The Washington Naval Disarmament Conference of 1922 limited the standard displacement of every participant’s own, individual aircraft carriers to no more than 27,000 tons, and limited the total Japanese aircraft carrier tonnage to 81,000 tons standard displacement. However, each country was allowed to keep two existing capital ship hulls for conversion to carriers, each with a displacement limit of 33,000 tons.  Japan’s Akagi and Amagi (later exchanged for battleship Kaga), then building as battlecruisers, absorbed most of this tonnage allocation. Japan’s first aircraft carrier, Hosho, though much smaller, accounted for much of the rest of the total carrier allocation for Japan. 

The treaty left a loophole of sorts, by not categorizing an aircraft carrying ship under 10,000 tons displacement as an aircraft carrier. Ryujo was designed to take advantage of this loophole before an anticipated change in treaty terms was enacted with the forthcoming London Naval Treaty of 1930. 

Design
The origins of Ryujo’s design have never been exactly clear. Many authoritative sources have stated that her design originated with the cancelled follow-up sisters to Hosho, which were themselves an enlarged version of Hosho. This design was tweaked to show a slim, cruiser-style hull with low freeboard and a fair amount of flair forward. The hull had minimal armor aside from some additional plating over and around her magazines and machinery spaces. The ship utilized powerful propulsive machinery, and a flight deck similar to Kaga’s as-built, topmost, flight deck.  Two elevators serviced a single hangar deck atop the hull with a capacity for 24 aircraft.

The original, final design was nominally 8,000 tons standard displacement, using a hull shape very similar to the just completed Aoba class heavy cruisers, though slightly shorter and wider. She was a flush deck design without a superimposed bridge island; the bridge was located forward at the bow, under the lip of the flight deck. The propulsion plant was drawn directly from the Takao class cruisers building concurrently, though only half that power plant was deemed necessary. She was equipped with six oil-fired Kampon boilers and two geared sets of turbines producing a total of 65,000 shp, for a top speed of 29 knots and a range of 10,000 nautical miles.  Two funnels exhausted downward from their amidships placement on the starboard side of the hull.

Armament consisted of six twin 12.7cm 40cal. dual purpose mounts placed on hull sponsons, plus six quad 13mm MG mounts placed on platforms ringing the flight deck. 

However, after the signing of the London Naval Treaty of 1930, the tonnage limitations of the design became meaningless and the Japanese Naval General Staff insisted on changes to increase the size of the air group. In turn, this meant adding a second hangar deck atop the first. Small hull bulges were added to help with stability. Ship’s displacement rose from a nominal 8,000tons to over 10,000 tons.  In order to abide by the terms of the naval treaties, all of the Japanese carriers’ displacements were under-reported, thereby making room for Ryujo. 

History
Ryujo (?? "Prancing Dragon") was laid down at the Mitsubishi Yokohama shipyard in November, 1929, with a planned completion date of March, 1932. However, the London Naval Treaty was signed in a few months later in April, 1930. Her design was subsequently reworked, with an additional hangar deck placed above the first, doubling her aircraft complement to 48 aircraft. The increased weight above the waterline raised her center of gravity, necessitated the addition of small hull bulges to increase stability, along with Sperry-licensed active stabilizers built by Mitsubishi.

The additional changes pushed back her completion date, and Ryujo was not commissioned into service until May 9, 1933. Even during trials, it was noticed that the combination of high top-weight and a narrow beam made her marginally unstable. High speed turns coupled with low fuel reserves made for a dangerous combination, and she had to avoid such type maneuvers. Low freeboard also made her a very wet ship. After trials and training, she spent time much time integrating a new air group.

The Tomozuru Incident of March 1934 (when a new, but top-heavy, torpedo boat capsized in a storm) prompted the IJN to review the stability of all their warships. Ryujo was promptly docked at Kure for new modifications to improve her stability. The more significant improvements included the replacement of her small hull bulges with larger ones, the addition of 550 tons of ballast in the keel and hull bottom, removing two of her six twin 12.7cm/40 cal. main battery mounts and replacing them with lighter twin 25mm AA mounts, raising the siting of her funnels by one deck, relocating many air intakes and exhausts to higher locations, and replacing her aerial masts with lighter versions. The work was completed in August, 1934, and Ryujo resumed duties, the majority of which involved evaluating the effectiveness of dive-bombing, torpedo, and scouting aircraft tactics.

Just a year later, Ryujo was one of several ships badly damaged in what became known as the 4^th Fleet incident. The IJN was conducting one of its annual Grand Fleet maneuvers when two of its fleets encountered a strong typhoon. Numerous ships of all types were badly damaged. Ryujo’s bridge, flight deck, and stern boat deck were badly damaged, while her lower hangar was flooded. Once again, Ryujo was docked at Kure Naval Base for both repairs and improvements. 

