Review on the Sprue, by Mike Quan, IPMS #3925

Skywave W-48, IJN Submarine Type I-400, "I-400 & I-401"

Retail price: 2200 yen in Japan, or $25 from Pacific Front Hobbies

The I-400 class submarine was, until recently, all but forgotten among the great submarines of the world. Not much was widely known about these boats as survivors were all scrapped shortly after the war.

At 393 feet in length and displacing 6,560 tons submerged and 3550 tons on the surface, they were the largest submarines built during World War Two. Even today, the I-400 class remains the largest conventionally powered submarines ever built!

The I-400 class had a speed of 20 knots surfaced and 7 knots submerged. With an operational endurance of four months and with their as-designed range of 33,000 nautical miles at 16 knots, they could make a round trip to any port in the world, including New York, . Despite the formidable 14 cm, (6"), deck gun carried and eight bow-mounted, torpedo tubes, the "main battery" for this class of vessel was their three Aichi M6A1 Seiran aircraft, armed with either 800 kg. bombs or a 45 cm diameter, (17.71"), aerial torpedo. Equally fascinating is the engineering that went into the design of the large, Sentoku (special submarine), type submarine to transport, service, and launch the Aichi bombers.

Starting in the late 1920's, Japan had been operating aircraft carrying submarines, and exploited this capability more than any other Navy. Initial development began in early 1942 for the ambitious strategic plan of attacking the Panama Canal Locks and rendering them inoperable by the use of attack bombers launched by submarines. In November 1942, a sub-launched, E14Y1 Glen aircraft equipped with 2 small bombs, on 2 different missions dropped bombs in wooded areas of Oregon. Spurred on by the potential of this method of attack, the IJN 5th Replenishment Program called for the construction of a total of 18 I-400 class vessels, along with the development, construction and training of the associated specialized Seiran bomber. Construction on the I-400 began on January 18th 1943 at the Kure Naval Arsenal at Honshu, with the I-401 and I-402 begun later at the Sasebo Naval Arsenal at Kyushu. The I-403 was to be built at the Kawasaki Heavy Industry Co., Ltd. at Kobe, but was never laid down. The last of the I-400 class whose keel was laid down was the I-404 at Kure Naval Arsenal in February 1944, but she was sunk while under construction after an air raid. The I-400 and I-401 were launched and sent, (along with the I-13 and I-14), on a mission to launch an aerial attack against Ulithi - the huge U.S. Navy ship anchorage in the western Pacific. As events transpired, the Japanese surrender caused this attack to be aborted at sea.

Even more interesting for modelers are the current stories circulating about the rumored refinishing of the Seirans while underway towards the aborted final mission. It is said that the Japanese sailors repainted the Seirans from their original green-over-gray colors to an overall silver camouflage complete with American Stars and Bars to deceive defenders into thinking the attackers were friendly!

Along with the efforts of the Smithsonian in restoring the sole surviving example of the Seiran, the recent kit releases in 48th and 72nd by Tamiya of the Seiran and Nanzan trainer aircraft have rekindled interest in the "Panama Canal Bombers." Although Aoshima already had a 1/700th kit of the I-400 as a part of the original Waterline Series, it was very dated, fit poorly, and accuracy was not far removed from the "toy" category. Skywave has been extremely prolific in 1999, and their latest release in 1/700th was eagerly welcomed. Two complete submarines are included in each box, and in contrast to the old Aoshima release, the subs can be completed as either a waterline, or as a full-hull model with display stand. Consisting of a total of 78 medium gray parts molded on three sprues, the surface detailing is very exquisite, capturing the sloping levels of the main deck as well as the widely spaced deck planks with the various cutouts to accommodate deck equipment. Drain holes, or "scuttles" if you prefer, in the hull, hangar door and sail are crisply represented; and the model very favorably matches available references. Two, four-piece Aichi Seiran aircraft are provided, and although not mentioned at all in the instructions, a third aircraft on the sprues represents the Nakajima C6N1 Myrt intended to perform scouting and post-attack assessment (from Truk!). Submarine construction breakdown follows the original Aoshima kit with the waterline hull split vertically to which the deck and sail are attached. The submerged hull is a separate, single add-on should a full-hull model be desired. A unique kit feature is the separate door to the aircraft hangar tube, which permits displaying the hangar tube open. Indeed, the Skywave instructions, (in Japanese, of course), show how to add plastic strip to the "floor" of the hangar area, as well as how to alter the Seiran to depict the "folded" airplane configuration for storage. Many interesting diorama possibilities come to mind with these options! If any faults can be found, it is limited to the lack of antennas on the deck aft of the sail - this being remedied by judicious use of stretched sprue or brass wire.

At around $13 per sub, the Skywave kit represents excellent value in 1999, especially when compared to the original retail of $2.25 for the Aoshima kit of the early 70's! All told, Skywave's new I-400 kit is a real winner, and with some discreet finishing, can lead to a solid contest contender!


1. The Maru Special, Japanese Naval Vessels #13 - I-400 and I-13 class submarines, July 1977. Excellent reference with color center section painting, and numerous black and white photos of the subs after surrendering to the U.S. Navy. Japanese text.

2. Monogram Close-Up #13 - Aichi M6A1 Seiran, 1975. Out of print, but it has some interesting data and photos of the I-400 subs with details of the hangar arrangements.

3. Those with Internet access should not miss the excellent website at: "The I-400 & I-401, The Forgotten Submarines" web page contains a wealth of information by a real fan of these submarines. Don't miss the link from this page to "The Transpacific Voyage of HIJMS I-400" at: for an excellent story by the U.S. Skipper who sailed her after the war.