Shōkaku (, "Soaring Crane") was the lead ship of her class of two aircraft carriers built for the Imperial Japanese Navy (IJN) shortly before the Pacific War. Along with her sister ship , she took part in several key naval battles during the war, including the attack on Pearl Harbor, the Battle of the Coral Sea, and the Battle of the Santa Cruz Islands, before being torpedoed and sunk by the U.S. submarine at the Battle of the Philippine Sea.
Design
The Shōkaku-class carriers were part of the same program that also included the s. No longer restricted by the provisions of the Washington Naval Treaty, which expired in December 1936, the Imperial Japanese Navy (IJN) was free to incorporate all those features they deemed most desirable in an aircraft carrier, namely high speed, a long radius of action, heavy protection and a large aircraft capacity. Shōkaku was laid down at Yokosuka Dockyard on 12 December 1937, launched on 1 June 1939, and commissioned on 8 August 1941.
With an efficient modern design, a displacement of about , and a top speed of , Shōkaku could carry 70–80 aircraft. Her enhanced protection compared favorably to that of contemporary Allied aircraft carriers and enabled Shōkaku to survive serious damage during the battles of the Coral Sea and Santa Cruz.
Hull
In appearance, Shōkaku resembled an enlarged , though with a longer overall length, wider beam and a larger island. As in Hiryū, the forecastle was raised to the level of the upper hangar deck to improve seakeeping. She also had a wider, more rounded and heavily flared bow which kept the flight deck dry in most sea conditions.
The carrier's forefoot was of the newly developed bulbous type, sometimes referred to informally as a Taylor pear, which served to reduce the hull's underwater drag within a given range of speeds, improving both the ship's speed and endurance. Unlike the larger bulbous forefeet fitted to the battleships and , however, Shōkakus did not protrude beyond the ship's stem.
Shōkaku was 10,000 tons heavier than , mainly due to the extra armor incorporated into the ship's design. Vertical protection consisted of on the main armor deck over the machinery, magazines and aviation fuel tanks, while horizontal protection consisted of along the waterline belt abreast the machinery spaces, reducing to outboard of the magazines.
Shōkaku normally stowed 150,000 gallons of avgas for operational use. Unlike British carriers, whose aviation fuel was stored in separate cylinders or coffer-dams surrounded by seawater, all pre-war Japanese carriers had their aviation fuel tanks built integral with the ship's hull, and Shōkaku was no exception. The dangers this posed, however, did not become evident until wartime experience demonstrated these were often prone to cracking and leaking as the shocks and stresses of hits or near-misses to the carrier's hull were inevitably transferred to and absorbed by the fuel tanks. Following the debacle at Midway in mid-1942, the empty air spaces around Shōkakus aviation fuel tanks, normally pumped full of inert carbon dioxide, were instead filled with concrete in an attempt to protect them from possible damage. But this did little to prevent volatile fumes spreading to the hangar decks in the event damage did occur, particularly demonstrated when Cavalla torpedoed and sank her.
Machinery
The geared turbines installed on Shōkaku were essentially the same as those on Sōryū, maximum power increasing by to . In spite of all the additional armor, greater displacement and a increase in draught, Shōkaku was able to attain a speed of just over during trials. Maximum fuel bunkerage was 4100 tons, giving her a radius of action of at . Two same-sized downward-curving funnels on the ship's starboard side, just abaft the island, vented exhaust gases horizontally from the boilers and were sufficiently angled to keep the flight deck free of smoke in most wind conditions.
Flight deck and hangars
Shōkakus long wood-planked flight deck ended short of the ship's bow and, just barely, short of the stern. It was supported by four steel pillars forward of the hangar box and by two pillars aft.
The flight deck and both hangars (upper and lower) were serviced by three elevators, the largest being the forward one at by , the middle and the rear elevators measured by . All three were capable of transferring aircraft weighing up to and raising or lowering them took approximately 15–20 seconds.