The work was carried out from October, 1936 through May 1937 and included raising the forecastle by one deck (3.1 meters), streamlining the bridge face and the leading edge of the flight deck (which also shortened it by 2 meters), creating sponsons for many of the walkways located outside the hull, eliminating an access door at the rear of the upper hangar deck, and upgrading her arresting wires. 

The China Incident of 1937 led to Japanese landing and occupation operations throughout coastal China. Ryujo, along with other IJN carriers Hosho and Kaga, engaged in active air support of these operations on and off through the end of 1939. Various air group tactics were employed and the composition of her air group changed over time as it was upgraded with newer aircraft types.

Ryujo underwent a refit between December, 1939 through the end of January, 1940. Afterwards, she became a training ship as well as flagship of the Third Carrier Division. Upon the establishment of the First Air Fleet (Kido Butai) in April, 1941, she became flagship of the Fourth Carrier Division, accompanied by Kasuga Maru (Taiyo), though Kasuga Maru was detached from the division at the end of December.

At the start of the Pacific War in December, 1941, she was assigned to support the invasion of the Philippines. Her aircraft (eighteen Nakajima B5N1 attack aircraft and twelve Mitsubishi A5M Claude fighters, four of each as spares) attacked the American naval base at Davao. After the fall of the Philippines, she supported Japanese occupation operations on the Malay Peninsula and the fall of Singapore. Subsequent activities included supporting the occupation of the Dutch East Indies, including attacking shipping around Sumatra and in the Java Strait. Her aircraft also participated in the Battle of the Java Sea, damaging the US destroyer Pope.

In the first week of April, 1942, Ryujo led a small task force (termed the Second Expeditionary Fleet, Malay Force) consisting of herself, six cruisers and four destroyers under Admiral Jisaboro Ozawa. This force operated in conjunction with Operation “C” ‘s raiding missions in the Indian Ocean by the Kido Butai. Ozawa’s force was tasked with raiding and destroy shipping in the Bay of Bengal to the east of India while the First Air Fleet swept further south. Before retiring, twenty ships were sunk by Ozawa’s force using both carrier aircraft and surface ship gun/torpedo fire.

Ryujo returned to Kure by late April for another refit. Her A5M fighters were replaced by sixteen A6M2 Zeros, while the number of B5Ns was boosted to twenty-one, spares, included. Her air group underwent training while she spent time in drydock. 

CarDiv4 also expanded with the arrival of the new carrier Junyo on May 3^rd. Later that month, CarDiv4 was assigned to the Northern Fleet as the air arm of the impending attack and invasion of several Aleutian Islands, to be conducted simultaneously with the Midway Operation.  Ryujo and Junyo launched two days of air attacks over June 3 and 4 against the US Army and Navy facilities at Dutch Harbor, Unalaska Island. Damage to the facilities was minimal, though several aircraft on both sides were lost. 

Beyond the subsequent occupation of Attu and Kiska islands, perhaps the most significant outcome was the loss of one of Ryujo’s A6M2 Zeros, piloted by PO Tadayoshi Koga. Koga’s Zero was damaged and he attempted to crash land on nearby Akutan lsland. In doing so, the plane landed intact on a mudflat but flipped over, breaking Koga’s neck. The Japanese had to abandon the aircraft, and the US Navy recovered it about a month later. It was shipped to San Diego, fully repaired, and flown for evaluation. As a result, its strengths and weaknesses were fully revealed. New air tactics to exploit these weaknesses were developed, while recent improvements made to the new USN F6F Hellcat fighter then testing were validated as being able to exploit those same weaknesses. 

Returning from the Aleutians, CarDiv 4 was joined by light carrier Zuiho, and together they continued on to the northernmost naval base in Japan at Ominato. There, a large reinforcement convoy to the Aleutians was gathering. This convoy, with CarDiv4, Zuiho, fleet carrier Zuikaku, and a significant number of other surface warships, departed for the Aleutians on June 28^th, successfully completed its mission, and returned to Japan in mid-July. Ryujo again underwent a small refit at Kure. 

In July, the Japanese Navy was reorganized in the wake of the loss of four fleet carriers at Midway the previous month. Ryujo, Junyo and Hiyo (Junyo’s new sister ship) were reassigned to Cardiv2. Ryujo’s air group was revised to twenty-four Zeros and nine Kates. 

On August 7^th, US naval and Marine forces invaded Guadalcanal and Tulagi in the Solomon Islands. Taken by surprise, the Japanese rushed to reinforce their forces in the area and counterattack American forces. Ryujo was temporarily attached to CarDiv1 (Zuikaku, Shokaku) as a replacement for light carrier Zuiho. Zuiho had just come out of a refit in dry-dock and was not yet fully operational. 

