Japanese aircraft carrier Shinano

Shinano (信濃) ?), named after the ancient Shinano Province, was an aircraft carrier of the Imperial Japanese Navy during World War II. Initially laid down as the third of the Yamato-class battleships, Shinano's partially complete hull was converted to an aircraft carrier in 1942, midway through construction. Over the next two years, Shinano was heavily modified to act as a large support carrier. When completed, she had a full-load displacement of 72,000 long tons (73,000 t), the largest aircraft carrier ever built at the time.

Commissioned in November 1944, Shinano was to transfer from the Yokosuka Naval Shipyard to Kure Naval Base to complete her outfitting and transfer a load of 100 Yokosuka MXY7 Ohka rocket-propelled kamikaze aircraft. While en route, Shinano was sunk by the American submarine USS Archer-Fish 10 days after her commissioning by only 4 torpedoes, due to the fact that no pumps and underwater doors were installed yet. {| class="toc" id="toc"

Contents
[hide] *1 Design and construction
 * 1.1 Hull
 * 1.2 Machinery
 * 1.3 Flight deck & hangar
 * 1.4 Armament
 * 1.5 Aircraft
 * 2 Commissioning and sinking
 * 3 Post-war analysis of the sinking
 * 4 See also
 * 5 Footnotes
 * 6 References
 * 7 External links
 * }

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 .[4]

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.[5]

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).[6]

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.[7] These were completed by 26 October. With a full-load displacement of 72,000 long tons (73,000 t),[3] Shinano was the largest aircraft carrier ever built, a record she would hold until the 80,000 long tons (81,000 t) USS Forrestal was launched in 1954.[8]

Shinano was primarily designed as a support carrier, with extensive facilities for aircraft repair and refitting.[8] 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;[3] instead, she was to carry reserve aircraft, fuel and ordnance in support of carrier task forces.[2] Shinano was officially launched on 8 October 1944, with Captain Toshio Abe in overall command of the vessel.

Hull
While the ship's original 410 mm (16 in) belt armor was halved to 205 mm (8.1 in), the armor over the machinery and magazine spaces, ranging from 102 mm (4.0 in) to 190 mm (7.5 in), was retained, forming the floor of the hangar deck. Large bulges on either side of the hull, below the waterline, provided the main defense against torpedoes, backed up by an armored bulkhead attached to and extending down from the belt armor; the bulkhead was intended to prevent splinters from piercing the main hull and, though not water-tight, was backed by a second one which was.[9]

Machinery
Shinano's 150,000 shp (110,000 kW) steam turbines, fed by 12 boilers, were of the same type as installed on Yamato. With greater fuel oil bunkerage than she would have had as a battleship, the carrier had a calculated cruising range of 10,000 miles (16,000 km) at 18 knots (33 km/h; 21 mph).[10]

Flight deck & hangar
Given the destruction wrought by American dive bombers at Midway, naval architect Fukuda opted to provide Shinano with an armored flight deck, capable of withstanding the impact of 454 kg (1,000 lb) bombs, the largest in the arsenal of the United States Navy at that time that could be carried by dive bombers.[1] The deck consisted of a 96 mm (3.8 in) layer of steel under which was a second layer of 19 mm (0.75 in) steel plate. The 840 mm (33 in) void between these two layers was reinforced with I-beams and the spaces between the beams filled with a composite mixture of cement, sawdust and latex.[11]

Shinano's armored flight deck copied British practice as seen in their Illustrious-class carriers but, whereas the hangars on British carriers formed an armored box with sides equal in width to the flight deck armor, the Japanese provided only an armored lid with unarmored sides.

