Design and development Devastation-class ironclad

right elevation , deck plan depicted in brassey s naval annual, 1887

the admiralty design board set forth requirements ocean-going monitors. these included requirement of 2 twin 12-inch gun turrets capable of firing 600-pound shells 280-degree firing arc. turrets require 14-inch armour protection, machinery spaces , shell rooms protected 12-inch-thick armour. further, reduce interference main guns, no masts or sails needed. ships need 2 steam engines security , minimum 12-knot speed. trans-atlantic concept changed coastal defence ship, low freeboard of 4 feet 6 inches (1.37 metres) specified.

the loss of hms captain in september 1871 led concerns stability of turret ships, , special committee set determine seaworthiness. changes design recommended. freeboard of design increased 10 feet 9 inches (3.28 metres). change extend armoured breastwork un-armoured structure sides of ship , carried aft improve stability @ large angles of heel. improved crew comfort adding accommodation , latrines, since not armoured have been riddled in battle, reducing stability of vessel.

in 1871 9-foot-long (2.7 m) model of devastation tested in water tank, , subsequently 18-foot-long (5.5 m) version. once devastation completed, tests carried out real ship. included building roll of 7 degrees having 400 men run , forth across deck 18 times. other tests involved taking sea rough weather, in 1 trial waves of 20 26 feet (6 8 m) encountered gave ship 14-degree roll either way.

in 1872 armour protection of turret subjected series of tests. replica of proposed turret constructed , tested @ shoeburyness in may 1872. 11-inch (280 mm) armour plate backed 15 inches (380 mm) of teak , 1.25-inch (32 mm) metal skin resisted hits 25-ton 12-inch gun firing @ range of 200 yards (180 m), although 1 shot hit joint between plates , opened gap 7 inches (180 mm) wide did not penetrate. second test involved hms hotspur firing 3 shots @ turret of hms glatton 25-ton gun @ range of 200 yards. first shot missed, second , third shots struck turret. turret not appreciably damaged, though theoretically should have been penetrated.