A total of 144 Tench (SS-417) class submarines were ordered during 1943-46. They had improved machinery and ballast tank arrangements and stronger hull than the Gato (SS-212) and Balao (SS-285) classes though were very similar in design. The Tench class were virtual copies of the Gato and Balao classes; however, they were more strongly built than the Gato/Balao classes and had a better internal layout, which increased their displacement by about 35-40 tons. The deck of the boat is made of teakwood, and the exterior is painted black.
The Tench class was a pre-snorkel submarine operating underwater on batteries, and powered by a diesel electric system. The Tench class was a late World War II submarine design that represented the continued attempt by the U.S. Navy to improve on the previously successful Gato/Balao classes. Only ten Tench class submarines, including USS Torsk, were commissioned in time to see service in the Pacific during World War II. The pressure hull consisted of 7/8-in high tensile steel. There were eight waterproof compartments in addition to the conning tower. They were equipped with four engine rooms, diesel-electric reduction gear, one auxiliary generator, four electric motors generating 5480 hp when submerged driven by two 126-cell batteries. Submerged endurance was 48 hours at 2 knots. Cruising range was 11,000 miles on the surface at 10 knots with 118,510 gallons of diesel fuel. Patrol duration was 75 days.
Thirty of the original 144 submarines of this class saw commissioned service; eighteen served during World War II. USS Torsk is a World War II Tench class submarine. USS Torsk is credited with firing the last torpedoes and sinking the last Japanese combatant ships of World War II, when on August 14, 1945, she sank the Japanese Coast Defense Vessel No. 13 and Coast Defense Vessel No. 47. With the sinking of these two vessels the U.S. Navy completed its mission, begun on December 7, 1941, to sweep the oceans of Japanese merchant shipping and warships.
Six (SS-429 thru 434) were cancelled in July 1944, two more (SS-427 and 428) in August 1945, and a further 105 were cancelled in January 1946 (SS-491 thru 562 and 437 thru 474). The first hull was laid down in August 1943 and the program continued up through the end of the war. Most of this class was built at Portsmouth Naval Shipyard (23 boats); Cramp, Electric Boat, and Boston Naval Shipyard each built one.
Four had their construction suspended and were completed to the GUPPY (Greater Underwater Propulsion Program) specification. The GUPPY I program meant streamlining exterior hull surfaces, increasing battery capacity, removal of deck guns, and compartment rearrangements. During this conversion all the boat's exterior guns were removed and the conning tower was enclosed by a new sail casing designed to reduce underwater water resistance. The GUPPY II program added a snorkel system that allowed the diesel engines to be operated while the boat was at periscope depth.
The class was removed from service 1963-75 as newer submarines were commissioned into the US Navy. Tigrone (SS-419) was the last boat of this class in commission; she decommissioned in June 1975. Three Tench class submarines were donated to become museums.
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