Due to the great weight of Shinano's flight deck armor, only a single aircraft hangar could be built atop the hull in order to maintain adequate stability. The hangar was 163 m (535 ft) long, 5.08 m (16.7 ft) high and 33.8 m (111 ft) wide, tapering down to just 20.08 m (65.9 ft) fore and aft due to the sheer of the hull.[10]

The new design for Shinano gave her hangar decks a lot of open space to facilitate jettisoning aircraft and ordnance in case of need, and her amidships belt armor was lightened somewhat.[7] <sup class="reference" id="cite_ref-Preston91_7-2">[8] Special attention was given to the on board gasoline tanks, even though built to withstand a 155mm shell. Many lessons had been learned from the loss of the carrier Taihō, on which Shinano´s flight deck would be modeled, which showed the fuel tank arrangement to be faulty. Torpedo hits in the vicinity could potentially permit gasoline vapors to leak beyond the cofferdam and there was also the worry of puncture by debris. Both of these worries were alleviated by pouring 2,400 metric tons of cement into the void spaces around the tanks as protection. Little else could be done due to the advanced state of construction. Another lesson from the Taiho resulted in the decision to install large ventilation fans on the hangar deck in case of damage to the gasoline system. Portable canvas wind scoops could also be rigged over the elevator opening to force more air inside.<sup class="reference" id="cite_ref-battleships_6-2">[7]

Armament
Shinano's primary defensive armament consisted of sixteen 127 mm (5.0 in) paired dual purpose guns mounted on projecting sponsons and arranged in eight batteries, four on either side of the flight deck.<sup class="reference" id="cite_ref-ShinanoClass_2-6">[3] Her close-range anti-aircraft armament was made up of 145 25 mm (0.98 in) Type 96 anti-aircraft guns,<sup class="reference" id="cite_ref-ShinanoClass_2-7">[3] and 336 127 mm (5.0 in) anti-aircraft rocket launchers in twelve 28-barrel turrets.<sup class="reference" id="cite_ref-Preston84-91_3-1">[4]

Aircraft
Shinano was also built to contain a maximum of 120 aircraft within her 265 m (869 ft) hull.<sup class="reference" id="cite_ref-Preston84-91_3-2">[4]

Commissioning and sinking
On 19 November 1944, Shinano was formally commissioned at Yokosuka, having spent the previous two weeks fitting out and performing minor trials.<sup class="reference" id="cite_ref-cfrecord_5-1">[6] By 1 October the crew had reported on board, 70 to 75 percent of which had no previous sea duty experience.<sup class="reference" id="cite_ref-battleships_6-3">[7] As a result of growing worry for her safety, due to a U.S. bomber fly-over, Japanese Naval Command ordered Shinano to Kure, where the remainder of her fitting-out would take place.<sup class="reference" id="cite_ref-cfrecord_5-2">[6] Naval Command wanted Shinano moved to Kure no later than 28 November. However, Abe asked for a delay in the sailing date. The majority of her watertight compartment doors had yet to be installed, the compartment air tests had not been conducted, and many holes for electrical cables, ventilation ducts and pipes had not been sealed.<sup class="reference" id="cite_ref-ShinanoClass_2-8">[3] Nor had the fire mains or drainage systems been completed as pumps had not been delivered.<sup class="reference" id="cite_ref-battleships_6-4">[7] He also wanted more time to train his new crew, and to give the crews of the destroyers a rest after returning from battle.<sup class="reference" id="cite_ref-SeaAssault_4-1">[5]

Abe's request was denied, and Shinano departed as scheduled at 18:00 on 28 November escorted by the destroyers  Isokaze ,  Yukikaze  and  Hamakaze . Abe commanded a crew of 2,176 officers and men. Also on board were 300 shipyard workers and 40 civilian employees. Watertight doors and hatches were left open for ease of access to machinery spaces, as were some manholes in the double and triple bottomed hull.<sup class="reference" id="cite_ref-battleships_6-5">[7] Abe would have preferred a daytime passage, but was unable to get Naval Command to provide air support; all available planes were needed for combat duty.<sup class="reference" id="cite_ref-Preston84_0-11">[1] <sup class="reference" id="cite_ref-SeaAssault_4-2">[5] She also carried six  Shinyo  suicide boats, and 50 Ohka suicide rockets.<sup class="reference" id="cite_ref-cfrecord_5-3">[6] Her orders were to go to Kure, where she would complete her fitting-out and commence to the Inland Sea after which Shinano was to take the Ohka east for "the relief of the Philippines".<sup class="reference" id="cite_ref-Reynolds284_11-0">[12] Abe was due to be promoted to rear admiral once Shinano completed her fitting-out, and take command of a fleet of attack carriers being built up in the east.<sup class="reference" id="cite_ref-SeaAssault_4-3">[5] Although Shinano was to act as a support carrier, she was also assigned her own air group, commanded by Lieutenant Commander Yoshio Shiga, a veteran of the attack on Pearl Harbor. Shiga's air group would have already been aboard when Shinano sortied for Kure, but four of the carrier's 12 boilers were not in service due to lack of parts. This cut her top speed from 27 kn (50 km/h; 31 mph) to 21 kn (39 km/h; 24 mph) — too slow for planes to launch without a headwind.<sup class="reference" id="cite_ref-SeaAssault_4-4">[5]

