thaddeus_c wrote: ↑
25 Dec 2021 17:00
guess the "bastard" u-boat Type VII could have come into play as a stop gap and/or complement to the smaller Type XXIII?
A better type VII ? Indeed:
Instead of a reconstruction of type IX, as it was proposed here, why not take type VII D, the minelayer (see picture below), or type VII F, the torpedo supplier?
Both types had an additional section of ca 10 meters aft the conning tower. A conversion would be much easier.
Remove the installations for the mines (or installations for torpedo transport in type VII F) and fill it with batteries. It would give a third 'Akku-Raum' and would easily add 50% more batteries. Or even more batteries, as there is more space available than in the two other 'Akku-Raum' rooms.
The most important quality of the VII D/ VII F: the section is already in the middle of the boat, so the center of mass would not be much shifted with the additional weight of the batteries. Balancing problems would be smaller because the design is already adjusted for the extra section. This would not be the case with a yet to be newly constructed type IX lookalike.
If the 'Munitionskammer' in the front is removed, 'Akku-Raum 2' could be increased to house a few more cells.
In all, these measures could give 60%-75% additional batteries which translates roughly in the same amount of additional submerged endurance. So instead of a range of 70 nautical miles it would have 115 nmi @ 4knots (that's over 28 hours submerged cruising endurance instead of 17). Above the batteries would be space for additional pressured air cylinders and crew accomondations as well as better hygienic facilities.
Italy (allied) and Netherlands (occupied) were farer advanced in snorkel technology. By simple 'inspiration', not to say copying, some german subs could have had basic snorkel installments to gain experience as early as 1940. By 1943 they could have had more reliable snorkels than in OTL and they could have been implemented in the turret design regularly instead of being retrofitted in a sort of tinkered provisional.
Then streamlining of the hull for submerged cruise. Besides of the removal of the deck gun and streamlining the turret, it appears to be beneficient to create a more closed surface of the upper deck via reduction of the grated deck space on the upper deck. In late war they did such convertions (sadly, I can't find a picture at the moment) to create a more closed, more rounded surface. Type VII is mainly a cylindrical pressure hull with some casing on its upper part, so removing/changing some of it could reduce drag in a very simple manner.
Although these measures would increase the submerged speed a bit, without new stronger electric motors - which probably would not fit in the hull - it would remain limited to 10-12 knots (at utmost best) for a duration of perhaps 30 minutes. However, a uboat with a reliable (!) snorkel that could cruise submerged at a speed of 8-10 knots would be much less endangered by aircraft.
Anyway, a new boat type would become necessary. For a start I would keep the conception of the XXI design, only with a circular pressure hull.
Kriegsmarine could have come up with simpler 'emergency' designs that resemble a compressed torpedo: Cylindrical hull. Conning tower. Diesel-electric propulsion. Instead of XXI and XXIII for ocean going and coastal role. Particularly, if they had started to look for succeeding types earlier than in OTL.
Even more advanced designs would be possible in theory:
Look at the Walter V80 boat. Its hull is a ~ 1970/80s design.
Having something like this with diesel-electric propulsion instead of hydrogen peroxide and in XXI scale by 1943 would be a entirely different thing.
With a disregard for u-boat design paradigms that were around since ww1 (unlikely to happen in Kriegsmarine structures) and real support of innovative men like Walter (likewise unlikely) a real submarine could have been made. We 'only' need a different Kriegsmarine for that.