Something I've always wondered about, but ever only gotten an answer to, was about the nonstandard Type-VII U-boats that were produced.

I understand that not all ships of a given class are going to be identical. For example at various times in the war you could find Somers class destroyers with 4x twin 5" gun mounts, or only 3x twin 5" gun mounts, or even the combination of 2x twin 5" guns and a single 5" gun. However, in all cases, the 5" guns were being removed to make room for other things, like additional AA armament.

Some Type-VIIC's were launched without all four bow tubes. U-72, U-78, U-80, U-554, and U-555 were only fitted with two tubes in the bow, and the stern tube.

In the case of those submarines, since all of them spent their entire career as training flotilla U-boats. The most logical explanation seems to be that they were purpose-built training boats, which could then do without having all four tubes forward for whatever reason, if that be additional bunk space, easier instruction on operating the tubes, etc.


However, the VIIC class U-203, U-331, U-351, U-401, U-431, and U-651, as well as the VIIB class U-83, appear to have been launched without a stern tube...

Since one of the main improvements of the VIIB/C over the A model WAS the internal stern tube and reload, and even the apparent training subs mentioned above had stern tubes, I find this a little odd... Does anyone know why these subs weren't just built like all the rest?