At 21:00, the American submarine USS Archer-Fish—commanded by Commander Joseph F. Enright—picked up Shinanos task group on her radar.<sup class="reference" id="cite_ref-Wheeler184_12-0">[13] Normally, Shinano would have been able to outrun Archer-Fish. However, the submarine was able to remain in pursuit of Shinano because the zig-zagging pattern of Shinano and her escorts—intended to avoid submarine attack—inadvertently turned the task group back into the sub's path on several occasions.<sup class="reference" id="cite_ref-SeaAssault_4-5">[5] <sup class="reference" id="cite_ref-Wheeler184_12-1">[13] Abe's zig-zagging was guided by his assumption that Archer-Fish was part of an American "wolfpack". He believed that Archer-Fish was being used as a decoy to lure away one of the escorting destroyers, allowing the rest of the pack a clear shot at Shinano. He actually ordered one of the destroyers to turn back when he spotted it trying to ram Archer-Fish, in part because he believed it left Shinano's bow exposed to an ambush.<sup class="reference" id="cite_ref-SeaAssault_4-6">[5] Additionally, Shinano was slowed because it was only running on four of her six operational boilers on two propeller shafts. Shinano was slowed further mid-pursuit after a bearing overheated one of the shafts, forcing a reduction in the propeller turns to reduce the operating RPMs of that engine. As a result, Shinano was forced to reduce its top speed to the same speed as most American subs.

On 29 November Abe was still worrying about the submarine spotted 48 hours earlier, and all three following destroyers kept changing course erratically. Once again the zig-zagging put Shinano into the path of Archer-Fish. At 3:05 am, Archer-Fish dived. Enright quickly moved Archer-Fish in front of the carrier group. However, just as Enright was about to loose his torpedoes, one of the destroyers on Shinano ' s starboard beam broke away and set course straight for Archer-Fish. Expecting depth charges, Enright ordered a descent to 62 feet, but the destroyer passed overhead seemingly unaware of them, after which Archer-Fish rose back to 60 feet. At 3:15 am, Archer-Fish fired six shallow-running torpedoes in sequence before diving to 400 feet to escape a depth charge attack from the escorts. Enright later said he set the torpedoes to run shallow in hopes of capsizing it.<sup class="reference" id="cite_ref-SeaAssault_4-7">[5]

Four of the six torpedoes found their mark. The first torpedo struck Shinano towards the stern, ripping through the hull into refrigerated areas and one of the empty aviation gasoline-storage tanks. The explosion also killed the sleeping engineering personnel in the compartments above. The second torpedo struck some 8 seconds after the first and 50 yards ahead into the starboard outboard propeller shaft, flooding the outboard engine-room. The third torpedo took out the No. 3 fireroom, killing every man on watch. The fourth and final torpedo detonated against the starboard air compressor room, flooding it and neighboring magazines while also rupturing the starboard oil-tank.<sup class="reference" id="cite_ref-SeaAssault_4-8">[5]

Abe quickly ordered a damage report and sounded battle stations. He initially thought Shinano had enough armor to withstand the damage, since American torpedoes had smaller warheads and fewer explosives than their Japanese counterparts. With this in mind, he ordered the navigator to maintain full speed. However, within minutes Shinano had already listed roughly 10 degrees to starboard. Archer-Fish ' s crew later reported seeing Shinano listing only minutes after the last torpedo hit. The executive officer later reported that only minutes after the last torpedo hit, he heard air rushing through gaps in the watertight doors which had been left untested before departure—a sign that seawater was rapidly entering the ship, proving the doors unfit.<sup class="reference" id="cite_ref-SeaAssault_4-9">[5] Though severe, the damage to Shinano was at first judged to be manageable, and the carrier continued under way.<sup class="reference" id="cite_ref-cfrecord_5-4">[6] The crew were confident in Shinano´s armor and its strength, which translated into lax efforts to save the ship initially.<sup class="reference" id="cite_ref-battleships_6-6">[7] Captain Abe ordered a change of course towards Shiono Point and for the ship to be righted by counter-flooding, which reduced the list to 7 degrees.<sup class="reference" id="cite_ref-SeaAssault_4-10">[5]

