Kawanishi N1K1 "Kyofu" 15-Shi Fighter Seaplane (K-20)

Le Chat · 29 January 2014

Hello,

I'm looking for a good drawing of the Kawanishi N1K1 Kyofu 1st prototype, with contra-prop. http://s478.photobucket.com/user/mokyme/media/Japanese%20Seaplanes/N1K1_kyofu_prototype_test-W-01.jpg.html

I have a drawing in the FAOW, but it seems to me crude.

I would built it in 1/48th scale from the Tamiya kit and I know that there are some differences comparing to standard models :
- larger spinner
- narrower cord fin
- narrower main float support
- no aerial mast (perhaps ?)
- different shape of cowl gun openings
- overall orange-yellow paint with cowl black and, perhaps, black paint under floats
and I think that's all.

Thank you very much.

Fabrice

blackkite · 29 January 2014

Hi! Kyofu. You can measure the size which you need.

Source : FAMOUS AIRPLANES OF THE WORLD No.124 KYOFU,SHIDEN, SHIDENKAI, BUNRINDO CO.,LTD. 5/1/2008,
ISBN978-4-89319-158-8
Japanese text says that the 1st prototype added large fillet at the wing root.(as you can see.)

Le Chat · 30 January 2014

Hello,

Thank you very much Blackkite ! I have the oldest FAOW # 53 :

http://i438.photobucket.com/albums/qq101/shigeko88/album%2027/faowblack531.jpg

So, the drawing shows not small fillet, but pics show large one. It will be more easiest to me to keep these large fillets at wing roots.

I suppose you read japanese. If yes, what colour was painted this 1st prototype ? I think that orange yellow is correct, but I found this built with a grey plane :

http://www.hyperscale.com/features/2000/rexrc_2.htm

Thank you.

Fabrice

blackkite · 30 January 2014

Le Chat said:
Hello,

Thank you very much Blackkite ! I have the oldest FAOW # 53 :

http://i438.photobucket.com/albums/qq101/shigeko88/album 27/faowblack531.jpg

So, the drawing shows not small fillet, but pics show large one. It will be more easiest to me to keep these large fillets at wing roots.

I suppose you read japanese. If yes, what colour was painted this 1st prototype ? I think that orange yellow is correct, but I found this built with a grey plane :

http://www.hyperscale.com/features/2000/rexrc_2.htm

Thank you.

Fabrice

Hi Le chat! Yes I can read Japanese because I'm a Japanese. Don't ask me about the color. It's my weak point. ;D
http://www9.plala.or.jp/fukugiya/72-064-kyofu.htm
This site says that,
"I thought that I would paint the experimental model of Kyofu yellow orange.
Then, since I heard that the experimental model of Kyofu carried out the first flight before from establishment of painting an experimental model in yellow orange at the time of the first flight, I painted the gray of SDE. "
Another site says that when Kyofu No.1 prototype meiden flight, strong vibration happened due to wing root stall, then lagre fillet added at the wing root immediately.

blackkite · 29 August 2015

Hi!
Kyofu at the Natinal Museum of the Pacific war.　Recent Maru magazine reported the detail of this aircraft.

http://www.pacificwarmuseum.org/

And other pictures.

Winston · 31 August 2015

Looks good indoors protect from the weather.

blackkite · 31 August 2015

Winston said:
Looks good indoors protect from the weather.

Yes it is!
Kyofu had a Kasei engine same as Raiden, but Kyofu did not have forced cooling fan.
Kyofu prototype and early production model did not have ram air intake for the engine at the front top of the engine nacelle.
Ram air intake and oil cooler are located in the engine nacelle for low drag, but perhaps this design did not work well. (low horse power and overheat?)
Kyofu late production model had ram air intake for the engine at the front top of the engine nacelle same as Shiden and Shiden-kai.

blackkite · 31 August 2015

These drawings are little strange compared with bottom actual Kyofu photo.

blackkite · 31 August 2015

Hi!

View: https://www.youtube.com/watch?v=bQ6YIUANJkQ

SlickDriver · 1 September 2015

I was over on the J-Aircraft org site and noticed that a member had posted a detailed set of drawing and pictures of a fuel purge system for the A6M2-N floats and was wondering if there was something similar for the N1K1 Kyofu.

