Barrow Built

T Class, 1935 - 1970

During the 1930s, the construction of overseas patrol submarines waned considerably, and so the Admiralty decided, in 1934-35, to build a new ocean-going boat to replace the Oberon, Parthian and Rainbow Classes - which had not lived up to expectations.

Triumph (pictured here) was lost on active service in the Aegean Sea in January 1942.

Requirements for the new class (defined as Patrol Submarines) demanded that they have a strong armament and a patrol duration of at least 42 days. Restricted by the limitations imposed by the London Naval Treaty, which allowed only 16 500 tons total of new construction submarines, the class was designed to have a displacement of about 100(1 tons so that a sufficient number could be built. The first-of-class, approved in the 1935 Programme, was built at Vickers and entered service in December 1938 under the name of Triton.

Fifty-three T Class submarines were eventually constructed, making it the largest class of ocean-going submarines ever built for the Royal Navy: the original order for the class was made under the growing threat of war, which forced the Admiralty to open its purse strings, and no fewer than 21 riveted-hull T boats, built between 1937 and 1941, followed Triton.

Displacing almost 400 tons less than the O, P and R Classes, this first group of 22 T Class submarines were noted for their simplicity of construction. They were superior to the O, P and R's in that they had greater submerged speed, better surface and underwater handling and more torpedo tubes. However, because the displacement limitations restricted the size and power of their engines to 2500 hp (surfaced) (1450 hp submerged), the maximum surface speed was lower.

The first T Class submarines were 275 feet long and displaced 1327 tons surfaced. Their 'surface' armament included one 4-inch gun and three 0.303-inch machine-guns, which were later replaced by, or supplemented by, one 20mm Oerlikon cannon. They were the last Royal Navy submarines designed for overseas patrol to have insufficient range for the Pacific.

HMS Thetis

One of the most distinguishing features of the Group 1 T boats was their high number of torpedo tubes: six bow tubes, which were reloadable from inside the pressure hull; two external bow tubes, contained in a bulbous bow casing; and two external tubes situated amidships, and so arranged as to fire ahead. This gave the class the phenomenal bow salvo of ten torpedo tubes, which the Royal Navy believed, would compensate for the inevitable errors that accompanied long-range attacks. As an alternative to this armament, a load of 18 mines could be carried.

Perhaps the most famous of the early T Class submarines was the ill-fated Thetis. Sailing, prior to handover, in Liverpool Bay on the morning of 1st June, 1939, Thetis had on board her 53-man crew and 50 passengers (Shipyard and Admiralty men concerned with the trials).

For her trial dive, Thetis was reluctant to submerge, and so her six bow tubes were checked. When Numbers 1 to 4 were correctly found empty, Numbers 5 and 6 were tested to confirm that each contained seawater. The test cock of No 6 tube squirted water but, strangely, the test cock of No 5 did not, and so was apparently empty. As there was only one way to be sure, the door was opened - and the sea roared in. Jammed by one of its clips, the watertight door couldn't be closed and, as two compartments flooded, Thetis nose-dived to the seabed 160 feet below,

With her stern protruding from the waves. Thetis remained undiscovered for a whole day and, although four men managed to escape, she became a tomb for the 99 men on board - despite the efforts of rescuers.

When Thetis was raised in November 1939, an investigation into the cause of this tragic accident revealed an incorrectly-wired bow cap indicator - showing the bow cap to be shut when it was open - and that the vital test cock was blocked with paint. To avoid any suggestion of a jinx on the boat, the Admiralty refitted and commissioned her, in November 1940, as Thunderbolt and, as an epitaph to her 'previous life', she entered service with a diagonal rusty line on her hull that could not be hidden.

THE WAR YEARS

Under the 1940 War Programme came the decision to build nine slightly modified T Class submarines. These modifications were made in the light of experience gained with the first group of T boats and the main changes were in the number and disposition of torpedo tubes, the outer hull shape and the use, in most of the modified vessels, of an electrically welded, rather than a riveted, construction. The latter change assisted deeper diving, improved the resistance to depth charge attack, and also enabled the shipbuilder to adopt the new technique of prefabricating the hull in sections in the shops and assembling large units at the building berth.

