as far as i know no western source has ever published one 



> Likewise the endurance of the Whiskey underwater was not as good as XXI . Whiskey got [email protected] 2knots while XXI got [email protected] 6knots or 340nm @ 5knots. In other cases of German U-boats; if you half the speed from 4-2 knots, you almost double the endurance. Going on that; suggests XXI could be able to do about 590 @ 2.5knots [160 hours vs 230 hours]


.


we would have to check, but it gets down to the power consumption and battery capacity



> Its quite clear from the samples Delcyros shared with us, the post war Destroyer Escorts had little or no chance of stopping modified American Guppy subs from attacking. These subs were less capable than the Type XXI in most respects [underwater speed and endurance plus quietness].




Some of the old hands that trained with me had served postwar on Q and Battle classes. They used to comment on these American Guppy subs. They were considered very noisy and rather easy to track and sinkl to be blunt about it, so I am at a loss to reconcile my practical real world experience with the theoretical book learned values you aere relying on. Guess for you the theory carries more weight than the practice. 



> Given the ease with which they attacked, I would suggest your comparison is doubtful. I was reading a piece on NATO Canadian carrier ASW missions and it seemed even a single SSK Sub was a very difficult enemy to defeat in most of the exercises they conducted through the 1950s and 60s. Perhaps by the late 1970s Sonar technology and ASW surveillance in general, had improved dramatically? I suggest you read his piece.




As young PWO officers we could, and did train in the tactical warfare school at HMAS Watson using a very large computer simulation . The facility is called HMAS Watson and occupied an entire 9 storey building. At those training sessions we used it to train and simulate a wide range of tactical situations, using a variety of technologies from the early 50's through to the very latest at the time. This included using post war DDs to do combat with various subarine types. As trainees we would divide into PWO teams and be sdent to different rooms that were decked out as differnt ship types. I rember it was very cool being in submarines...you had a periscope that presented various targets and the like. Usually we trained with only RAN types loaded into the database, but we could and did simulate foreign types on occasion. That included USN Guppy types. For these older types we would usually load the older Darings and Battle class DDs of the 50s and 60s. 

With carrier support, there was nothing special or unusual in hunting a Guppy. It was harder than finding a W or Z class boat, but much easier than finding an Oberon. We also sometimes trained as the attacking subs,and i can categorically tell you that it was never easy to deliver an attack against a defended target. nice story, completely at odds with my experience as a PWO. 


I can only repeat, that with the passage of time, the scales tipped more in favour of the sub, not the other way around as you are repeatedly asserting. Things have gotten harder for the escorts with time, not easier. 

After my experience with Del telling me the Bismarck was unsinkable, i will reserve my comments about his claims.


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## delcyros (Jun 8, 2012)

Thanks Parsifal for sharing Your insights. From my perspective, operational ASW experience is a very important factor here, which lends credibility and weight to Your posts. 

There are still a couple of issues, I´d like to outline, knowing that questions may be raised, which cannot be answered generally but they may be discussed to the one or other direction.

The question of applicability to XXI is likely not a straigthforward one. Sometimes it can be really difficult to detect, let alone intercept even world-war 2 Diesel boats with 1980´s ASW technology, referring to the attack carried out by an obsolete, ww2 buildt and equipped argentine Uboat in the Falkland war against HMS SHEFFIELD with a determined ASW screen. The torpedo attack was unsuccessful because the torpedoes were of 1940´s vintage technology. This would be in line with Your argument that a effectively guided stand off weapon is required for the XXI to be very successful against ASW. 

The question whether or not such a weapon would be aviable to the XXI can be discussed on Rößler´s reference about german torpedo development, in my mind the most exhoustive study done to the subject with plenty of references to primary sources and written by a person, who was in touch with R&D and deployment of modern torpedoes in the post war german navy.

According to aviable sources, there were multiple guided torpedoes types developed in ww2. Not all of them can be considered successful. But in order to limit the discussion on feasable torpedo types and likely deploymental problems I will limit the response to few types.

In April 1945, XXI in service with operational flotilla 11, stationed in Bergen / Norway were equipped with an improved programmable and long range torpedo (LuT) with a straight running capability of ca. 8000m @ 40 kts on batteries. The programmable pattern allowed to shoot the torpedo independent from the submarine´s position and heading and down to a depth of 40m below the surface (OT-I). At target, the LuT could run pre-programmed patterns which would be very nasty in a convoi but help very little against escorts. Pattern sweeps also greatly limited the range of the device.
Also in service among type XXI and XXIII was an improved homing torpedo (T-Vb Zaunkönig II or Gnat in allied terminology). This torpedo was specified as an anti-escort homing torpedo with a range of 7000m at 27kts and better signal processing than the predecessor T-Va. The allied response to it would likely be a new type Foxer been slipped by the escorts. Foxer were responsible for ca. 15% T-Va failures in a post war study. Most of the homig torpedoes failed by either early or end detonation or detonation within the wake of the target according to a post war evaluation report (roughly 60%).
Not included at Bergen were wire guided or active homing torpedoes. These do exist and are referred to as "Geier" (active sonar homing) or "Lerche" (wire guided, passive homing), passing the german navy acceptance trials to february 1945. Production of these torpedoes was started at wars end. It appears to be improbable that much or any of these torpedoes would have been issued to submarines before july 1945.

