Submarine max depth questions.

World War II General WWII Discussion
#1

I have read dozens of books on WWII history but most of my reading has to do with tanks and infantry. I’ve recently read five books on various submarines and u-boats and have become totally engrossed with them. I’m a numbers guy and am curious about max depth achieved in an American sub and a German u-boat. Most of what I read so far on the American side listed 400’ as the max depth that they would dive to, while the German counterpart regularly went well below that depth, even as deep at 600’. Any idea what the max depth achieved by an American sub and a German u-boat were during the war? Why could the German u-boat go so much deeper?

Having just watched Das Boot where they go as deep as 280 meters, (918’) is this pure fiction? Any documented cases of a sub or u-boat surviving well beyond their theoretical crush depth.

#2

Hi Husky, there would probably be some unwillingness on the part of military authorities to disclose the max operating depth and crush depth of submarines in that e.g. in respect of Western Allied and friendly powers, many nations were operating diesel-electric submarines which were essentially streamlined US War II boats for a long-time after WW II. Because a WW2 military submarine, has many perforations in its hull e.g. a large number of torpedo tubes, diesel engines outake(s) and intake(s), a hull penetrating penetrating periscope, packing glands on the prop shaft, etc and there would be variations in stiffness and strength along its hull, it must have been a huge task to mathematically calculate the crush depth of the submarine in the days before programable software computers. As for practical testing, this poses a major engineering challenge, in that to test a submarine in an artifical tank, that would require the tank to be capable of being pressurized to the depths it was believed likely would crush the hull and would also kill the submarine tested. Furthermore, whilst steel does have some elastic properties, it is far from a fully elastic materiel and therefor it is unwise to test an submarine at a very extreme depth, in that if this is not purely a test boat but one that will be required to be used on active service, such testing may weaken the submarine and make it less capable of being dived deep in a wartime combat situation. In respect of the US submarines, given the inadequate nature of the Japanese ASW capabilities, they might simply not have needed to nor sought to dive as deep as German subs which were under pressure from ever more numerous and ever more technically better equipped US and UK ASW forces. Furthermore, because of the very desperate nature of the German U boat campaign, it is very possible that many U boats dived to particularly deep depths and the majority were crushed at that depth or started to take on water to the extent that they were pushed to an even greater depth and were crushed and a few survived either either because they were so well built that they could sustain a very deep depth without water ingress or that if they suffered some flooding they were on the sea-bed anyway and thus could not be forced deeper. Because it is highly unlikely even two identical WW2 submarines built by the same shipyard will be equally strong because of attention to detail or lack thereof, level of skill of different shipyard workers, etc, etc it is very possible that two otherwise identical submarines would have quite some difference in their crush depth. Furthermore because a submarine underwater has either a slight negative buoyancy or neutral buoyancy or a very slight posative buoyancy it takes very little flooding to overwhelm the reserve buoyancy held in the compressed air tanks, furthermore diesel electric World War II subs had very little propulsive power available underwater running on their electric motors which meant in the event of flooding they had very little possibility to use the hydroplanes to fly the submarine to or nearer the surface in the event of flooding.

http://hnsa.org/doc/index.htm

http://www.maritime.org/fleetsub/

http://www.submarineresearch.com/bull58.html

http://hnsa.org/doc/uboat/index.htm#par141

http://en.wikipedia.org/wiki/Crush_depth

http://www.physicsforums.com/archive/index.php/t-122838.html

http://www.youtube.com/watch?v=rhdzRc_tOVY

http://www.submarineresearch.com/bull31.html

Hope that helps
Adrian Wainer

#3

German Type XXI boats were supposed to have a max depth of 330 meters (about 1082 feet).

As an example: Boat U-2540 (Oberleutnant z. S. Rudolf Schultz) in Bremerhaven submarine museeum. U-2540 was sunk by its crew on May 4, 1945. It was lifted in 1957 and put in serviece in the Bundesmarine in 1960 named “Wilhelm Bauer”.

