The Pacific War Online Encyclopedia
|Previous: Porpoise Class, British Submarines||Table of Contents||Next: Port Arthur|
|Tonnage||1310 tons standard displacement
1934 tons submerged
|Dimensions||301' by 24'9" by 12'10"
91.7m by 7.54m by 3.91m
|Maximum speed||18 knots surfaced
8 knots submerged
|Armament||4 21" bow/2 21" stern torpedo
tubes (16 torpedoes)
1 3"/50 AA gun
||1-shaft diesel-electric (4300
|Bunkerage||300 tons diesel oil|
|Range||11,000 nautical miles (20,400 km) at 10 knots surfaced
50 nautical miles (90 km) at 5 knots submerged
||1942: Engines replaced and two external forward torpedo tubes added.
The Porpoises were completed in 1935-1937 as the first boats of the P program. They represented a trend away from the cruiser submarine concept towards smaller, handier boats. However, they still had atrocious dive times, though they were capable of diving deep and were quite habitable (for submarines.)
The hulls were essentially enlarged Cachalots with more room in the engine spaces to accommodate two more generator engines. They were the last U.S. submarines to use full double-hull construction; all later submarines would use partial double-hull construction. The machinery was the first pure diesel-electric installation in the U.S. submarine force and suffered from some serious teething problems, including motors that flashed over at full voltage, so that the engines could not be run at full power until the motors were rebuilt or replaced. The boats were also the first equipped with the so-called poppet valve, or bubble eliminator, a device that vented the torpedo tubes into a special tank and thereby prevented the escape of a large, highly visible bubble of air whenever a torpedo was launched.
Both ships were transferred to the East Coast for training duty in late 1943.
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