Tamiya 1/350 I-400

I made this kit a few years ago now; but only now have taken its picture. It's Tamiya's I-400 kit. The I-400/I-401 are fairly famous (I mean I saw a comprehensive documentary on them out of PBS), so I'll skip the info dump this time. 

Just for context, the Imperial Japanese Navy (IJN) had some exceptionally large submarines, as the expected combat zone was the entirety of the Pacific Ocean. The Japanese warmed up to the aircraft-carrying subs for a few reasons. First, some of their submarine classes were large simply because they were built for trans-pacific operations. Second, for those finding things in the Pacific reasons, the idea of scout aircraft was seen as sensible, regardless of what job the submarine was assigned to. The Japanese were also really good at submarines, and really good at aircraft carriers, so making it practical came much easier. Finally, the Japanese were also the people who made floatplane versions of their fighters to operate air cover in remote Pacific islands, so clearly they were just willing to give it a whirl. You can see this wiki list for the full deets, but Japan not only had one-off aircraft carrying submarines, it has several production classes of them. Most carried one or two float-planes. In addition to scouting, they got up to some stuff as well: a submarine launched aircraft became the only Axis warplane to bomb north America (twice!) and this was repeated over Wellington, NZ, and Sydney, Australia. 

Despite Nazi Germany's efforts, the true Amerika bomber was a two seat floatplane. 

The B-class submarines, the most common type carrying aircraft went through three iterations with the B1s commissioning 20 hulls, the B2s commissioning 6, and the B3/4 series commissioning 3.

Two shots post-surrender to the Americans. The aircraft hanger attracted a lot of attention.

 

The 800 pound gorilla of aircraft carrying submarines in a few ways is the I-400 class. Admiral Yamamoto might have crafted his crushing victory at Pearl Harbor and then his crushing defeat at Midway, but he at least got the war with the United States was a long-shot that was going to require some risky bets. One of these was the I-400 series. As conceived, the I-400 class would carry three modern floatplanes in its hanger. Possessing a global spanning range, these submarines would sail to distant shores where defenses would be light, then strike at strategic targets of the enemy. Yamamoto thought that having a fleet of 18 of these massive submarines would give the Imperial Japanese Navy a truly incredible wildcard - the ability to strike anywhere the ocean touched with the equivalent of a fleet carrier's worth of aircraft.

The I-400. (The hanger being transparent on one side is a kit detail.)

 It should be said that this idea was profound. Previously, submarines were either fleet assets or merchant raiders. Being able to damage the enemy's ability to make war directly was a strategic attack, not a tactical one, and one that would change the world post war.

The I-400  next to a Mk.7 German U-boat.

So the Japanese started work on some hecka chonk'in submarines. Put it this way: The Mk. VII U-boat displaced 769 tons surfaced and 871 tons submerged, was 67 m (220 ft) long, and sailed with 40-50 crew. The fleet submarine that the USN used to blockade Japan was the Gato class. It displaced 1500 tons surfaced and 2500 tons submerged, was 95 m (311 ft) long, and sailed with 60 crew. The I-400 series displaced 6,600 tons, was 122 m (400 ft) long, and sailed with 144 officers and men. To put it another way, the I-400 series was longer than a Fletcher class destroyer, but displaced three times what the Fletcher class did when submerged. The sub could also boast snorkels and sound-deadening tiles. The sub had a test depth of 100m, making her another submarine that could in theory reach her test depth with her stern still on the surface. She had dual pressure hulls in a figure-8 arrangement, sitting side by side. This was necessary to give the stability needed to sit a large, heavy aircraft hanger atop the main hull. 

It's a bit hard to make out, but I added the ribs of the hanger. 

