The Pacific War Online Encyclopedia
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|1526 tons standard
2010 tons submerged
|311'0" by 27'3" by 16'8"
95.0m by 8.3m by 5.1m
||to 400 feet (120 m) as
to 600 feet (180m) in practice
|6 21" (53cm) bow / 4 21" stern torpedo
tubes (24 torpedoes)
1 5"/25 gun
||2-shaft diesel-electric (5400
shp surface, 2740 shp submerged)
|365 tons diesel oil|
|11,000 nautical miles (20,000 km) at 10 knots on surface
96 nautical miles (180 km) at 2 knots submerged
||SD air warning
SJ surface search radar
In late 1944, ST fire control radar became available.
Most modifications made to the Gatos were also made to the Balaos.
The Balaos were completed in 1943-45 and were essentially Gatos with strengthened hulls. This allowed them to dive deeper, which was tactically important when evading Japanese depth charge attacks. The boats so resembled the Gatos In every other respect that the Navy was able to conceal the design change throughout the duration of the war. The Japanese, who apparently were aware of the standard 250' (76 meter) design depth of the American prewar submarine classes, were unaware of the greater diving depth of the wartime submarine classes until this information was leaked by a Congressman back from a junket in the Pacific.
The increase in hull thickness without any other
significant design changes was possible because the Gatos
used a considerable amount of lead
ballast. Increasing the hull thickness provided the extra weight
needed to eliminate the expensive lead ballast while increasing
the dive depth.
The hull plate on the Balaos was increased in thickness from 0.5625" (14.3mm) to 0.875" (22.2mm) and the plate material was upgraded from mild steel to high-tensile steel (HTS). It was calculated that this would increase the crush depth to 900 feet (270m) but other components, such as propeller shaft glands and the trim pump, could not be redesigned quickly to take the higher pressure and the maximum design operating depth was set to 400 feet (120m). As it turned out, the composition of high-tensile steel was changed from a chrome-vanadium steel alloy to a slightly weaker titanium-manganese steel alloy whose manufacture fewer scarce resources, so the large safety factor was beneficial. A Gould centrifugal pump was adopted in 1944 that could operate at 600 feet (180m) depth or more, and the refitted Balaos were thereafter able to more fully exploit their thick skins.
A particularly important improvement to the boats was the development of a slow, heavy-duty motor that replaced the older high-speed motors and reduction gears. Besides increasing reliability and saving space, the new motors eliminated the characteristic loud whine produced by the reduction gear. This was ready in time to be installed on new boats commissioned from July 1944 onwards. Another improvement was elimination of phenolic insulating materials, which burned when exposed to flame or electrical arcs (as from short circuits) to produce toxic smoke. The replacement, melamine insulation, has enough nitrogen in its chemical makeup to produce inert nitrogen gas when charred, which suppressed burning.
|completed 1943-4-15 (Mare Island)|
|completed 1943-10-15 (Mare Island)||Sunk by circling torpedo
1944-10-24 in Formosa
|completed 1943-12-28 (Mare
|arrived 1944-1||Sunk by aircraft 1945-8-6 in
|arrived 1944-1||Sunk 1944-6-14 off northeast
|completed 1944-3-9 (Mare Island)|
|completed 1944-3-31 (Mare Island)|
|arrived 1944-4-10||Sunk 1944-10-24 in Formosa Strait
|completed 1944-5-22 (Mare Island)|
|arrived 1944-6||Sunk by aircraft 1945-2-4 off
|completed 1944-8-3 (Mare Island)|
|completed 1944-10-18 (Mare Island)|
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