G'morning NB: coffee? You posted --> well, just how much explosives could a sub like that carry to do any real damage?
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the British turned to the newly designed X Craft midget submarines. The planned attack, Operation Source, included attacks on Tirpitz, Scharnhorst, and Lützow. The X Craft were - towed by large submarines to their destinations - where they could slip under anti-torpedo nets to each drop - two powerful 2 tonne mines - on the sea bed under the bottom of the target.
The mines caused extensive damage to the ship; the first exploded abreast of turret Caesar and the second detonated 45 to 55 m (148 to 180 ft) off the port bow. A fuel oil tank was ruptured, shell plating was torn, a large indentation was formed in the bottom of the ship and bulkheads in the double bottom buckled. Some 1,430 t (1,410 long tons; 1,580 short tons) of water flooded the ship in fuel tanks and void spaces in the double bottom of the port side, which caused a list of one to two degrees, which was balanced by counter-flooding on the starboard side. The flooding damaged all of the turbo-generators in generator room No. 2, and all apart from one generator in generator room No. 1 were disabled by broken steam lines or severed power cables. Turret Dora was thrown from its bearings and could not be rotated; this was particularly significant, as there were no heavy-lift cranes in Norway powerful enough to lift the turret and place it back on its bearings. The ship's two Arado Ar 196 floatplanes were thrown by the explosive concussion and completely destroyed. Repairs were conducted by the repair ship Neumark; historians Robert Garzke and Robert Dulin remarked that the successful repair effort was "one of the most notable feats of naval engineering during the Second World War." Repairs lasted until 2 April 1944; full speed trials were scheduled for the following day in Altafjord.
The bouncing bombs were considerably larger, --> its overall weight was 9,250 pounds (4,196 kg), of which 6,600 pounds (2,994 kg) was Torpex.
So it IS feasible, practical is another matter. Just remember, it was not with,the intention of broaching the dam itself, but destroying it's generating system, effectively the same.
Don Jose de La Mancha