Royal Netherlands Navy / Koninklijke Marine



Walrus (ex US Balao) class Submarine





in service


S 802 HNLMS Walrus (1)


ex USS Icefish / SS 367

S 803 HNLMS Zeeleeuw (1)


ex USS Hawkbill / SS 366


General Information:

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 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 Archer-Fish (SS-311) brought down what remains to this date the largest ship sunk by a submarine, the Japanese aircraft carrier Shinano.


Technical characteristics (as built):

Length: 95,02 meters

Beam: 8,31 meters

Draft: 5,13 meters

Displacement: 1550 tons (surfaced) / 2463 tons (submerged)

Propulsion: diesel-electric

4 General Motors 16-278A V16 diesel engines (2740 hp)

2 shafts / 2 propellers

Speed: 20,25 knots (surfaced) / 8,75 knots (submerged)

Crew: 80


Armament (as built):

10 21 (533mm) torpedo-tubes (6 forward / 4 aft)

1 5/25 cal. (127mm) deck-gun

1 Bofors 40mm cannon

1 Oerlikon 20mm cannon


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