Balao-class submarine

The Balao-class was a successful design of United States Navy submarine used during World War II, and with 122 units built, the largest class of submarines in the United States Navy. An improvement on the earlier Gato-class, the boats had slight internal differences. The most significant improvement was the use of thicker, higher yield strength steel in the pressure hull skins and frames, which increased their test depth to 400 ft. Tang actually achieved a depth of 612 ft during a test dive, and exceeded that test depth when taking on water in the forward torpedo room while evading a destroyer.

Propulsion
The propulsion of the Balao-class submarines was generally similar to that of the preceding Gato-class. Like their predecessors, they were true diesel-electric submarines: their four diesel engines powered electrical generators, and electric motors drove the shafts. There was no direct connection between the main engines and the shafts.

Balao-class submarines received main engines from one of two manufacturers. Fairbanks-Morse supplied Model 38D8⅛ opposed piston engines, and General Motors' Cleveland Diesel division supplied Model 16-248 and 16-278A V16 engines. Earlier Fairbanks-Morse boats received a 9-cylinder version of the Model 38D8⅛, while boats from USS Sand Lance (SS-381) onward received 10-cylinder engines. Earlier GM boats received Model 16-248 engines, but beginning with USS Perch (SS-313) Model 16-278A engines were used. In each case, the newer engines had greater displacement than the old, but were rated at the same power; they operated at lower mean effective pressure for greater reliability. Both the F-M and GM engines were two-stroke cycle types.

Two submarines, USS Unicorn (SS-429) and USS Vendace (SS-430), were to receive Hooven-Owens-Rentschler (H.O.R.) diesels, but both boats were cancelled.

Two manufacturers supplied electric motors for the Balao-class. Elliott Company motors were fitted primarily to boats with Fairbanks-Morse engines. General Electric motors were fitted primarily to boats with General Motors engines, but some Fairbanks-Morse boats received GE motors. Allis-Chalmers motors were to be used in SS-530 through SS-536, but those seven boats were cancelled before even receiving names.

Earlier submarines carried four high-speed electric motors (two per shaft), which had to be fitted with reduction gears to slow their outputs down to an appropriate speed for the shafts. This reduction gearing was very noisy, and made the submarine easier to detect with hydrophones. A handful of late Balao-class submarines received low-speed double armature motors which drove the shafts directly and were much quieter, but this improvement was not universally fitted until the succeeding Tench-class. As the diesel engines were not directly connected to the shafts, the electric motors had to drive the shafts all the time.

The Balao-class was successful, and one of its class USS Archer-Fish (SS-311) brought down what remains the largest warship sunk by a submarine, the Japanese aircraft carrier Shinano (59,000 tons).

Operational submarines
As of 2007 USS Tusk (SS-426), a Balao-class submarine, was one of the last two operational submarines in the world built during World War II. It was transferred to Taiwan in the early 1970s.

Museums
Eight Balao-class submarines are open to public viewing. They primarily depend on revenue generated by visitors to keep them operational and up to U.S. Navy standards; each boat gets a yearly inspection and a "report card". Some boats, like Batfish and Pampanito, encourage youth functions and allow a group of volunteers to sleep overnight in the crew's quarters. The following is a complete list of Balao-class museum boats:


 * USS Batfish (SS-310) at War Memorial Park in Muskogee, Oklahoma
 * USS Becuna (SS-319) at Independence Seaport Museum in Philadelphia, Pennsylvania
 * USS Bowfin (SS-287) at USS Bowfin Submarine Museum & Park in Honolulu, Hawaii
 * USS Clamagore (SS-343) at Patriot's Point in Mount Pleasant, South Carolina
 * USS Ling (SS-297) at New Jersey Naval Museum in Hackensack, New Jersey
 * USS Lionfish (SS-298) at Battleship Cove in Fall River, Massachusetts
 * USS Pampanito (SS-383) at San Francisco Maritime National Historical Park in San Francisco, California, which played the part of USS Stingray in the movie Down Periscope
 * USS Razorback (SS-394) at Arkansas Inland Maritime Museum in North Little Rock, Arkansas