D Class: Coastal Submarines
It had been known for some time that the C Class would have to be the last of the original design of submarine.
In order to move forward, major changes would need to be made to submarine design. The outcome of much deliberation, was the D Class.
The first order would be placed under the 1906 -07 submarine building programme.
Gone was the potentially dangerous single petrol engine. This was replaced by two diesel engines, giving the Royal Navy its first twin screw submarine.
Twice the length of the C Class, more fuel could be carried thus increasing the time spent at sea. The Navy's first true Overseas submarine had arrived.
With the main ballast tanks external to the pressure hull, there was far more space inside. This allowed for improved accommodation spaces and a larger crew.
These boats were also the first to carry a gun and the first to be designed to carry wireless equipment.
The wireless worked on a wavelength of 200 meters and had a range of 30 miles.
Another improvement to the armament, was the addition on an 18" stern torpedo tube.
It had been intended to build 19 D Class boats but while the first boats were still under construction, another new and improved design (the E Class ) had been approved.
In all 8 of the class were completed. D9 and D10 both to be built at Chatham became E1 and E2.
During the first World War, all boats in the class served in Home Waters. They were based at Dover, Harwich, Immingham and Blyth. Their were successes for two boats, D7 sinking U45 in 1917 and D4 sinking UB72 in 1918.
Four boats, D2,D3 D5 and D6 were all lost during the war. Of the remaining four boats,D1 was sunk as a Target after the war, D4;D7 and D8 were used for training before being sold in 1921.
The D Class submarine had been a leap forward and would lay the foundation in submarine design for many years to come.