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Submarine implosion


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#1 Charles Markuss

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Posted 06 July 2008 - 03:24 AM

Page 3-2, section 3.1.6 Implosion. All submarines had a built-in safety factor which allowed them to descend below their design depth. German U-boats had a safety factor of 2, i.e. they were safe down to twice their design depth and their captains had fewer qualms about taking their boats to their structural limits than allied submariners. British submarines were built with a safety factor of 1.7-1.75, while Japanese and US boats had a safety factor of 1.5.The list below contains the deepest dives survived by world war two boats, based on years of research. It will be seen that rule 3.1.6 is a bit severe.Nationality Vessel Class Depth reached Design depthUK H 1 old H 162.5’ 100’UK Sealion S group 1 300’ approx. 210.5’USA Swordfish Salmon 320’ 250’Japan I 65 I 153 KD 5 325’ 200’USA Sailfish Salmon 327’ 250’UK Shark S group 1 330.5’ 210.5’USA S 38 Old S 350’ 200’UK Upright U 352.75’ 212.75’UK P 51 U 372.75’ 212.75’Italy Mameli Mameli 380’ 295’USA Thresher T 400’ 250’USA Harder Gato 400’ 300’UK Ultimatum U 412.75’ 212.75’USA Haddock Gato 415’ 300’USA Gudgeon T 425’ 250’USA Pollack P 450’ approx. 250’USA Albacore Gato 450’ 300’Japan I 45 I 15 B 2 450’ 325’Japan I 8 I 1 J 3 450’ 300’UK Safari S group 2 461.5’ 311.5’UK Taurus T group 2 464.75’ 314.75’Germany U 2234 XXIII 492’ 492’/262’*UK Perseus P 493.6’ 313.6’ (513.6’ max. limit) UK Thunderbolt T group 1 494.75’ 314.75’USA Puffer Gato 500’ 300’UK Seraph S group 2 510.5’ 310.5’UK Subtle S group 2 510.5’ 310.5’UK Splendid S group 2 > 510.5’ 310.5’UK Tempest T group 1 514.75’ 314.75’Italy Malaspina Marconi 520’ 300’ approx.USA Gurnard Gato 530’ 300’USA Sandlance Balao 550’ 400’USA Bowfin Balao 560’ 400’USA Grouper Gato 60’ 300’USA Salmon Salmon >600’ 250’USA Tang Balao 700’ approx. 400’Germany U 99 VII B 720’ 492’Germany U 2506 XXI 721’ 433’ approx.**Germany U 2529 XXI 721’ 433’ approx.** Germany various VII + IX 820-900’ 492’Germany U 128 IX C 829’ 492’Germany U 96 VII C 918’ 492-590’Germany U 953 VII C 935’ 492-590’Germany U 230 VII C 984’ 492-590’Germany U 190 IX C 1020’ 492’* Safe depth of 492’ only recalculated correctly at 262’ after ex-U 2326 imploded in post-war French dive. ** Crush depth recalculated at 1082’ after earlier figures too optimistic.

#2 Jim O'Neil

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Posted 06 July 2008 - 08:56 AM

This is all good data, but exceptional as well. It's also only the successes ... we don't know a bit about when some may have failed. Perhaps the probability of failure curve is a bit severe, but that is what the captains and crew were told not to exceed ... USS TANG did not choose to go to 700 feet, and no sane Sub Skipper would have tied it.Doctrine overrides capability here, as the only reason many of (all?) these subs went so deep was to survive certain death otherwise or due to loss of control.No one planned to use such extreme depth depths.As for the shallow attacks by the British, perhaps you have a good point, and some exception should be made for their boats.... it might also explain some of the the high losses the Royal Navy suffered (35%); certainly the Med was a very dangerous place to operate.

#3 Charles Markuss

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Posted 07 July 2008 - 08:06 AM

Thanks for replying. I admit that some of the incidents catalogued were involuntary dives, as you say, but by no means all. Certainly I would not expect a submarine to implode at safe depth + 55%.Anyway, the stuff is there for players do mess with or not as they please.The British loss rate in the Med was about 50%, though usually not due to operating in very shallow water as done in the Pacific. The main Axis convoy routes were all in deeper water.Even the Kerkennah Bank was about 150' deep. Loss factors include transparency of water down to about 100' (as off Norway during the Spring thaw), short British sub periscopes - especially U class boats - Italian minefields sown in water up to 600' deep, proximity of air bases in Sicily, Crete and Italy, German assistance with sonar equipment and operators for Italian escorts, Itaiian escort crew quality.

#4 Jim O'Neil

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Posted 07 July 2008 - 12:10 PM

I concur that safe depth plus 55% is most likely OK ... it's the surprises we all hate.The commander of a ship has a great deal of responsibility (far more than most people comprehend) and a mistake can easily be his career or worse. I they tell you safe depth is 300 feet, you best have a fine reason for going to 450 feet, as hazarding your command will get you a Courts Martial.Paraphrasing Napoleon "violating the laws of warfare is sometimes necessary, but it is the superior commander who knows when he can violate them to his advantage".The Med was a very dangerous pace for submarines, I believe the Italians also suffered heavily there.

#5 Lonnie Gill

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Posted 11 July 2008 - 11:51 AM

Good discussion guys.The rule was written to provide some uncertainty for those who chose to go beyond design depth. Gamers always have a tendency to push everything to the absolute limit, where as Bravo commented, real commanders were not inclined to push the envelope without an extreme reason. [My hats off to those who chanced it, knowing they were riding in hulls built by the lowest bidder!] Besides, there was some uncertainty regarding the many through-hull fittings with subs that had been at sea for a while, scrimping on maintenance or which had gone through previous attacks and might have developed an unexpected weakness. It doesn't take much to be fatal at those pressures.So, the rule was designed to encourage some more historic caution in this area. Those who find it a bit heavy handed may want to modify the table. Let us know your suggestions; you may have a better idea we can incorporate in a future amendment.LONNIE




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