The advent of oil powered ships eased the actual transfer requirements of at-sea fueling, along with better technologies and techniques. The USN first successfully achieved underway replenishment in 1917, shortly after entering the first World War. By the 1920s, both the USN and the Imperial Japanese Navy recognized the need for such a dedicated capability in the vast expanses of the Pacific Ocean. Both navies developed several classes of oil tankers for this purpose. By the Pacific War’s start, both navies had turned to relatively fast, commercially built oil tankers designed to naval requirements.

At the start of the Pacific War in late 1941, Japan actually possessed more such ships dedicated to fleet UNREP operations in this theater than did the United States. In and of itself, the IJN task force that attacked Pearl Harbor had seven (of eight assigned) UNREP tankers attached to it. Plus, several more were tasked to the various other IJN operations coordinating with the Pearl Harbor attack. However, it soon became apparent to the Japanese that they had underestimated the pace and scope of such operations, not to mention the potential duration of the war, and that more such ships were urgently required. 

More tankers were ordered from commercial yards in early 1942. Fast carrier task force requirements soon dictated the additional need for UNREP ships to carry not only oil but avgas as well. And, as the war progressed, there was belated recognition of the need for better air reconnaissance and ASW patrols in the absence of any dedicated aircraft carrier, or substantive naval, escort. This meant further adaptations of the tanker hull to handle these new requirements.
 

Design

The Japanese UNREP tankers utilized at the start of the war were, for the most part, all based on one design unofficially known as the Kawasaki Type tanker. In the early 1930s, several IJN subsidized, commercial prototypes had been constructed according to naval specifications that emphasized speed as well as oil capacity. Eventually, the best qualities of those ships were integrated into a revised design from the Kawasaki Shipbuilding Corporation. This was a single screw, diesel-engined design generating 8,500 to 11,000shp (depending on construction batch), with a top speed of 19.5knots.  They displaced approximately 10,000GRT, carried approximately 100,000 barrels of oil, had an overall length of 525 feet, a beam of over 65 feet, and a draft at full load of over 37 feet.

Twelve such vessels were built by Kawasaki in the mid to late 1930s, in three succeeding batches with small variations between them.  Three more half-sisters were built to a slightly different design by Mitsubishi that utilized the same hull.  A fourth variant, also utilizing the same hull but using steam boilers and a geared turbine, was constructed by the Harima Dock Company (Kurushio Maru).

All the new tankers ordered in early 1942 to supplement the original ships were based on the Harima design with the steam driven turbine.  These were among the first of the Japanese standardized wartime tanker designs and became known as the 1TL tanker. Ultimately, 19 such vessels were built collectively by Harima, Mitsubishi and Kawasaki.

The need for avgas as part of an UNREP capability was recognized by the IJN just before the outbreak of hostilities with the US. Their intent was to design an improved class of tankers with such a capability and have them built in naval yards. However, all their naval shipyard construction capacity was already taken by urgent new warship construction. So, the IJN chose to modify the same Harima design into a dedicated class of ships, all to be built by Harima. These would eventually be known as the Kazahaya class tankers.

This design again utilized the same basic Kawasaki type tanker hull along with the Harima designed powerplant, visually differing from the concurrent 1TL design only in the use of a smaller and more compact forward bridge structure (similar to the superstructure seen on the repair ship Akashi or on the Chitose class seaplane carriers) along with a heavier armament.  The powerplant utilized two Kampon boilers coupled to an Ishikawajima geared turbine, producing 9,500shp for a top speed of 16.5knots. Oil storage was approximately 10,000 tons, with another 1000 tons capacity devoted to avgas.

After the debacle at Midway and the loss of Guadalcanal, the inability of the IJN to muster sufficient air assets at sea for ASW work or air reconnaissance for both fleet and convoy activities became more apparent. This circumstance dictated some new requirements of the Kazahaya design while these ships were just beginning construction. Another modified design was cast, in which the ship would gain aviation related facilities in addition to its UNREP capabilities. These new facilities would include an aircraft handling deck large enough to handle six floatplanes, a deck edge catapult place to starboard, aircraft handling cranes, a small magazine for ordinance, plus some aircraft maintenance and servicing features. 

