HMS C24 was one of 38 C-class submarines built for the Royal Navy in the first decade of the 20th century. The boat survived the First World War and was sold for scrap in 1921.

The C-class boats of the 1907–08 and subsequent Naval Programmes were modified to improve their speed, both above and below the surface. The submarine had a length of 142 feet 3 inches (43.4 m) overall, a beam of 13 feet 7 inches (4.1 m) and a mean draft of 11 feet 6 inches (3.5 m). They displaced 290 long tons (290 t) on the surface and 320 long tons (330 t) submerged. The C-class submarines had a crew of two officers and fourteen ratings.^[1]

For surface running, the boats were powered by a single 12-cylinder^[2] 600-brake-horsepower (447 kW) Vickers petrol engine that drove one propeller shaft. When submerged the propeller was driven by a 300-horsepower (224 kW) electric motor.^[1] They could reach 13 knots (24 km/h; 15 mph) on the surface and 8 knots (15 km/h; 9.2 mph) underwater. On the surface, the C class had a range of 910 nautical miles (1,690 km; 1,050 mi) at 12 knots (22 km/h; 14 mph).^[3]

The boats were armed with two 18-inch (45 cm) torpedo tubes in the bow. They could carry a pair of reload torpedoes, but generally did not as they would have to remove an equal weight of fuel in compensation.^[4]

HMS C24 was built by Vickers, Barrow. She was laid down on 12 February 1908 and was commissioned on 5 May 1909. The boat was used in the first successful U-boat trap. The tactic was to use a decoy trawler to tow a submarine. When a U-boat was sighted, the tow line and communication line was slipped and the submarine would attack the U-boat. Operating with the trawler Taranaki, C24 sank U-40 25 miles (40 km)in the North Sea off Eyemouth on 23 June 1915. The tactic was partly successful, but later was abandoned after the loss of two C-class submarines, in both cases with the loss of their entire crews.

HMS C24 was sold on 29 May 1921 in Sunderland.

• Akermann, Paul (2002). Encyclopaedia of British Submarines 1901–1955 (reprint of the 1989 ed.). Penzance, Cornwall: Periscope Publishing. ISBN 1-904381-05-7.
• 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.
• Gardiner, Robert & Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships 1906–1921. Annapolis, Maryland: Naval Institute Press. ISBN 0-85177-245-5.
• Harrison, A. N. (January 1979). "The Development of HM Submarines From Holland No. 1 (1901) to Porpoise (1930) (BR3043)". RN Subs. Retrieved 27 September 2022.

• MaritimeQuest HMS C24 pages