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Type XXI U-boats, also known as "''Elektroboote''" (German: "electric boats"), were a class of German diesel-electric submarines designed and operated during the Second World War. They were the first submarines designed to operate primarily submerged, rather than as surface ships that could submerge as a means to escape detection or launch an attack. ==Description== The key features of the Type XXI were the hydrodynamically streamlined hull and conning tower, and the large number of battery cells, roughly triple that of the Type VIIC. This gave these boats great underwater range, and dramatically reduced the time spent on or near the surface. They could travel submerged at about for two or three days before recharging batteries, which took less than five hours using the Schnorchel. The Type XXI was also far quieter than the VIIC, making it harder to detect when submerged. The Type XXI's streamlined and hydro-dynamically clean hull design allowed high submerged speed. The ability to outrun many surface ships while submerged, combined with improved dive times (also a product of the new hull form), made it far harder to chase and destroy. It also gave the boat a 'sprint ability' when positioning itself for an attack. Older boats had to surface to sprint into position. This often revealed a boat's location, especially after aircraft became available for convoy escort. The new hull design also reduced visibility by marine or airborne radar when surfaced; whether this was a goal of the design or coincidence is still debated. They also featured an elctric torpedo-reloading system that allowed all six bow torpedo tubes to be reloaded faster than a Type VIIC could reload one tube. The Type XXI could fire 18 torpedoes in under 20 minutes. The class also featured a very sensitive passive sonar for the time, housed in the "chin" of the hull. The Type XXIs also had better facilities than previous U-boat classes, including a freezer for food. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Type XXI submarine」の詳細全文を読む スポンサード リンク
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