HMS Spearhead

The last 17 boats of the third batch were significantly modified from the earlier boats. They had a stronger hull, carried more fuel and their armament was revised. The submarines had a length of 217 feet (66.1 m) overall, a beam of 23 feet 9 inches (7.2 m) and a draft of 14 feet 1 inch (4.3 m). They displaced 814 long tons (827 t) on the surface and 990 long tons (1,010 t) submerged.[1] The S-class submarines had a crew of 48 officers and ratings. They had a diving depth of 350 feet (106.7 m).[2]

For surface running, the boats were powered by two 950-brake-horsepower (708 kW) diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 650-horsepower (485 kW) electric motor.[3] They could reach 14.75 knots (27.32 km/h; 16.97 mph) on the surface and 9 knots (17 km/h; 10 mph) underwater.[1] On the surface, the third batch boats had a range of 7,500 nautical miles (13,900 km; 8,600 mi) at 10 knots (19 km/h; 12 mph) and 120 nmi (220 km; 140 mi) at 3 knots (5.6 km/h; 3.5 mph) submerged.[2]

Spearhead was armed with six 21 inch (533 mm) torpedo tubes in the bow. She carried six reload torpedoes for a grand total of a dozen torpedoes. Twelve mines could be carried in lieu of the torpedoes. The boat was also equipped with a 4-inch (102 mm) deck gun.[1]

HMS Spearhead was laid down at Cammell Laird's Birkenhead shipyard on 18 August 1943, was launched on 2 October 1944 and completed on 21 December 1944.[4] So far she has been the only ship of the Royal Navy to bear the name Spearhead.[5] Spearhead survived the Second World War and was sold to the Portuguese in August 1948 and renamed NRP Neptuno.

• Akermann, Paul (2002). Encyclopaedia of British Submarines 1901–1955 (reprint of the 1989 ed.). Penzance, Cornwall: Periscope Publishing. ISBN 1-904381-05-7.
• Bagnasco, Erminio (1977). Submarines of World War Two. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-962-6.
• Blackman, Raymond V. B. (1962). Jane's Fighting Ships 1962–63. London: Sampson Low, Marston & Co., Ltd.
• Chesneau, Roger, ed. (1980). Conway's All the World's Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press. ISBN 0-85177-146-7.
• Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
• McCartney, Innes (2006). British Submarines 1939–1945. New Vanguard. Vol. 129. Oxford, UK: Osprey. ISBN 1-84603-007-2.