Kawasaki Ki-121-I "Hitofuki"; 105th sentai, 23rd dokuritsu chutai (New canopy!)

Dizzyfugu · July 22, 2012, 11:56:45 PM

A new week a new whif from the stockpile - a rather small one. Herewith I present to you the Kawasaki Ki-121-I "Hitofuki":

Some background:
The Kawasaki Ki-121 was an experimental fighter aircraft that used a license-built (Kawasaki) DB 601 liquid-cooled engine, the Ha-40, augmented by a turbosupercharger. This was at that time an unusual choice because the majority of Japanese aircraft at that time used air-cooled radial engines.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

The Ki-121 was designed by Takeo Doi and his deputy Shin Owada of Kawasaki Aircraft Industries (Kawasaki Kokuki Kogyo K.K.) in 1942, who had already designed the Ki-60 and Ki-61 interceptors in 1940. The emphasis in the requirements was for a high speed and a good rate of climb, along with a cannon armament. This was in due response to a complete change from the usual IJAAF penchant for lightly armed, highly manoeuvrable fighters with lightweight structures, which proved to be unsatisfactory against heavy bombers and their escort fighters.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

The first prototype of the Ki-121 emerged in March 1943 as a compact, all metal, stressed skin monoplane, bearing a strong resemblance to the Ki-61. Its tapered wings featured initially square wing tips and were built around a system of three spars; a Warren truss main spar and two auxiliary spars. The rear spar carried the split flaps and long, narrow chord ailerons, while the front spar incorporated the undercarriage pivot points. The undercarriage track was 3 metres (9 ft 10 in). The pilot's seat was mounted over the rear spar, the cockpit sported a bubble canopy, another innovative feature that allowed the pilot excellent view.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

The first prototype was powered by an imported DB 601A-1 with a radial compressor, rated at 960 hp. This was soon replaced by an Aichi AE1 Atsuta 12 engine (a license-built, modified version of the DB 601) which was mated with a turbo supercharger, installed on the port fuselage side, right behind the engine block. This new engine put out 1.560 hp and drove a four-bladed propeller. This especially improved performance at greater heights.

Another innovative feature of the Ki-121 was the steam vapour cooling system for its engine, which had been successfully tested in parallel for the heavy Ki-64 fighter on a Ki-61 test bed. The system was installed in the outer wings. It effectively reduced drag and made an external radiator superfluous. The oil cooler was mounted under the engine (the first prototype sported a single radiator bath, which was later replaced by two drum coolers). A total fuel capacity of 550 l (121 Imp gal) was carried in self-sealing fuel tanks in the lower hull and inner wings, which could be augmented by 2 x 200 l (44 Imp gal) drop tanks under wing hardpoints.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

The armament consisted of two synchronized, fuselage mounted 12.7 mm calibre Ho-103 machine guns which were set in a "staggered" configuration (the port weapon slightly further forward than that to starboard) just above and behind the engine. In the prototype, one German-made Mauser MG 151/20 20 mm cannon was housed in each wing, just outside of the landing gear wells and the propeller's radius. The wing hardpoints could, alternatively to the drop tanks, carry a maximum bomb weight of 160kg each or unguided 60 lbs. air-to-air rockets.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

From the start of flight testing it became apparent that the original design was seriously flawed in several key areas. The take-off run was unacceptably long, while in flight the aircraft displayed some directional instability, excessively heavy controls and poor control response. The spinning characteristics were described as 'dangerous' and the stalling speed was very high. On the positive side, the re-engined Ki-121 prototype showed an impressive top speed of 640 kilometres per hour (400 mph) and a very good rate of climb. Additionally, the cooling system worked well and reliably, only the oil cooler capacity had to be improved.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

As a result the second prototype, which was still being built, was hurriedly modified in an attempt to mitigate some of the more undesirable traits. Some 100 kilograms (220 lb) was removed, primarily by replacing the MG 151 cannons with Ho-5 machine guns and through structural simplifications. The stabilizer areas were tremendously enlarged (both vertical and horizontal fins). Coupled with a slight increase in wing area to 16.80 m² (180.8 ft²) through rounded wing tip extensions this resulted in a slightly lower wing loading and better handling characteristics. Detail changes were also made to airframe sealing and to the contours of the oil cooler air intakes.
Flight tests carried on, and while most shortcomings could be ironed out, the modified prototypes still displayed most of the shortcomings, just to a lesser extent. The supercharged engine also caused teething troubles – maintenance requirements were high. By this time Kawasaki's Ki-100, which had also been designed as a dedicated interceptor as a Ki-61 derivate, was also beginning to show promise and the Koku Hombu selected this type in fulfilment of its requirements.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

Nevertheless, the Ki-121 was approved by the Koku Hombu as 'Army Type 6 Fighter' because of its high speed. An order was placed for one additional prototype and eighteen pre-production aircraft with even more enlarged tail fins. These bore the designation Ki-121-I and were named "Hitofuki" ('gust of wind' or 'blast'). A further version with enlarged wing span as a high altitude interceptor, the Ki-121-II, was also in the design stage, but did not become hardware. The use of 2 × 30 mm (1.18 in) Ho-155 cannon in the wings was also envisioned.

