1935 - 1970: S Class
During the modernisation of the submarine force in the early 1930s, the Royal Navy became aware of the need for smaller boats, suitable for employment in the North Sea and restricted waters such as the Mediterranean. In response to this requirement, orders were placed for medium-sized patrol submarines, from which the Swordfish and Shark Classes were evolved.
Based on the saddle-tank construction of the L Class submarines, which they were designed to replace, the 12 vessels of these two classes proved so useful that an improved version was put into mass production during the Second World War. 217 feet long and displacing 872 tons (surfaced), the improved S boats gave outstanding war service under the most difficult conditions, and there is some justification for describing them as the most important of all the Royal Navy's submarines in the pre-missile era.
IMPROVED S CLASS SUBMARINES
Fifty Improved S Class submarines were launched between 1940 and 1945, making the S Class the largest single group of submarines built for the Royal Navy: a total of 62 were constructed over a period of 15 years. In one respect, the S Class was unique in that they were the only class to remain in production throughout the war period - which is a fair measure of their success.
As can be imagined, there were considerable variations in a design which spanned 15 years, and modifications as a result of war experience could only be incorporated depending on the stage of construction reached. Although not, in themselves, above average, the combination of the S boats' qualities, together with the reliability of their equipment and the great ease of operation and maintenance, made them very effective and safe.
No modifications were made to the first five vessels of the War Programme (Safari, Sahib, Saracen, Satyr and Sceptre). but an external stern torpedo tube was added to the group of boats that followed, bringing the number of tubes up to seven, and the number of available torpedoes to 13. This change was indicative of the varied armament of S Class submarines. Many boats were fitted with a 20mm Oerlikon cannon, mounted on a platform aft of the periscopes, which replaced or supplemented three portable 0.303-inch machine-guns. 18 vessels, built towards the end of the war and intended to operate in the Far East, had their standard 3-inch gun replaced by a 4-inch gun, mounted inside a low breastwork, forward of the conning tower. In addition, the boats fitted with the 4-inch gun had their stern torpedo tube removed - from weight considerations.
To extend their radius of action, submarines operating in the Far East during the war had some of their main ballast tanks converted to oil fuel tanks, increasing the fuel load from 72 tons to a maximum of 98 tons. All boats stationed in this theatre proceeded on patrol carrying as much additional stores as possible particularly food and ammunition stowed in all manner of unlikely spaces (an ammunition locker was placed under the Wardroom table, and shells were even stored in the engine room). Naturally, this practice became a matter of some concern and, although strict regulations were imposed on the stowage of ammunition (particularly regarding temperature requirements), the rules were never completely adhered to. By these measures, the S boats managed to achieve long patrol times in operational areas; the record of 49 days was set by Sirdar.
During 1941 and 1942, S Class submarines were fitted with the first radar sets for surface as well as air search, and during the first stages of the war S boats were very active in the North Sea and the Mediterranean. As a result, losses were rather heavy and, in the North Sea alone, six of the class were lost in 1940. As the war progressed, however, the class became more adept, and were particularly successful against other submarines. Of the 62 S Class submarines built, 17 were lost during the war: nine in the North Sea and Atlantic; six in the Mediterranean; and two in the Pacific and Indian Oceans.
Detailed drawings of the Sunfish (Group 2) Chatham Yard dated 28/5/1937 show two man escape chambers forward and aft. and a collapsible boat under the casing. It seems unlikely the Sunfish was the only one of the early Group 1 and Group 2 so fitted. Certainly the WWII Group 3 did not have the escape chambers as shown in a detailed drawing for Stubborn, Surf and Syrtis and a later drawing of the improved Subtle, 1953.
Post war a number of S class were improved like the Subtle and the detail is shown in Diesel Submarines 1948-1958. This was a significant addition to the fleet, providing small submarines for excercises etc. Indeed, useful if the Cold War had turned 'hot', as they merely lacked range not armament, ASDIC or Radar compared to the A boats in the fleet in 1948 and some remained in service in the sixties, but all the data is in the articles.
The detail of the conversion of the Sleuth 1944 and six others to follow is shown inDiesel Submarines 1948-1958. The Scostman was given a major conversion to a fast trial submarine in 1948.
It is reputed that an S Class submarine, HMS Statesman, fired the last torpedo of the Second World War, when she sank a Japanese derelict. The ability of the submarine to operate stealthily made the S Class ideal for secretive missions, and the clandestine operations of the Vickers built Seraph provide one of the most fascinating stories of the Second World War, and earned her the nickname HMS Cloak and Dagger