With regard to the Whiskey class, the soviet´s themselve didn´t considered their Diesel-electric Whiskey class as a full aequivalent to the XXI in russian sources. The aequivalent was to be the ZULU-class in performance, though even the ZULU´s were not nearly as silent, particularely while snorting at periscope depth. The reason for the difference was a difference in perception of sound insulation persistent because of the soviet choice of sound detection gears. The soviets considered much of the care of the XXI sound insulation (f.e. the hydraulic drive and clutch, which dampens the sound of the main motors, rubber pads between structures and virtually all mechanical equipments) as complicated and excessive because they very late attained the knowledge that low frequency noise allows longer detection ranges in the open ocean than high or medium frequency noise in littoral waters of the Black Sea and Baltic.
I have some data for db noise vs speed for german XXIII (very little) and XXI (good sample) but little to compare that with except for the GUPPY boats which were compared in trials off Key West with U-2513 in 1946 and then again in 1948 with GUPPY´s. The immediate post ww2 noise discimination limit for wet immobile platforms using the HE-effect on the instruments employed in these trials was 70db. The XXI could be not be heard at 3kts and barely be heard at 5 kts on it´s main motors by an immobile listening platform and it´s signature was entirely lost in background noise when running on it´s creep motors even as close as 200 yards away with 6.2 kts (the maximum speed U-2513 could run on creep engines). A fleet boat could be heard at 2 kts, a GUPPY at 3 kts in compared conditions. 
The HE data for U-2513 are those:





perhaps Parsifal can comment on those data.


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## delcyros (Jun 8, 2012)

> The prize against conventional subs is of course to force the target to submerge in the first instance (thereby greatly increasing the survivability of your shipping because the sub loses its range and mobility advantages. In the second instance, the golden prize is to detect that submerged sub, achieve a firing solution and sink him. No submarine, at any time in history has ever been able to achieve that outcome every time. A type XXI as a piece of high tech kit was more likley than a Type VII, but not immune to detection and the density of the defences in 1945 would have meant its losses would still have been heavy.
> 
> To deliver an effective attack, a Type XXI equipped with unguided weaponary has to close to about 1000 yards to be effective. With a heavy amount of aircover, and the density of defences available to the allies in 1945, that a very tall ask. The germans hoped to counter that problem by attacking submerged using massed broadsides of Gnats. i have serious doubts that those tactics would have been all that effective. gnat was a weapon system more or less easily countered using towed arrays



I agree mostly. One of the limitations of type 144 ASDIC (note, type 144 represents not standart ASDIC gear but the very final evolution developed in ww2 and served afterwards, similar to the XXI developmental timeframe) is accuracy of depth. Late ww2 ASDIC was not mounted on a stabilized platform and generally was incapable of accurate depth determination and failed at depths larger than 400ft. Type 144 gave serious improvements though still wasn´t stabilized,resulting in problems at depth determination and detection at depths larger than 800ft. That beeing said, 800ft is among the maximum XXI could operate with a reasonable tolerance to hull failure (it´s below testing depth and close to crush depth which was 304m in US water presure cassion tests and 285m in british tests).

However, with regard to the Gnat as a method of firing massed salvo´s I disagree. The Gnat wasn´t intended for that purpose. Massed salvos were to be fired with LuT pattern running torpedoes against convoi, not with Gnat. At least according to the operational instructions type XXI issued by the KM. I am also convinced that the efficiency of GNAT is often overemphasized in the literature. It´s a credible anti-escort homing torpedo (and in that functio can mess up even the most careful search patterns when the escorts are forced to step aside) but other than that it´s functionlity is limited.

To understand the issues involved here, one need to discuss or at least comprehend the problems for attacker and defender of a convoi.

For the escorts, the success is not necessarely to sink an XXI, it´s enough to deter the Uboat from intercepting and attacking the convoi.
For the submarine, the problem is that it will be limited on battery endurance during the approach or-alternatively, a vely long distance needs to be kept while snorting. Older boats lost their strategic deterrence when forced to submerge due to the fact that the one hour endurance at 6 kts with maybe 7kts top speed wasn´t nearly enough to enage a convoi unless it is detected within a narrow fan of the boats course and on convergent courses. 
The US operational research group Report No-51 (1946) "ASW IN WORLD WAR II" goes into some details explaining the variables here.

An interesting function given there is the ability to attack dependent on the varyables of speed, endurance and angle to convoi. XXI are credited with a submerged endurance of 11 hours at 10 kts. originally, the boat was designed with an intended endurance of 1 hour at 18kts, though issues in hull and propellor design and in particular problems created by high current power in the batteries ensured that the XXI couldn´t achieve 18kts top speed and the endurance with full batteries was limited to 1 hour 20 minutes at 16kts rather than the tehoretical 1 hour and 40 minutes. Still, it had excessive endurance for lower speeds, particularely lower than 14kts, when the high current drop in battery output ceased to be an issue. 

HC-convois had about 9.5 kts cruise speed, there were faster convois with 12 to 14 kts and slower ones proceeding with only 7kts. For an old boat, which could sustain only 4 kts for an hour or two this meant that the boat needs to be positioned within a fan of 64 deg along the convois heading when fist detected to make the intercept possible. Additionally, the detection range needs to be fairly small (8 to 6nm) to ensure that the boat can attain an atacking position before the batteries are depleted.
XXI boats would have more tactical ellbow-space. With 80% battery capacity, they could still run 6 hours submerged on 10 kts while maintening a reserve capacity larger than 2 hours at this speed. Thus, they could be positioned anywhere in a fan 185 deg wide along the convoi´s heading. Spaced 20nm away, 92 deg abeam to the convoi an XXI would find itselfe in a possible position, which may trigger an intercept attempt. This capability is important in my mind, because it allowed the Uboats to regain their strategic dangerousness, which the old boats completely were deprived off, due to their limited mobility and endurance operating submerged.


