experimental submarine built royal_navy world war meet navy goal overseas submarine capable knots mph surface diesel engines period unreliable powerful steam turbines proposed instead meet requirement proved slower designed unstable consequently modified anti submarine patrol vessel paid end war sold scrapping design hms developed meet requirement royal_navy large submarine capable operating fleet surfaced speed knots earlier british submarines single vessels built vickers navy interested evaluating designs captain captain submarines previously served naval italy kept abreast italian submarine developments notably included double submarines designed boats class ordered invited submit design meet requirement wary heavy oil diesel engines guarantee success engines power required time prepared design geared steam turbines having speed knots surface displacement tons design modified include guns kept main dimensions original design greater displacement endurance description overall length beam draught feet inches displaced long tons surface long tons submerged partial double hull extended length upper portion double hull controlled free flooding rest devoted watertight flats ballast fuel tanks hull divided compartments seven watertight bulkheads diving depth time known records sea trials survived shutting boiler funnel sealing boiler required minute quarter included switching electric motors marked contrast contemporary vickers designs attention paid safety arrangements including extensive subdivision indicator telephone released inside submarine provided external air connections charged high pressure line provide air manned compartment living spaces furthermore main ballast tanks blown end ship propulsion parsons geared impulse reaction steam turbine sets driving propeller shafts turbines powered single yarrow type boiler designed produce total shaft horsepower working pressure psi kpa cm2 increase working temperature fitted electric motors combined output battery rooms battery cells uncertain ship reached designed speed knots surface unlikely given increased displacement original design maximum speed knots mph underwater carry long tons fuel oil builders estimated gave endurance nautical miles speed knots mph surface batteries submerged endurance nautical miles speed knots mph armament tubes inch torpedoes bow stepped vertically positioned stem notch keel preserve fine lines bow inch torpedo tubes positioned beam amidships torpedo tube provided inch guns fitted deck disappearing mounts fore aft conning tower covered watertight preserve submarine construction service ordered august laid february start world war months later greatly hindered completion launched march hms commissioned april completion renamed day completed july captained commander post completion trials lasted months evaluate steam power submarine use learned operation steam submarines helped subsequent design steam powered class fleet submarines proved unstable presumably pump water controlled free flooding spaces quickly upper double hull problems coupled fact slow work fleet originally envisioned meant impossible effective warship laid trials july reverted original converted surface patrol vessel june january torpedo tubes disappearing guns removed given forecastle bridge funnel fixed place extended rearmed pair pounder inch guns depth charges weapons suitable new role anti submarine patrol boat joined 1st destroyer flotilla portsmouth completion sea trials known subsequent service paid october stricken navy list january sold scrapping pounds portsmouth july reported
HMS Swordfish (1916)