Japanese Aircraft Carrier Shinano - Design and Construction

Design and Construction

Shinano was initially designed as the third Yamato-class battleship with her keel being laid down in June 1940 at the Yokosuka Naval Dockyard. Named after the ancient Shinano Province, the vessel would have been one of the three largest battleships ever constructed. In mid-1941, construction on Shinano's hull was temporarily suspended so as to allow personnel and equipment to be utilized for other naval projects in response to approaching hostilities. Had she been completed as a battleship, her armament and armor would have been nearly identical to that of her sister ships Yamato and Musashi.

As with Yamato and Musashi, Shinano's existence was kept a closely guarded secret. A tall fence was erected on three sides of the graving dock and those working on the conversion were confined to the yard compound. Serious punishment—up to and including death—awaited anyone who breathed a word about Japan's new carrier. As a result, Shinano was the only major warship built in the 20th century never to have been officially photographed during its construction. Only a single photograph is known to exist of the ship, taken by a civilian photographic technician aboard a harbor tug during Shinano's initial sea trials in Tokyo Bay on 11 November 1944.

Following Japan's disastrous loss of four fleet carriers at the Battle of Midway in June 1942, the decision was made to convert Shinano's unfinished hull into an aircraft carrier. Fortuitously, her hull was only 45 percent complete by that time, with structural work complete up to the lower deck and only major machinery parts installed. Conversion planning began that same month under the direction of Vice Admiral Keiji Fukuda of the Imperial Japanese Navy Technical Department (or Kampon).

Shinano's launch on 8 October 1944 was marred by what some considered an ill-omened accident. During the floating-out procedure, one of the caissons at the end of the dock unexpectedly lifted as the water rose to the level of the harbor (no one had checked to ensure that all the caissons were properly ballasted with seawater). The sudden inrush of water into the graving dock pushed the carrier into the forward end, damaging the bow structure below the waterline and necessitating another dry-dock for repairs. These were completed by 26 October. With a full-load displacement of 72,000 long tons (73,000 t), Shinano was the largest aircraft carrier yet built, a record she would hold until the 80,000 long tons (81,000 t) USS Forrestal was launched in 1954.

Shinano was primarily designed as a support carrier, with extensive facilities for aircraft repair and refitting. Shinano herself was intended to have a small fighter complement for defensive purposes, but was not intended to act as a fleet carrier despite her size; instead, she was to carry reserve aircraft, fuel and ordnance in support of carrier task forces. Shinano was officially launched on 8 October 1944, with Captain Toshio Abe in overall command of the vessel.