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## davebender (Jun 8, 2012)

Type XXI submarines were designed to be quiet underwater with a streamlined hull and special silent running electric motors for normal cruising. In theory that should have made them quite a bit quieter then converted Guppy boats.


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## parsifal (Jun 8, 2012)

Quoting and relying on published noise figures is problematic at the best of times. The RANs experience with its new Collins class ( a derivative of the type 471 class) is a good illustration. As designed, and in theory these ships had noise signatures about half that of the Oberons they were meant to replace. The noise made by the Collins class submarines was in fact problematic and unforeseen, which compromised their ability to stay hidden, and turned out to be a major problem with the design that took years to resolve (eventually it was resolved but it took some time). In the original requisition, the RAN guidelines for the noise signature of the new submarines were vague; for example, asking that they be "twice as quiet" as the Oberons. Expectations and operational requirements also changed between the 1987 contract signing and when the submarines began operating in the late 1990s. The major element of the noise signature for the Oberon class was machinery noise transmitted through the hull; this was successfully avoided during construction of the Collins class by mounting machinery on platforms isolated from the hull. 

However, further noise testing during 1996 and 1997 found that the hydrodynamic noise signature—the noise made by a submarine passing through the water—was excessive, particularly at high speed. The shape of the hull was the main cause: although a scale model of the design had been tested during the funded study and was found to have a minimal signature, the hull shape was changed after the contract was signed, primarily by a 2-metre (6.6 ft) lengthening of the submarine and a redesign of the bow dome to accommodate the larger-than-expected main sonar and reduce its blind spot (the baffles). The design had not been retested, as who would pay for this could not be agreed on. Propeller cavitation, caused by water flow over control surfaces onto the enlarged blue ocean props at certain speeds was the other main noisemaker. Cavitation had not been a problem with earlier Swedish submarine designs or during early testing of the Type 471 design, but the propeller had to be redesigned late in the process to provide more power so as to cope with blue water conditions , and like the redesigned hull, was not retested. Subsequent studies by the Defence Science and Technology Organisation showed that the submarine's hull shape, particularly the redesigned sonar dome, the fin, and the rear of the submarine, focused the displaced water into two turbulent streams; when the seven propeller blades hit these streams, the propeller's vibration was increased, causing cavitation. After delays measured in years these problems were fixed by modifying the casing of the submarine with fibreglass fairings.

For a pretty good summary of the noise signatures of the Oberon class, I would rely on a Canadian study , with the following links provided. Oberons were developed from the Type XXI, at least in concept, and from my reading were “250% quieter” (whatever that means). Whatever the precise meaning of that statement, it must surely be conceded that oberons would be much quieter than the type XXI. According to the Canadians, Oberons have a noise signature under the conditions they specified in their 1994 evaluations of around 20-40 mhz at creeping speeds. That appears to be louder than those US test you have quoted (though I admit I may be misunderstanding the data you are presenting. The canadian evaluations are however consistent with the noise signatures I have seen for the Collins class, which noise signatures of less than 10 mhz at creep speeds.

http://pubs.drdc.gc.ca/PDFS/unc107/p534367_A1b.pdf

The upshot of all this, is however that you cannot assume that “oils are oils” from just one study. On the basis of that USN post war study, that appears to make the Type XXIs even quieter than the Type 471s, a design more than 40 years younger. Clearly something is wrong. Either the two studies are not comparable ( a very likely conclusion) or the US studies are not accurate. I discount the chances the Canadian and australian trials results are innaccurate, since they tend to reinforce each other.


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## psteel (Jun 9, 2012)

While we are required to bow to your experiences they don't apply to WW-II experiences and therefor may not be of as much use. Worse some of us have referenced to submariners who say differently. Whos right whos wrong? Not my place to say.

Unfortunately it doesn't matter what we believe it only matters what we can prove. If we are relying on canadian results we are in trouble.


Report No-51 (1946) "ASW IN WORLD WAR II"

Covers allot of things. It mostly showed the huge gap between theoretical expected performance and actual battle results.

It showed the theoretical effectiveness of a ballistic ASW weapon was rarely ever reached in actual battle in fact taking years of combat to approach this value.
It shows that the faster the U-boat the harder it is to be targeted using ballistic ASW weapons which included Squid and probably applies to Limbo as well. The faster the U-boat went the more the 'average error distance' increased which impacted accuracy.
It also showed that real war detections attempts were ½ to ¼ as effective as the training detections runs and attacks.



BTW looking at this site GUPPY on batteries this guy calculates it gets one hour at 13-14knots or 20 hours at about 6 knots.

Barrow Submariners Association


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## parsifal (Jun 10, 2012)

> Covers allot of things. It mostly showed the huge gap between theoretical expected performance and actual battle results


.

