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The Great Torpedo Scandal emerged and peaked between December 1941 and August 1943, but some of its roots went back twenty five years. It involved primarily the Mk.14 and three distinct problems, depth control, the magnetic influence exploder and the contact exploder, whose effects collectively eroded the performance of the torpedoes. The scandal was not that there were problems in what was then a relatively new weapon, but rather the refusal by the ordnance establishment to verify the problems quickly and make appropriate alterations. The fact that after twenty five years of service the Mk.10 had newly discovered depth control problems adds weight to the characterization of the collection of problems and responses as a scandal. These comments should, however, be mitigated a little by the fact that each of the Mk.14 problems obscured the next. Although BuOrd did not identify the final problem, contact exploder malfunction when a torpedo running at high speed struck the target at ninety degrees, their response, once the difficulty had been identified, was notably prompt. In spite of the promptness of BuOrd's response, by the time it reached Pearl Harbor a number of relatively simple solutions to the problem had been proposed, and modifications had already been designed and implemented. This was, however, almost two years after the United States entered WW II.


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Depth control problems with US torpedoes were suspected by the Newport Torpedo Station (NTS-Newport) and BuOrd even before the United States entered WW II. On 5 January 1942 BuOrd, based on earlier (1941) testing, advised that the Mk.10 torpedo, which had entered service in 1915 and was still used in S-class submarines, ran four feet deeper than set.... In a mood of desperation, the operating forces made their own running depth determinations, using fishnets for depth measurement, at Frenchman's Bay in Australia on 20 June 1942. These measurements indicated that the depth errors were probably more like eleven feet.... it was not until August of 1942, after intervention by the CNO, Admiral Ernest J.King, that they re-investigated and agreed that there was a ten foot depth error in the Mk.14 system. Interim instructions for fixing the problem were issued very quickly and kits to effect an official alteration were distributed in late 1942.... The Mk.14 problem required both a calibration modification and a modification to sense water pressure in the midships section and the latter was implemented beginning in the last half of 1943.

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The magnetic influence exploder was unquestionably responsible for sinking some, perhaps even a large fraction, of the 1.4 million gross registry tons of Japanese merchant ships sunk by submarines between December 1941 and August 1943. Reports from submarine commanding officers of apparent magnetic influence exploder failure, mainly duds and prematures, finally led to CinCPac ordering the disabling of the magnetic influence feature on 24 June 1943. ComSubSoWesPac reluctantly followed suit in December 1943. CinCPac's order was issued eighteen months after Jacobs, on Sargo's first war patrol, ordered the deactivation of the magnetic influence portion of the Mk.6 exploders in his torpedoes and incidentally got into considerable difficulty for doing so. Magnetic influence exploders were not used by US Navy submarines through the balance of WW II.

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Once the depth problem had been fixed and the magnetic influence feature of the Mk.6 exploder deactivated, it came the turn of the impact exploder to demonstrate its merit. Unfortunately the initial result was a plethora of duds, solid hits on targets without warhead detonations14. This problem was suspected earlier, but it was not until the other two problems had been eliminated that there was unequivocal evidence of a problem with the impact exploder. This difficulty was a further frustration for the operating forces, but fortunately it was quickly diagnosed. The key to the problem was again the increased speed of Mk.14. The impact portion of the Mk.6 exploder was exactly the same as that which had been used in the Mk.4 and Mk.5 exploders. The Mk.4 worked entirely satisfactorily in the 33.5 knot Mk.13 torpedo. What was overlooked was that in going from 33.5 knots to 46.3 knots the inertial forces involved in striking the target at normal incidence were almost doubled. These greatly increased inertial forces were sufficient to bend the vertical pins that guided the firing pin block. The displacement was sometimes enough to cause the firing pins to miss the percussion caps, resulting in a dud. In cases of oblique hits, the forces were smaller and the impact exploder more often operated properly. Several war patrols, especially those cited above, convinced ComSubPac, VAdm Charles Lockwood, that there was a problem and he again resorted to experiment. Firings at a cliff in Hawaii demonstrated that some torpedoes did not detonate when they hit the cliff. A rather risky disassembly of a dud revealed the distortion of the guide pins. It was a simple solution to make aluminum alloy (rather than steel) firing pin blocks and lighten them as much as possible thus reducing the inertial forces to a level that did not distort the guide pins. Another solution was to use an electrical detonator and a ball switch to fire the warhead. This too was relatively easy to implement and soon became standard.

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Once these and other less significant problems were solved, the Mk.14 torpedo became a reliable and important weapon. After WW II, it was modified to accommodate electrical fire control settings, gyro angle, depth and speed, and as Mk.14 Mod.5 remained in service until 1980.

