Iron Duke class battleship
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| Missing image HMS_Iron_Duke_(1912).jpg HMS Iron Duke | |
| General Characteristics | 
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| Displacement: | 25,000 tons (normal), 29,500 deep load |
| Length: | 622 feet 9 inches |
| Beam: | 90 feet |
| Draught: | 32 feet 9 inches |
| Propulsion: | 4 shaft Parsons Turbines, driving four propellers, 18 Babcock & Wilcox or Yarrow boilers delivering 29,000 hp |
| Speed: | 21.25 knots |
| Range: | 14,000 nm at 10 knots |
| Complement: | 925 |
| Armament: | Main battery: ten 13.5"/45 guns in five twin turrets Secondary battery: twelve 6"/45 guns in single casemate mountings; two 3"/20 anti-aircraft guns |
The Iron Duke class battleships of the Royal Navy were four battleships, Benbow, Emperor of India, Iron Duke, and Marlborough. Launched from October 1912 to November 1913, this fourth class of Royal Navy super-dreadnoughts had the same ten 13.5" guns in five centerline twin turrets as before.
They were essentially King George V-class battleships with improved armour and an improved secondary armament of 6-in weapons instead of 4-in. The underwater protection scheme relied on an incomplete torpedo bulkhead, with coal bunkers protecting those areas that lacked a bulkhead. This makes an intersting comparison to the corresponding German design, which employed a complete torpedo bulkhead.
The move to 6-in guns had been necessary for some time because of the growing size of destroyers, but had been impossible until Admiral Fisher, with his preference for a purely all-big-gun armament, had left the Admiralty. The secondary armament was well disposed except for 4 guns mounted low in the stern, in the innovative but incorrect belief that destroyers would be silhouetted against the horizon - these gun positions were eventually plated over. (An alternate perspective on the value of a large secondary battery is provided by several authors and commentators, who argue that the 6-inch battery in these ships consumed 2000 tons of displacement; were worthless in battle; were important holes in the side subject to flooding; were poorly-armoured pathways through which a ship-crippling secondary magazine explosion might be triggered; and medium-calibre weapons could have been carried much more cheaply and effectively on smaller screening vessels).
Although they were designed for the 21-knot battle line as before, they became overloaded and by the end of the war, struggled to maintain station and apparently did not often steam at more than 19 knots. However, naval opinion was that they were a successful design, and hardly less effective than the Revenge class of 2 years later.
The Iron Dukes were followed by the famous Queen Elizabeth's.
Benbow, Iron Duke and Marlborough participated in the battle of Jutland. Emperor of India was sunk as a target ship in 1931, Benbow was sold for scrap in 1929, and Marlborough was sold for scrap in 1932. Iron Duke survived the longest after being converted to a training ship as the result of the Washington Naval Treaty, and was sold for scrap in 1946.
| Iron Duke-class battleship |
| Iron Duke | Marlborough | Benbow | Emperor of India |
| List of battleships of the Royal Navy |