HMS G7 was a British G-class submarine built for the Royal Navy during World War I.
The G-class submarines were designed by the Admiralty in response to a rumour that the Germans were building double-hulled submarines for overseas duties. The submarines had a length of 187feet overall, a beam of 22feet and a mean draft of 13feet. They displaced 703LT on the surface and 837LT submerged. The G-class submarines had a crew of 30 officers and ratings. They had a partial double hull.[1]
For surface running, the boats were powered by two 8000NaN0 Vickers two-stroke diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 420hp electric motor. They could reach 14.25kn on the surface and underwater. On the surface, the G class had a range of 2400nmi at .[1]
The boats were intended to be armed with one 21-inch (53.3 cm) torpedo tube in the bow and two 18-inch (45 cm) torpedo tubes on the beam. This was revised, however, while they were under construction, the 21-inch tube was moved to the stern and two additional 18-inch tubes were added in the bow. They carried two 21-inch and eight 18-inch torpedoes. The G-class submarines were also armed with a single 31NaN1 deck gun.[1]
Like the rest of her class, G7s role was to patrol an area of the North Sea in search of German U-boats. On 15 April 1917, G7 was patrolling between Lerwick and Bergen when she sighted the German submarine . G7 fired a torpedo at U-30 and after an exchange of gunfire the German submarine dived away. Although U-30 escaped unscathed, G7 had interrupted U30s attempts to sink two Norwegian merchant ships. One,, which still had a boarding party from U-30 aboard, returned to Bergen under her own steam, while the second, the Borgila, had been abandoned by her crew. G7 put a salvage party aboard Borgila until the Norwegian destroyer arrived to take over.[2]
In October 1918 G7 was on patrol in the North Sea. Communications were lost on 23 October and she was declared lost on 1 November.