The British Battleship. Norman Friedman
protected 9ft rangefinder occupying the ridge at the rear of the turret. This and all other British battleship turrets prior to Hood had three sighting hoods: two for the gunlayers and one containing two sights in the middle for the trainer who pointed the turret. At least in theory, the gunlayers were expected to maintain continuous aim on the target, using increasingly responsive hydraulic controls. The use of sighting ports just above the face of the turret made it impossible to superimpose turrets. However, once periscopic sights were introduced in HMS Neptune, the guns of an upper turret could be fired close to the axis of the lower one without disabling the turret operators. In Hood the sights were at the front of the turret with ports in the turret face plate. In Nelson the periscopes were eliminated altogether, but a local director sight was let into the side of the turret. (Dr David Stevens, RAN Seapower Centre)
During the decade leading up to the First World War, standard armour-piercing (AP) shells employed caps as antidotes to the new lightweight armours, to the extent that they seemed to revive the prospects of medium-calibre rapid-fire secondary guns. About 1905 it seemed that at the assumed battle range (4000 to 6000 yds) all practicable armour was useless against heavy capped AP shells. Armour was retained mainly against high explosive (HE) shells fired by smaller weapons. On this basis armoured cruisers and battleships were on much the same footing. As heavier guns entered service, this logic reversed: thin armour was penetrable, but heavy armour was once more worthwhile.
Shell development continued after the war. In 1935, in connection with the design of the new King George V class, DNO provided graphs of current shell performance as well as of the performance of projected 15in guns (which several other navies planned to use, despite the attempt to fix maximum calibre at 14in as part of the new London Treaty). It appeared that the figures for the projected 15in gun represented an advance in striking power over that of Hood equivalent to about 6000 yds greater range against a 13½in belt. Another 250ft/sec in muzzle velocity might buy 5000 more yards, with extremely bad consequences for a ship designed against current 15in guns. DTD and DTSD both saw these data as a reason to consider a new gun (not to mention much more armour). DNO pointed out that of the 6000 yds, only about 1100 yds was due to increased muzzle velocity; the rest was due to improvements in shape of head and in piercing qualities of more modern shells – which could of course be fired by existing ships with 15in guns.
HMS Emperor of India shows her rangefinder covers and her periscope hoods. She is hoisting out a paravane, developed during the First World War to protect against moored mines. This is presumably a post-war photograph, since neither turret appears to show deflection markings.
Once guns ‘overmatched’ armour (which generally meant that armour was thinner than one calibre), they could penetrate at increasing range. For example, in 1912 retired Admiral Fisher likened the new 15in gun to the 12in guns firing capped ammunition which had justified the thinly armoured battlecruiser in 1905.
Fire Control
Gun performance in action was determined by fire control.13 Between 1904 and 1914 the Royal Navy made a greater effort in this area than any other navy. From about 1904 onwards, it developed a method of firing effectively at what were then considered long ranges. Its system combined spotters aloft (to estimate how far off target the current solution was) with calculators in a transmitting station under armour. The transmitting station computed the range and train angle to be used by the gunners. In Dreadnought and her immediate successors the spotting position was a fire-control top at the masthead, containing a rangefinder and instruments (Dumaresqs) used to estimate the rate of change of range.
The first stage of fire-control improvement was the simplest: cancelling out the firing ship’s roll and later its pitch and yaw.14 In 1899 Captain Percy Scott discovered that the best gunners compensated for a ship’s roll by elevating and depressing their guns to point continuously at the target. That was not too difficult for secondary guns, but for heavy guns it required delicately-controlled machinery. Guns were elevated and depressed by hydraulic rams or pistons and trained by six-or seven-cylinder hydraulic engines or swashplate engines. Six-cylinder training engines were fitted in 12in dreadnought mountings except aboard Colossus, Hercules and Agincourt. The 13.5in Coventry Ordnance Works (COW) mountings had COW-designed seven-cylinder engines. All other dreadnoughts and super-dreadnoughts had swashplate engines, which offered smoother motion. They could be controlled either by a valve, which regulated hydraulic pressure or by a hand control which moved the swashplate itself (its angle to the pistons of the engine determined how rapidly the shaft revolved).
HMS Neptune shows her prototype director, the cylinder on the platform under her foretop, about 1912, when she was fleet flagship.
The Royal Navy found hydraulic machinery better than electric for such delicate work (the US Navy preferred electric turret machinery). Unsatisfactory electric turret machinery in HMS Invincible was replaced by hydraulics in 1912. Hydraulics were liked because they were simple and reliable; their movements were noiseless and steady and completely under control even with the heaviest loads. Pressure was always available once the pumps were started. The system was cold, hence could be used in magazines and in shell rooms. However, it was also inefficient, requiring the same power whether fully loaded or not; and it was cumbersome, as it required large pressure pipes and even larger exhaust pipes leading back to the tanks. Water in it could freeze in cold weather; joints had to be kept watertight; valves could score.
The director, also invented by Scott, was an alternative way to cancel out roll and pitch. Scott came to doubt heavy guns could be continuously aimed, so he turned the problem inside out. A single sight aloft would be continuously-aimed. Its single key could fire a salvo when guns at fixed elevation came ‘onto’ the target. Instead of calculating elevation and bearing for each turret, the transmitting station would pass its orders through the director, which would incorporate corrections (depending on turret position and target range and bearing) for each turret. Crews would apply these orders. Since all of the guns would be firing at the same target using the same fire-control solution, the director could apply spotting corrections to all of them. This was a brilliant invention. Its only major flaw was demonstrated at Jutland: the director might not be focussed on the target the ship’s spotter was observing. The post-war British fire-control system solved that by placing the spotter (control) in the director, which became a director control tower (DCT). It first appeared in the Nelson class.
The prototype director was installed on board HMS Neptune, which was fleet flagship at the time, in 1911. Although initial trials were somewhat disappointing, they showed that the director was worthwhile and an improved version was tested on board HMS Thunderer in 1912. It had three operators: sight-setter, layer and trainer. The layer fired the ship’s guns, just as a gunlayer in a turret fired his. Trials against Thunderer’s sister-ship Orion were spectacularly successful and during 1913 the Admiralty placed two large orders with Vickers, to be spread over the next two fiscal years, one for twelve ships (King George V and Iron Duke classes plus the battlecruisers Queen Mary and Tiger and the earlier battleships Monarch and Thunderer) and one for seventeen ships (all remaining dreadnoughts except Conqueror and Australia).15 The production prototype was installed on board HMS Ajax in 1913. On the outbreak of war in 1914 directors equipped the three prototype ships (Neptune, Thunderer and Ajax) and five others (Iron Duke, Marlborough, King George V, Centurion and Monarch). Installations were then suspended for three months, probably because they seemed to require extended time in a dockyard. Scott helped develop an installation which could be made largely by a ship’s own crew and the programme resumed. By the time of Jutland only the two battleships bought at the outbreak of war, HMS Erin and Agincourt, had not yet been equipped.
All of these directors were encased in small vertical cylinders pierced for their sights. During the First World War some directors were modified with small shields (looking like eyelids) over the opening. They were probably