“D” Class.
(Completed 1908–11.)
D’s 1, 2, 3, 4, 5, 6, 7, 8.
These are all modern vessels of the sea-going type, and are of considerable fighting value. They, however, differ slightly from each other: D.1 has a submerged displacement of 595 tons; D.2 of 600 tons; and the remaining vessels of this class of 620 tons. They have an approximate length of 150 feet and a beam of 15 feet. Heavy-oil engines of 1,200 H.-P. drive them at a maximum speed of 16 knots an hour on the surface, and electric motors of 550 H.-P. give them a submerged speed of just over 10 knots an hour. All these vessels have twin-screws situated below the centre line. Their cruising range on the surface is 4,000 miles, and when submerged 120 knots at 7 knots an hour. These vessels were the first to be fitted with a special and more efficient pattern of electric storage battery and a safer type of electric motor. The armament of the “D’s” consists of two bow and one stern tube with six 18-inch Whitehead torpedoes. D’s 4, 5, 6, 7, and 8 are also fitted with a small quick-firing, high-angle gun for defence against air-craft. This gun is fixed on a disappearing mounting, enabling it to be quickly and almost automatically lowered into a watertight cavity in the superstructure before the submarine dives below the surface. The complement of these vessels is twenty-one officers and men.
Photo, Cribb, Southsea.]
THE BRITISH SUBMARINE “C.34.”
Displacement, 320 tons; Speed, 14·9 knots; Armament, 2 bow torpedo tubes.
There are 37 vessels of this class, completed between 1906–12.