Structurally, the hull and powerplant remained the same, though the topside arrangements changed from the then typical three island tanker arrangement to a two-island setup. The aircraft handling deck was placed midships, as a raised platform on trestles above the open main deck. The deck had rails, aircraft trolleys and turntables, all to expedite aircraft handling. The catapult was placed forward on this deck, on the starboard side. 

The forward well deck was plated in to better accommodate the placement of the bridge structure as well as enhanced AA, additional derricks and booms for handling fuel lines. The basic aft tanker superstructure and funnel was retained, though with the addition of aircraft handling cranes and greater AA protection. In fact, the ship received a substantial AA package for an naval auxiliary, including two twin 12.7cm mounts, and at least seven triple twin 25mm mounts. Some single 25mm AA mounts are also said to have been added. Six plus one spare Aichi E13A “Jake” seaplanes were to be embarked, though alternate use of the Aichi B7A torpedo-dive bomber for attack missions was also contemplated, without recovery of the aircraft.

Besides the oil and avgas capacities, additional provision was made to carry food supplies. The avgas capacity was lowered by 200 tons.  Included was fresh water (750 tons), a two-week supply of fresh vegetables for 2800 men, and food for 1100 men for 30 days. Ship displacement rose to 18, 300 tons. 

Ship History

Hayasui was the third vessel of the Kazahaya class oil tankers, though she was not laid down at the Harima Dock Company until February 1, 1943. She was launched on December 25th and completed on April 24, 1944. After a few days training, she was assigned to a convoy bound for Singapore, but collided with submarine I-155 soon after departure in Japanese waters.

Quickly repaired at Sasebo, Hayasui was escorted to Philippine waters where she joined the First Supply Fleet and tankers Kokuyo Maru, Nichei Maru and Seiyo Marus as the UNREP support for Japanese naval forces in what became the Battle of the Philippine Sea. Hayasui helped refuel both the Vanguard “C” Force and the Main “A” Force of the Japanese fleet on June 16-17, 1944. Afterwards, the First Supply Force rendezvoused with the Second Supply Force at a point to the west of the clash, to await results and orders.

On June 20th, the Supply Force was attacked by a sizable flight of aircraft from USS Wasp. Three of six tankers were damaged. Hayasui was hit by one bomb while near missed by two others and set afire.  Her damage control was effective, and the fires extinguished. Still serviceable, she headed for Borneo to load oil needed in Manila. The other two bombed tankers incurred severe damage and had to be scuttled.

Enroute, she met up with the damaged tanker Itsukushima Maru and transferred approx. 2000 tons of that ship’s fuel into her own tanks so that Itsukushima Maru could stabilize and proceed with her own repairs. Both ships arrived together at Manila by the beginning of July. Hayasui soon departed for Japan, arriving at Sasebo in early August after stops in Formosa (Taiwan) and Kure. 

Hayasui departed mid-August for Singapore as part of HI-71, a very large reinforcement convoy, then departed again for Manila still with convoy HI-71.  HI-71 was reinforced with a heavy ASW escort for this second leg of the trip.  Off the Philippines on the 18th, the convoy was attacked by the submarine USS Rasher. The convoy split up after Rasher torpedoed and sank two large ships including the escort carrier Taiyo.

A second submarine, USS Bluefish, then joined in the attacks. Bluefish torpedoed and hit Hayasui with at least two torpedoes in a surface attack in the early morning hours of the 19th. Hayasui went dead in the water and started settling slowly at the stern. Several hours later, Bluefish torpedoed Hayasui yet again with three more torpedoes. She sank shortly thereafter. Personnel losses are not known.
 

This is conjecture, but it seems apparent that the rise of the anime based Kantai Collection in Japan (more than 3 million registered players) is the driving force behind the arrival of this kit. Aoshima heavily markets 1/700 IJN ships as part of the merchandising that supports the popularity of these anthropomorphic characters. As time has gone on, more characters based on historical ships have been needed. So, Aoshima had been producing more obscure and unique ship kits to feed the marketing machine. Hence, this kit, which was first offered as a new Kantai Collection kit. 

