B Class

The 'B' Class were an improvement on the 'A' Class and the Holland both in terms of endurance and conditions for the rather larger crew of two officers and thirteen ratings and almost doubling the displacement of the 'A' Class.

There were still no dividing bulkheads, accommodation space nor ventilation of the living area. A deck casing was fitted to this class in the hope of improving movement about the boat when surfaced.This Class was also the first British submarine to be built with a second pair of hydroplanes in addition to those fitted astern. These were initially fitted on the forward side of the conning tower, but later on were transferred further forward to the bows. This had been experimented with on A7 and would subsequently be fitted in all British submarines. Still rather limited in endurance and meant for defensive purposes.The two 18 inch torpedo tubes in this class were angled downwards in the belief that torpedoes would be discharged while the submarine rose to the surface. Two reload torpedoes were carried.This Class were still powered by a 16 cylinder petrol engine.