|Laid down:||14 February 1910|
|Launched:||14 January 1911|
|Commissioned:||14 December 1911|
|Fate:||Sold 19 December 1921 to H. Pounds|
|Class and type:||D-class submarine|
|Displacement:||Surfaced= 483 tons / Submerged= 595 tons|
|Length:||163.0 ft (49.7 m) (oa)|
|Beam:||13.6 ft (4.1 m) (oa)|
|Propulsion:||550 hp (410 kW) electric 1,750 hp (1,300 kW) diesel twin screws|
|Armament:||3 x 18-inch (46 cm) torpedo tubes (2 forward, one aft)|
The D-class submarines were designed as improved and enlarged versions of the preceding C class, with diesel engines replacing the dangerous petrol engines used earlier. D3 and subsequent boats were slightly larger than the earlier boats. They had a length of 164 feet 7 inches (50.2 m) overall, a beam of 20 feet 5 inches (6.2 m) and a mean draught of 11 feet 5 inches (3.5 m). They displaced 495 long tons (503 t) on the surface and 620 long tons (630 t) submerged. The D-class submarines had a crew of 25 officers and other ranks and were the first to adopt saddle tanks.
For surface running, the boats were powered by two 600-brake-horsepower (447 kW) diesels, each driving one propeller shaft. When submerged each propeller was driven by a 275-horsepower (205 kW) electric motor. They could reach 14 knots (26 km/h; 16 mph) on the surface and 9 knots (17 km/h; 10 mph) underwater. On the surface, the D class had a range of 2,500 nautical miles (4,600 km; 2,900 mi) at 10 knots (19 km/h; 12 mph).
Construction and career
D7 was laid down on 14 February 1910 by Chatham Dockyard, launched 14 January 1911 and was commissioned on 14 December 1911. D7 torpedoed the German submarine U-45 on the surface with a single shot from 800 yards (730 m) off the North coast of Ireland on 12 September 1917. The torpedo was launched from the stern torpedo tube. Then on 10 February 1918, D7 was mistakenly depth charged by HMS Pelican but she survived. D7 collided with a U-boat in May 1918. Her periscopes were damaged but she escaped otherwise unscathed. D7 was sold on 19 December 1921 to H. Pounds.
- Harrison, Chapter 4
- Gardiner & Gray, p. 87
- Akermann, Paul (2002). Encyclopaedia of British Submarines 1901–1955 (reprint of the 1989 ed.). Penzance, Cornwall: Periscope Publishing. ISBN 1-904381-05-7.
- Colledge, J. J.; Warlow, Ben (2006) . Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8. OCLC 67375475.
- Gardiner, Robert & Gray, Randal, eds. (1984). Conway's All the World's Fighting Ships: 1906–1921. Annapolis, Maryland: Naval Institute Press. ISBN 0-85177-245-5.
- Harrison, A. N. (January 1979). "The Development of HM Submarines From Holland No. 1 (1901) to Porpoise (1930) (BR3043)". Submariners Association: Barrow in Furness Branch. Retrieved 19 August 2015.