The Hector-class ironclads, like their immediate predecessors, the Defence class, were designed as smaller and cheaper versions of the Warrior-class armoured frigates.

[1] The hull was subdivided by watertight transverse bulkheads into 92 compartments and had a double bottom underneath the engine and boiler rooms.

[4] Each of the Hector-class ships had one 2-cylinder horizontal return connecting-rod steam engine driving a single 18-foot (5.5 m) propeller.

The ships carried only 450 long tons (460 t) of coal because they were overweight,[5] enough to steam 800 nautical miles (1,500 km; 920 mi) at full speed.

This was modified during Hector's construction to four rifled 110-pounder breech-loading guns mounted on the upper deck and twenty-four 68-pounders on the broadside.

Firing tests carried out in September 1861 against an armoured target, however, proved that the 110-pounder was inferior to the 68-pounder smoothbore gun in armour penetration and repeated incidents of breech explosions during the Battles for Shimonoseki and the Bombardment of Kagoshima in 1863–64 caused the navy to withdraw the gun from service shortly afterwards.

[10] The Hector-class ships had a wrought iron waterline armour belt, 4.5 inches (114 mm) thick, that covered 216 feet (65.8 m) amidships and left the bow and stern unprotected.

To protect against raking fire the belt was closed off by 4.5-inch transverse bulkheads at each end at lower deck level.

[6] She was paid off at Portsmouth in 1886 and remained there until 1900 when she briefly became part of the torpedo school HMS Vernon as a store hulk.

Hector became the first British warship to have wireless telegraphy installed when she conducted the first trials of the new equipment for the Royal Navy.

[18] The ship was converted to a kite balloon storeship in 1915, during World War I, and her name was changed to HMS Valiant III.

[12] She was offered for sale in 1922, but there were no takers so the ship was converted into a floating oil tank in 1926 and towed to Hamoaze.