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, G13s role was to patrol an area of the North Sea in search of German U-boats. On 10 March 1917 G13 torpedoed and sank the German submarine UC-43 off the Shetland Islands, about 9miles NW of Muckle Flugga Lighthouse. Lieutenant Commander George Fagan Bradshaw was awarded the Distinguished Service Order for his command in this action.
G13 survived the war and was sold for scrap in 1923.