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Swiftsure-class ironclad
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The Swiftsure-class ironclads consisted of two central-battery ships built for the Royal Navy (RN) during the 1870s, HMS Swiftsure and HMS Triumph. They were specifically designed for service as flagships on the Pacific Station where coal was very expensive and they needed to minimize their use of coal by using their sails as often as possible.
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Background and description
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The Swiftsure class was designed by Edward Reed, the Chief Constructor of the RN. The ships were second-class ironclads intended for the Pacific Station[1] where coal was very expensive so the ships' sailing qualities had to be equal to their performance under steam. The lines of the hull were based on that of the Defence class, albeit with the latter's plough-shaped bow was replaced by the pointed ram bow of the Audacious class.[2] The shape of the stern was also modified with a narrower, elliptical shape.[3] The RN had discovered that biofouling was worse on iron hulls than on wooden ones[1] and without a British-controlled dockyard available on the station until Esquimalt was completed in 1886 to clean the hull, Reed was forced to sheath the hull of the Swiftsures with 6 inches (15 cm) of wooden which was covered with copper as the electrolytic effect between copper and iron prevented the copper from being directly attached to the iron hull.[4]
The ships were 280 feet (85.3 m) long between perpendiculars, a beam of 55 feet (16.8 m) and had a draught of 25 feet (7.6 m). The Swiftsure-class ships displaced 6,640–6,910 long tons (6,750–7,020 t) and had a tonnage of 3,893 tons burthen.[5] They had a complement of 450 officers and ratings.[1]
The ships were fitted wuth a single two-cylinder, horizontal-return, connecting-rod steam engine built by Maudslay, Sons and Field that was rated at 800 nominal horsepower. It drove the shaft of the 23-foot-6-inch (7.16 m) propeller[6] using steam provided by six rectangular fire-tube boilers.[1] Swiftsure reached a speed of 13.8 knots (25.6 km/h; 15.9 mph) from 4,913 indicated horsepower (3,664 kW) during her sea trials while Triumph made 13.5 knots (25.0 km/h; 15.5 mph) from 5,114 indicated horsepower (3,814 kW) during hers. They carried 540–550 long tons (550–560 t) of coal to give them ranges of 1,640–1,680 nautical miles (3,040–3,110 km; 1,890–1,930 mi) at 10 knots (19 km/h; 12 mph).[5]
The Swiftsure class was initially ship-rigged with three masts and had a sail area of 32,900 square feet (3,060 m2), excluding stunsails. Around 1877–1878 they were re-rigged as barques with their sail area reduced to 22,750 square feet (2,114 m2). To reduce drag, the funnel was telescopic and could be lowered and the propeller could be hoisted into the hull.[6] Under sail alone, they could reach 12.5 knots (23.2 km/h; 14.4 mph).[5]
Armament and armour
The main battery of the Swiftsure-class ships consisted of 10 RML 9-inch (229 mm) rifled muzzle-loading guns. Six of these were positioned on the main deck, three on each broadside, and the other four guns were mounted on the corners of the upper deck box battery. The battery protruded over the sides of the ships to give the guns a certain amount of end-on fire.[7] The shell of the nine-inch gun weighed 254 pounds (115.2 kg) while the gun itself weighed 12 long tons (12 t). It had a muzzle velocity of 1,420 ft/s (430 m/s) and was rated with the ability to penetrate 11.3 inches (287 mm) of wrought-iron armour at the muzzle.[8]
The ships were equipped with four RML 6 in (152 mm) (71 cwt)[Note 1] guns as chase guns, two in the bow and another pair in the stern.[5] They fired a 64-pound (29.0 kg), 6.3-inch (160 mm) shell.[8] They also had six RBL 20-pounder (3.75 in (95 mm)) rifled breech-loading guns that were used as saluting guns.[5] In 1878, the ships received four 14-inch (356 mm) torpedo launchers on the main deck and the 6-inch guns were replaced by four breech-loading BL 5-inch guns during the mid-1880s.[1][7]
The wrought-iron, waterline armour belt of the Swiftsure class covered the entire length of the ships. It was eight inches (203 mm) thick amidships, backed by 8–10 inches (203–254 mm) of teak, and thinned to six inches towards the ends of the ships. The main deck citadel's ends were protected by a 5-inch (127 mm) forward bulkhead and a 4-inch (102 mm) one aft. The sides and embrasures of the upper battery were 6 inches thick, but its ends were unprotected. The ships also had a one-man conning tower with walls 3 inches (76 mm) thick.[9]
The intention was to make the ships good performers under sail, while at the same time being stable ships and good gun platforms. At the design stage it had been suggested by the Committee on Designs that the ships should be built with their artillery mounted in two turrets, with some smaller guns positioned fore and aft. As there was at that time not sufficient experience with turret-mounted armament, and none at all with turrets in first-class battleships, the idea did not find favour and this class was completed with a broadside box battery deployed on two levels, on the main and on the upper deck.
All ranks were berthed on the main deck; berthing for seamen in previous classes had been on the lower deck. As the officers' accommodation was well ventilated and well lit, the ships were universally popular.
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Ships
Service history
The two ships spent some time in reserve, but in their active careers they took turns as flagship of the Pacific station.
Notes
- "Cwt" is the abbreviation for hundredweight, 71 cwt referring to the weight of the gun.
Citations
References
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