Iagree with ths statement and its context, however the conclusions you are drawing are faulty. The statement should apply equally to both submarine techs and ASW techs. it should be appliesd with even greater vigour for new and untried technolgies, like the tyoe XXI over proven techs, because new techs invariably will have unforeseen bugs and weaknesses 



> It showed the theoretical effectiveness of a ballistic ASW weapon was rarely ever reached in actual battle in fact taking years of combat to approach this value.



what value? theoretical and actual effectiveness also affects submarine techs just as badly




> It shows that the faster the U-boat the harder it is to be targeted using ballistic ASW weapons which included Squid and probably applies to Limbo as well. The faster the U-boat went the more the 'average error distance' increased which impacted accuracy.[/QUOTE
> 
> This is one of those classic situations where a relatively minor problem is paraded as a panacea for a lot of other problems. high speed does indeed cause a significant and exponential drop in wepon accuracy. You might also add that high speed (by the tracking escort) also affects the performance of its sonar. From that it is tempting to argue that attacking at high speed will reduce the vulnerability of the sub. and in doing so you would be 100% incorrect. Travelling faster underwater greater increases the vulnerability of the sub, because its noise signature also goes up exponentially as speed increses. There are several reasons for that, including increased machienery noise, increased hydrostatic noise (noise from the hull passing through the water, noise from increased hull cavitation, and lastly increased noise from cavitiation from the props. This applies aas much today as it did in 1945....a sub that has been detected, is generally dead if it tries to cut and run. It has to use temperature and salinity layers, creeping tactics and silent running to evade its hunters....not running.


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## Lucky13 (Jun 10, 2012)

Very interesting stuff gentlemen!


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## delcyros (Jun 10, 2012)

I have little time to spare (working on a different project right now), but let me add some data to the discussion.

Most and foremost, what do You understand under the term "wonder weapon", gentlemen? This term is so vague and misleading that in my perspective it requires at least a definition, otherwise people may start claiming different aspects without comprehension of the historical meaning of the term.

Davebender wrote:


> Type XXI submarines were designed to be quiet underwater with a streamlined hull and special silent running electric motors for normal cruising. In theory that should have made them quite a bit quieter then converted Guppy boats.



Yes, this is likely correct. US postwar comparative studies at high frequencies (1946 trials with U-2513) and detailed low frequency trials 1948 suggest that the XXI boats comissioned for trial purposes were significantly quiter and less distinctive in their sounds at all speeds compared than the GUPPY converted Tench fleet boat against the instruments and in those specific trial conditions. The differences were considerable enough to trigger much work in quiting all equipment and propeller noises as much as possible in the TANG class. The US, by that period already went into low frequency buisness. The soviets didn´t, resulting in comparably noisy submarines well into the 60´s.

Parsifal wrote:


> For a pretty good summary of the noise signatures of the Oberon class, I would rely on a Canadian study , with the following links provided. Oberons were developed from the Type XXI, at least in concept, and from my reading were “250% quieter” (whatever that means). Whatever the precise meaning of that statement, it must surely be conceded that oberons would be much quieter than the type XXI. According to the Canadians, Oberons have a noise signature under the conditions they specified in their 1994 evaluations of around 20-40 mhz at creeping speeds. That appears to be louder than those US test you have quoted (though I admit I may be misunderstanding the data you are presenting. The canadian evaluations are however consistent with the noise signatures I have seen for the Collins class, which noise signatures of less than 10 mhz at creep speeds.



The OBERON trial data You referred to are very interesting, thanks a lot for this contribution. I would also agree that the details of trial conditions likely would render the data incomparative. Still, these are primary source data and have their value. I know that the services differed in db-definition. In Soviet services, f.e. the measurement differed and required higher salinity than in US trials and a different signal strength, resulting in 27db in russian data beeing similar to 20 db under US definition. German sound taking data, differ, too (caused by the lower salinity of the Baltic Sea) but I admit I don´t know the british definitions.
But I´m curious, how did the british determined that the OBERON´s were 250% quiter than the XXI when they didn´t conducted any sound trials on either XXI or XXIII? The only dedicated sound trials conducted by the RN after ww2 with captured german boats were on two 1943 vintage type VIIC models, similar except for one having ALBERICH anti-ASDIC coating while the other hadn´t. These trials were in order to determine and quantify the possible effect of rubber coating. Without comparative data, I am inclined to guess that no qualitative asessement is possible between type XXI and OBERON class.
The few data aviable under identic trial conditions refer to U-2513 off Key West against a US fleet boat (Tench class) with rather high frequency listening devices prevalent in the late ww2 period and some detailed comparative studies between a GUPPY I and U-3008 (or it´s equipments, to be precise) in 1948 using a GHG low frequency unit (later BQR-2).



> (...) The statement should apply equally to both submarine techs and ASW techs. it should be appliesd with even greater vigour for new and untried technolgies, like the tyoe XXI over proven techs, because new techs invariably will have unforeseen bugs and weaknesses



This is entirely found to be correct. The principal reason, in my mind, why the XXI wasn´t rushed into combat zone was the necessarity to work out or at least mediate it´s technical bugs and issues. The class reached operational status not before april 1945 and was in trial status as late as march. And that despite the fact that most components of type XXI -as opposed to entirely new propulsion plants of type XVII and XXVI- were based on already prooven technologies (Diesel electric, hydraulic gear, snorkel, GHG, S-device). Several of the unprooven ones (100m deep OT-II firing circuits for the tubes), SP-SUBROC and it´s aiming device, several decois were simply dropped or delayed in the pipeline rather than worked out. 


I have also compiled endurance data for XXI and extracted them from the range/speed data in operational instructions type XXI.




Note that what I consider important here is the excess reserve battery capacity of the type. A GUPPY-II (1949)can sustain 14.5 kts at the one hour rating, a FOXTROT-class (1959) can sustain 14kts for even 2 hours and the XXI (1945) 14kts for 2 hours and 50 minutes. WHISKEY- and ZULU class are in between GUPPY and FOXTROT. Indeed, I was kind of surprised (to say the very least) to find the notion in XXI op. instr. that it is directly suggested to carry out an intercept as long as the remaining battery capacity at the time of firing the torpedoes is 20% or more. That appeared to be very low to me in the first view but then again, 20% remaining battery capacity would still allow many hours endurance in an XXI, similar to a GUPPY at 50-60% capacity. Of course, I could have looked into Friedman or Roberts, who outlined this excess battery capacity in their early works, too...

