The Courageous class consisted of three battlecruisers known as "large light cruisers" built for the Royal Navy during the First World War. The class was nominally designed to support the Baltic Project, a plan by Admiral of the Fleet Lord Fisher that was intended to land troops on the German Baltic Coast. Ships of this class were fast but very lightly armoured, with only a few heavy guns. They were given a shallow draught, in part to allow them to operate in the shallow waters of the Baltic but also reflecting experience gained earlier in the war. To maximize their speed, the Courageous-class battlecruisers were the first capital ships of the Royal Navy to use geared steam turbines and small-tube boilers.
The first two ships, and , were commissioned in 1917 and spent the war patrolling the North Sea. They participated in the Second Battle of Heligoland Bight in November 1917 and were present when the High Seas Fleet surrendered a year later. Their half-sister was designed with a pair of guns, the largest guns ever fitted on a ship of the Royal Navy, but was modified during construction to take a flying-off deck and hangar in lieu of her forward turret and barbette. After some patrols in the North Sea, her rear turret was removed and another flight deck added. Her aircraft attacked the Zeppelin sheds during the Tondern raid in July 1918.
All three ships were laid up after the war, but were rebuilt into the Courageous-class aircraft carriers during the 1920s. Glorious and Courageous were sunk early in the Second World War and Furious was sold for scrap in 1948.
Design and description
The first two Courageous-class battlecruisers were designed in 1915 to meet a set of requirements laid down by the First Sea Lord, Admiral Fisher, with his Baltic Project in mind. They were to be large enough to ensure that they could maintain their speed in heavy weather, have a powerful armament and a speed of at least to allow them to outrun enemy light cruisers. Their protection was to be light for a cruiser, with of armour between the waterline and the forecastle deck, anti-torpedo bulges amidships and the machinery as far inboard as possible, protected by triple torpedo bulkheads. Shallow draught was of the utmost importance and all other factors were to be subordinated to this. The Director of Naval Construction (DNC), Sir Eustace Tennyson-d'Eyncourt, responded on 23 February 1915 with a smaller version of the s with one less gun turret and reduced armour protection. The Chancellor of the Exchequer had forbidden any further construction of ships larger than light cruisers in 1915, so Fisher designated the ships as "large light cruisers" to evade this prohibition. If this restriction had not been in place, the ships would have been built as improved versions of the preceding Renown class. The two ships were laid down a few months later under a veil of secrecy, so they became known in the Royal Navy as "Lord Fisher's hush-hush cruisers" and their odd design also earned them the nickname of the Outrageous class.Burt, p. 303.
Their half-sister Furious was designed a few months later to meet a revised requirement specifying an armament of two BL 18-inch Mk I guns, the largest guns ever fitted on a Royal Navy ship, in single turrets with the ability to use twin gun turrets if the 18-inch guns were unsatisfactory. Gunnery experts criticized this decision because the long time between salvoes would make spotting corrections useless and reduce the rate of fire and thus the probability of a direct hit. Her secondary armament was upgraded to BL Mk I guns, rather than the guns used by the first two ships, to compensate for the weakness of the two main guns against fast-moving targets like destroyers. Her displacement and beam were increased over that of her half-sisters with slightly less draught.
The Baltic Project was only one justification for the ships. Admiral Fisher wrote in a letter to the DNC on 16 March 1915: "I've told the First Lord that the more that I consider the qualities of your design of the Big Light Battle Cruisers, the more that I am impressed by its exceeding excellence and simplicity—all the three vital requisites of gunpower, speed and draught so well balanced!"Roberts, p. 51. In fact they could be considered the epitome of Fisher's belief in the paramount importance of speed over everything else. Fisher's adherence to this principle is highlighted in a letter he wrote to Churchill concerning the battleships of the 1912–13 Naval Estimates. In the letter, dated April 1912, Fisher stated: "There must be sacrifice of armour ... There must be further VERY GREAT INCREASE IN SPEED ... your speed must vastly exceed [that of] your possible enemy!"Roberts, p. 46.
Fisher's desire for a shallow draught was not merely based on the need to allow for inshore operations; ships tended to operate closer to deep load than anticipated and were often found lacking in freeboard, reserve buoyancy and safety against underwater attack. This experience led the DNC to reconsider the proportions of the hull to rectify the problems identified thus far. The Courageous-class ships were the first products of that re-evaluation.Roberts, p. 53.
General characteristics The Courageous-class ships had an overall length of , a beam of , and a draught of at deep load. They displaced normally and at deep load. They had a metacentric height of at deep load and a complete double bottom.Roberts, pp. 64–65.
Their half-sister Furious was the same length, but had a beam of and a draught of at deep load. She displaced at load and at deep load. She had a metacentric height of at deep load.
