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SS-170 V-8 Chachalot

The Chachalot class was basically an Americanized U-boat. Even before V-5 and V-6 had been completed and V-7 laid down, submarine officer opinion had begun to shift in favor of smaller boats similar to Germany's 1,200-ton U-135 design from World War One. Then, when the London Naval Treaty of 1930 for the first time imposed international limits on total submarine tonnage, the incentive to build smaller ships became especially compelling. This design incorporated the first complete double hull in a US submarine and had an 11,000 nm range at 19 kts.

The two V-8 class scout cruiser submarines were authorized in the FY1932 program; V-8 (SC-4) was laid down at Portsmouth Navy Yard and V-9 (SC-5) at Electric Boat in October 1931. In February 1931 they were assigned the names Cachalot and Cuttlefish, replacing their pennant numbers V-8 and V-9 and in July 1931 they received the designations SS-170 and SS-171.

At 271 feet overall and only 1,130 tons surface displacement, Cachalot and Cuttlefish were even smaller than the T-boats of 15 years earlier. The engineering plant consisted of two innovative, MAN-designed, compact main engines supposedly capable of delivering 1,535 horsepower each, plus a single diesel generator rated at 440 horsepower.

Although the boats approached 17 knots on trials, the new MAN engines failed repeatedly from excessive vibration and were replaced in 1938 by two General Motors GM 16-258 diesels with reduction gearing. It was also evident that the design was crowded. The prototype Torpedo Data Computer was tested in these boats. They were modeled after the German U-135 with a full double hull replacing the partial double hull in the V-7 design. In 1933, it was planned that three more torpedoes would be stored externally on this class but this was not done in practice.

Perhaps of most interest was the Navy's assignment of Cuttlefish to the Electric Boat Company, the first submarine award to a private yard since the last of the S-class boats in 1921. Accordingly, Cuttlefish differed from her Portsmouth-built sister, Cachalot, in many respects, including more spacious internal arrangements, the first installation of air conditioning on a U.S. submarine, and the first partial use of welding (vice riveting) in hull fabrication. Moreover, Cachalot and Cuttlefish served as the first test beds for the Mark I torpedo data computer that revolutionized underwater fire control in the mid-1930s.

Unfortunately, because small size severely limited their speed, endurance, and weapons load, neither boat was successful under the conditions of the Pacific war. Each did three scoreless war patrols in the central and western Pacific, and Cachalot did one in Alaskan waters, but by late 1942, it was clear both were out-classed and worn out, and they finished the war at New London as training ships. The two were decommissioned in October 1945 -- they were scrapped in early 1947.



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Page last modified: 22-07-2011 17:41:44 ZULU