HMAS Sydney (D48) - Design

Design

Sydney was one of three Modified Leander class light cruisers acquired by the RAN during the late 1930s. Although the first ship of the class to join the RAN, Sydney was the third ship in what came to be known as the Perth class: Perth and Hobart operated with the Royal Navy for a short period before they were purchased by Australia in 1938. Like most British cruisers, the Leanders were designed for long range patrols, scouting, and trade protection duties.

Sydney's displacement ranged between 6,701 tons (light) and 8,940 tons (full load), with a standard displacement of 7,198 tons: improved fabrication and welding techniques made her 52 tons lighter than her sister ships. She had a length of 530 feet (160 m) between perpendiculars and 562 feet 4 inches (171.40 m) overall,(I) a beam of 56 feet 8.5 inches (17.285 m), and a draught at standard displacement between 15 feet 3 inches (4.65 m) forward and 17 feet 3 inches (5.26 m) aft.

The ship was propelled by four Admiralty 3-drum boilers, feeding Parsons geared turbines, which supplied 72,000 shaft horsepower (54,000 kW) to the four propeller shafts. Unlike the first five Leanders, which had a single machinery space (consisting of all six boilers in one compartment and all six turbines in another), Sydney was designed with two redundant machine spaces, a design practice adopted from the United States Navy. The cruiser had two boilers and the turbines for the outer shafts forward, and two boilers and the turbines for the inner shafts aft; as steam from any boiler could be routed to any turbine, the ship could continue operating if one space was damaged. Each space had its own exhaust funnel, giving the modified ships a different profile to the single-funnelled early Leanders; an arrangement which contributed to naval historian Henry Lenton's description of the Modified Leanders as "the most handsome cruisers ever built by the Royal Navy, with a symmetry that was as attractive as it was functional."

Sydney and her sister ships were constructed from 1-inch (25 mm) hull plating, with a 3-inch (76 mm) armour belt over the machinery spaces (the lengthening of this belt from 84 to 141 feet (26 to 43 m) to adequately cover both spaces negated the weight reduction from their reorganisation), and 2-inch (51 mm) plates over the shell rooms and magazines. Sydney was the first Australian warship fitted with asdic; a Type 125 unit in a retractable pattern 3069 dome. The retractable sonar dome, located near the bow, was a weak point in the hull.

One of the cruiser's early commanding officers, Royal Navy Captain J.W.A. Waller, believed that the ship's single director control tower was a weak point in the design. The director control tower was the highest compartment on the ship, from where personnel would determine the range and optimum firing angle for a gun salvo, then transmit this information to the gun turrets: the actual firing could be controlled from the tower or the turret. Waller believed that the centralised system could be destroyed with a single hit, or the wiring linking the compartment to the turrets could be severed, forcing the four turrets to rely on independent control. Although Waller suggested that a second tower be installed aft to provide redundancy, it was deferred indefinitely as subsequent commanding officers did not share his concerns, and combat experiences of other Leander class cruisers showed that the system was more robust than expected.