Sea Skimmer wrote:On the matter of Japanese ASW sucking. It did in large part, but something worth considering is that the average speed of Japanese merchant ships was much higher then those of the allies. Allied ships which were fast, over about 10-12 knots, always sailed independently. Those defended convoys meanwhile traveled slow, often painfully slow at as little as 4 knots owing to the hoards of pre WW1 era scows floating around. 8 knots was a ‘fast’ convoy. This often meant the convoy was just a good collection of slow targets before adequate escorts could be provided mid war.

Japan meanwhile had far less shipping, but almost all ships were built with government subsidies for the specific reason of ensuring they had high speed for war service. This meant most of Japans ships could make more then 10-12 knots, often more like 15-17 knots which gave them a fair bit of protection from a submerged sub.

Thanas wrote:

Sea Skimmer wrote:On the matter of Japanese ASW sucking. It did in large part, but something worth considering is that the average speed of Japanese merchant ships was much higher then those of the allies. Allied ships which were fast, over about 10-12 knots, always sailed independently. Those defended convoys meanwhile traveled slow, often painfully slow at as little as 4 knots owing to the hoards of pre WW1 era scows floating around. 8 knots was a ‘fast’ convoy. This often meant the convoy was just a good collection of slow targets before adequate escorts could be provided mid war.

Japan meanwhile had far less shipping, but almost all ships were built with government subsidies for the specific reason of ensuring they had high speed for war service. This meant most of Japans ships could make more then 10-12 knots, often more like 15-17 knots which gave them a fair bit of protection from a submerged sub.

Yes, but US subs were built for fast surface speed as well.

IMO it is a bit pointless to compare the two submarine forces. Both had far different enemies and had different levels of support to rely on as you said.

Sea Skimmer wrote:American subs did very well against the Atlantic ASW groups; the USN sent a number of subs over to play with the top groups in late 1945 when everyone was still fresh from war experience. The end conclusion was that the best counter to hunting down a submarine with equally high technology was another submarine, and the first trials of hunter killers began in 1946.

Thanas wrote:Oh, I agree that the USN had the better submarine force for the job at hand. However, I very much doubt it would have performed as well as the KM did against British ASW, whereas I very much doubt, no scrap that, I am sure that the KM would not have been able to conduct such an anti-shipping campaign over those long distances.

Thanas wrote:

Sea Skimmer wrote:American subs did very well against the Atlantic ASW groups; the USN sent a number of subs over to play with the top groups in late 1945 when everyone was still fresh from war experience. The end conclusion was that the best counter to hunting down a submarine with equally high technology was another submarine, and the first trials of hunter killers began in 1946.

That sounds very interesting. Do you have a link to that?

Oberst Tharnow wrote:Where are the differences between the Atlantic and the Pacific theatre? Why does a submarine for the pacific be build differently than one for the Atlantic?
Other than longer ranges in the Pacific, i do not really see the differences - so what are they?

PeZook wrote:

Oberst Tharnow wrote:Where are the differences between the Atlantic and the Pacific theatre? Why does a submarine for the pacific be build differently than one for the Atlantic?
Other than longer ranges in the Pacific, i do not really see the differences - so what are they?

Why do you think that's such a minor difference? It's a massive problem for the majority of the German u-boat fleet equipped with dinky little Type VIIs, for which a 30-day patrol was long, and 90 days was absolute hell for the crews, who had no shower, one toilet for 40 men and little space for provisions.

In order to run long patrols, you need a bigger boat not just in order to accomodate more fuel: you need it to have plenty of torpedoes to provide adequate loiter time at the destination, you need better crew facilities and more space for provisions, you need a machine shop of some sort...lots of stuff. And to top it off, you need more boats per a given number of ships on patrol, due to long time taken returning to base/going out on patrol. Distance is a horrible tyrant.

Vehrec wrote:Don't forget the tropical climate in much of the pacific theater that would turn any non air-conditioned boat into a steam chamber. Conversely, the cold waters of the north atlantic would seem to make a heater of some sort an absolute necessity. You need more food-maybe refrigeration to preserve the non-canned goods. Your engines need to be able to go longer between maintenance in a dock, and they need to be able to cruise farther. So the engines need to be built to higher tolerences. You might begin to see now why it's a different thing to fight in the different oceans.

Sea Skimmer wrote:US submarines had one marked technological advantage over all other nations’ submarines too, in the form of the Torpedo Data Computer. The US’s TDC could actually track a target, and be ready to feed an accurate solution to the torpedo gyro at any time.