I have little data for other submarines but it appeared that the TANG class did 1 hour at 17.5 kts and 43 hours at 3.0kts. The high speed endurance is comparable to XXI (had it been able to achieve such a high speed) but the silent speed endurance is not more than one quarter of it. Admittently, the comparably low figure (43 hours) at ultra silent speed (3.0 kts for the TANG) compared to a Fleet boat is likely caused by the much increased hotal load for the much increased, powerful suites of electronic equipment carried aboard a TANG class Diesel-electric attacking submarine. Why the TANG hadn´t used economical and ultra quite creep engines, I didn´t understood. The XXI benefitted much by those in it´s endurance at this speed region. U-3507 conducted speed and endurance trials off Pillau in march 1945 with new and fully loaded batteries and had an endurance of 162 hours and 20 minutes at the power run required to attain 3.0 kts on creep motors (this long term trial was in port, range specified was 487nm).


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## psteel (Jun 10, 2012)

parsifal said:


> .
> 
> This is one of those classic situations where a relatively minor problem is paraded as a panacea for a lot of other problems. high speed does indeed cause a significant and exponential drop in wepon accuracy. You might also add that high speed (by the tracking escort) also affects the performance of its sonar. From that it is tempting to argue that attacking at high speed will reduce the vulnerability of the sub. and in doing so you would be 100% incorrect. Travelling faster underwater greater increases the vulnerability of the sub, because its noise signature also goes up exponentially as speed increses. There are several reasons for that, including increased machienery noise, increased hydrostatic noise (noise from the hull passing through the water, noise from increased hull cavitation, and lastly increased noise from cavitiation from the props. This applies aas much today as it did in 1945....a sub that has been detected, is generally dead if it tries to cut and run. It has to use temperature and salinity layers, creeping tactics and silent running to evade its hunters....not running.



Yes thats all understood but unfortnately not relevant to the specific case of Type XXI usage in 1945/46. Passive sonar was not the allied strength. There passive sonars would not have made any difference . The increased noise signature would have made up for the reduced passive sonar effectiveness resulting in the same detection range. ASDIC was a better bet for the allies at that time.

The Allies gambled on active sonar and it would have taken years for them to reverse course.

This is why I'm respectfully suggesting your 1970s experience base, doesn't really translate well in to a end of WW-II situation. There was just too much different.


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## psteel (Jun 10, 2012)

From what I’ve read about _wunderwaffen _, one can dump the blame on Hitler himself. Prior to Hitler taking control of the military in mid 1930s, there was a long term strategic plan in place to rebuild Germany to mount an mechanized preventative war against the European powers by the early 1940s. This envisaged sufficient stockpiled military supplies munitions to conduct 1 year of continuous fully mechanized warfare with a WW-I sized armed forces. In addition to this another year of resources needed to build the second years supplies munitions was to be stockpiled and by the third year the economy was to have reached 'total war mobilization' levels. In addition to superior doctrine superior armaments and new high tech innovations were planned to give German troops a decisive edge in battle.

When Hitler inquired as to the progress of this plan in the mid 1930s, he was informed that, at the rate things were going, the plan could not be ready before the mid 1940s. Hitler baulked at this and threw the plan out replacing it with his own ideas. These included NO STOCKPILING of anything. There would be no steps towards 'total war economy' since the war he envisaged would be over quickly. Hitler instead would cobble together a 'limited war' strategy based on his superior will power with Germany’s superior race plus what treaties and agreements he could make, to fast track the entire rearmament program by the early 1940s.

When war came prematurely in 1939 Hitler was forced to chuck part of his plan and take the needed steps to build up the armaments needed for a limited war. All long term plans and armaments [including experimental] were shelved to reverse the economy into more basic armaments....but only for a short war to occupy Europe and Russia prior to turning west and dealing with the Brits and Americans. When all this fell apart in Russia in 1941, Hitler was forced again to reverse course and fast track total war economy. When that appeared to have failed by late wars, Hitler grasped at Wunderwaffen to save Germany and himself.


BTW Delycros , great post. You do seem to know your material.


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## parsifal (Jun 10, 2012)

> Yes thats all understood but unfortnately not relevant to the specific case of Type XXI usage in 1945/46. Passive sonar was not the allied strength. There passive sonars would not have made any difference . The increased noise signature would have made up for the reduced passive sonar effectiveness resulting in the same detection range. ASDIC was a better bet for the allies at that time.



Passive detection had predatyed ASDIC in WWI. It was a principal means of detection in WWI. Between the wars all the major nations with submarines developed passive systems. The principal weakness of these early passive systems was that the listening ship had to be stationary to use the gear. Whilst I am not a real expert on wartime submarine techs, I do know enough to know that British subs entered the war carrying two types of passive listening gear, and that this gear was used to hunt and sink a number of German ships. The Americans also used a similar capability in their Pacific subs, and mated passive underwater detection with both active sonars and surface radar. I believe the british did the same,and considerable resources wre poured into the development of passive detection systems, such that by wars end, detection whilst moving at slow speed was practised. 

