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taschoene wrote:

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BenRoethig wrote:

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Most modern diesels are going to spend most of their time of the surface. You need the diesels to charge the batteries and the diesels need air.

Modern diesels have something that most wartime subs lacked -- good snorkels that allow them to run engines at periscope depth, not actually surfaced. Besides, the indiscretion rate (the ratio of engine run time to battery time) is pretty favorable as long as the sub sticks to loitering on the battery and doesn't try to sprint for prolonged periods.

Of course, submarines are pretty much restricted to fairly low speeds while snorkeling. All the anti-radar coating in the world won't help when the search radars can pick up the feathery plume of spray that a snorkel generates as more than a few knots.

CVA02 wrote:

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PMN1 wrote:

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The RN WW1 R class were an exception, designed in 1917 as submarine hunter with (according to D K Brown's ' The Grand Fleet) a surface speed of around 9.5kt and a submerged speed of 12.5 - 15kts.

Question on this, given the RN had already shown what was possible, why did no-one else copy this?

http://warships1discussionboards.yuku.com/topic/3850?page=1

There wasn't any purpose to submarine with a specialist "anti-submarine" mission in an era of unguided "straight runner" torpedos and underwater "fire control" that was limited to a periscope and a crude hydrophone. In any case, there wasn't much use for a submarine with such a slow surface speed - especially when underwater performance was solely useful for evasion, not attack. Throughout WWII, the most successful submarine doctrines employed surfaced attacks, whether it was the German "wolfpacks" or the American tactics in the Pacific. Only in the face of overwhelming an ASW defense were submarines limited to underwater attacks, and in general, underwater performance wasn't terribly useful in sinking enemy shipping, only in evading a strong enemy anti-submarine defense. In short, while the American GUPPY rebuilds and later Tang and Darter classes were superior from the post-war standpoint, on a one-to-one basis, such underwater optimized boats would have destroyed less Japanese tonnage in WWII. Coordinated surface tactics, employing radar, were successful against the minimal Japanese ASW capability. In contrast, against the overwhelming Allied ASW response in the North Atlantic, the Germans were forced to seek optimal underwater performance. In short the R-class boats were 3 decades premature in concept. Perhaps you could have argue that a class with higher underwater performance might have saved lives in the Mediterranean where British submarines engaged the Italians, but it is doubtful that it would have been terribly consequential to the broader war effort, as the Italian ASW effort probably wasn't enough to justify the effort.

I remember reading that the generator capacity of the ww1-era R-class boats was insufficient for them to actually charge their batteries while underway.