have dived twice as deep as the previous VIICs. These boats would have been very similar in external appearance to the VIIC/41 but with two periscopes in the tower and would have carried two more torpedoes. Contracts were signed for 164 boats and a few boats were laid down, but all were cancelled on 30 September 1943 in favor of the new Type XXI, and none was advanced enough in construction to be launched. It was powered by the same engines as the VIIC. Type VIID The type VIID boats, designed in 1939 and 1940, were a lengthened – by – version of the VIIC for use as a minelayer. The mines were carried in, and released from, three banks of five vertical tubes just aft of the conning tower. The extended hull also improved fuel and food storage. On the surface the boat used two supercharged Germaniawerft, 6 cylinder, 4-stroke F46 diesels delivering 3,200 bhp (2,400 kW) at between 470 and 490 rpm. When submerged the boat used two AEG GU 460/8-276 electric motors giving a total of 750 shp (560 kW) at 285 rpm. Only one () managed to survive the war; the other five were sunk, killing all crew members. Type VIIF The Type VIIF boats were designed in 1941 as supply boats to rearm U-boats at sea once they had used up their torpedoes. This required a lengthened hull and they were the largest and heaviest type VII boats built. They were armed identically with the other Type VIIs except that they could have up to 39 torpedoes onboard and had no deck guns. Only four Type VIIFs were built. Two of them, and , were sent to support the Monsun Gruppe in the Far East; and remained in the Atlantic. Type VIIF U-boats used the same engines as the Type VIID class. Three were sunk during the war; the surviving boat was surrendered to the Allies following Germany's capitulation. Like most surrendered U-boats, it was subsequently scuttled by the Royal Navy. Specifications Notes References Bibliography Rossler, Eberhard (1981). The U-Boat. Annapolis, Maryland (USA): Naval Institute Press. . Stern, Robert C. (1991). Type VII U-boats. Annapolis, Maryland (USA): Naval Institute Press. . Submarine classes World War II submarines of Germany