The diesel engines of the V boats developed 450 bhp at 450 rev/min and were the first Vickers-built submarine engines to have steel cylinder jackets - previously these had been of cast iron. The battery consisted of 132 Exide cells - small for the size of boat considering that the A Class of less than half the displacement carried 120 cells. The designed submerged speed was still attained, although this at the expense of endurance.
Vickers claimed that the V Class could dive to 150 feet as against 100 feet in the conventional submarines of the period. Although the pressure hull sections were far from circular, this depth was possible because the strength of the hull was increased by the external framing between the inner and outer hulls.
The armament of the class was two 18-inch bow torpedo tubes, positioned low in the vessel. Two spare torpedoes, without warheads, were stowed on the starboard side of the torpedo room one above the other, with the warheads nearby on the flat. The torpedo hatch was mechanically-operated as in the E Class. Some records state that a 12-pounder gun was fitted but this would have been done after completion at Barrow. All four V Class submarines were taken out of service in July 1919.
Nautilus was a bold experiment - with an increase in surface displacement and a change from the saddle tank type of construction to a double-hull. She was a twin shaft vessel with two Vickers diesel engines, each of 1850 hp, two main motors of 500 bhp and 352 Exide cells in two battery tanks.
In December 1913, after discussing the German submarine programme, the Admiralty decided that they should prepare a design for an overseas patrol boat of about E Class surface displacement, of partial double-hull construction and with single 21-inch torpedo tubes forward and aft and two 18-inch beam tubes. This would be the G Class.
G Class Submarines
1914-1921
In June 1914, five G Class submarines, G1 to G5, were ordered from Chatham Dockyard and one month later G6 and G7 were ordered from Armstrong Whitworth. Vickers engines of the E Class type were fitted in all seven boats, although it was originally intended to fit G6 and G7 with Nuremberg (MAN) and Sulzer engines. (Difficulties obtaining the Sulzer engine and the impracticability of a MAN design prevented this.) In November 1914, Vickers were given orders for six more boats, G8 to G13, and to build the engines for four of the class building at Chatham. G14 was ordered from Scotts on the Clyde.