To this modified group of submarines was fitted, at the extreme stern, an additional external torpedo tube, whilst the two tubes amidships were repositioned aft of the conning tower, angled to fire astern. These changes altered the shape and silhouette of the class, as did the removal of the bulbous bow casing which had created a notable bow wave which, when running at periscope depth, hampered visibility and the correct trim of the boat. As a result of these alterations, the second group of boats were more streamlined, and the openings for the two external tubes were more clearly visible.

The two faces of T Class submarines. Above: one of the first - HMS Tally-Ho and, below, HMS Taciturn showing the radical changes that resulted from the 1951/56 rebuilding programme.

In addition to their eleven 21-inch torpedo tubes. Group 2 T Class submarines were fitted with a 4-inch gun, a 20mm Oerlikon cannon on a platform aft of the periscopes and three 0.303-inch machine-guns on removable mountings.

Additional orders in the 1941 and 1942 programmes meant that a total of 31 modified T Class submarines entered service between 1942 and 1946. 21 of which were laid down at Vickers, although a number of these were completed at other yards. Of the 22 Group 1 submarines constructed, eight were built exclusively at Barrow, along with other British submarines. The T boats ordered in the 1941 and 1942 programmes were fitted with surface and air search radar sets.

During the Second World War, T Class submarines operated successfully in all the theatres in which the Royal Navy was committed and many of the Group 2 boats were further modified for employment in the Far East - several ballast tanks were changed into fuel tanks, thereby increasing the fuel load from 132 to 230 tons and surface range from 8000 to 11 000 miles at 10 knots. In a theatre where it took up to a week to sail from base to the operational area. This increase in range, together with increased stores capacity enabled long patrols to be carried out - the record being 56 days by the Barrow-built Tantalus, 40 days of which were spent in the patrol area.

Although the T Class obtained satisfactory results, the fact that they were one of the classes which bore the brunt of Second World War submarine operations meant that they were subjected to the highest loss rate. For example, 13 boats were lost in the Mediterranean, despite the fact that large enemy vessels were very vulnerable in that sea. Nevertheless, the T Class were particularly successful against submarines, and 13 boats (six of which were Barrow-built) sank 13 enemy submarines: six Italian, four German and three Japanese.

HMS Totem

In January 1943, Thunderbolt, ex Thetis, transported 'chariot' type assault craft which penetrated the harbour of Palermo and sank the hull of the Italian light cruiser Ulpio Traiano, which was being fitted out. Other major successes included the sinking of two cruisers - the 5700-ton Kuma and the 13 000-ton Ashigara - by the 'Barrovians' Tallyho and Trenchant respectively, whilst, in August 1941, another Vickers boat, the Triumph, managed to seriously damage the 12 000-ton cruiser Bolzano.

At the end of the war, most T Class submarines were placed in reserve, taken out of service or ceded to other countries. Most of the early T Class, with riveted hulls, could not be fully modernised, but five - Tireless, Token and the Barrow-built Tapir, Talent and Teredo - were streamlined and completely refitted with six bow tubes, modern sonar and a fin-shaped conning tower. In 1951-56, eight of the welded-hull boats were completely rebuilt in a manner similar to the American 'Guppy' programme. The eight converted were: Tabard, Truncheon, Thermopylae, Totem, Turpin and the Vickers-built Trump, Tiptoe and Taciturn. Their hulls were cut in two and new sections added to their length, they were streamlined and their underwater propulsion capacity was increased enormously to give twice the previous submerged speed, and increased endurance. At the same time, sensing and detection equipment was updated.

Although in later years their speed of 15 to 25 knots surfaced and 9 knots submerged was judged to be inadequate, a proof of their high reputation for reliability is demonstrated by T Class submarines, which after many refits, were still in active service with a Foreign Navy in the early 1970s.

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