The Balao class was a successful
design of United States Navy submarine used during World War II, and with 128
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, which increased their test depth
to 400 feet (120 m).
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 diesel engines and the shafts.
Balao class submarines received diesel engines from one of two manufacturers.
Fairbanks-Morse supplied Model 38D8-⅛ opposed piston engines, and
General Motors' 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
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
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 to this date the largest ship sunk by a submarine,
the Japanese aircraft carrier Shinano.
Length: 95,02 meters
Beam: 8,31 meters
Draft: 5,13 meters
Displacement: 1550 tons (surfaced) / 2463 tons
4 General Motors 16-278A V16 diesel
engines (2740 hp)
2 shafts / 2
Speed: 20,25 knots (surfaced) / 8,75