submarine to sink a ship in World War II, both scuttled in Kupfermühlen Bay on 4 May 1945). The boat was powered on the surface by two MAN AG, 6-cylinder, 4-stroke M6V 40/46 diesel engines, giving a total of at 470 to 485 rpm. When submerged it was propelled by two Brown, Boveri & Cie (BBC) GG UB 720/8 double-acting electric motors, giving a total of at 322 rpm. Type VIIB The VIIA had limited fuel capacity, so 24 Type VIIB boats were built between 1936 and 1940 with an additional 33 tonnes of fuel in external saddle tanks, which added another of range at surfaced. More powerful engines made them slightly faster than the VIIA. They had two rudders for greater agility. The torpedo armament was improved by moving the aft tube to the inside of the boat. Now an additional aft torpedo could be carried below the deck plating of the aft torpedo room (which also served as the electric motor room) and two watertight compartments under the upper deck could hold two additional torpedoes, giving it a total of 14 torpedoes. The only exception was , which lacked a stern tube and carried only 12 torpedoes. Type VIIBs included many of the most famous U-boats of World War II, including (the most successful), Günther Prien's , Otto Kretschmer's , and Joachim Schepke's . On the surface the boat was powered by two supercharged MAN, 6 cylinder 4-stroke M6V 40/46 diesels (except for U-45 to U-50, U-83, U-85, U-87, U-99, U-100, and U-102, which were powered by two supercharged Germaniawerft 6-cylinder 4-stroke F46 diesels) giving a total of at 470 to 490 rpm. When submerged, the boat was powered by two AEG GU 460/8-276 (except in U-45, U-46, U-49, U-51, U-52, U-54, U-73 to U-76, U-99 and U-100, which retained the BBC motor of the VIIA) electric motors, giving a total of at 295 rpm. Type VIIC The Type VIIC was the workhorse of the German U-boat force, with 568 commissioned from 1940 to 1945. The first VIIC boat commissioned was the in 1940. The Type VIIC was an effective fighting machine and was seen almost everywhere U-boats operated, although its range of only 8,500 nautical miles was not as great as that of the larger Type IX (11,000 nautical miles), severely limiting the time it could spend in the far reaches of the western and southern Atlantic