Challenger-class cruiser
The "Challenger"-class cruisers were a pair of second-class protected cruisers built for the Royal Navy in the first decade of the 20th century. One ship, , was later transferred to the Royal Australian Navy. Design and description. The "Challenger"-class cruisers were essentially repeats of the previous "Highflyer" class, albeit with more powerful propulsion machinery. They were designed to displace . The ships had a length between perpendiculars of , a beam of and a draught of . Their crew consisted of 490 officers and other ranks. The ships were powered by two 4-cylinder triple-expansion steam engines, each driving  one shaft, using steam provided by 18 Babcock & Wilcox () 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 and rated the ships at . The boilers were designed to produce enough steam to allow the engines to reach . The ships easily exceeded their designed power and speeds during their sea trials. They carried a maximum of of coal. The main armament of the "Challenger" class consisted  of 11 quick-firing (QF) Mk I guns. One gun was mounted on the forecastle and two others were positioned on the quarterdeck. The remaining eight guns were placed port and starboard amidships. They had a maximum range of approximately with their shells. Eight QF 12-pounder 12 cwt guns were fitted for defence against torpedo boats. One additional 12-pounder 8 cwt gun could be dismounted for service ashore. They also carried six 3-pounder Hotchkiss guns and two submerged 18-inch (450 mm) torpedo tubes. The ships' protective deck armour ranged in thickness from . The engine hatches were  protected by of armour. The main guns were fitted with 3-inch gun shields and the conning tower had armour 6 inches thick.