You've pointed out something there that I didn't even think to look at!

I went back and checked, the boats made with two bow tubes and one stern tube, U-72, U-78, U-80, U-554, and U-555. All of those were used exclusively for training.

U-72, U-78, and U-80 were all ordered January 25, 1939. The first to Germaniawerft and the second two to Bremer Vulkan. 554 and 555 were both ordered September 25 1939 and both went to Blohm & Voss. I'm curious to see the bow torpedo tube arrangement on those. My first instinct was that they had left off a pair of tubes, leaving one per side, to give more room for other stuff on a training boat. My second thought about that is that they might have built them with only the pair of tubes on one side so that instructors would have room to stand and observe the loading of the other set of tubes.

In any case, I'm getting more and more confident that at least THOSE U-boats were intended to be used purely as training and instructional U-boats. You don't need all four tubes up front for that, just enough machinery to train the crew on how it all works.


As you mentioned, U-83, U-203, U-331, U-351, U-401, U-431 and U-651 were each built by a different shipyard. U-83 I find particularly interesting as it's the only VIIB to be 'different', was ordered long before the others, and just like the VIIC's missing a stern tube was made at a different yard.

Maybe you're right about these being design trials boats for the shipyards, I can't really think of a good reason to drop the stern tube without adding something else, other than as some kind of experiment. Personally, I think that given their experience with the VIIA they had to be aware of the stern tube being of value, so they wouldn't drop it completely just to see what happened.