By the mid-19th century steam engines had been fitted in some wooden ships of the line. But the Royal Navy was shocked when, in 1858, the French started building La Gloire.
Inboard profile of HMS Warrior.
This was the first armour-hulled ship. However, because French industry could not make an iron hull, the Gloire had to be built of wood protected by 11 cm (4.5 in) of iron.
An all-iron hull
The bows of HMS Warrior during construction.
Iron cladding the wooden British fleet was the simplest way of responding to this French challenge.
However, Sir John Pakingham, the First Lord of the Admiralty, supported the idea of a completely iron hull. So, the Warrior was ordered in June 1859.
A sectional model of the Warrior.
The Warrior was protected with 11 cm (4.5 in) tongue-and-grooved plating over 65 m (213 ft) of her 128 m (420 ft) long hull. Each armour plate was 4.5 m (15 ft) by 1 m (3 ft) and weighed 4 tons.
She had a 57-section double bottom hull for 73 m (240 ft) of her length, and was also subdivided into a further 35 watertight compartments amidships. She had a width of 18 m (58 ft 4 in) and a draft (the amount of hull below the waterline) of 8 m (26 ft).
Steam power
View of the stern of HMS Warrior.
Warrior's 10 rectangular boilers generated enough power to turn a 10 ton, 7 m (23 ft) propeller. The propeller could be lifted into a space above the waterline where it was held in place by large metal bars.
Even without a dockyard it could be hoisted up on deck for examination. You can see the propeller shaft and stern of the ship in this picture, made during its construction at the Thames Ironworks.
Main deck of HMS Warrior as fitted. 