Passive systems were not fitted to Allied surface ships were not fitted, not because they were not available, as their usage in Allied subs clearly demonstrates, but simply because they were not needed. Allied escorts needed a weapon that was of maximum usage whilst underway, and really were unworried about giving their position away to a U-Boat. A U-Boat attacking a surface escort wasnt going to live that long anyway.

So your claim that Allied advances passive detection was not available or not effective is just not supported by the facts. Passive detection was used extensively by all allied submarine forces, and appears to have assisted in kills of enemy subs. if Active sonars were proving inneffective there is no reason to suggest that the allies would not fall back onto their WWI experience and use their 1945 techs in their ASW forces. 



> The Allies gambled on active sonar and it would have taken years for them to reverse course.



Err no, incorrect. The RN and the USN each developed at least two Passive systems that I have read about and used them operationally. There were at least two decated research establishments that I know of in Britiain dedicated to the purpose and at least a further one in the US. German development did lead the allied effort, but that a big stretch, to the point of misrepresentation, to say the allies had litle or no capability in the field. They had consiserable capability, and considerable manufacturing capability, as well as considerable operational experience using the type. 



> This is why I'm respectfully suggesting your 1970s experience base, doesn't really translate well in to a end of WW-II situation. There was just too much different.



No, I would put it to you that you dont want to recognise my practical experience because it interfers with your preconceived notions about what the Type XXI was capable of. And whilst i am using that experience, I am not relying on it. I am using it at a yardstick to demonstrate the surrealism in the arguments being submitted relating to the the alleged immunity of the Type XXI. Just so we are clear, the Type XXI would have been a tough opponent, but not undetectable and not unsinkable. it would have suffered heavy casualties given the thickness of the allied ASW defences if used operationally on an extensive basis. in the same way as the Tiger tank or the Bismarck, technical superiority would count for little in the face of Allied overall superiority of numbers and other key areas areas of technology and operations.


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## psteel (Jun 10, 2012)

No one said they didn't have passive sonars , but its clear they invested most of the industry into ASDIC systems.

Most passive sonars of this period were only able to detect 'battery powered subs' at about 2-3km ; roughly the same as ASDIC, but as you may have read on ORG 51; there effectiveness was orders of magnitude less than ASDIC systems, since they were passive systems. 

Against a 'diesel sub' such passive sonars would have double the detection range and effectiveness , but such sonars would only get these ranges if the searcher was drifting.

Such sonars would not have helped the allies much, in any anti Type XXI war. An ASDIC system could work up to 15-20 knots attack speed - but with reduced effective range- they were still more effective. 

German passive sonars seem to have been much better, with detection ranges several times the above figures.


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## delcyros (Jun 11, 2012)

Passive sound detection was invented through world war one as outlined by Parsifal and was practicised by the RN through ww2. The method of application was a unified active / passive sound detection device to be known as ASDIC developed in the interwar period. The passive detection part was by a mechanically steered hydrophone.

In comparison to german active sound detection ("Schallortung" or "S"-device) and passive detection systems the major difference of the allied sets was the choosen, rather high frequency range. The active element had a range depending on conditions of 1,500 yard to 3,000 yard with a 5 degrees bearing accuracy, the passive element often did not reach this range.

German passive detection gears typically consisted of an integrated arrey of multiple crystal hydrophones steered electronically (by field manifold manipulation, rather than by turning of the elements), a solution which doesn´t produce any noise. Also, the frequency isn´t in the Khz range but in the Hz range.
The loss of db transmission is not similar at every frequency. low frequency arreys, such as GHG operaing in the 20-6000Hz region suffer a 75db loss at 40km range and 500Hz, while operating in the 6Khz frequency would have lost 105db at this range, everything else equal. That has to do with absorbtion of sound in water, which is significantly lower at low frequencies, the continuous level of sound propagation, where only very little loss at range occurs in the requency range 50 Hz to 200 Hz. At higher frequencies than 200Hz, the loss of sound level equals 6 db for a doubling from 200Hz, f.e. So why did the german switched to low frequency ranges?
This had to do with the technical issues involved in arrey solutions. The electrical delay for phase shift compensation has only a low resolution at high frequencies. In order to attain a higher resolution, the designers turned to lower frequency ranges. Surprisingly, they found that the absorbtion of sound was much weaker in low freqency ranges, creating very substantial differences in detection ranges between allied and german sets. Indeed, the differences are significant. The active element ranged to 100hm (10,940 yard) with initially (1935) 1.5 degrees, later (mid ww2) 1 degrees mean bearing accuracy but down to 1/30 degrees at very high frequencies. Altough the range differed with sound conditions, the active S-device, working on medium frequencies of 1000 to 10000Hz, could range at 4,000 yard and less even under worse conditions sufficiently precise to be integrated in firecontroll targeting computing.
The low frequency GHG unit could detect at much extremer ranges, 30km to 300km, though such ranges varied widely (caused by bottom return effects, which were not fully understood in ww2) and were often found impractical and thus created much discomfort with the technology. Direct detection out to 20km was possible in the open Atlantic in most conditions with an accuracy much dependent on the choosen frequency (8 deg at 500Hz, 4 deg at 1000 Hz, 2 deg at 2000 Hz, 1 deg at 4000Hz and 0.7-0.8 deg at 6000Hz). Thus, the longer the range, the better the return of the low frequencies but the worse it´s accuracy.
Of course, one has to understand that sound strength is dependent on source and not equal at all frequencies. It interferes with background noises and is highly varyable. That beeing said, the differences in capabilities between active and passive german and allied set´s is a true one.


