Imperial Japanese Battleship Aki
Semi-Dreadnought of 1911
Bristling with big guns, yet harmoniously designed, Aki cruises the picturesquely eroded coast of Japan. Click here for wider view.
Japan's first dreadnought battleships were to have been Satsuma and Aki, designed for an all-12" armament. These were also the first battleships to be built entirely in Japan. Satsuma was laid down at Yokosuka Naval Arsenal in 1906, completing 1910, and Aki was started at the Kure Naval Arsenal in 1907. However, Aki's gestation was dilated by some 10 months because fitting out facilities and machinery were allocated to the semi-dreadnought battlecruiser Tsukuba instead. Compromises were made in the ships' armament. It proved impossible to obtain so many 12" guns because the full-bore arms race had armaments manufacturers running behind. The newborn Dreadnought era had brought about a clamor for all-12" gunned battleships -- a clamor that was not limited to Europe alone. Therefore the Satsumas somewhat unwillingly were modified to carry only two 12" turrets along with a very stiff secondary armament of twelve 10" guns, all carried in twin turrets amidships as in the French Danton class or the British Lord Nelson class.
These two ships had some important differences. The Aki's builders took advantage of experience with her sister. The newer ship boasted twin Brown-Curtis turbine engines developing 28,710 hp (21,409 kW) for a speed of 20.5 kts, while her sister could only make 18.25 kts with reciprocating engines developing 17,300 shp (12,901 kW). Aki's armor was also somewhat stronger and her hull slightly enlarged compared to her sister. The two could be distinguished easily by their different funnel arrangements: Aki had three (a taller, oblong forefunnel and two large round ones), while Satsuma had only two (one large round one forward and a smaller, flattened after funnel), hinting at the profound differences below decks.
Plans and Specifications
6" shown here were actually 4.7". For enlarged schematic with key to armor thicknesses, click here.
Specifications for the Aki (where the 2 ships differ, Satsuma's figures are shown [in brackets]):
Dimensions: 450' x 83'7" x 27'6" LWL: 482' Displacement: 20,100 tons std; 21,800 tons deep laden. [Satsuma Displacement: 19,372 tons std; 19,700 tons deep laden.] Armament: (4) 12"/45 cal (2x2), (12) 10"/45 (6x2), (8) 4.7"/40, (3) 3"/40, and (4) 3"/28 guns; (5) submerged 18" torpedo tubes. Armor: Krupp Cemented type throughout. 9"/4" belt; 10" turrets, casemates, and conning tower; 9½"/7" barbettes; 3" deck. Fuel capacity: 3,000 tons of coal plus 172 tons bunker oil. [Satsuma: 1,200 tons of coal std; 2,860 tons maximum, plus 377 tons of bunker oil.] Propulsion: (20) coal-fired Miyabara boilers; (2) Brown-Curtis turbine engines developing 28,710 shp, shafted to twin screw. Maximum speed: 20.5 kts. [Satsuma: (20) coal-fired Miyabara boilers; 2-shaft inverted vertical triple expansion engines developing 17,300 shp; 18.25 kts.] Crew: 931 [Satsuma: 887.]
Metric specs:
Dimensions: 137.16m x 25.5m x 8.38m. LWL: 147m. Displacement: 20,100 tons std; 21,800 tons deep laden. [Satsuma Displacement: 19,372 tons std; 19,700 tons deep laden.] Armament: (4) 305 mm/45 cal (2x2), (12) 254 mm/45 (6x2), (8) 120 mm/40, (3) 76 mm/40, and (4) 76 mm/28 guns; (5) submerged 45 cm torpedo tubes. Armor: Krupp Cemented type throughout. 229/100 mm belt; 254 mm turrets, casemates; 254 mm conning tower; 240/180 mm barbettes; 76 mm deck. Fuel capacity: 3,000 tons of coal plus 172 tons bunker oil. [Satsuma: 1,200 tons of coal std; 2,860 tons maximum, plus 377 tons of bunker oil.] Propulsion: (15) coal-fired Miyabara boilers; (2) Brown-Curtis turbine engines developing 21,409 kW, shafted to twin screw. Maximum speed: 38 km/hr. [Satsuma: (20) coal-fired Miyabara boilers; 2-shaft inverted vertical triple expansion engines developing 12,901 kW; 33.8 km/hr.] Crew: 931 [Satsuma: 887.]
Wartime Duty
In WWI, both ships saw patrol duty. Satsuma took part in the Battle of Qingdao and the occupation of the Carolines. Aki had no combat experience. Her most exciting performance in the Great War was to run aground on a sandbar in Tokyo Bay in November 1914.
As a result of the Washington Naval Agreement, both ships were voluntarily destroyed by Japan. Satsuma was expended as a target, being sunk by gunfire from the newer dreadnoughts Kongo and Hyuga in Sept. 1924. She went to the bottom some 56 km NE of Miyake, an island south of Tokyo. Aki was decommissioned on Sept. 20, 1923 and also expended as a target for naval artillery. In a ceremony witnessed by Crown Prince (later Emperor) Hirohito and a clutch of Japanese military brass, the ship was sunk by 16" gunfire from the new Nagato and Mutsu off the Chiba coast on Sept. 9, 1924. However, some of her larger guns had been removed earlier. These were reused as coastal artillery around Tokyo Bay.
Some SatsumAki Snaps:
A Petite Portfolio
Aki burning up the course on trials in March 1911. Her turbine engines gave her a better than 2-knot advantage over her piston-engined sister ship. Click here for an awesome full-screen view -- YOU ARE THERE!
A more distant and less dramatic shot of Aki on trials, silhouetted against the light. Jane's Fighting Ships
Aki at anchor. Enlarge
Menacing and imperious, bristling with guns -- the Aki.
Satsuma in profile. Aside from the funnel arrangement, she seems nearly identical to her sister, but we know better.
Aki with aeroplane, the rising form of naval power that would soon eclipse the battleship.
