HMS
Zealous was given a straight
stem and a rounded stern, but her hull was otherwise unmodified from her original form; it had been found that lengthening the hull, as was done in the earlier , led to longitudinal weakness. Her conversion to a
central-battery ironclad therefore cost less than that of any of her contemporaries, though this was offset with a shorter battery and therefore a less effective broadside. She also carried less armour than the earlier class, and was nearly a knot slower; however, as she was built to serve in distant waters, and not expected to face opposing ships of significant force, these shortcomings were thought acceptable.
Zealous was
long between perpendiculars and had a
beam of . The ship had a
draught of forward and aft. She displaced .
Propulsion Zealous had a simple horizontal 2-cylinder
horizontal return connecting-rod steam engine driving a single four-bladed, propeller. Steam was provided by eight rectangular
fire-tube boilers at a working pressure of . The engine produced during the ship's
sea trials in November 1866 which gave her a maximum speed of .
Zealous carried a maximum of of coal. She was
ship rigged with three masts and had a sail area of . Her best speed with the propeller disconnected and under sail alone was .
Armament All of the available and guns had already been earmarked for other, more powerful ships.
Zealous therefore received an armament of guns, which were deemed adequate for her expected service activity, and which, indeed, she retained for the whole of her active career. She was the only battleship ever to have a uniform armament of this calibre, and she, and her
half sister , were the only Victorian ironclads to retain their original armament unchanged through their entire active careers.
Zealous was armed with twenty 7-inch
rifled muzzle-loading guns. Four of these guns were mounted on the upper deck as
chase guns, two each fore and aft. The 16-calibre
7-inch gun weighed and fired a shell. It was credited with the nominal ability to penetrate armour.
Armour Zealous had a complete
waterline belt of
wrought iron that was thick amidships and tapered to thick at the bow and stern. From the level of the main deck, it reached below the
waterline. The guns on the main deck amidships were protected by a section of 4.5-inch armour, long, with 4.5-inch transverse
bulkheads at each end which left the
chase guns unprotected. The armour was backed by the sides of the ship which consisted of of
teak. The total weight of her armour was . ==Service history==