The Colossus-class battleships were a pair of dreadnought battleships built for the Royal Navy (RN) at the end of the first decade of the 20th century, the last battleships built for the RN. The sister ships spent their whole careers assigned to the Home and Grand Fleets, often serving as flagships. Aside from participating in the Battle of Jutland in May 1916, and the inconclusive action of 19 August several months later, their service during the First World War generally consisted of routine patrols and training in the North Sea.
The Colossus class were deemed obsolete by the end of the war in 1918 and were reduced to reserve the following year. Hercules was sold for scrap in 1921, although Colossus was briefly used as a training ship. She was hulked in 1923 and sold for scrap five years later.
Background and design The initial 1909–1910 Naval Programme included two dreadnoughts and a battlecruiser, but was later increased to six dreadnoughts and two battlecruisers as a result of public pressure on the government due to the Anglo-German naval arms race. The original pair of battleships became the Colossus class and were improved versions of the preceding battleship, . On 19 November 1908, Rear-Admiral Sir John Jellicoe, the Third Sea Lord and Controller of the Navy, proposed the changes that he would like to make to the Neptunes design. He wanted to redistribute the armour from locations not exposed to enemy fire to those that were and to fit 21-inch (533 mm) torpedoes in lieu of the 18-inch (450 mm) weapons used in the earlier ship; the number of spare torpedoes were to be increased as well. Likely prompted by an earlier memo from Admiral Francis Bridgeman, commander-in-chief of the Home Fleet, Jellicoe wanted to eliminate the mainmast and transfer most of the functions of its spotting top to an armoured spotting tower atop the conning tower in the superstructure. The Director of Naval Ordnance (DNO), Rear-Admiral Reginald Bacon, argued that the spotting top in the foremast should be retained. Jellicoe was willing to slightly increase the new design's displacement over Neptune, but it could not cost any more, which placed major constraints on the Director of Naval Construction (DNC), Sir Philip Watts.Brooks 1995, pp. 42–44; Friedman 2015, pp. 111–12, 114
The DNC objected to the loss of the mainmast as he believed that it was needed to support a boat-handling derrick, but was overruled by the Admiralty, which preferred to position the tripod foremast behind the forward funnel with the tripod legs facing forward to allow the vertical leg to be used to support the derrick. This all but guaranteed that the hot funnel gases could render the spotting top uninhabitable. The short height of the funnel also bedevilled the bridge with smoke until it was raised in 1912, although this exacerbated the problem for the spotting top. The decision to space the wing turrets more closely together also made the smoke problem worse; because it reduced the space available to the aft boiler room which meant that the forward funnel had to accommodate the exhausts of a dozen boilers compared to the aft funnel's six, further increasing the smoke from the forward funnel.Friedman 2015, p.112; Burt, p. 126
All eight capital ships of the 1909–1910 Naval Programme had the same arrangement of masts and funnels; only the two battlecruisers had their foremast and forward funnel positions exchanged at considerable expense.Brooks 1995, pp. 44–46 David K. Brown, naval architect and historian, commented on the whole fiasco: "It is amazing that it took so long to attain a satisfactory arrangement, which was caused by the DNO's insistence on sighting hoods in the roofs of turrets and Jellicoe's obsession with boat-handling arrangements. These unsatisfactory layouts reduced firepower, prejudiced torpedo protection and probably added to cost. As DNO and then as Controller, Jellicoe must accept much of the blame for the unsatisfactory layout of the earlier ships."Brown, pp. 41–42
Like Neptune, the wing turrets of the Colossus-class ships were staggered "en echelon" so that all five turrets could shoot on the broadside, although in practice the blast damage to the superstructure and boats made this impractical except in an emergency. The design also perpetuated siting the ship's boats on girders over the two wing turrets to reduce the length of the vessel. However, if the girders were damaged during combat, they could fall onto the turrets, immobilising them. The bridge and its associated compass platform was also situated above the conning tower, which similarly risked being obscured if the bridge collapsed.Brooks 1995, p. 44; Brown, pp. 38–40
Description The Colossus-class ships had an overall length of , a beam of () or () and a deep draught of . They displaced at normal load and at deep load. Their crew numbered 751–778 officers and ratings upon completion and 791 in July 1916.Burt, p. 121
The ships were powered by two sets of Parsons direct-drive steam turbines. The Colossus class were the first British dreadnoughts that had three engine rooms. The outer propeller shafts were coupled to the high-pressure turbines in the outer engine rooms and these exhausted into low-pressure turbines in the centre engine room which drove the inner shafts. The turbines used steam provided by eighteen water-tube boilers at a working pressure of . They were rated at and were intended to give the dreadnoughts a maximum speed of . During their sea trials, the sister ships handily exceeded their designed speed and horsepower. They carried a maximum of of coal and an additional of fuel oil that was sprayed on the coal to increase its burn rate. This gave them a range of at a cruising speed of .Burt, pp. 31, 64, 121, 124
Armament and armour
The Colossus class was equipped with ten 50-calibre breech-loading (BL) Mark XI guns in five hydraulically powered twin-gun turrets, three along the centreline and the remaining two as wing turrets. The centreline turrets were designated 'A', 'X' and 'Y', from front to rear, and the port and starboard wing turrets were 'P' and 'Q' respectively. The guns had a maximum elevation of +20° which gave them a range of . They fired projectiles at a muzzle velocity of at a rate of two rounds per minute.Friedman 2011, pp. 62–63 The ships carried 100 shells per gun. Her wing turrets were staggered "en echelon" so all five turrets could shoot on the broadside, although in practice the blast damage to the superstructure and boats made this impractical except in an emergency.