Winston · 1 September 2015

Looking at FAOTW #53 I can't seem to find any drawing of the float. I think only the A6M2-N had this.

blackkite · 1 September 2015

Loren said:
I was over on the J-Aircraft org site and noticed that a member had posted a detailed set of drawing and pictures of a fuel purge system for the A6M2-N floats and was wondering if there was something similar for the N1K1 Kyofu.

Oh what a detailed information!

Thanks a lot.
I will check N1K1 Kyofu float design.
Kyofu has shot down B-24(1/16/1944), and caused a damage to B-29(1/2/1945).

windswords · 2 September 2015

Here is what I have on the N1K1 prototype:

This matches the photo of the paint scheme used on the prototype

windswords · 2 September 2015

Le Chat said:
So, the drawing shows not small fillet, but pics show large one. It will be more easiest to me to keep these large fillets at wing roots.

I suppose you read japanese. If yes, what colour was painted this 1st prototype ? I think that orange yellow is correct, but I found this built with a grey plane :

http://www.hyperscale.com/features/2000/rexrc_2.htm

Thank you.

Fabrice

I have a pic of a gray N1K1 that says it is the third prototype. If that's correct I would assume that the first two prototypes were the standard orange-yellow color:

Stargazer · 2 September 2015

blackkite · 4 September 2015

Thanks my friends for very rare items.

Japanese wikipedia says that

One Kyofu fighter was rushed into a battle with F6F in Chiba-prefecture Tate Yama in February 16, 1945.
Caused a damage to F6F was reported as a result of the fight competition. This was the only military gain Kyufu mentioned to an enemy fighter.

airman · 18 October 2023

There are any information and data about N1K2 proposed large version of Kyofu ?

blackkite · 11 November 2024

Hi!

http://roswitha.jp/[10]shinden@kyoufu@.html

At the Smithsonian Institution's Paul E. Gerber Facility in Washington, Maryland, USA

blackkite · 11 November 2024

『[太平洋戦争博物館/米テキサス]強風11型』

National Museum of the Pacific War. Fredericksburg, TX.340 East Austin StreetFr…

ameblo.jp

Aurum · Tuesday at 06:28

airman said:
...large version of Kyofu ?

large/larger version — what do you mean?

Arjen · Tuesday at 07:51

@Aurum
From Japanese Aircraft of the Pacific War by René J Francillon, Putnam 1987.

The curtailment of the Kyofu production in favour of the Shiden, its land-based development, prevented the realization of an advanced floatplane version, the N1K2, which was to have been powered by a 1,900 hp Mitsubishi MK4R Kasei 23.

airman · Tuesday at 14:51

Arjen said:
@Aurum
From Japanese Aircraft of the Pacific War by René J Francillon, Putnam 1987

Ok, so it never were realized a project .

blackkite · Thursday at 04:12

Hi! We can see Kyofu laminar flow wing (LB wing) designed by Ichiro Tani through these pictures.

Photos of rare Japanese NIK Kyofu seaplane

Unrestored parts of a Japanese NIK Kyofu aircraft, codenamed Rex by the Allies, are stored in a National Naval Aviation Museum warehouse at Naval Air Station Pensacola on Thursday, March 14, 2019. Only 97 NIK Kyofu aircraft were manufactured and this is one of only 3 still in existence. Currently, t

www.pnj.com

blackkite · Thursday at 04:59

View: https://www.youtube.com/watch?v=5iif-JZJRgg

blackkite · Saturday at 03:08

Engine and fuselage shape
The Mitsubishi Kasei (output: approximately 1,500 hp) was used as the most powerful engine available at the time. Although the Kasei had a large output, its diameter (1,340 mm) was relatively large for a fighter, and it was expected that the nose, where the engine was located, would be the widest part of the aircraft, as in a normal single-engine fighter. Kawanishi therefore focused on a spindle-shaped fuselage shape similar to that of the Raiden, which also had the Kasei. At the time, wind tunnel experiments at the Naval Arsenal showed that for a fuselage with the same maximum cross-sectional area, it was more advantageous to have the maximum area closer to the center of the fuselage in terms of reducing drag, and the spindle-shaped fuselage was an application of this. In order to achieve the spindle shape, the engine was placed closer to the center of the fuselage and the front of the cowl was narrowed, and the propeller shaft was extended to accommodate the resulting clearance from the engine to the front end of the cowl. This was the same procedure as the Raiden, but the aircraft was not equipped with an engine cooling fan to compensate for the air flow rate from the narrow cowl opening.

