fourth ships john class monitors built impressed use ironclads american civil war design based uss monitor designed supervision swedish born inventor coincidentally designer monitor built sweden delivered ran aground following year seriously damaged ship reconstructed given modern breech loading guns sold scrap design description ironclads designed meet need swedish norwegian navies small shallow draft armored ships capable defending coastal waters uss monitor larger virginia early interest sweden new type warship ideal coastal defense duties designer builder monitor born sweden american citizen offered share design response sent lieutenant united_states study monitor design construction arrived july toured rolling mills gun visited different ironclads construction returned sweden having completed drawings monitor type ship supervision ship measured meters long overall beam meters draft meters displaced metric tons long tons divided main compartments watertight bulkheads time flying bridge later superstructure added ship gun turret funnel initially crew numbered officers men increased modified additional weapons propulsion ships twin cylinder steam engines designed driving single bladed meter propeller engines powered fire tube boilers working pressure psi kpa cm2 engines produced total indicated horsepower gave monitors maximum speed knots mph calm waters ships carried tonnes long tons coal day steaming armament armed pair armstrong millimeter rifled muzzle loading guns gun constructed steel weighed long tons ship carried millimeter gun reconstruction gun turret fixed place modified serve barbette new breech loading millimeter guns received millimeter millimeter guns mounted superstructure addition millimeter hotchkiss barrel revolving guns mounted superstructure fired shell weighing muzzle velocity gave range yards rate fire rounds minute armor ships complete waterline armor belt wrought iron meters high millimeters thick armor consisted plates backed millimeters wood lower edge belt millimeters thick plates thick maximum thickness armored deck millimeters layers gun turret armor consisted layers iron totalling millimeters thickness monitors inside turret lined catch splinters base turret protected millimeter millimeters high turret roof millimeters thick conning tower positioned turret sides layers millimeters thick funnel protected layers armor total thickness millimeters half height service built monitor type ship laid norwegian parliament authorized construction sweden cost norwegian launched completed september year ship ran aground june pulled rocks ship ammunition iron ballast long tons coal removed repairs completed july cost court inquiry found ship commander pilot liable repairs parliament released obligation years later visited sweden occasion visiting sweden west coast ports early 1870s laid refit mobilized personal union sweden norway dissolved returned reserve afterward sold scrap
HNoMS Mjølner (1868)