Their secondary armament consisted of sixteen 50-calibre BL four-inch (102 mm) Mark VII guns. These guns were installed in unshielded single mounts in the superstructure.Parkes, p. 519 The guns had a maximum elevation of +15° which gave them a range of . They fired projectiles at a muzzle velocity of .Friedman 2011, pp. 97–98 They were provided with 150 rounds per gun. Four 3-pounder () saluting guns were also carried. The ships were equipped with three 21-inch submerged torpedo tubes, one on each broadside and another in the stern, for which 18 torpedoes were provided.Friedman 2015, p. 112
The Colossus class had a waterline belt of Krupp cemented armour that was thick between the fore and rear barbettes that reduced to outside the central armoured citadel, but did not reach the bow or stern. This made them the first British battleships since 1893 not to have a complete belt of armour at the waterline. The belt covered the side of the hull from above the waterline to below where it thinned to at its bottom edge. Above this was a strake of 8-inch armour. The forward oblique bulkheads connected the waterline and upper armour belts to the 'A' barbette. Similarly the aft bulkhead connected the armour belts to 'Y' barbette, although it was 8 inches thick. The exposed faces of the three centreline barbettes were protected by armour thick above the main deck and thinned to 4 or below it. The wing barbettes were similar except that they had 11 inches of armour on their outer faces. The gun turrets had 11-inch faces and sides with 3-inch roofs.Burt, p. 122
The three armoured decks ranged in thickness from with the greater thicknesses outside the central armoured citadel. The front and sides of the conning tower were protected by 11-inch plates, although the roof was 3 inches thick. The spotting tower behind and above the conning tower had sides and the torpedo-control tower aft had 3-inch sides and a 2-inch roof. In the interests of saving weight, the Colossus-class ships eliminated the anti-torpedo bulkheads that protected the engine and boiler rooms, reverting to the scheme in the older dreadnoughts that placed them only outboard of the magazines with the same thickness from . They did retain the 1-inch armour plates protecting the boiler uptakes.Burt, p. 124
Fire control
The control position for the main armament were located in the spotting tops at the head of the foremast. Data from a Barr and Stroud coincidence rangefinder located there was input into a Dumaresq mechanical computer and electrically transmitted to Vickers range clocks located in the transmitting station located beneath each position on the main deck, where it was converted into range and deflection data for use by the guns. The target's data was also graphically recorded on a plotting table to assist the gunnery officer in predicting the movement of the target. The turrets, transmitting stations, and control positions could be connected in almost any combination.Brooks 1995, pp. 40–41 By 1912, another nine-foot rangefinder was added at the forward side of the compass platform.Friedman 2015, p. 115 In late 1914, more nine-foot rangefinders, protected by armoured hoods, were installed on the turret roofs.
Fire-control technology advanced quickly during the years between the Colossus-class ships' commissioning and the start of World War I, and the most important development was the director firing system. This consisted of a fire-control director mounted high in the ship which electrically provided data to the turrets via pointers, which the turret crew were to follow. The director layer fired the guns simultaneously which aided in spotting the shell splashes and minimised the effects of the roll on the dispersion of the shells.Brooks 2005, p. 48 While the exact dates of installation are unknown, both ships were equipped with a director by December 1915.Brooks 1996, p. 168
Another development was the Dreyer Fire-control Table that combined the functions of the Dumaresq and the range clock in the transmission stations. Hercules was probably fitted with a prototype table when its inventor, Commander Frederic Dreyer, was assigned to the ship at the end of 1911. The ship retained that instrument at least until February 1916, although it had been replaced by a Mark I table by 1918. Colossus received her Mark I table by early 1916.Brooks 2005, pp. 157–59, 175, 182
Modifications