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]
C7 was built by Vickers at their Barrow-in-Furness shipyard, laid down on 9 December 1905 and was commissioned on 23 May 1907. The boat is often mistakenly credited with sinking on 5 April 1917 off the coast of The Netherlands. However, this attack was made against, which survived.[4] C7 was sold on 20 December 1919.