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ANTONY PRESTON, JOHN BATCHELOR
Although the number of builders had dwindled to three as a result of the Depression, American industry had little trouble in expanding the output of diesel engines and electric motors, so when the Bureau of Ships asked for three additional yard, two commercial builders and one Navy Yard to undertake submarine building, they able to provide them.
American S25 (SS130) (side elevation)
At this point it opportune to insert a note; about the classificaition of US submarines. From 1911 all submarines were assigned class letters and hull numbers, and the old fish and reptile names were discarded. The "V" series were distinguished by the numbers V1-V9 as Fleet Submarines, but in 1920 the designations SS (Submarine), SF (Fleet Submarine), SC (Cruiser Submarine) and SM (Minelaying Submarine) were introduced as a temporary measure, with their own A, B, C and D pendant numbes. Thus the USS Cachalot, for example, was simultaneously known for a while as SS170, C1 and V8, but in 1910 this multiple system was swept away, and only SS-numbers were retained. The fish names were reintroduced in 1931 with the Barracuda (SS163) and continued until the first Polaris submarine was launched in 1959.
The Pacific was seen clearly as the area of any future conflict, so American designs emphasised high surface endurance, habitability and good torpedo capacity. After the unsatisfactory experiments with, cruiser-submarines in the 1920s, the "P" Group of 1933-1938 was developed through the "S" and "T" classes into the 1,500-ton "g" Class of 1940. In view of the limited number of yards available, standardisation of design was essential, and although three classes were built, they were so similar as to be virtually identical, the famous Gato and Balao Classes, and the later Tench Class. With an overall length of 311 ft 9 in and a beam of 27 ft 3 in, they had welded hulls and diesel-electric drive, i.e. diesel generators driving electric motors coupled to the shafts through reduction gears. This method had also been introduced in contemporary British submarines, and replaced the former dual diesel or electric drive in older submarines.
American S25 (SS130). The "S" Class was the last design produced for the USN in the First World War, and in 1941 a few units were stationed in the Far East. They proved to have too little endurance for the Pacific, and so they were withdrawn. S25 was lent to the Royal Navy for training, and then became the Polish Jastrzab. She was sunk in error by friendly ships in 1942
All wartime US submarines had the same double hull divided into eight watertight compartments, with six ballast tanks and four fuel tanks, though stronger hulls were introduced in the Balao and Tench Classes. The armament was heavy, six torpedo-tubes forward and four aft, with stowage for 14 reload torpedoes, and a deck gun. During the war the gun changed from one 3-in/50 cal to 4-in or 5-in and a heavy battery of 40-mm or 20-mm AA guns, and configuration of conning towers changed to accommodate them. But for all, their heavy armament and generally excellent design, US submarines began the war with serious disadvantage: like the German U-Boats they suffered from defective torpedoes. The magnetic pistol was to blame as well, and for the first two years many attacks on Japanese targets were useless It is strange that two countries with a high reputation for their engineering standards should have introduced a new weapon without spotting its weakness until long after it had entered service.
The Japanese, on the other hand, did not approach the submarine problem as systematically as the Americans. By 1940 there was a noticeable ladk of medium-sized boats to supplement the large cruiser-types which seemed to fascinate their admirals unduly. The 1940 Additional Programme tried to rectify this with an order for more than 80 of the K6 Type, 1,100-tonners armed with four torpedo-tubes. Although rather small they had a theoretical range of 11,000 miles at 12 knots, about equal to an early Gato, and were considered to be a very successful design. Production problems resulted in only 18 being completed, RO35-RO50 and RO55 and RO56, and all but one were sunk.