This was longer than the Mersey, the longest wooden-hulled ship in the Royal Navy. They had a beam of and a draught of . The ships displaced . The hull was subdivided by watertight transverse bulkheads into 92 compartments and had a double bottom underneath the engine and boiler rooms. Two bilge keels were fitted (the first used by the Royal Navy), which significantly reduced the roll of the ships. Because of their length the ships proved to be very sluggish while manoeuvring, as Warrior proved when she collided with in 1868. The Warrior-class ships trimmed down by the bow, not least because they were fitted with a iron knee placed at the bow to give it a traditionally pleasing shape. This also prevented the ships from ramming any other ships. The bowsprit was shortened after completion in an effort to reduce the trim, but it was not noticeably successful. Propulsion The Warrior-class ships had one 2-cylinder trunk steam engine made by John Penn and Sons driving a single propeller. Ten rectangular boilers provided steam to the engine at a working pressure of . The engine produced a total of and was the most powerful thus far built for a warship. On sea trials in October 1861 Warrior had a maximum speed around ; Black Prince was about a half knot slower. The ships carried of coal, enough to steam at . The ironclads were ship rigged and had a sail area of . The lower masts were made of wood, but the other masts were iron. Warrior made under sail, but Black Prince could only do . Under both sail and steam Warrior once logged . Both funnels were semi-retractable to reduce wind resistance while under sail alone. The ships' propellers could be hoisted up into the stern of the ship to reduce drag while under sail. They were the largest hoistable propellers ever made and required about 600 men to be raised. Armament The armament of the Warrior-class ships was intended to be 40 smoothbore, muzzle-loading 68-pounder guns, 19 on each side on the main deck and one each fore and aft as chase guns on the upper deck. This was modified during construction to ten rifled 110-pounder breech-loading guns, twenty-six 68-pounders, and four rifled breech-loading 40-pounder guns as saluting guns. The 40-pounder guns were to have been replaced by 70-pounder guns, but these failed their tests and