The Panama Canal, through which all US
warships transiting from the Atlantic to the Pacific must pass, was the Achilles heel of
the US Navy, or so Admiral Yamamoto thought in 1942. The attack had to be covert- surface
warships would be sighted long before approaching Central America, so the vessel of choice
would be an immense submarine capable of stowing three modern fighter bombers that could
be launched near the target. Several of these subs could launch enough aircraft to
severely damage the canal and choke off US fleet deployment. That was the
theory. The subs required by the audacious weren't even completed until 1944 and by
that time the IJN was almost a spent force. These super-subs never fulfilled their
designed roles; its unclear if they actually fought at all. Two of them were captured
at war's end and eventually scuttled in US waters.
Overview
The IJN submarine I-400 is among the most intriguing subs of World War II. Not only
was it the largest submarine at 394' long and displaying 5,220 tons, the I-400
series also featured three advanced Aichi M6A1 Seiran fighter bomber aircraft, eight
torpedo tubes, and enough conventional weaponry to qualify as a light destroyer. Then
there is the I-400's distinctive appearance - bulging aircraft hanger bays
protruding from the huge superstructure, and the offset conning tower. In addition
there was a folding deck crane, snorkel rig, and radar. All in all the I-400 is a
fascinating subject and unique subject.
I acquired my Aoshima kit through sight unseen via an internet trade, so I
was unfamiliar with the kit's quality - or lack thereof. The box art is the best thing
about this kit, believe me. The quality of the parts ranges from acceptable to
wretched- the AA guns, crane and periscopes are the worst I've ever seen, but the hull is
not too bad, and the deck has some nice details. The floatplane is poorly molded with
an obvious seam line down the middle, but at least the shape is good. It was immediately
obvious that only the hull, deck and superstructure were usable. Everything else had to
go.
The inspiration, and believe me, you need inspiration to tackle this
Aoshima kit, was a local modeler who had scratchbuilt a 1/200 scale I-400. Even more
impressive than the quality of Paul Eisenberg's scratchbuilt I-400 was the fact that it
was done at all. I thought I was the only person interested in this beast.
The hull is split in two halves running bow to stern. The fit is
marginal, and when the deck is placed atop the hull, the first major problem arises - the
deck sits about a scale meter above the sides of the hull. There only solution (short
of not building the kit at all) is to sand the bottom of the deck part until it is less
than half a millimeter thick. I accomplished this by affixing 200 grit sandpaper to the
table and working the deck over it for about 30 minutes. Not very enjoyable but the huge
improvement in the deck's fit and appearance made it worthwhile. In order to check overall
appearance I tacked the superstructure to the deck. Hmm, still not right. The sub seemed
too low in the (imagined) water, so I fastened the waterline bottom plate, which adds
about 2 mm.
The superstructure was next. I wanted to show the sub
with an open hangar bay, so I removed the nose of the bay with a razor saw. The
remaining door piece was too stubby, so I glued some sheet styrene to the back of it, and
when dry, drilled out the inside of the hanger door with a mototool. While I was at it, I
ground away the inside of the hangar itself sufficiently to allow insertion of a rolled
lead foil tube.
Using a small drill bit I added numerous flooding holes to the hangar
door, and then added stretched sprue hinges. Now working now at the conning tower
level, the overly thick sides of the open bridge were thinned with the mototool. I
discarded the kit periscope assembly and made a more delicate piece from sheet plastic and
stretched sprue. Dry fitting the superstructure to the hull revealed a model that just did
not look right compared to the line drawing in Jentsura's Warships of the IJN. I took
proportional measurements of the drawing against the model and it became clear that
Aoshima calls for a superstructure placement that is nearly a centimeter too far
forward-that would be 7 meters on the real vessel! I repositioned and cemented
the superstructure to the deck with liquid glue. This necessitated my extending the
catapult a few millimeters; the floatplane obscures this extension. Ah, now it
was looking very proper.
The I-400 features a large snorkel conduit running down the starboard side
of the superstructure which I replicated with a bit of thin solder. I
fashioned a snorkel support housing from plastic bits. I wanted more density in the
in the vicinity of the superstructure, so I added thin wire handrails that run the
length of the hangar. Also placed in random spots are density bits such as small
squares and rectangles cut from resin flash. These represent panels and
hatches. Doors are photoetched items from Gold Medal. Moving towards the
stern, strakes were fashioned from styrene and glued aft of the 5.5" gun on both
sides. New aerial supports were made from sprue, and a small dorsal fin was
fabricated from plastic sheet.
In the bow area the dive planes were replaced with brass parts from a
Tom's Royal Navy sub set. Skywave anchors replaced the pathetic Aoshima
renderings. The floatplane crane was scratched from plastic and positioned stowed in
its deck slot. The railings come primarily from the Tom's sub set, with the exception
of the bow railings, which are cut down generic IJN railing.
Moving onto the guns, the 5.5" deck gun is a Skywave part from their
IJN gunset. The trio of triple 25mm mounts are from the very new White Ensign Models
photoetched gunset. In a nutshell, I spent almost as much time assembling these guns as I
did the rest of the model, but they are worth the effort as they add a delicacy and
realism not previously available. The single 25mm aft of the bridge is also
WEM. (Actually, this project was dead in the water for some time, but with the
advent of these WEM guns I was reinspired to complete this model as a showcase for these
parts. I removed the Skywave plastic AA guns and replaced them with the WEM parts).
Last, but not least, is the Aichi floatplane. I built two- one with
folded wing parts, and one fully assembled, ready for flight. Each is the original
Aoshima part, but extensively re-shaped and sanded with small files. The panel lines
were sanded off, as were the spinners. The props were replaced with Tom's PE parts, and
new spinners were shaped from sprue chucked in the mototool.
As to color, it is clear these vessels were a dark shade of grey if not
black. Figuring in scale effect, and wanting a shade lighter to compensate for a dark
wash, (and unconcerned about the Color Police), I sprayed Pollyscale Ocean Grey acrylic
overall. The wooden deck was painted grey-brown color, then planks were brushed on
with a similar shades using an OO brush. Next I sprayed a coat of acrylic varathane to
gloss the model-this keeps the wash from bleeding into unwanted spots. A brown-black
watercolor mixture was brushed into all scribed details and around all joint seams around
the superstructure. I used another brush dipped in acrylic extender to clean up any
wash mess, and also to streak the wash down from the dive vents along the sides of the
hull. I lightly drybrushed select areas using a mixture of
Ocean Grey and white. Finally, I matte sprayed overall using Pactra Acrylic Flat.
Rust colored pastel chalks along the hull sides added a nice touch. The I-400
numerals were hand painted with white watercolor. The Seiran is standard IJN dark
green and light grey. The markings are hand painted, the canopy is coated with acrylic
varathane.
Final touches included a flag, stretched sprue aerials, a PE air search
radar array aft of the bridge, and PE crew figures from Gold Medal's excellent relief
etched figure set. The Serrian was placed on its launch cradle, with its maintenance
crew tending to it.

Epilogue
The Aoshima I-400 has to be one of THE WORST waterline kits available. Throw it a bone
because it's a dog. Luckily, there are excellent photoetched replacements for many
of the miserable kit parts; and with only moderate parts cleanup and repositioning, a
really nice model of this fascinating vessel is possible. If you want an easy
build of a large IJN floatplane sub, get Skywave's I-13/14. This kit is a beauty- and the
I-13 is very similar to the I-400. Failing that, get out the pooper scooper and build
Aoshima's I-400 kit. My character is much improved for it.
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