Triton Class: Large Patrol Submarine
Ordered under the 1935 - 1938 programmes, fifteen boats of this class were completed between 1938 and 1941 at an average cost of £350,000 per boat.
Two were built at Chatham, Tigris and Torbay.
Despite being restrained by Naval Treaties and government budgets, these boats were packed with 10 torpedo tubes. Eight of the tubes being in the bow and two more forward of the bridge.
The class suffered two major disasters. The first, in 1939 when Thetis was lost during her trials in Liverpool Bay. The second, just days after the war had started, Oxley, failed to send a recognition signal and was sunk by Triton. Only two survivors from Oxley were picked up.
Following the Thetis sinking, many modifications were made to the class. Hard lessons learnt would see improvements in the future T Class submarines.
The 'Thetis Clip' would become an integral part of submarine torpedo tube design.
Thetis Clip: to prevent the rear doors of torpedo tubes being fully opened, a large screw clip was fitted. Should the tube prove to be flooded, the door could be shut by screwing home the clip. If the tube was safe to open, the clip could be unfastened and the rear door opened.
This first tranche of T Class were used to evaluate new diesel engines. A diesel developed by Vickers was installed in the boats built in their yard. A different engine was used at Cammell Laird and new Admiralty Diesels were used for the Chatham built boats.
Nine of the class were lost during the war and one, Taku, was taken out of service after being damaged by mines.