The Royal Navy had not been keen to sacrifice its advantage in steam ships of the line , but was determined that the first British ironclad would outmatch the French ships in every respect , particularly speed . A fast ship would have the advantage of being able to choose a range of engagement which could make her invulnerable to enemy fire . The British specification was more a large , powerful frigate than a ship @-@ of @-@ the @-@ line . The requirement for speed meant a very long vessel , which had to be built from iron . The result was the construction of two Warrior @-@ class ironclads ; HMS Warrior and HMS Black Prince . The ships had a successful design , though there were necessarily compromises between ' sea @-@ keeping ' , strategic range and armour protection ; their weapons were more effective than that of Gloire , and with the largest set of steam engines yet fitted to a ship they could steam at 14 @.@ 3 knots ( 26 @.@ 5 km / h ) . Yet the Gloire and her sisters had full iron @-@ armour protection along the waterline and the battery itself . Warrior and Black Prince ( but also the smaller Defence and Resistance ) were obliged to concentrate their armour in a central ' citadel ' or ' armoured box ' , leaving many main deck guns and the fore and aft sections of the vessel unprotected . The use of iron in the construction of Warrior also came with some drawbacks ; iron hulls required more regular and intensive repairs than wooden hulls , and iron was more susceptible to fouling by marine life .