HMS Thor - Service History

Service History

T-class submarines fought in all theatres in the Second World War and suffered around 25 percent losses. They were particularly vulnerable in the Mediterranean, where their large size made them easily visible from the air in the clear waters, but they had much more success elsewhere.

After the war, all surviving Group One and Two boats were scrapped and the remainder fitted with snorts.

In the late 1940s and 1950s, most were streamlined for quiet and higher-speed underwater operation against Soviet submarines, in place of the anti-surface-ship role that they had been designed for. In January 1948, it was formally acknowledged that the main operational function of the British submarine fleet would now be to intercept Soviet submarines slipping out of their bases in Northern Russia to attack British and Allied merchant vessels. The following April, the Assistant Chief of Naval Staff, Rear-Admiral Geoffrey Oliver, circulated a paper in which he proposed that British submarines take a more offensive role by attacking Soviet submarines off the Northern Russian coast and mining the waters in the area. With the dramatically reduced surface fleet following the end of the Second World War, he commented that this was one of the few methods the Royal Navy had for "getting to the enemy on his home ground."

Much of the work carried out on the submarines was underpinned by results of measurements made using Tradewind, which had been modified in July 1945 – September 1946 to become an acoustic trials submarine, with external tubes and guns removed, the bridge faired, the hull streamlined and some internal torpedo tubes blanked over.

Starting in 1948, eight newer all-welded boats underwent extensive "Super-T" conversion at Chatham Dockyard. The modifications included the removal of deck guns and the replacement of the conning tower with a "sail", a smooth-surfaced and far more symmetrical and streamlined tower. An extra battery was installed, and a new section of hull inserted to accommodate an extra pair of motors and switchgear. This varied between 14 ft (4.3 m) in the earlier conversions and 17 ft 6 in (5.33 m) in the later ones. These changes allowed an underwater speed of 15 knots (28 km/h) or more and increased the endurance to around 32 hours at 3 knots (6 km/h). The first boats to undergo this modification were Taciturn in November 1948 – March 1951, followed by Turpin in June 1949 – September 1951. The programme was completed with the conversion of Trump in February 1954 – June 1956.

The conversion was not entirely successful since the metacentric height was reduced, making the boats roll heavily on the surface in rough weather. This was alleviated in 1953 in those conversions which had been completed by increasing the buoyancy by raising the capacity of a main ballast tank by 50 tons. This was done by merging it with an existing emergency oil fuel tank. For the four boats remaining to be converted, increase in buoyancy was achieved by lengthening the extra hull section to be inserted from 14 ft (4.3 m) to 17 ft 6 in (5.33 m). The effect was to lengthen the control room and strict instructions were issued that this space was not to be used for extra equipment otherwise the improved buoyancy would be affected.

In the meantime, in December 1950, approval was made for the streamlining of five riveted boats. This was a much less extensive process with the removal of deck guns, external torpedo tubes and the replacement of the conning tower with a "sail" and the batteries replaced with more modern versions providing a 23 percent increase in power. The work was much more straightforward than the conversion of the welded boats and was undertaken during normal refit. The first riveted boat to undergo this modification was Tireless in 1951.

The last operational Royal Navy boat of the class was Tiptoe, which was decommissioned on 29 August 1969. The last T class boat in service with Royal Navy, albeit non-operationally, was Tabard which was permanently moored as a static training submarine at the HMS Dolphin shore-establishment from 1969 until 1974, when she was replaced by HMS Alliance.

The last operational boat anywhere was the INS Dolphin, formerly HMS Truncheon, one of three T-class boats (and two S-class ones) sold to the Israeli Navy; it was decommissioned in 1977.

Another submarine sold to Israel, Totem renamed INS Dakar, was lost in the Mediterranean in 1969 while on passage from Scotland to Haifa. Although the wreck was discovered in 1999, the cause of the accident remains uncertain.