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 142feet overall, a beam of 13feet and a mean draft of 11feet. They displaced 290LT on the surface and 320LT 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] 6000NaN0 Vickers petrol engine that drove one propeller shaft. When submerged the propeller was driven by a 300hp electric motor.[1] They could reach 13kn on the surface and underwater. On the surface, the C class had a range of 910nmi at .[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]
C26 was built by Vickers, Barrow. She was laid down on 14 February 1908 and was commissioned on 28 May 1909. C26 was part of the Baltic operations from 1915 to 1918. The boat was scuttled at Helsinki 1.5miles off Grohara Light on 4 April 1918 to avoid seizure by advancing German forces. HMS C26 was salvaged in August 1953 for breaking up in Finland.