#4

Another comment on crush depths - nobody in their right mind is going to let their submarine go below the test depth (i.e. that depth the shipyard says is safe and has been tested on builder’s trials) voluntarily. It’s only going to happen when you are being actively hunted by a competent ASW force, and it’s your only way out. This happened to the Germans in the North Atlantic (very deep), the British in the Mediterranean (generally pretty shallow) and rarely to the Americans in the Pacific (the Japanese weren’t very good). Hence, the overwhelming majority of experience of being hunted into very great depths will be on the part of the Germans.
Oh, and one other thought (think it’s been covered before) - nobody will ever know that a submarine failed due to water pressure rather than depth charging if it was being actively hunted at the time it sank. It’s still a kill either way, but is relevant when working out the hull strength…

#5

That’s actually quite a modern looking sub, especially for 1945.

#6

It certainly is, still I don’t really know what modifications had been done before the sub was re-commissioned by the modern german Navy.

#7

according this it was 500 feet. various types

[[crush depth](crush depth)

U-1 – U-2 – U-3 – U-4 – U-5 – U-6 U-7 – U-8 – U-9 – U-10 – U-11 – U-12 – U-13 – U-14 – U-15 – U-16 – U-17 – U-18 – U-19 – U-20 – U-21 – U-22 – U-23 – U-24 – U-120 – U-121 U-56 – U-57 – U-58 – U-59 – U-60 – U-61 – U-62 – U-63 U-137 – U-138 – U-139 – U-140 – U-141 – U-142 – U-143 – U-144 – U-145 – U-146 – U-147 – U-148 – U-149 – U-150 – U-151 – U-152

these are but a few really. you can find all UBoats [URL=“http://www.uboat.net/boats/listing.html”]here](http://www.battle-fleet.com/pw/his/uboat1.htm) going all the way up to U4712.

U995 was posted. heres its record
http://www.uboat.net/boats/u995.htm

I always wondered why Doenitz, even to the end of the war, kept sending boats and crews out to sea. they had no chance of survival. the UBoats suffered the highest faltality rate of any service or branch. allied and Axis.

#8

Thats a really good question. Surely some historian or other as looked at it. I’d be really suprised if Doenitz had not placed his reasoning in his written reports to Hitler or his policy for his subordinates. His post war remarks or writing may have some clues as well.

I can only make wild guesses that he was a fanatic like the others, or that he was badly informed about the effectiveness of his submarines.

#9

he knew in time the allies would defeat his Uboats. mainly thru technological advancements and shear numbers. I heard he told his crews to die with honor and dignity. he lost more than 32,000 sailors and 781 boats. that’s appalling.
http://www.carpenoctem.tv/military/doenitz.html

#10

When the TypeXXI took to sea, it was the most modern submarine in the world.
It is the sire of at least three very widely used classes postwar.

It’s hull form is also that of the world’s first two nuclear submarines, USS Nautilus and USS Trident. Both of those are in essence TypeXXI’s overscale, with reactors and turbines replacing both the Diesel Electric and Walther propulsion systems that had been used in or planned for the XXI.

Regarding the modernisation of the Wilhelm Bauer: The flak turrets were removed, acoustic coatings on the hull were renewed, and later, transisitorised electronics replaced some of the wartime equipment. Naturally, the sonar was correspondingly improved, among various other things.

Regards, Uyraell.

#11

Yeah, and to add to this, the 30,000+ Kriegsmarine sailors lost were out of something on the order 40,000 total U-boat men…

Appalling indeed. Especially since they were marginalized as little more than a nuisance by 1944. I saw a documentary on the History Channel (Military :D) that said increasing cases of crew sabotage took place as boats were docked in the pens in order to delay or prevent patrols, which would have been “eternal” ones at that point, as the War advanced into the final two years…

Who can blame them?