The C class was essentially a repeat of the preceding B class, albeit with better performance underwater. The submarine had a length of 142feet overall, a beam of 13feet and a mean draft of 11feet. They displaced 287LT on the surface and 316LT 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 16-cylinder 6000NaN0 Vickers petrol engine that drove one propeller shaft. When submerged the propeller was driven by a 300hp electric motor.[1] They could reach 12kn on the surface and underwater. On the surface, the C class had a range of 910nmi at .[2]
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.[3]
C11 was built by Vickers at their Barrow-in-Furness shipyard, laid down on 6 April 1906 and was commissioned on 3 September 1907. The boat was sunk in a collision with the collier Eddystone in the North Sea south of Cromer, Norfolk on 14 July 1909.[4] There were only three survivors. Attempts were made to salvage the stricken submarine but they were abandoned in September 1909, after only a single body had been recovered.[5] The wreck was rediscovered in the late 1990s.