Plans to stop enroute at the Japanese naval base at Truk were dropped when an American task force that included a carrier was spotted near the Solomon Islands on August 21^st. While CarDiv 1 was assigned the task of finding and intercepting of American carrier forces, Ryujo was to be split off from CarDiv 1 and given a small escort of heavy cruiser Tone and two destroyers, Amatsukaze and Tokitsukaze.

Ryujo’s group was tasked with reconnoitering the approaches to Guadalcanal in advance of a reinforcement convoy of troops then enroute. If no carriers were spotted, she was to attack Henderson Field on Guadalcanal to suppress ground-based air power.  As a landing of August 25^th was anticipated for the reinforcements, the attack against Henderson Field was slated for the 24^th. 

In the very early morning hours of August 24^th, Ryujo’s group split off from the main Japanese strike force and proceeded to a point 200 miles north of Henderson Field. Around 8AM, and again around 10:30AM, this Detached Force was spotted by American PBY scout aircraft, which radioed in their discovery. Between 11:20AM and 12:30PM, Ryujo launched two small air strikes totaling fifteen Zeros and six Kates against Henderson Field. They arrived over Henderson Field around 2:30PM and proceeded to attack with bombs and strafing. Little damage was done, but the arriving force ran into a large combat patrol of American F4F Wildcat fighters and some US Army P-400s. Three Zeros and three Kates were shot down in exchange for three Wildcats. A fourth Kate crash-landed.

In the meantime, Ryujo was dodging some bombs dropped by search aircraft from the carrier USS Enterprise. Belatedly, she then launched several Zeros to act as her combat air patrol. Acting on the earlier PBY search sightings, the other US carrier in the vicinity, Saratoga, had launched a large strike force to attack Ryujo. That force consisted of thirty-one Dauntless dive bombers and eight Avenger torpedo planes. The long range of the strike ruled out the inclusion of any fighter escort. 

Saratoga’s aircraft found and attacked Ryujo around 2PM. Ryujo was hit by four bombs, near missed by several others, and absorbed one torpedo hit aft on the starboard side. The torpedo hit flooded the starboard engine room, and her speed began to fall off. No aircraft were lost by either side during the attack. 

The flooding increased rapidly and steadily. Ryujo came to a halt within half an hour, and was forced to order “abandon ship” by 3:15PM. Destroyer Amatsukaze came alongside to remove personnel, but was forced away when several B-17s attacked. No bomb hits were recorded. Amatsukaze eventually took aboard all the remaining personnel and backed away. Ryujo then capsized and sank, stern first. Seven officers, 113 men and four aircraft were lost with her. 

Ryujo’s activities in China, and over the first few months of the Pacific War are detailed in her Tabulated Record of Movement (TROM) at: http://www.combinedfleet.com/ryujo.htm

A review of those activities reveals that Ryujo was an extremely active, even hard-used, ship in those years. Her air groups were fundamental in evaluating the various aircraft types coming into navy service and just as important, in developing various operational tactics that would guide Japanese carrier operations in the future. Further, many of the personnel who served aboard her would move on to key positions aboard newer ships entering the fleet, bringing their expertise and knowledge with them. 

The hull comes in three pieces, consisting of forward, center and aft sections.  Each hull section is packaged individually inside a clear plastic bag.   Pretty much everything is printed onto the hull sections.  I mean everything:  bollards, chocks, capstans, platforms, accommodation ladders, cable reels, piping, some directors, the funnels and more.   The 3D printed resin is slightly tacky to the touch, though the longer I've had the model, the less pronounced this has become.  Devin Poore, who is intimately involved in 3D printing in his day job, suggests cleaning the hull with isopropyl alcohol, then let it dry in the sun.

Unlike most 3D printed parts you receive, most of the printing supports have been removed (probably so they could use smaller box to package the model in), so the hull parts don't come on the familiar "print rafts".   There are more supports to be removed (these are called out in the instructions) and all the attachment points will need to be cleaned up and sanded smooth before you can begin construction. 

While, overall, the detail is good, here are a few things I noticed:   There is a rough patch on the forward section of the hull, starboard side, just by the keel.  The hull lines have visible print lines on all three sections, especially on the bottom of the hulls.  Also, on the bulges on either side of the center section, there are visible print lines, in a pattern that almost looks like wood grain.   Hopefully, some light sanding or priming will hide/remove these lines.  There is a partial hangar deck included (nice touch), so you can position either - or both - of the aircraft elevators in the lowered position.  There is a series of gridlines printed inside the hull, which shouldn't be visible even with the elevators lowered.   I'm assuming there are to provide strength to the hull, to prevent warping.

While, as mentioned, most of the detail comes printed integral to the hull, it seems to me that some of it would have been better off being printed separately.   Examples of this include the platform the runs around the hull, and some details like the accommodation ladder and the detail on the funnels.  The biggest challenge I foresee when building this kit will be properly lining up the three hull sections so they (and the aforementioned platform) match.   Some locating pins (and matching holes) on the mating surfaces of the hull sections would have been helpful.  Also, with so much detail printed into the hull, getting into tight spaces to fill and sand the inevitable seam is going to be tricky. 

