| HMS C24|
5 May 1909
26 November 1908
| 12 February 1908|
Sold, 29 May 1921
12 February 1908
| 290 long tons (290 t) surfaced
320 long tons (330 t) submerged|
HMS C21 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.
HMS C24 Wikipedia
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.
For surface running, the boats were powered by a single 12-cylinder 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. 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).
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.
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. She operated with the decoy trawler Taranaki. They were able to sink U-40 25 miles (40 km) off Eyemouth in the North Sea on 23 June 1915.
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. The tactic was partly successful, but was abandoned after the loss of two C class submarines. In both cases, all the crew were lost. HMS C24 was sold on 29 May 1921 in Sunderland.