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## delcyros (Jun 11, 2012)

I once more reiterate my question regarding the charackter of the term "Wonder weapon".

I try to understand what exactly is meant with the question. I will forward the following list (which doesn´t necessrely need to be understood as complete):

[+] An illusionary object or weapon to be developed in the far or near future. A paper project.
[+] A weapon / system developed and attributed "war decisive effect" or strategic effect by the propaganda
[+] A weapon / system developed but not exploited of mere advanced technical details, whiches effect is limited to the tactical level
[+] A weapon / system developed with mere interesting technical deteails with unquantified effect on tactical or strategic level
[+] something else?

The XXI submarine type in my opinion (I may be wrong) is not a paper project. It isn´t invulnerable, either. It definetly wouldn´t have delayed soviet advancing ground forces by a minute, f.e. Though according to several post war studies conducted by the allied, it had the very practical outlook to render all ASW efforts carefully developed to counter the Uboat thread useless:

[1] the adoption of the Snorkel rendered detection by air in the night impractical according to operational experiences
[2] the adoption of RAM coated snorkels (see U-3008 trials), rendered new not yet introduced radars like APS-20 very unlikely to attain radar fixes on a snorting boat at night. The ECM mast would give pre waring in most cases
[3] the adoption of "Kurier" burst messaging (420 ms message) rendered HF/DF unable to attain a fix on an U-boat, thus routing of convois away from Uboat concentration couldn´t rely anymore on data gathered by HF/DF.
[4] the adoption of higher submerged speed and endurance greatly augmented the intercept fan and range to a target while approaching submerged, rendering obsolete the previous tactic of pressing a boat under the surface to prevent it making an intercept
[5] the adoption of 6 tubes + rapid reload gear greatly enhanced offensive potential on target
[6] the adoption of quiting technology and creep engines not only enhanced endurance but also made detection by HE impossible with period allied listening devices when operating on creep motors ("silent" by period allied sound detection devices operating at their respective frequencies), thus unknowingly relying entirely on active sonar for the purpose of detection.
[7] the adoption of deep submergence depth exceeded the limit of operational depth of Mk24 FIDO and the detection depth of ww2 ASDIC and approached the detection limit of post ww2 type 144 ASDIC.
[8] active ASDIC detection didn´t worked at speeds higher than 12 kts or poor seastate.


ORG 51, f.e. considers an XXI about four times as effective as an old boat in the offense and about eight times as effective in the defense. I consider this qualitative interpretation interesting as it would allow to relate the number of boats in the North Atlantic required to disrupt convois.

In the final period of ww2, f.e. in average 39 Uboats were at sea each month. They accounted for an average of only nine merchant vessels sunk per month (=0.23 / Uboat / month) while in average 18.9 Uboats were sunk per month.
Thus, an average number of 50 XXI at Sea per month (requiring at least 100 XXI our of the 120 produced to be in operational status) would result in an appreciable statistic likelyhood of 46 merchant vessels sunk per month in average (this same period) for a mean of 13 XXI sunk per month. Kind of comparable to the period July 1942 to June 1943 which was achieved by twice the number of submarines at Sea. One should factor in that even those very heavy losses in merchant shipping were replaced, thus even larger numbers of Uboats are required to have a decisive effect.

Thus, in my opinion, general statements are misleading. This applies to both sides of the discussion. XXI isn´t completely immune to ASW, so it can´t be claimed that it would have defeated convois by it´s mere presence. Similarely, it would be difficult to sustain the idea that an appreciable number of them would have had no effect on convois or would have suffered very heavy casualties on hands of the ASW.

Strictly, my opinion, of course


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## davebender (Jun 11, 2012)

> Prior to Hitler taking control of the military in mid 1930s, there was a long term strategic plan in place to rebuild Germany to mount an mechanized preventative war against the European powers by the early 1940s.


What makes you think Hitler had control over events in Austria, Czechoslovakia, Yugoslavia and Danzig? What makes you think Hitler had control over aggressive Marxist governments being installed in France and Spain? Those crisis would happen no matter who occupies the Reichskanzlei. Hitler's reaction to those events wasn't perfect but there's no guarantee Angela Merkel would muddle through any better.


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## psteel (Jun 11, 2012)

davebender said:


> What makes you think Hitler had control over events in Austria, Czechoslovakia, Yugoslavia and Danzig? What makes you think Hitler had control over aggressive Marxist governments being installed in France and Spain? Those crisis would happen no matter who occupies the Reichskanzlei. Hitler's reaction to those events wasn't perfect but there's no guarantee Angela Merkel would muddle through any better.



I was only speaking to the direction the german military was developing. It seemed to be well on track before he stuck his ore in.


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## davebender (Jun 11, 2012)

In the case of 3/4 track vehicles that's absolutely correct. The German Army began research during the late 1920s and many of the basic vehicle specifications were written by 1933. Some models such as the Sd.Kfz.6 and Sd.Kfz.7 were in production during 1935. The entire 3/4 track fleet included advanced suspension. Pretty amazing Germany could develop such advanced vehicles while spending only 1% of GDP on national defense.

On the other hand 3/4 track vehicles were about the only equipment programs receiving substantial funding prior to 1935. Perhaps that's because artillery tractors were allowed under the Versallies Treaty.


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## tyrodtom (Jun 11, 2012)

You don't say what year they were spending 1% of their GDP on national defense, but in 1935 Germany spend 10% of their GDP on the military.

That was more than any other country in Europe at the time, and it increased greatly every year thereafter.


