mid-June the slipway had been deleted from the design and the ship's armament had been revised to consist of eleven guns and only a single anti-aircraft gun. By this time, the uncertainty about the best configuration for an aircraft carrier had increased to the point that the Admiralty forbade the builder from working above the hangar deck without express permission. Later that year the ship's design was revised again to incorporate a single island, her lifts were changed to a uniform size of , and her armament was altered to ten 6-inch guns and four 4-inch anti-aircraft guns. These changes increased her displacement to . Construction was suspended after Hermes was launched in September 1919 as the Admiralty awaited the results of flight trials with Eagle and . Her design was modified in March 1920 with an island superstructure and funnel to starboard, and the forward catapult was removed. The logic behind placing the island to starboard was that pilots generally preferred to turn to port when recovering from an aborted landing. A prominent tripod mast was added to house the fire-control systems for her guns. The last revisions were made to the ship's design in May 1921, after the trials with Argus and Eagle. The lifts were moved further apart to allow for more space for the arresting gear and they were enlarged to allow the wings of her aircraft to be spread in the hangar. Her anti-ship armament was reduced to six guns and her flight deck was faired into the bow. Description Hermes had an overall length of , a beam of , and a draught of at deep load. She displaced at standard load. Each of the ship's two sets of Parsons geared steam turbines drove one propeller shaft at a speed of . Steam was supplied by six Yarrow boilers operating at a pressure of . The turbines were designed for a total of , but they produced during her sea trials, giving Hermes a speed of . The ship carried of fuel oil which gave her a range of at . The ship's flight deck was long and her lifts' dimensions were . Her hangar was long, wide and high. Hermes was fitted with longitudinal arresting gear. A large crane was positioned behind the island. Because of her size, the ship was able to carry only about 20 aircraft. Bulk petrol storage consisted of