blackkite · Saturday at 03:13

Main wing
The main wing for the Kyofu was a mid-wing configuration that had less interference resistance with the fuselage and was less likely to be hit by water splashes during takeoff. A laminar flow wing was also adopted as the wing shape. A laminar flow wing is a wing shape that delays the turbulent transition of the airflow over the wing and reduces air resistance, and it was expected to be effective in increasing speed. At the time, various shapes of laminar flow wings were researched and were also used on several military aircraft (such as the P-51 and the Saiun), but the one adopted for the Kyofu was the LB-type laminar flow wing invented by Professor Ichiro Tani of Tokyo Imperial University (now the University of Tokyo). The maximum thickness position of a normal wing's cross section is around 30% of the wing chord, but the maximum thickness position of the LB-type laminar flow wing is at about 40% of the wing chord, which makes the pressure gradient positive and expands the area where the airflow flows stably (the wing of the Shiun is also an LB-type laminar flow wing). In order for a laminar flow wing to be effective, the wing surface must be very smooth, but there is also a view that it may have been difficult to achieve the necessary precision with the machining technology of the time . The Kyofu that required high speeds also meant high wing loading, and in order to balance takeoff and landing performance, the wing root angle was an unusually large 4 degrees for a fighter, and on the first flight, as soon as the flaps were retracted, turbulence from the wing root stall struck the horizontal stabilizer, causing vibrations. As a countermeasure, the fillets were enlarged.

blackkite · Saturday at 03:20

Flap
To gain an advantage in maneuverability, especially turning ability, in combat with land-based and carrier-based aircraft, Kawanishi developed an automatic air combat flap that automatically operates the Fowler flaps at the optimal angle according to speed and load. This was a unique invention by Kawanishi that enables automatic adjustment of the flaps using a container filled with mercury (a type of manometer (liquid column pressure gauge)) to detect dynamic pressure and load. The Kyoufu had a relatively large wing loading to achieve high speed, but this automatic air combat flap succeeded in giving it turning ability that could keep up with the Type 2 floatplane fighter, which had a smaller wing loading. The device installed on the Kyoufu was a prototype, and a more complete version was installed on the Shiden.

blackkite · 2024-11-18T03:08:44-0500

Floats
The floats consisted of a main float under the fuselage and auxiliary floats under both wings, similar to the type 2 seaplane fighter. The main floats were supported at the front by a V-shaped strut with a small angle, and at the rear by a thin, wide strut in the axial direction, each designed to reduce air resistance (this is the opposite of the strut arrangement on the type 2 seaplane fighter. Initially, the auxiliary floats were considered to be retractable like those on the Shiun, but after the troubles with the Shhiun, they were made fixed to avoid complicating the mechanism.

‹•—

blackkite · 2024-11-18T03:18:25-0500

Propeller
Contra-rotating propellers on Kyofu's prototype
The prototype used a contra-rotating propeller with two propeller blades, just like the Shiun, to eliminate the deflection of the aircraft caused by the spiral propeller wake. This made takeoff and landing on water easier, and the maneuverability and directional stability were good, and it was very well received by test pilots. However, it was not possible to eliminate the poor maintainability and oil leakage caused by the complexity of the propeller reduction gear, which was also a problem with the Shiun, so the mass-produced model was switched to a normal three-blade propeller. However, in the early production model, a gap was left where the second propeller was supposed to be, giving the propeller spinner a distinctive appearance of protruding forward from the cowl opening.
In addition, in later production models, the collective exhaust pipe was changed to a thrust-type single exhaust pipe, and the front end of the cowl was extended, and the rear of the propeller spinner, which had redundant space as a remnant of the contra-rotating propeller, was covered by the cowl.
The left torque of the Kasei engine, with a takeoff output of 1,460 horsepower, was so strong that the foot bar had to be operated with considerable force to counteract it, making takeoff and landing on water difficult.

Justo Miranda · 2024-11-18T03:57:48-0500

Some additional info here

Justo Miranda · 2024-11-18T04:00:33-0500

Post-2

Justo Miranda · 2024-11-18T04:04:55-0500

Post-3

Kawanishi N1K1 "Kyofu" 15-Shi Fighter Seaplane (K-20)

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