When Shinano sailed only 4 of her 12 boilers were functional due to shortage of parts. This reduced her sped making it difficult to lunch her planes. Her sped was cut from 27 to 21 knots – too slow to launch without headwind.
Badly damaged, the carrier continued underway, but soon progressive flooding over the next few hours cause the carrier to list to starboard. Because of this the captain ordered 3 boiler rooms counter-flooded to compensate the listing. Then the carrier’s boiler feedwater system failed. All efforts to control flooding now failed in part because most of the crew was not well trained in damage control. (Remember our school of the boat)
By 0745 the carrier had lost all power and ceased forward motion. Two of her escorts tried to tow the carrier in an attempt to beach her – but failed. At 1018 the captain gave orders to abandon ship and was listing 30 degrees. At 1057 on 29 Nov. she capsized and sank taking 1,400 sailors and some civilian workers with her. The captain and navigator were among the dead.
Postwar analysis by the US Naval Technical Mission to Japan concluded that Shinano had serious design flaws. Specifically, the joint between the antiprojectile 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. 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 reported hearing large amounts of water entering the ship only minutes after the last torpedo hit, and blamed this 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'd worked properly
