Fleet Boat Dive Depths

[cmdrk]

According to Dick O'Kane's book about the Wahoo (Gato-Class) and Tang (Balao-Class) there was quite an improvement in dive depths.

He recounts the Wahoo with a rated depth of 300 ft sinking to 350 ft while under a DC attack. A valve had jammed as they dived causing the boat to exceed safe depth. Later he recounts another DC attack while diving, the diving officer asked what depth and Mush Morton just said 'Take her down'. The diving officer used his own discretion and levelled the boat when the depth gauge pegged. O'Kane estimated it was around 400 ft.

In his book on the Tang, O'Kane conducted some 'deep deep' test dives during shakedown. The Tang was rated at 430 ft. His first test dive exposed some problems with valves, fittings, and the sound heads gear. After fixing those, he took the Tang down below 600 ft without a problem or strain.

Wahoo was commissioned May 1942. Tang was commissioned Oct 1943.

Nothing like a UBoat (Type VIIC max depth rating 220m), but the Fleet Boats were tougher than their ratings indicate.

Conversions (rounded)
300ft = 91m
350ft = 106m
400ft = 122m
600ft = 183m

150m = 492ft
200m = 656ft

[CCIP]

Technically, the Type VII and Type IX U-boats were also rated at 90m/300ft before the war, though they clearly could do better. As even the American boats illustrate - a well-built sub can go well past its rated depth.

The real difference was that the U-boat commanders, facing tougher odds, were forced to push it exponentially more often as they faced much tougher ASW measures and had in fact made a practice of just out-diving depth charges (which worked very well in early war).

I couldn't speculate on how well the boats were built comparatively. I can say that German boats were generally far less compromising in terms of maximizing performance and toughness, since they made no real concessions for comfort whatsoever. But for all we know, the American hulls could be just as good :hmm:

[DeepSix]

Several U.S. boats experienced very deep combat dives - 500 to 600 feet or more. Starting with the Balao boats (I think), their rated depths were increased - these later boats were called "thick-skinned." U.S. boats also routinely "out-dived" depth charges, at least initially, because Japanese DC only worked to about 150 feet.

I'm not trying to jump on the defensive, but I certainly don't think U.S. boats were any less capable or at all compromised by "comforts." They were neither poorly designed nor of weak construction. They did have technical flaws in the form of poor torpedoes and the crappy H.O.R. (the U.S. licensee for M.A.N.) engines. Eventually the torpedo problems were sorted out, and all the HORs were replaced by Winton/GM or Fairbanks-Morse engines. There were other lessons learned that produced modifications during the course of the war, but basically U.S. boats were very survivable.

Again, not trying to be defensive, but there's always a tendency to compare U-boats and fleet subs and make some sort of general conclusion or speculation about which one was better. I think that's a real mistake; the bottom line is that U.S. boats were designed based on a completely different doctrine of submarine warfare, indeed on a different strategic view of the world. It's fair to say the doctrine was faulty, but I don't think the boats were.

Pre-war doctrine shaped the course of fleet boat research and development almost entirely apart from the same process that produced the U-boats. In other words, it's not like Electric Boat looked over plans for the Type VII and then rejected them (although, to its chagrin, the Bureau of Ordnance *did* reject the German torpedo design). They started out intended for coastal defense (more or less as mobile, submersible coastal artillery) and evolved into a pre-war boat that was intended to operate in conjunction with - and in support of - the U.S. surface fleet - mainly as scouts.

In the development stage, it was not thought that they would be used, tactically, in the same way that Doenitz later used his U-boats (it was not even a given that they would be used offensively). Quite the opposite - after World War I the submarine was villified by the American public and even by the Navy itself, and submarine R&D sort of languished as a result because no one really knew what to do with the thing. This was true in Britain as well; the British even introduced an interwar treaty effort to eliminate subs altogether. Comparing U-boats and fleet subs is, IMO, mostly a wasted effort - I mean, they're apples and oranges.

Sorry, didn't mean to go off there :lol: - it's just that people seem to overlook the context of military tech - and context is everything.

[CCIP]

Again, not trying to be defensive, but there's always a tendency to compare U-boats and fleet subs and make some sort of general conclusion or speculation about which one was better. I think that's a real mistake; the bottom line is that U.S. boats were designed based on a completely different doctrine of submarine warfare, indeed on a different strategic view of the world. It's fair to say the doctrine was faulty, but I don't think the boats were.


I agree. There's no reason either one was better - and if ultimate success is any indication, the US boats proved that their disadvantages didn't mean defeat.

To be fair, I think we can say that an American boat would do as poorly in North Atlantic convoy combat as your typical wolfpack U-boat would do in the vast Pacific. Context is everything.

...all the more reason I look forward to SHIV. It's a different kind of war, different advantages, different challenges. I personally expect anything but merely and SHIII with an American style makeover for disguised U-boats :up:

[DeepSix]

...To be fair, I think we can say that an American boat would do as poorly in North Atlantic convoy combat as your typical wolfpack U-boat would do in the vast Pacific....

Never thought of it that way; good point. :up:


...all the more reason I look forward to SHIV. It's a different kind of war, different advantages, different challenges. I personally expect anything but merely and SHIII with an American style makeover for disguised U-boats :up:

Definitely! :rock:

[cmdrk]

True - the pacific is a very different theater to operate in. US boats had to be bigger to obtain the operational ranges to make them effective.

In way the destruction of the battle fleet at Pearl forced the admirals to use subs more effectively. Inter-war strategy saw the sub being an extension of the fleet - as in a scouting screen. Their pre-war operational doctrine was like the Japanese. But after Pearl, there was no battle fleet and the carrier task forces moved too fast - so they took the battle to the enemy independently (for the most part).

As a side comment - it is a good thing the US boats had radar, it gave them the extra time they needed to get beneath the waves.

[cmdrk]

CCIP:
To be fair, I think we can say that an American boat would do as poorly in North Atlantic convoy combat as your typical wolfpack U-boat would do in the vast Pacific. Context is everything.

Yes, even the German's larger boats didn't do as well against Atlantic convoys.

In Mulligan's book 'Lone Wolf', Henke's U-515 (type IX) did poorly when tasked to attack convoys. His larger boat was spotted easier and he had difficulty shaking attacks. His worst beatings came from convoy escorts. He did much better haunting the African coast. The U-515's war total was 21 ships. It was done in by the same Hunter-Killer group that captured the U-505.

I think the U-515 battle gave the US HK commander the idea a capture was possible.