The war's soon end however stopped the construction of further planes. The number of prototypes remained two, and twelve Ki-121-I pre-production aircraft with marginal improvements reached frontline squadrons in April 1945. It is not known if the Ki-121 was actively involved in homeland defence, it never received an allied code name - active planes will probably have been mistaken for Ki-61 fighters. Eventually, the Ki-121 did not progress any further. Its place was taken by the less complicated and more promising Ki-100 with a radial engine.

General characteristics:
Crew: 1
Length: 8.90 m (29 ft 2 in)
Wingspan: 10.58 m (34 ft 9 in)
Height: 3.05 m (10 ft 0 in)
Wing area: 16.80 m² (180.8 ft²)
Empty weight: 2.580 kg (5.690 lb)
Max. take-off weight: 3,900 kg (8,600 lb)

Performance:
Maximum speed: 640 km/h (345 kn, 400 mph) at 7,500 m (24,600 ft)
Range: 950 km (515 nmi, 590 mi)
Service ceiling: 11,500 m (37,730 ft)
Time to 5,000 m altitude: 4 min 47 sec
Engine: 1 supercharged Aichi AE1T Atsuta 12 twelve-cylinder inverted vee liquid-cooled engine, rated at 1,560 hp for take-off, 1,340 hp at 2,100 m and 1,190 hp at 5,800 m.

Armament:
2 × 12.7 mm Ho-103 machine guns, 400 rpg, in the nose
2 × 20 mm Ho-5 cannon, 250 rpg, in the wings
Bombs: 2 × 160 kg (350 lb) bombs or 2 x 200 l (44 Imp gal) drop tanks on underwing hardpoints

The kit and its assembly
The fictional Ki-121 actually is an Italian Macchi C.205 'Veltro' (an Italeri kit). I settled on this machine since it can easily be mistaken for a Ki-61 – e. g. both planes used the same DB 601 engine, and originally I just wanted to create a colour version in Japanese markings. But with building progress, things turned more and more Frankenstein, so that only hull and wings are original.

Cosmetic surgery and replacement parts include:

● Bubble canopy from an A-1 Skyraider single seater (a bit large, took some putty work...)
● Rear fuselage section was lowered for the new bubble canopy
● Horizontal stabilizers from a DH.88 Comet
● Vertical stabilizer is the tip of a Ju 188 elevator
● New wheels on the original (though reversed) main landing gear struts
● Scratch-built, semi-recessed turbocharger on port side
● Relocating the original air intake to starboard, w/o the sand filter
● For-bladed propeller and spinner from a Spitfire Mk. XVI
● Wing hardpoints (empty, though, for the sake of the plane's clear lines)
● The original C.205's radiator bath was omitted
● Flaps were lowered/opened, with some interior details

No dramatic change was intended, since the C.205's lines are pretty elegant and IMHO match Kawasaki's designs of the era, like the Ki-61 or Ki-64, well. The result is a compact machine, reminiscent of a heavily shrunk Blackburn Firebrand prototype?

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion): Work in progress by dizzyfugu, on Flickr

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion): Work in progress by dizzyfugu, on Flickr

Painting:
Since the fictional history of the Ki-121 only saw a couple of fighters in uncertain front line use, I settled on a typical late IJAAF livery based on various sources and references: overall blank metal (Testor's Metallizer Aluminium Plate #1401) with a black anti-glare panel (Humbrol 33), coupled with an improvised, dark green camouflage on the upper surfaces and some colourful squadron markings.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion): Work in progress by dizzyfugu, on Flickr

Cockpit interior surfaces were painted in 'Aodake Iro', simulated with a base of Aluminium (Humbrol 56) and a coat of translucent blue paint on top of that. The landing gear wells were painted in a mix of Humbrol 225 (Mid Stone) and 155 (Olive Drab), for a greenish tan colour.

Hinomaru and squadron emblems come from the scrap box. The blue markings are fictional, the red dragon head emblems come from an aftermarket decal sheet. They belong to the JASDF 105 Sqn, which flew Ki-61 from Aug.'44-Aug. '45, so it is IMHO a potential/plausible user for the Ki-121-I. This sentai later switched to F-86D interceptors - and from these machines come the emblems.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion): Work in progress by dizzyfugu, on Flickr

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion): Work in progress by dizzyfugu, on Flickr

Since the improvised camouflage easily chipped/weathered (no primer was applied), a slightly ratty look was intended. Hence, decals were already applied onto the aluminium base coat, after basic markings like the glare panel or the yellow identification marks (with Humbrol 69) on the wings' leading edges had been painted. Then, Humbrol's Maskol was dabbed onto certain areas with a toothbrush and a fine, stiff-bristled brush around markings and hinomaru.

