The Tench class, built between 1944 and 1951, represents the pinnacle of the United States submarine weapon during the Second
World War; the last units remained in service until 1975. Albeit the previous Balao class was an excellent design in most aspects,
extensive patrol experience during war time showed up several issues that were addressed in the new class. The new direct-drive
electric motors were much quieter than the reduction gear arrangement installed in the previous classes. The new subdivision,
with eight watertight compartments besides the conning tower, and a more solid construction, with a steel pressure hull of up
to eight inches in thickness, rendered these submarines as more apt for survivality than their predecessors. But not everything
was so good. The Tench class - like the preceding classes - was justifiably criticized due to its poor underwater maneuverability,
a defect which was never solved despite the efforts.
From 1947 the units of the Tench class were subject to upgrades imposed by the achievements of German wartime technology: the
outer surfaces were streamlined, so every deck gun was removed, and the capacity of the batteries was increased. This conversion
program was called GUPPY (Greater Underwater Propulsion Power Program) and had in total seven stages called GUPPY I, GUPPY II,
GUPPY IA, Fleet Snorkel, GUPPY IIA, GUPPY IB, and GUPPY III. The largest part of the units received as well a number of experimental
modifications: snorkel, sonar test platforms, radar pickets, missile launchers, target boats and amphibious transports. After
receiving these updates, the North American attack submarines should have matched as much as possible the standards set by the
German Type XXI in 1943 (at least leaving apart the poor underwater maneuverability).
Tench class: 33 units (SS-417 to SS-424, SS-427, SS-428, SS-435 to SS-437, SS-475 to SS-490, SS-522 to SS-525)
Type: Attack submarine
Length: 95 meters
Beam: 8.3 meters
Draught: 5.2 meters
Displacement (surfaced): 1595 tonnes
Displacement (submerged): 2455-2468 tonnes
Propulsion: 2 x shaft, 4 x Diesel-electric group 1350 horsepower, 2 x electric motor 1370 horsepower, 252 x battery cell
Speed (surfaced): 20.25 knots (37.5 kilometers/hour)
Speed (submerged): 8.75 knots (16.2 kilometers/hour)
Range (surfaced): 11000 nautical miles (20000 kilometers) at 10 knots
Range (submerged): 100 nautical miles (185 kilometers) at 3 knots
Test depth: 120 meters
Complement: 81
Armament: 10 x 533-millimeter torpedo tube (6 at prow, 4 astern), 28 x torpedo, 1-2 x 127-millimeter 25-caliber deck cannon,
diverse configurations with 40 or 20-millimeter antiaircraft cannons and 7.62 or 12.7-millimeter machine guns
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