The Challenger-class cruisers were essentially repeats of the previous Highflyer class, albeit with more powerful propulsion machinery. They were designed to displace 5,880 long tons (5,970 t). The ships had a length between perpendiculars of 355 feet (108.2 m), a beam of 56 feet (17.1 m) and a draught of 21 feet 3 inches (6.5 m). Their crew consisted of 490 officers and other ranks.[1]
The ships were powered by two 4-cylinder triple-expansion steam engines, each driving one shaft, using steam provided by 18 Babcock & Wilcox (Challenger) or Dürr (Encounter) water-tube boilers. These boilers were heavier and bulkier, but more powerful than the Belleville boilers used in the Highflyer class. Sir William White, Director of Naval Construction, was uncertain if the extra power would offset the weight sufficiently to reach 21 knots (39 km/h; 24 mph) and rated the ships at 20.75 knots (38.43 km/h; 23.88 mph). The boilers were designed to produce enough steam to allow the engines to reach 12,500 indicated horsepower (9,300 kW).[2] The ships easily exceeded their designed power and speeds during their sea trials.[3] They carried a maximum of 1,150 long tons (1,170 t) of coal.[1]
The ships' protective deck armour ranged in thickness from 1.5 to 3 inches (38 to 76 mm). The engine hatches were protected by 5-inch (127 mm) of armour. The main guns were fitted with 3-inch gun shields and the conning tower had armour 6 inches thick.[3]
Corbett, Julian. Naval Operations to the Battle of the Falklands. History of the Great War: Based on Official Documents. Vol. I (2nd, reprint of the 1938 ed.). London and Nashville, Tennessee: Imperial War Museum and Battery Press. ISBN0-89839-256-X.
Friedman, Norman (2012). British Cruisers of the Victorian Era. Barnsley, South Yorkshire, UK: Seaforth. ISBN978-1-59114-068-9.
Friedman, Norman (2011). Naval Weapons of World War One. Barnsley, South Yorkshire, UK: Seaforth. ISBN978-1-84832-100-7.
Gardiner, Robert & Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships 1906–1921. Annapolis, Maryland: Naval Institute Press. ISBN0-85177-245-5.