On top of that, green mottles and streaks (Humbrol 159, Khaki Drab, as a simultaion of the IJAAF's "A.2 Olive Green" tone) were applied with a small brush. The idea was to create a hand-painted look, with aluminium shimmering through and many extra worn areas that show even more bare metal skin.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

After rubbing the Maskol off, the metal surface was sealed with a semi-matte, water-based varnish, while the glare panel remained matte, as well as the propeller (spinner in Red Brown, Humbrol 160, blades in Testor's 'Rubber', #1183). Worn look and details were augmented by a light wash with black ink and some light dry painting, e .g. for exhaust marks and gun smoke residues.

NARSES2 · July 23, 2012, 01:16:54 AM

Very nice, got that "tired" look that these Japanese aircraft had down to a "T"

Why however does it remind me of a Martin Baker project or maybe the Miles M.20 ?

Dizzyfugu · July 23, 2012, 01:29:28 AM

It's the relatively long nose and the slender fuselage - even though this is still OOB. An M.B. 5 ancestry was not intended, but the overall look has something British about it. As I mentioned, I was a bit reminded of the Fairey Firebrand, due to the tail design?

NARSES2 · July 23, 2012, 01:41:15 AM

Quote from: Dizzyfugu on July 23, 2012, 01:29:28 AM
As I mentioned, I was a bit reminded of the Fairey Firebrand, due to the tail design?

Yup I can see that as well. There was of course a history of co-operation between Britain and Japan up until about the Washington Naval Treaties

Tophe · July 24, 2012, 08:51:37 AM

Wonderful transformation of a C.205, congratulations!

ysi_maniac · July 24, 2012, 09:45:35 AM

What a collection of whiffs are you posting lately!

Dizzyfugu · August 10, 2014, 06:25:23 AM

Hmm,

I revive this since I did a mod on the kit - I normally do no update to finished projects, but the Ki-121 deserved one. Somebody mentioned that the canopy (came from a 1:72 Airfix A-1) looked a bit too bulbous for the slender aircraft - and that was right.
It bugged me, so I decided to replace the canopy with a vacu piece which actually belongs to a Hawker Sea Fury (Special Hobby). The shape is similar, but it is shorter and smaller in any dimension.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

Blending it into the fuselage without ruining too much of the paintwork was not easy, but worked quite fine.

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

While the difference is only recognizable at cloe look I think the smaller hood improves the model's overall silhouette considerably?

As a consequence, some more/new beauty pics of the Ki-121 (which also saw a relocation of the antenna mast):

1:72 Kawasaki Ki-121-I "Hitofuki", 105th sentai, 23rd dokuritsu chutai - (Whif/Luft'46/kit conversion) by dizzyfugu, on Flickr

Dizzyfugu · August 10, 2014, 07:31:51 AM

Yup, totally agree - but the canopy was the worst flaw in this mash-up.

All the surfaces have different shapes, so the overall look is a bitty inconsistent...

McGreig · August 10, 2014, 08:01:13 AM

On the original, I thought that the bubble canopy spoiled it by not looking Japanese enough. However, I can see now that it was the size more than the shape - the new canopy is a great improvement

Well done for going back and making the change - it was definitely worth it

Allan · August 27, 2014, 10:18:29 PM

very nice looks like it can fly very fast convincing build
Allan

PACOPEPE · August 28, 2014, 02:54:03 AM

Quote from: Allan on August 27, 2014, 10:18:29 PM
very nice looks like it can fly very fast convincing build
Allan

Fantastic once more! .
Only one thing: I made the "Ki 121"

.
Search, Nakajima Ki 121 Kendra

Dizzyfugu · August 28, 2014, 06:33:47 AM

Uh, no snatching intended - this things just happen if you look for real world "gaps". Happened with my CF-151 build, too, someone already used that number for a helicopter IIRC...

PACOPEPE · August 28, 2014, 11:22:30 PM

Excuse me; obviously it´s a joke.

Great work, great imagination, fantastic pics.

Your kit reminds me to french Dewoitine 520.

All the best
Fran

DogfighterZen · August 29, 2014, 09:58:41 AM

Once again, very nice work on both the build and the pics!!

perttime · August 29, 2014, 12:10:38 PM

Oh yes!
The smaller canopy is much better. Still slightly Anglo-Saxon?