At dawn Shinano was still making 18 knots with the remaining boilers and machinery when the starboard boiler-room flooded completely and increased the list to 20 degrees, at which point the port trimming tanks valves rose above the waterline and became ineffective. Speed dropped to 10 knots and the port boiler rooms were ordered flooded in desperation, stemming the list momentarily before it continued.<sup class="reference" id="cite_ref-SeaAssault_4-11">[5] All efforts to control the flooding failed, in part because most of the crew was not well trained in damage control.<sup class="reference" id="cite_ref-SeaAssault_4-12">[5] No flooding boundaries were set up either, which would be the norm, and few portable pumps were available or properly used by the inexperienced crew.<sup class="reference" id="cite_ref-battleships_6-7">[7]

At 06:00, Shinano ' s boiler feed water was exhausted. At 7:45 am, she lost all power, and ceased all forward motion shortly afterward. Panic increasingly spread among the crew, who were also confused by the mix of civilian personnel in similar uniform who were "disobeying" orders given to them.<sup class="reference" id="cite_ref-battleships_6-8">[7] At 08:50, Captain Abe messaged the destroyers Hamakaze and Isokaze to take her in tow, to attempt beaching her on Cape Ushio. However, the two escorts only displaced 5,000 long tons (5,100 t) between them, not nearly enough to overcome the list. The first cables snapped under the strain from pulling the waterlogged ship, and the second attempt was aborted for fear of injury to the men.<sup class="reference" id="cite_ref-cfrecord_5-5">[6] <sup class="reference" id="cite_ref-SeaAssault_4-13">[5]

At 10:18, Abe gave the order to abandon ship; by this time Shinano was listing 30 degrees to starboard. As she heeled her flightdeck touched the water, which flowed into the open deck elevator; sucking mobs of sailors back into the ship as she sank. At 10:57 Shinano finally capsized and sank 200 km (110 nmi; 120 mi) southeast of Shingū( WikiMiniAtlas 32°0′N 137°0′E﻿ / ﻿32°N 137°E ﻿ / 32; 137), her stern slipping under first with the bow pointing skyward. She took 1,435 men and officers to their deaths, including Abe and both of his navigators. Rescued were 55 officers, 993 petty officers and men, plus 32 civilians for a total of 1,080 survivors.<sup class="reference" id="cite_ref-13">[14] The survivors of Shinano ' s sinking were quarantined in Japan for several months following her sinking.<sup class="reference" id="cite_ref-cfrecord_5-6">[6]

Post-war analysis of the sinking
Post-war analysis by the U.S. Naval Technical Mission to Japan claimed that Shinano had serious design flaws.<sup class="reference" id="cite_ref-14">[15] Specifically, the joint between the anti-projectile armor on the hull and the anti-torpedo bulge on the underwater body was poorly designed; Archer-Fish's torpedoes all exploded along this joint. Also, the force of the torpedo explosions dislodged an H-beam in one of the boiler rooms. The dislodged beam turned into a giant battering ram that punched a hole between two of the boiler rooms. In addition, the failure to test for watertightness played a role.<sup class="reference" id="cite_ref-TR27_15-0">[16] Survivors claimed that they were unable to control the flooding because the water poured in too fast; some claimed to have seen rivets between seams burst and allow water to surge through. The executive officer blamed the large amount of water that entered the ship so soon after the last hit on the failure to air-test the compartments. Additionally, the ship's list to starboard caused the pumping valves to rise above sea level, which would have made it impossible to counter-flood and right the ship even if they had worked properly.<sup class="reference" id="cite_ref-SeaAssault_4-14">[5]