Propulsion To save weight and space the Courageous-class ships were the first large warships in the Royal Navy to have geared steam turbines and small-tube boilers despite the latter's significantly heavier maintenance requirements. Furthermore, to save design time, the turbine installation used in the light cruiser , the navy's first cruiser with geared turbines, was simply doubled. The Parsons turbines were arranged in two engine rooms and each of the turbines drove one of the four propeller shafts. Furiouss propellers were in diameter. The turbines were powered by eighteen Yarrow boilers equally divided among three boiler rooms. They were designed to produce a total of at a working pressure of , but achieved slightly more than that during Gloriouss trials, although she did not reach her designed speed of .Roberts, pp. 71, 74, 76, 79.
They were designed to normally carry of fuel oil, but could carry a maximum of . At full capacity, they could steam for an estimated at a speed of .Burt, p. 306.
Armament The Courageous-class ships mounted four BL 15-inch Mark I guns in two twin hydraulically powered Mark I turrets, one each fore (designated the 'A' turret) and aft (the 'Y' turret). These turrets were originally intended for a that was canceled shortly after the war began.Burt, pp. 291, 308. The guns could be depressed to −3° and elevated to 20°; they could be loaded at any angle up to 20°, although loading at high angles tended to slow the gun's return to battery (firing position). The ships carried 120 shells per gun. They fired projectiles at a muzzle velocity of ; this provided a maximum range of with armour-piercing shells.
The Courageous-class ships were designed with 18 BL 4-inch Mark IX guns, fitted in six triple mounts. These were manually powered and quite cumbersome in use as they required a crew of thirty-two men to load and train the guns. The gun's rate of fire was only 10 to 12 rounds per minute as the loaders kept getting in each other's way. They had a maximum depression of −10° and a maximum elevation of 30°. They fired a high explosive shell at a muzzle velocity of . At maximum elevation the guns had a maximum range of . The ships carried 120 rounds for each gun.
Each ship mounted a pair of QF 3 inch 20 cwt"cwt" is the abbreviation for hundredweight, 30 cwt referring to the weight of the gun. anti-aircraft guns on single high-angle Mark II mountings. These were mounted abreast the mainmast in the Courageous-class ships and before the funnel on Furious. The gun had a maximum depression of 10° and a maximum elevation of 90°. It fired a shell at a muzzle velocity of at a rate of fire of 12–14 rounds per minute. They had a maximum effective ceiling of . All three ships carried ten torpedoes and mounted two submerged side-loading torpedo tubes fitted near 'A' turret. They were loaded and traversed by hydraulic power, but fired by compressed air.Roberts, p. 83.
The 18-inch BL Mark I gun carried by Furious was derived from the 15-inch Mark I gun used in her half-sisters. It was intended to be mounted in two single-gun turrets derived from the twin-gun 15-inch Mark I/N turret, and her barbettes were designed to accommodate either turret in case problems arose with the 18-inch gun's development, but only one turret was actually fitted. The gun could depress to −3° and elevate to a maximum of 30°. It fired a , 4 crh armour-piercing, capped shell at a muzzle velocity of to a distance of . It could fire one round per minute and the ship carried sixty rounds of ammunition. The turret's revolving mass was , only slightly more than the of its predecessor.
Furiouss secondary armament consisted of 11 BL 5.5-inch Mk I guns. The guns had a maximum elevation of 25° on their pivot mounts. They fired projectiles at a muzzle velocity of at a rate of 12 rounds per minute. Their maximum range was at 25° elevation.
Fire control The main guns of the Courageous-class ships could be controlled from either of the two fire-control directors. The primary director was mounted above the conning tower in an armoured hood and the other was in the fore-top on the foremast.Roberts, p. 93. The secondary armament was also director-controlled.McBride, p. 106. Each turret was provided with a rangefinder in an armoured housing on the turret roof. The fore-top was equipped with a rangefinder as was the torpedo control tower above the rear superstructure. The anti-aircraft guns were controlled by a simple rangefinder mounted on the aft superstructure.Burt, p. 307.
Protection Unlike on other British battlecruisers, the bulk of the armour of the Courageous-class ships was made from high-tensile steel, a type of steel used structurally in other ships. Their waterline belt consisted of covered by a skin. It ran from barbette to barbette with a one-inch extension forward to the two-inch forward bulkhead well short of the bow. The belt had a height of , of which was below the designed waterline. From the forward barbette a three-inch bulkhead extended out to the ship's side between the upper and lower decks and a comparable bulkhead was in place at the rear barbette as well. Four decks were armoured with thicknesses varying from , with the greatest thicknesses over the magazines and the steering gear. After the loss of three battlecruisers to magazine explosions during the Battle of Jutland, of extra protection was added to the deck around the magazines.Burt, pp. 308, 313.
The turrets, barbettes and conning tower were made from Krupp cemented armour. The turret faces were thick while their sides ranged from in thickness and the roof was thick. The barbettes had a maximum thickness of above the main deck, but reduced in thickness to between the lower and main decks. The conning tower armour was thick and it had a three-inch roof. The primary fire-control director atop the conning tower was protected by an armoured hood. The face of the hood was six inches thick, its sides were two inches thick and its roof was protected by three inches of armour. A communications tube with three-inch sides ran from the conning tower down to the lower conning position on the main deck. The torpedo bulkheads were increased during building from to in thickness.Roberts, pp. 54, 106, 113.