NAVYPEDIA

Ships

Name	No	Yard No	Builder	Laid down	Launched	Comp	Fate
D1	I71		Vickers, Barrow	5.1907	16.5.1908	9.1909	sunk as target 23.10.1918
D2	I72		Vickers, Barrow	7.1909	22.5.1910	3.1911	sunk 25.11.1914
D3	I73		Vickers, Barrow	3.1910	17.10.1910	8.1911	sunk 15.3.1918
D4	I74		Vickers, Barrow	2.1910	27.5.1911	11.1911	sold 12.1921
D5	I75		Vickers, Barrow	2.1910	28.8.1911	1.1912	sunk 3.11.1914
D6	I76		Vickers, Barrow	2.1910	23.10.1911	4.1912	sunk 26.6.1918
D7	I77		Chatham DYd	2.1910	14.1.1911	12.1911	sold 12.1921
D8	I78		Chatham DYd	2.1910	23.9.1911	3.1912	sold 12.1921

Technical data

Displacement standard, t
Displacement normal, t	D1: 483 / 595 D2: 489 / 603 D3 - 8: 495 / 620
Length, m	D1: 49.7 D2: 49.4 D3 - 8: 50.2
Breadth, m	D1: 6.10 D2: 6.25 D3 - 8: 6.23
Draught, m	D1: 3.18 D2: 3.29 D3 - 8: 3.48
No of shafts	2
Machinery	2 6-cyl Vickers diesels / 2 electric motors
Power, h. p.	1200 / 550
Max speed, kts	14 / 9
Fuel, t	diesel oil: 35
Endurance, nm(kts)	2500(10) / 45(5)
Armament	3 - 450 TT (2 bow, 1 stern, 6)
Complement	25
Diving depth operational, m	30

Project history

Approved 1906, and were the first British submarines with an overseas patrolling capability. Apart from the introduction of diesels most of the improvements stemmed from the big increase in displacement. More internal volume and a bigger crew lightened the work-load on a long patrol. The diesel engines also helped by eliminating the dangerous petrol vapour which had caused numerous explosions in the early boats. The adoption of saddle tanks increased internal space, while twin screws gave greater manoeuvrability. Earlier submarines had been fitted to receive radio messages but the 'D' class could transmit as well for the first time, an extendable mast being rigged by hand when needed. Although contemporary references suggest that the entire class were fitted with guns, and many with 2-12pdr, only D4 had one, on a platform which folded down into the casing. This arrangement was not a success, and later the gun was given a fixed position on deck. With their larger conning tower, and full-length casings the 'D' class marked a clean break with the tiny 'A's, 'B's and 'C's. D1 was authorised under 1906-07 Estimates, D2 under 1908-09 Estimates and remainder under 1909-10 Estimates.

Modernizations

None.

Naval service

D2 was sunk by German patrol boats off the Ems estuary 25.11.1914. D3 was sunk in error by a French airship in the Channel 15.3.1918. D5 was mined 3.11.1914 in the North Sea. D6 was torpedoed 26.6.1918 by German submarine UB73 off Northern Ireland.