It's aircraft and facilities were similarly advanced. The aircraft designed for the subs, the Aichi M6A Seiran (storm from a clear sky) was a sleek floatplane that could carry bombs or heavy torpedoes. Carried three to a sub, these aircraft could unfold, be armed by deck crew, and be flung into the sky by a compressed air catapult in half an hour. A system borrowed from the stillborn German aircraft carrier Graf Zeppelin allowed prewarming of the Seiran's engine oil, so time did not have to be spent warming the aircraft up. (Because of the challenges of taking off, piston engine aircraft are warmed up on the deck to make sure they are limber for having the throttles pinned for takeoff.) One final note: the aircraft could optionally launch without floats. The aircraft could of course return to ditch by the submarine, but by the time I-400 and I-401 were being launched, kamikaze missions were quite normal. 

With one Aircraft fully assembled. There's a assembly/loading crane that collapses into the deck, as well as a big radio aerial that I left reteacted, though if she was getting ready to launch aircraft, both of those would be visible. 

The conning tower was asymmetric to the hanger, I'm guessing so the plumbing of the periscopes, snorkel, etc could be easily connected to the hull. This meant that when submerged, the sub would drift to the left.  

The bow. The eight torpedo tubes fired the 'long lance' navel torpedo, the best torpedo of the Second World War. I think I lost the original anchor, and a 1/700 Kaga Aircraft Carrier I built donated one.

As a sub that might get caught on the surface, it had a heavy AA armament. 

Closeup of the open aircraft hatch. You may wonder how the aircraft came out of there. The restriction is ultimately the propeller, but you can make everything else fold. 

Example Serins. 

The wings fold, the tail has sections that fold. 

The pontoons come out of small hatches in front of the hanger.

Two additional aircraft are snug in the hanger. 

Now all you have to do is sail across the Pacific undetected!

When this idea was conceived, only the Japanese had perfected coordinated strikes from multiple carrier decks, so the idea is that 18 subs launch 54 aircraft was not farfetched. The first target for the sub fleet was going to be the locks at either end of Lake Gatun, the artificial lake at the top of the Panama Canal. If they were destroyed, the lake would drain, and it would take six months before the canal was usable again. One unlucky American soldier who had been stationed in the Canal zone who'd later been captured and tortured had given the Japanese a great deal of useful intel on canal defenses.

As y'all know, this didn't happen. It was the summer of 1945 when two submarines had been made operational. By then, it was judged that knocking out the Panama canal would do little to improve Japan's military situation. At the highest levels of command, there was a second mission discussed. Thanks to the Imperial Japanese Army's fucking horrific biowarface research, Japan had viable biological weapons. It was suggested that these subs be used to infest LA or San Fransisco with anthrax-carrying fleas or similar. This was not done, thankfully, though why not is controversial. I've read a quote on the internet that ultimately they decided further escalation in this already extraordinarily nasty war was the last thing needed. It could also be that the IJN hated the idea of using the IJA's weapon so much they nixed the idea, and if that sounds weird, you should know that the IJN and IJA spent the 1930s and World War 2 so hostile to each other that you could describe it as a low grade civil war.

So, the two I-400s reassigned to attack the main staging atoll the U.S. Navy was using in its invasion of Okinawa. (A third I-400 class had been completed as a blockade runner, but was not commissioned by the war's end.) The flight crews of the two subs were told on the way that 1) I guess the brass decided y'all are Kamikaze pilots, and 2) we're going to repaint the aircraft in American colors for you to sneak in for maximum effect. This second part was a war crime, and strenuously objected to by the flight crews, who considered such a move dishonorable. The atomic bombings fortunately happened during this voyage, and both subs surrendered to the Americans, who up until the point they appeared had no clue that the subs existed. Both were studied extensively by the US Navy, which informed their attempts at putting missiles on subs. Both were eventually scuttled in deep water to keep them out of the hands of the Soviets, who via the Japanese surrender document had some legal claim to at least examine the subs. 

One Seiran still exists, brought back to the United States, it was restored and now sits in the Smithsonian's aviation museum. If you go there and see it, know it is the end on a very wild story.