The Hayasui kit is molded in a light gray styrene plastic with a fair amount of detail. Plans of the ship have survived, and it’s clear that Aoshima has leaned heavily on those, as well as using information and photos of other 1TL tankers. The hull and large structures are sharply molded, the plastic is clean with no soft or greasy aspects, and there was no flash on my kit. 

The fit of the kit is of Hayasui is pretty much as built and sunk, given that her service life lasted but four months.

A large waterline ballast weight is provided, and the base of the hull has a raised interior perimeter section to cradle it.
 

Generally, the molded-on detailing is surprisingly sharp and well scaled.  The watertight doors on either side of the superstructure immediately come to mind, as they are very crisp and have sharply delineated hinges and dogs. Molded onto the aft deck are a trough for the refueling lines, mooring bits, winches, hatches, and what appears to be a new kind of fender for protecting the hull during refueling. (I know these fenders appear on the plans, but I have to say that I’ve never seen an actual example of this type. Those on the deck are really too short in height to be anything more than a representation.) Selected areas of deck treading are noticeably nice.  On the other hand, the yardarms of the upper masts seem slightly clunky, but I think that is mostly due to the very small cross-bracing that is part of each yardarm, which is understandably overscale due to the limitations of the injection process. A bit of heaviness is also true of the kingposts, and booms.

The aircraft handling deck has recessed seams to help denote the wooden planking, and the planking seems closer to scale than some other examples from different makers. The aircraft trolley rails and turntables are also nicely done. The underside of the platform has placement positions for the platform supports, and there is some thick cross-bracing, which will largely be hidden from view. 

The sharpness of the detailing is much as with the previous sprue. The old-style gooseneck air intakes are well done with deep recesses and none of the mold seams that usually plaque this type of detail. The funnels have molded on ladders, small platforms and auxiliary piping that show off quite well. The top of the aft superstructure is much the same, particularly the skylights for the engineering space. Conversely the sides of the structure are notable bare, and the access doors crude. I realize that the plans don’t show much detail in this area, hence the bareness of the bulkheads, but hatches are hatches. I don’t understand why these aren’t as nice as the ones on the bridge, with dogs and hinges included. 

The forecastle deck is well done, with areas of treaded plating, mooring bits, cargo winches, hatches, a decent anchor windlass (far better than the usual blob or block of plastic), a raised platform for number one mount, the forward portion of the trough for the refueling hose, and more of the fenders. 

The well deck has a large base for supporting the catapult as well two small, stand-alone compartments, but other details are nonexistent. Again, the plans are not clear on the actual arrangements on this deck, and most of it would be hidden from view, given the deck overhead and the support pillars lining the sides. 

The AA platforms are all well done with low bulwarks, treaded metal surfaces, ammo boxes and truss supports underneath them. The heavy booms for the aircraft handling cranes are pretty good for plastic, with recessed lattice work on all four sides for the booms, and a nicely scaled hook. The catapult is a bit of an oddity in that it is longer than the usual Kure Model Type 2 catapult. Scale-wise it works out to approximately 25.2m. I don’t know if this is correct or not for this ship. 

Included are three of each of the following: 1) Nakajima B6N2 “Jill” torpedo bomber with folded wings, 2) Nakajima C6N “Myrt” carrier based fast reconnaissance aircraft, 3) Aichi B7A2 “Grace” torpedo-dive bomber with folded wingtips, and 4) Mitsubishi A7M Reppu “Sam” fighter with folding wingtips.  All the aircraft can have their wings or wing tips glued into a flight ready position. The Jill and Grace come with aerial torpedoes, while the Myrt comes with a long range external drop tank. All have engraved panel and canopy lines. All appear to be pretty nice for this scale.

Only the Aichi Grace was potentially carried by this ship. I say potentially because nothing was ever actually embarked other than Aichi E13A Jakes.

The other pages have a step-by-step progression of assembly using exploded, three-point perspective illustrations.  There’s also an illustrated parts guide.

It’s also a very welcome addition to the available kits of IJN fleet auxiliaries.

This kit was courtesy of my wallet, via HobbyLink Japan. The cost, less shipping, was $19.85.  Note that there are now also several additional boxings of the kit: as a Kantai Collection kit, as a Super Detail Version, and as a Limited Edition kit, each with different add-ons and pricing.