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## davebender (Jun 11, 2012)

What is your source for that data?


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## tyrodtom (Jun 12, 2012)

The Devils Disciples by Anthony Read, Alternatehistory.com, Wiki. and others.

And what's your sources ?


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## davebender (Jun 12, 2012)

*Germany GDP.* Billions of RM. (Rezessionen in historischer Betrachtung, Dr. Norbert Räth)
1930. 82.4
1931. 69.0
1932. 56.7
1933. 58.4
1934. 65.5
1935. 73.1
1936. 81.2
1937. 90.9
1938. 100.2
1939. 109.3

*Germany Military Budget.* Billions of RM. (Richard Gaettens).
1933. 1.9. 3.3% of GDP.
1934. 1.9. 2.9% of GDP.
1935. 4.0. 5.5% of GDP.
1936. 5.8. 7.1% of GDP.
1937. 8.2. 9.0% of GDP.
1938. 18.4. 18.4% of GDP.

1933 to 1938. per Niall Ferguson.
German GDP grew by an average of 11% per year. This was accomplished without significant inflation.
…..Austrian GNP rose 12.8% during 1938 and 13.3% during 1939.


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## tyrodtom (Jun 12, 2012)

Looks like my 10 % is off a lot less percentage wise, than your 1%.


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## delcyros (Jun 13, 2012)

I graphically tried to outline the approach problem for an XXI submarine versus a convoi:






By delcyros at 2012-06-12

To be shown here is a convoi made up from 28 M/V (6nm wide) in dark grey in the middle with three perimeters, each 10, 20 or 30nm distant from the convoi. The convoi is assumed to proceed with 10 kts maintening a steady heading (an HX-derivate).

Starting battery capacity of the XXI is assumed to be 70%, rather than 90% (legend) or 100% (full). Typical patrolling levels ranged from 90% to 60% at patrol station. A further 20% remaining battery capacity has to be kept as reserve when the boat achieved firing range (red, around the convoi) in order to be able to disengage.
Thus, only 50% of the full capacity can be used for the intercept.
The possible positions related to the convoi are given in the drawing for 14 kts sprint, 10kts submerged cruise and 6kts creep (silent speed).


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## psteel (Jun 13, 2012)

Thanks Delcyros for the detailed diagram. I wonder for comparison could you show what a Type VII with Schnorkel could attempt in the same situation?


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## delcyros (Jun 14, 2012)

Unfortunately, I have not (yet) enough information for type VII to outline a similar type of physical limit of approach analysis.


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## psteel (Jun 14, 2012)

Thanks anyway. If you do find such info it would interesting to compare. I've read that the Type XXIII had a better schrnorkel than the XXI and could cruise at up to 12knots. I also gather that a new 12knot schnorkel was finished at the end of the war for the UBoat fleet. Any idea how that would change the above diagram with a XXI plus 12 knot schnorkel?


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## delcyros (Jun 15, 2012)

Type XXI snorkel was cleared for 10 kts submerged cruise (10.42 kts in trials).
Type XXIII snorkel was cleared to 12 kts submerged cruise.

Note that at these levels of speed, no charging of the batteries is possible and there may even be electric motors switched on to augment the Diesels. Parctical recharging speeds varied between 6 and 7.5 kts for XXI and 5 to 7 kts for XXIII. At higher speeds than 6 kts, the improved sonar was disfunctional, too. 

So my assumption is that nobody would dare to snort an extensive time at maximum submerged cruise speed on Diesels. The pume of smoke isn´t visually invisible, the amount of sound generated creates a noisy signal and can be detected from quite some distance. Another problem is the wave created by the snorkel. While the Wesh-coated snorkel head itselfe may be close to invisible (within the ground clutter return) to radar detection, the wave created at high snorting speed is not invisible and microwave radar sets could detect and discriminate wave signals, particularely at very calm Seas (in the 70´s it was seastate +1 kts and You are safe, indicating very slow snorting speeds).
Thus, I don´t expect a lot of change.


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## psteel (Jul 25, 2012)

From what I can read Schnorkel and Periscopes are very difficult to detect visually. A notional detection range of 5-6nm is possible but sweep rates are based on 2nm width in calm seas and 1/2 nm wide in rough seas 10-40nm²/hr. In theory they are not visible to visual or radar, in sea state 4 or more. WW-II warship type radar is unlikely to get sweep rates of more than 6 miles wide against Schnorkel/periscope targets, suggesting sweep rates of only about 72 nm²/hr [12 knots cruise]. To completely cover the inner zone of a 12kt convoy is going to require over 1/2 dozen escorts. Sweeping for submerged targets over the same convoy zone for late war ASDIC is going to require about a dozen escorts. I've read that ideally 16 escorts were recommended to cover a convoy. I guess the last 4 escorts are for rapid investigating of possible contact and extended pursuit.

This should provide a zone about 6nm wide around a convoy where they can detect most submarine approaches and dispatch an effective counter attack force.


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## psteel (Jul 29, 2012)

Sea Keeping - Battleship vs Heavy Cruiser in Battleship Vs Battleship Forum

At this site [post 10] shows how stormy seas effect merchant ships and a 10 knot convoy in heavy seas [force 7] is only going to be able to manage ~ 7-8 knots depending on how big the merchant ships are. Even a regular storm would result in convoy speeds of ~9 knots.

I have read that if submarines are diving deep , they are not effected by such weather and even at medium depth the speed loss is hardly noticable.

Based on Delcyros diagrames the heavier the seas the better the conditions for true submarine to catch a convoy.


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