HMS Inflexible (1876)

Royal Navy turret ironclad

HMS Inflexible was a Victorian ironclad battleship carrying her main armament in centrally placed turrets. The ship was constructed in the 1870s for the Royal Navy to oppose the perceived growing threat from the Italian Regia Marina in the Mediterranean. The Italian Navy had started constructing a pair of battleships, Italian ironclad Duilio and Italian ironclad Enrico Dandolo, equipped with four Armstrong 17.7 inch (450 mm) guns weighing 100 tons each. These were superior to the armament of any ship in the British Mediterranean Squadron, and Inflexible was designed as a counter to them. Inflexible mounted larger guns than those of any previous British warship and had the thickest armour ever to be fitted to a Royal Navy ship. Controversially, she was designed so that if her un armoured ends should be seriously damaged in action and become water logged, the buoyancy of the armoured centre section of the ship would keep her afloat and upright. The ship was the first major warship to depend in part for the protection of her buoyancy on a horizontal armoured deck below the water line rather than armoured sides along the waterline.

A heavily armoured citadel 75 feet (23 m) wide and 110 feet (34 m) long was located amidships, which would keep the ship afloat and stable regardless of what happened to the ends. This citadel contained the main guns, the boilers and the engines. The ends were unarmoured, but with a armoured deck 6–8 ft below the waterline to limit damage to the underwater section to keep them buoyant. Coal bunkers were located over the armoured deck and surrounded by 4 feet (1 m) compartments filled with cork. The ship had bunker capacity for 400 tons of coal below the deck for use during combat, when the above deck bunkers would be inaccessible and possibly flooded. The structure above the armoured deck also contained a large number of watertight compartments to further preserve buoyancy. There was also light superstructure to provide crew accommodation, and freeboard in rough weather, although anticipated to be seriously damaged in any major engagement. Barnaby wanted a ship both broader than existing designs to minimise rolling and as short as possible to reduce its size as a target. Making a ship broader compared to its length was known to reduce its speed, so the innovative technique of water tank tests on models, pioneered by William Froude, was used to finalise a design. This was ten feet wider than Duillo and twenty one feet shorter, the smallest ever ratio of length to breadth in a metal first class warship. Once the outline design was agreed, the detailed architectural design was done by William White and she was laid down at Portsmouth Dockyard on 24 February 1874.

Inflexible was launched 27 April 1876. Later that year the MP Edward Reed, formerly Director of Naval Construction, visited the Italian ships and subsequently questioned their stability if the unarmoured ends were flooded. As Inflexible was of similar design, he raised grave concerns about this to the Admiralty. When this had no effect he publicised his charges in The Times in June 1877. An editorial in the same edition, 18 June, said "it is said that the unarmoured ends are, in fact, the corks on which she floats, that she cannot swim without them, and it would appear that if she lost one she would capsize". Further exchanges followed until in July, construction was halted on Inflexible (and two other smaller ships, and ) whilst a hastily convened committee examined the design. In their report published in December 1877, they concluded that it would be hard for gunfire to completely flood the unarmoured but heavily compartmentalised and partially cork filled ends. However, if this was managed then the ship would just be stable, listing to about 35 degrees heel. The turrets were rotated hydraulically, taking around a minute to perform a complete rotation. Inflexibles guns were muzzle loaded, and because of their length could not be reloaded from inside the turrets. Consequently reloading was done using hydraulic rams fitted outside the two turrets underneath an armoured glacis. To reload the guns, the turret was rotated to align the guns with the rams, and the guns depressed so that the rams could push the gunpowder charge and 1,684 pound shell into it. The rams had to be extended twice: First, to extinguish any burning material remaining inside the gun using a sponge and water jet fixed to the end of the ram, and then again after charge, shell and wadding had been placed on a loading tray in front of it to be driven into the gun. The shell had a copper disk at its base which engaged with rifled grooves cut into the barrel to spin the shell, rather than zinc studs used on earlier designs. Tests showed that the normal full charge of 450 pounds of brown prismatic gunpowder would produce a muzzle velocity of , which could penetrate of wrought iron armour at The muzzle loading took between 2.5 and four minutes. This was less surprising than it might seem to modern eyes, because it was expected that naval battles would be fought at a range of only a couple of thousand metres. The advent of steam power meant that ships were no longer restricted in manoeuvring by wind direction and had led to a belief that it would be possible to steer into enemy ships. Rams turned out to be a handicap in retrospect, as several warships were accidentally sunk by them – for example
by in 1875, and by in 1893. Whilst this showed the considerable potency of a ram, it also demonstrated the inadequate manoeuvring characteristics of many of the ships equipped with them. The ram was designed to be removable to avoid damage during accidental collisions, but although other ships customarily carried theirs detached, Inflexible seems to have kept hers in place. The ram was a solid iron forging supported by an extension of the armoured deck which turned downwards behind it.

On completion the ship was sent to join the Mediterranean squadron. She took part in the bombardment of Alexandria on 11 July 1882 during the Urabi Revolt, firing 88 shells

She was refitted in Portsmouth in 1885, when the full sailing rig was removed. She was in the Fleet Reserve until 1890, except for brief service in the 1887 review and the manoeuvres of 1889 and 1890. She was re commissioned for the Mediterranean Fleet from 1890 to 1893, serving thereafter as Portsmouth guard ship until 1897. From there she went to Fleet Reserve, and in April 1902 to Dockyard Reserve, until sold at Chatham in 1903 for scrap.