I-400 in 1:350 from Tamiya
The idea for these giant subs came from Admiral Yamamoto. The plan was to take the war to the US by bombing the cities along it's coasts with submarine launched aircraft. The sub would have to be big enough to carry enough fuel for the round trip Japan-US west coast and to carry at least two airplanes.
Just how big they were can be seen when you put the model of the I-400 beside the model of a Japanese destroyer and a german Typ VIIc U-boat in the same scale. They were the biggest subs built until the nuclear subs in the 1960's.
18 of these giants were ordered but only three were completed. The general idea of bombing the US west coast was later changed to a plan to bomb the locks of the Panama Canal. As the US forces came nearer to Japan the plan was again changed, the new target being the naval base at Ulithi.
Japan surrendered before the attack could be made and the US took over the boats and of course studied them thoroughly. The living conditions for the crew were appalling. Some 150 men were cramped together without neither air conditioning nor cold storage for food. When decontaminated after the surrender, some 25 buckets of dead rats were removed.
In order to prevent the soviets from learning from the subs they were sunk as target practice for new torpedoes.
Tamiya's kit is excellent, really a shake and bake kit. I built it basically from the box, only adding some PE from the spares box. In order to make the display a bit educational I put one plane in the hangar opening, one on the catapult and one flying.
Tamiya' painting guide is wrong though. The subs were not painted with anti fouling paint below the waterline. Instead thy were covered with a rubber compound designed to make them harder to detect with sonars. I tried to depict that by painting the underwater hull brownish green to make it look like it was overgrown with algae.