for Submariners

by Hamilton 1:1 Communications, LLC

Balao Class Submarine (Diesel)
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The Balao Class submarines


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 feet (120 m). Tang actually achieved a depth of 612 ft (187 m) during a test dive, and exceeded that test depth when taking on water in the forward torpedo room while evading a destroyer.


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 38D8-⅛ opposed piston engines, and General Motor' Electro-Motive Diesel division supplied Model 16 V16 engines. Earlier Fairbanks-Morse boats received a 9-cylinder version of the Model 38D8-⅛, 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. 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 Archerfish (SS-311) brought down what remains the largest ship 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 the Republic of China in the early 1970s.


Portsmouth Naval Shipyard,
Cramp Shipbuilding Company
Mare Island Naval Shipyard
Electric Boat Company
Manitowoc Shipbuilding Company
1,526 tons surfaced,
2,391–2,424 tons submerged
311 feet 6 inches (95 m)
27 feet 3 inches-27 feet 4 inches (8.3 m)
16 feet ten inches (5.13 m)
4 × diesel engines driving electric generators;
2 × 126-cell Sargo batteries
4 × high-speed electric motors with reduction gears or
2 × low-speed electric motors
Two propellers; 5,400 shp (4,000 kW) surfaced,
2,740 shp (2,040 kW) submerged
20.25 knots surfaced (38 km)
8.75 knots submerged (16 km)
Test Depth:
400 Feet (120 m)
10 Officers 70-71 men
10× 21 in (530 m) torpedo tubes
(Six forward, two aft)
24 torpedoes
1 x 5 inch (127 mm) 25 caliber deck gun
Bofors 40 mm, and Oerlikon 20 mm cannon