was an armored cruiser (Sōkō jun'yōkan) built for the Imperial Japanese Navy (IJN) in the late 1890s. As Japan lacked the industrial capacity to build such warships herself, the ship was built in Germany. She participated in most of the naval battles of the Russo-Japanese War of 1904–05, and was lightly damaged during the Battle of the Yellow Sea and the Battle of Tsushima. Yakumo saw no combat during World War I and began the first of many training cruises in 1917, although she was not officially reclassified as a training ship until 1931. Her last training cruise was in 1939, but the ship continued to conduct training in home waters throughout the Pacific War. Yakumo became a repatriation transport after the war and was broken up in 1946–47.
Background and design
The 1896 Naval Expansion Plan was made after the First Sino-Japanese War, and included four armored cruisers in addition to four more battleships, all of which had to be ordered from overseas shipyards as Japan lacked the capability to build them itself. Further consideration of the Russian building program caused the IJN to believe that the battleships ordered under the original plan would not be sufficient to counter the Imperial Russian Navy. Budgetary limitations prevented ordering more battleships, and the IJN decided to expand the number of more affordable armored cruisers to be ordered from four to six ships, believing that the recent introduction of tougher Krupp cemented armor would allow them to stand in the line of battle. The revised plan is commonly known as the "Six-Six Fleet". The first four ships were built by Armstrong Whitworth in the United Kingdom, but the last two ships were built in Germany and France. To ensure ammunition compatibility, the IJN required their builders to use the same British guns as the other four ships. In general, the IJN provided only a sketch design and specifications that each builder had to comply with; otherwise each builder was free to build the ships as they saw fit. Unlike most of their contemporaries which were designed for commerce raiding or to defend colonies and trade routes, Yakumo and her half-sisters were intended as fleet scouts and to be employed in the battleline.
Description
The ship was long overall and between perpendiculars. She had a beam of and had an average draft of . Yakumo displaced at normal load and at deep load. The ship had a metacentric height of . She had a double bottom and her hull was subdivided into 247 watertight compartments. Her crew consisted of 670 officers and enlisted men.
Yakumo had two 4-cylinder triple-expansion steam engines, each driving a single propeller shaft. Steam for the engines was provided by 24 Belleville boilers and the engines were rated at a total of . The ship had a designed speed of and reached during her sea trials from . She carried up to of coal and could steam for at a speed of .
Armament
The main armament for all of the "Six-Six Fleet" armored cruisers was four Armstrong Whitworth-built 45-caliber eight-inch guns in twin-gun turrets fore and aft of the superstructure. The electrically operated turrets were capable of 130° rotation left and right, and the guns could be elevated to +30° and depressed to −5°. The turret accommodated 65 shells, but could only be reloaded through doors in the turret floor and the ship's deck that allowed the electric winch in the turret to hoist shells up from the shell room deep in the hull. The ship carried a total of 320 eight-inch shells. The guns were manually loaded and had a rate of fire about 1.2 rounds per minute. The 203-millimeter gun fired armor-piercing (AP) projectiles at a muzzle velocity of to a range of .
The secondary armament consisted of a dozen Elswick Ordnance Company "Pattern Z" quick-firing (QF), 40-caliber, 6-inch guns. Only four of these guns were not mounted in armored casemates on the main and upper decks, and their mounts on the upper deck were protected by gun shields. Their AP shells were fired at a muzzle velocity of . The guns were provided with 150 rounds each. Yakumo was also equipped with a dozen 40-caliber QF 12-pounder 12-cwt guns and eight QF 2.5-pounder Yamauchi guns as close-range defense against torpedo boats. The former gun fired , projectiles at a muzzle velocity of .
Yakumo was equipped with five torpedo tubes, one above water in the bow and four submerged tubes, two on each broadside. The Type 30 torpedo had a warhead and three range/speed settings: at , at or at .