groups adopted a modern oil-fired design, but the four boilers in the middle compartment were coal-fired, so that cruising fuel could be easily obtained in foreign ports where oil was not available. The drawback being that they produced much less power, only generating one-sixth of the ships' total output. The steam from the boilers was ducted into two funnels, the uptakes from the coal-fired central group being split and trunked in with those from the oil-fired ones fore and aft. The turbines were rated at to give the ships a design speed of 30 knots. A fuel supply of of fuel oil and of coal was supposed to give a steaming range of at . In the event, only Hawkins and Vindictive were completed with this engine installation. During her sea trials in 1919, Hawkins reached a speed of from about at deep load, a slightly disappointing figure as she had been designed for at this displacement. In November 1917 the Admiralty decided to replace the coal-fired boilers in the three least-advanced ships with four oil-fired ones, but only Raleigh actually received this modification, which increased her power to for a theoretical . The following year, Raleigh reached her designed speed during her trials. Effingham and Frobisher exchanged their coal-fired boilers for a single pair of oil-fired boilers which gave them for a design speed of . These three ships stowed of oil which was designed to give them the same range of at . The ships' machinery arrangements would be further modified in later refits and reconstructions. Armament The main armament of the Hawkins-class ships consisted of seven 45-calibre Mk VI guns in single mounts protected by gun shields. The guns fired projectiles at a muzzle velocity of to their maximum range of . The ships stowed 150 rounds per gun. The mounts were initially hand-worked, but they were refitted with power-operated elevation and traverse motors after the war. Powered-loading gear was never fitted and the guns could only be hand-loaded up to 10° elevation. The requirements for long lines of ammunition-handlers, physically passing rounds and cartridges along the deck from the shell-hoist to each gun (and in the case of the superfiring forward gun, physically passing them up from one deck to the next) were particularly inconvenient, and in terms of manpower, were described as "absurdly out of proportion" to the ship's cruiser role and firepower. The ships