Click to enlarge
I400 09 small.jpg (31513 bytes)
Aoshima's I-400

New Life for the IJN Super Sub
Jim Gordon

Photographed by Rob Mackie
(Click here for the photo gallery at the end of the article)

(Editor's Note: This model took Best-in-Show at the Silicon Valley Kickoff Classic 28 February 1999)

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.

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. 

I400 13 small.jpg (18438 bytes)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.

I400 04.jpg (45488 bytes)

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.

Click thumbnail image to view full size picture

I400 05.jpg (29874 bytes) I400 08.jpg (60034 bytes) I400 12.jpg (41467 bytes) I400 01.jpg (36280 bytes)
I400 08.jpg (60034 bytes)