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''Tench''-class submarines were a type of submarine built for the United States Navy (USN) between 1944 and 1951. They were an evolutionary improvement over the ''Gato'' and ''Balao'' classes, only about 35 to 40 tons larger, but more strongly built and with a slightly improved internal layout. One of the ballast tanks was converted to carry fuel, increasing range from to . This improvement was also made on some boats of the previous two classes.〔Friedman through 1945, pp. 209, 351〕 Further improvements were made beginning with SS-435, which are sometimes referred to as the ''Corsair'' class. Initial plans called for 84 to be built, but 55 were cancelled in 1944 and 1945 when it became apparent that they would not be needed to defeat Japan. The remaining 29 were commissioned between October 1944 (''Tench'') and February 1951 (''Grenadier''). ==Design== The as-built diesel-electric propulsion layout was the same as the last few ''Balao'' class, with four Fairbanks-Morse or General Motors Cleveland Division two-stroke diesel engines supplying two low-speed double-armature direct-drive electric motors to drive two shafts. All except received the Fairbanks-Morse 38D 8-1/8 engine with 10 cylinders; ''Corsair'' had GM 16-278A engines. The direct-drive electric motors were much quieter than the reduction gear arrangement of previous classes, and they made the drive train much more reliable due to the fact that the gearing was an element prone to shock damage from depth charges.〔Johnston, pp. 11〕 Two 126-cell ''Sargo''-type lead-acid batteries provided submerged power to the electric motors. A design weakness of earlier classes solved by the ''Tench'' re-design were the ballast tank vent riser pipes that passed through the interior of the boat in the forward and after torpedo rooms. These pipes allowed #1 and #7 Main Ballast Tanks (MBT) (located in the single hull sections of the boat) to vent air during diving and allowing water to flood into them from below. The tops of these tanks formed the walking deck in the interior of both rooms and thus the normal location of the vent valves (the top of the tank) could not be used. The riser pipes allowed the tanks to vent but when the tanks were full these pipes contained water at full submergence pressure ''inside'' the torpedo rooms. If these pipes ruptured during depth charge attack, catastrophic flooding would occur. Solving this problem initially proved quite difficult, but ultimately required the complete rearrangement of the ballast tanks. #1 MBT was moved to a location forward of the end of the pressure hull, thus allowing it to vent directly into the superstructure like the rest of the MBT's. This move eliminated the riser pipes completely. #7 MBT, after stability and buoyancy calculations were run was found to be redundant and was converted to a variable fuel oil tank as mentioned above. These changes forced the rearrangement of the associated piping runs and the location of many of the other tanks. Remarkably, these changes resulted in a boat that was visually almost indistinguishable from the earlier ''Balao'' class, with the exception of a sharper angle (or knuckle) at the lower corner of the bow (only visible when the boat was drydocked).〔Johnston, pp. 11〕 A side benefit of the tank rearrangement was that these boats could carry four additional torpedoes in the forward torpedo room, for a total of 28. This was a change that had been asked for by submarine crews much earlier, but could not be accommodated in the earlier designs due to the lack of space in the torpedo rooms.〔Johnston, pp.11-12〕 Many targets in the Pacific War were sampans or otherwise not worth a torpedo, so the deck gun was an important weapon. Due to war experience, most ''Tench'' class were armed with a 5 inch (127 mm)/25 caliber gun, and some boats had two of these. Additional anti-aircraft guns included single 40mm Bofors and twin 20mm Oerlikon mounts, usually one of each. 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「Tench-class submarine」の詳細全文を読む スポンサード リンク
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