Ibuki as of 1909:
![[ img ]](http://i.imgur.com/Uq1hlNT.png)
Kurama as of 1911:
![[ img ]](http://i.imgur.com/EXwrziQ.png)
The Ibuki-class ships were originally ordered during the Russo-Japanese War, on 31 January 1905, as Tsukuba-class armored cruisers. Before construction began, however, they were redesigned to incorporate 8-inch (203 mm) guns in four twin turrets rather than the dozen 6-inch (152 mm) guns in single mounts of the earlier ships. This required a larger hull to fit the turrets and thus more power from additional boilers to keep the same speed as the Tsukuba-class ships. These ships were given battleship-grade armament to overpower existing armored cruisers and were intended to fight in the battleline with battleships, much as had the two Kasuga-class armored cruisers had done in the Battles of the Yellow Sea and Tsushima during the Russo-Japanese War.
The ships had an overall length of 485 feet (147.8 m) and a length between perpendiculars of 450 feet (137.2 m), a beam of 75 feet 6 inches (23.0 m), and a normal draught of 26 feet 1 inch (8.0 m). They displaced 14,636 long tons (14,871 t) at normal load and 15,595 long tons (15,845 t) at full load.
Both ships were intended to be powered by vertical triple-expansion steam engines, but the long construction delays suffered by Ibuki made it possible for her to serve as a test-bed for the steam turbine. Four sets of Curtis turbines were ordered from the Fore River Shipbuilding Co., two each for Ibuki and the battleship Aki. Ibuki was equipped with two turbine sets, each driving one shaft, which developed a total of 24,000 shaft horsepower (18,000 kW), Kurama used the traditional pair of four-cylinder reciprocating steam engines with a power rating of 22,500 indicated horsepower (16,800 kW).
The Ibuki-class armored cruisers were armed with four 45-caliber 12-inch 41st Year Type guns, mounted in twin-gun hydraulically powered centreline turrets. The guns had an elevation range of −3°/+23° and normally loaded their rounds at an angle of +5°, although loading at any angle up to +13° was theoretically possible. They fired 850-pound (386 kg) projectiles at a muzzle velocity of 2,800 ft/s (850 m/s); this provided a maximum range of 24,000 yd (22,000 m) with armour-piercing (AP) shells. The intermediate armament was much heavier than the older ships, with four twin-gun turrets equipped with 45-calibre 8-inch 41st Year Type guns mounted on each side. The guns could be elevated to +30° which gave them a maximum range of around 23,000 yards (21,000 m). Their 254-pound (115 kg) projectiles were fired at a muzzle velocity of 2,495 ft/s (760 m/s).
Defense against torpedo boats was mainly provided by fourteen 40-caliber 4.7-inch 41st Year Type quick-firing (QF) guns, all but two of which were mounted in casemates in the sides of the hull. The gun fired a 45-pound (20 kg) shell at a muzzle velocity of 2,150 ft/s (660 m/s). The ships were also equipped with four 40-caliber 12-pounder 12 cwt QF guns and four 23-caliber 12-pounder QF guns on high-angle mounts. Both of these guns fired 12.5-pound (5.67 kg) shells with muzzle velocities of 2,300 ft/s (700 m/s) and 1,500 feet per second (450 m/s) respectively. In addition, the cruisers were fitted with three submerged 18-inch (457 mm) torpedo tubes, one on each broadside and one in the stern. Each tube was provided with one training torpedo and two normal torpedoes.
Construction of both ships was delayed by a lack of facilities at their shipyards, a shortage of appropriately trained workers and their low priority for building. Kurama 's lengthy building time at Yokosuka Naval Arsenal was slowed because priority was given to the building of the battleships Kawachi and Settsu and the repair and reconstruction of the ex-Russian ships captured after the Battle of Tsushima. Ibuki had to wait to have her keel laid until the slipway used by the battleship Aki became available after Aki was launched. Kure Naval Arsenal took advantage of the delay with Ibuki to stockpile material and components and set a record between keel-laying and launching of five months, a figure only bettered by Portsmouth Naval Dockyard when they built the battleship Dreadnought in only four months.
The development of the battlecruiser the year before Ibuki was completed made her and her sister ship Kurama obsolete before they were completed because the battlecruisers were much more heavily armed and faster. On 28 August 1912, the Ibukis were re-classified as battlecruisers. Both ships played a small role in World War I as they unsuccessfully hunted for the German East Asia Squadron and the commerce-raider SMS Emden and protected troop convoys in the Pacific Ocean shortly after the war began. The ships were sold for scrap in 1923 in accordance with the terms of the Washington Naval Treaty.
description courtesy of Wikipedia.
