Hawkins Class Cruiser - Design

Design

Although the Hawkins class were the first heavy cruisers built for the Royal Navy, they were designed as improved versions of the Birmingham sub-class of the "Town" class light cruisers, thus they were initially known as the "Improved Birmingham" type. Their lineage descended through an intermediate sketch design of 1912 known as the "Atlantic Cruiser", armed with a combination of 7.5 and 6 inch (190 and 152 mm) guns, designed to counter reported large German cruisers armed with 170 mm (6.8 inch) guns.

In 1915, a new design of cruiser was prepared for trade protection on distant waters, for which a heavy armament, long range and high speed was required; meaning a large ship. Previous large cruisers had been of the armoured cruiser or protected cruiser type. These ships had been made obsolete by the adoption of oil-firing and the steam turbine engine and had been superseded by the battlecruiser and the light cruiser. The Hawkins design was basically a light cruiser enlarged sufficiently to increase their range and armament as required. A mixed armament of 9.2 and 6 inch was rejected after wartime experience illustrated the difficulty of controlling a mixed battery as shell splashes could not be differentiated. Thus, a uniform battery of 7.5 inch calibre was adopted, controlled by the innovation of director firing.

The development of director firing made the planned armament obsolete, as director control relies on "straddles" in which some shells in a given salvo are seen to fall short of the target and some long. As long as straddles are maintained, some percentage of the shots will be hits. With a main battery consisting of only two guns, a straddle of one shell falling short and one long mathematically eliminates the possibility of a hit, while a uniform six-gun broadside allows the possibility of up to four hits out of a straddle.

The boilers were initially a combination of coal and oil firing to ensure a supply of fuel on distant stations; coal being more available and the ships could cruise on coal firing alone. The installed power was 60,000 shp for 30 knots (56 km/h). However, only Hawkins and Vindictive were completed as such. The other ships were not constructed with much haste and were completed post-war with oil-firing only, increasing power to 70,000 shp for 31 knots (57 km/h).

These ships did not suit the Royal Navy's post-World War I needs well, as Britain needed numbers of cruisers, rather than individually powerful ships. As breaking them up on the slips would have been an unwarranted waste of money, they were completed anyway. At just under 10,000 tons and armed with 7.5-inch guns, they became the prototype of the heavy cruiser designs based on limitations set by the Washington Naval Treaty in 1922.