page_title: HMS Illustrious (1896)
section_title: Design
hierarchical_section_title: HMS Illustrious (1896) / Design
caption_attribution_description: Right elevation and decks depicting British Majestic class battleship. Numbers on top diagram show armour thickness (shaded areas) in inches. Numbers on bottom diagram show size of guns in inches or shell weight.
context_page_description: The third HMS Illustrious of the British Royal Navy was a Majestic-class pre-dreadnought battleship. The ship was built at the Chatham Dockyard; her keel was laid down in March 1895, her completed hull was launched in September 1896, and she was commissioned into the fleet in April 1898. She was armed with a main battery of four 12-inch guns and a secondary battery of twelve 6-inch guns. The ship had a top speed of 16 knots.
  Illustrious was assigned to the Mediterranean Fleet until 1904. Transferred to the Channel Fleet she underwent a refit which was duly completed in early 1906. Rendered obsolete by the emergence of the new dreadnoughts, she served with the Home Fleet from 1908. One of the oldest battleships in the Royal Navy when World War I broke out, she served as a guard ship at various regions around Northern England until late 1915. Her main armament was removed and she then served as a store ship for the remainder of the war. She was decommissioned in 1919 and scrapped the following year.
context_section_description: Illustrious was 421 feet (128 m) long overall and had a beam of 75 ft (23 m) and a draft of 27 ft (8.2 m). She displaced up to 16,060 t (15,810 long tons) at full combat load. Her propulsion system consisted of two 3-cylinder triple expansion engines powered by eight coal-fired cylindrical boilers. By 1907–1908, she was re-boilered with oil-fired models. Her engines provided a top speed of 16 knots (30 km/h; 18 mph) at 10,000 indicated horsepower (7,500 kW). The Majestics were considered good seaboats with an easy roll and good steamers, although they suffered from high fuel consumption. She had a crew of 672 officers and ratings.
  The ship was armed with a main battery of four BL 12-inch Mk VIII guns in twin-gun turrets, one forward and one aft. The turrets were placed on circular barbettes, unlike six of her sisters, which retained earlier pear-shaped barbettes. Illustrious also carried a secondary battery of twelve QF 6-inch /40 guns. They were mounted in casemates in two gun decks amidships. She also carried sixteen QF 12-pounder guns and twelve QF 2-pounder guns for defence against torpedo boats. She was also equipped with five 18 in (457 mm) torpedo tubes, four of which were submerged in the ship's hull, with the last in a deck-mounted launcher. 
  Illustrious and the other ships of her class had 9 inches (229 mm) of Harvey armour, which allowed equal protection with less cost in weight compared to previous types of armour. This allowed Illustrious and her sisters to have a deeper and lighter belt than previous battleships without any loss in protection. The barbettes for the main battery were protected with 14 in (356 mm) of armour, and the conning tower had the same thickness of steel on the sides. The ship's armoured deck was 2.5 to 4.5 in (64 to 114 mm) thick.
caption: Right elevation, deck plan, and hull section as depicted in Brassey's Naval Annual 1902
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