While the plating on the box looks pretty good, the planking looks - to they eye - to be over scale. 

The aft part of the flight deck is very brittle - the edges of the flight deck are peeling away at the very aft corners of this part. 

The AA guns are packaged in two of these boxes.  Detail is pretty good, though not up to the same quality as Black Cat Models offerings.  Of these weapons, the 12.7cm guns look to be the best of the bunch. 

Dan Kaplan's comments
What comes to mind about the kit is:
• Great detailing
• Nice to see hangar decks and elevator wells with some detail. Not sure if there are coverings for the hanger deck supports.
• Two prominent seams to fill (Oy!) And how best to do that? Ditto the walkways/sponsons separated by those seams.
• Conversely, flight deck seams should be well disguised by the transverse deck planking. 
• All those printing raft attachment points that must be cleanly cut away (Oy x 2!)
• Nice PE
• Instruction book seems comprehensive.
• Not sure how printed guns and boats compares with other brands. 
• Aircraft purchased separately. Increases cost.

Can’t really speak to any production flaws

Devin Poore's comments
1. Alignment of the hull sections will be tricky. I would love to see some sort of alignment aids between the three hull sections, either a pin-and-hole type setup in the parts to allow them to key together, or even something as simple as a channel completely through the center section that terminates in the bow 
    and stern sections, so that a matching diameter of brass tubing can pass through to align the pieces. Either of these solutions should be very simple to implement. 
2. The detail on the hull is impressive, but in places there’s honestly too much of it. The long platform that runs around nearly the entire hull is split by the hull sectioning, and it’s going to be very difficult to, first, make sure it’s aligned with itself while trying to get the hull itself aligned, and, second, once that 
     is accomplished, it’s going to be tricky to sand the resultant seam in that platform. Sanding the seams of the hull pieces overall will be an issue in several locations, not only because of that platform, but also due to details printed as part of the hull. It’s going to be very difficult to get into those tight areas 
     and sand, which will likely result in some of the detail on the hull being lost.
3. I’d much rather see the flight deck made from etched brass, or at least laser cut and scribed acrylic sheet. The current piece, printed in three sections as well, comes out of the box warped and with little rigidity.
4. Overall it’s an impressive looking kit. I’d much rather see less focus on trying to make the hull sections as “one piece prints”, and more attention to how the resulting sections are going to be assembled. Leave off some of the detail that’s undoubtedly going to be lost to sanding. 

Final thoughts
First - thanks to Keith, Dan and Devin for providing their feedback.  Here are my final thoughts... 

On the plus side, we have a 1/350 model of the Imperial Japanese Navy carrier Ryujo, which took part in some important operations during the Pacific War - including the opening moves against the Philippines and the Battle of the Eastern Solomons. Overall, the detail runs from fair to really good (outside of that rough patch on the lower, forward hull sections), and you get almost everything you need - other than aircraft, which are an additional cost - in the box to build this model. The instruction booklet is, for the most part, well done. 

On the negative side, I see the three part hull being very problematic, especially with all the detail that is printed onto the hull.  I understand the limitation of 3D printing and the need to break the hull down into sections, but, as mentioned above, that platform that runs around the hull should have been either a separate part, or photo-etch.   I also think the alignment is going to be very tricky and agree with Devin that some sort of key should have been printed into the sections to ensure proper alignment.  The biggest issue I see, after proper alignment, is filling, sanding and polishing the seam so it's not visible.  Especially with all the detail in the way.  The second biggest issue it the flight deck.   Getting those parts to fit level onto the hull - then matching them up with a minimal seam - is going to take some work. 

I think the photo-etch is pedestrian, at best, but that some details - like the wind deflector, accommodation ladders the details on the funnels - would be better representative with photo-etch parts.  I also think the inclined ladders would have been better served as separate parts, not one continuous part. 

In the final analysis, I find this release to be a mixed bag.   It's innovative, it's a unique subject and it's got some great details.  Kudos to 3D-Wild for thinking out of the box, being bold and producing a model of this ship.  Conversely, I think an average modeler would struggle with this kit, due to the complexity of joining the three hull sections together.  If you are up for the challenge, and are a big fan of the Imperial Japanese Navy, then you might like this kit.   It will certainly fill a niche in your scale model fleet.   However, I can only recommend it for experienced modelers, and/or those aforementioned IJN fanatics, who are up for a challenge.

This is 3D-Wild's 1:350 IJN Ryujo Aircraft Carrier Full Hull Model Kit, kit number DAR00.  It's priced at $198.00 USD (aircraft sold separately), and is available directly from 3D-Wild, who I'd like to thank for this review sample.