Kayaba Katsuodori concept plane- Nobi scaled to 1/33

[Isaac]

I came across the design of Japanese concept planes sort of reluctantly after building many Luft 46 aircraft designs. The first aircraft that caught my eye was this little flying wing powered by a ram jet and 4 booster rockets. I found a 1/72 scale plastic model kit by a company called Meng. At that scale, it was a mere 4.8 inches in wing span. It is a simple model to build.



The next step was when I saw Nobi's 1/48 scale paper version. Since I do not build in that scale ( not in paper ), I contacted him and got his permission to scale it up to 1/33 scale , common to my other paper planes ( scale factor was 1.45 ) and post the build log here.



Since the kit is extremely simple and has few parts, it was relatively quick build.


At first, I decided to build it at its original scale of 1/48 so I can see what may be some of the issues to scale up.



A bit of history.
I purchased the Japanese Secret Projects book by Edwin M. Dyer, III which is a good reference with information 3 views and hypothetical paint schemes. That book relies on many Japanese artist for the colors.



Kyaba back in 1937 was interested in Ram Jet engines. Those are engines that unlike conventional Jets have no rotating compressors or turbines. They rely on the aircraft forward speed to compress the air ( it is rammed to the inlet ), then you spray fuel in the combustion chamber and it then expels aft when expending. Simple in every respect, but inefficient below 400 MPH. So you really need the aircraft to go fast first and then turn this engine on. The way to do it is to rely on another power source like rocket motors and then switch to Ram power.
During WW II, when Japan realized it needed to intercept high altitude B-29 bombers, they tried different types. Some brought from Germany ( like the Me-163 Komet ) and modified locally. The Katsuodori was another way to do it. The concept never left the drawing boards and most likely would have been more dangerous to the pilots and ground crews since the liquid rockets proposed had bad habit of exploding on the ground.

Lastly, Katsuodori is a name of a bird that swoops down and hunts fish ( like a Kingfisher ) Katsu = fish Dori or Tori = bird



Isaac

[Isaac]

Here is the published 1/48 scale build.

Few parts as shown. The fuselage is barrel like with the cockpit and aft fairing on top and the wings mounted shoulder high. Vertical fins are on the wing tips.


Parts



Sub assemblies




Wing spars
I decided to use wood coffee stirs as wing spar. This supports them better and keeps them straight.



Wings mated



Model done


For now, I decided not to add the 4 external rockets


Compare to 1/72 scale.





Cheers

Isaac

[Yu Gyokubun]

Isaac san,

I didn't know about this plane. They tried to emply flying wing for compensating lack of engine power?

Both your paper and plastic model look cool.

B-29 reminds me of what my mom would say when I was a boy. She said no Japanese interceptor reached to that high when B-29 fly over Yokohama in formation flight and their shining airframe looked beautiful then she knew the was will end soon.

One more thing is "shoot down B-29 with bamboo spear" that if then government encouraged people to practice and later, for certain period, the expression was used to express to do something impossible.

Even if this plane had been realized, it would have ended up confetti....

BTW, for me Japanese the name Katsuodori doesn't sound much like gallant fighter plane.

Yu

[Don Boose]

A most interesting model, Isaac.

And some interesting comments about that period, Yu-sama.

Don

[Isaac]

Originally Posted by Yu Gyokubun

Isaac san,

I didn't know about this plane. They tried to emply flying wing for compensating lack of engine power?

Both your paper and plastic model look cool.



Yu

Yu san

I have attached some information from my Nihongo book on the subject of Japanese project planes. Here are a few pages describing the Katsuodori.

If you want to translate some of the information, please do.


Enjoy






Isaac

[rockpaperscissor]

That really came out good. Very attractive model. Did you encounter any problems during the build with fit or order of assembly? I have the file, and plan to build it (someday) in 1/72 scale.

[Isaac]

The model scales nicely from 1/48 to 1/33 scale. The scale factor is 1.45. I did it simply by printing the various parts by this scale on card stock ( 160 g weight ).



Since the assembly is identical to the 1/48, there will be few words to add. However, I did cut out the area for a cockpit and will later build an interior as well as make a vacuform clear canopy. In addition, I will build a dolly to support the model just like my plastic one in 1/72 scale.

Fuselage




Wings
I have used wood coffee stir sticks for internal spars. Much stronger and straight.




Wings attached.



Vertical fins
Only addition was to have an inner cardboard filler to give it some volume.



Also,
I am taking a little break from my Ta-183 build.

Iruma airbase is having its annual airshow this weekend November 3rd. I plan to be there again!!!!!!!!!!!!!!!!!!!!!


Cheers


Isaac

[Yu Gyokubun]

Isaac san,
Thank you for the book.
I quickly scan through the book. It’s a shame that after the ku-2, which was a base of Kayabakatsuodori, run into trouble in 1941, development of Kayabakatsuodori was terminated.
Have a nice weekend at Iruma
Yu

[Isaac]

Originally Posted by rockpaperscissor

That really came out good. Very attractive model. Did you encounter any problems during the build with fit or order of assembly? I have the file, and plan to build it (someday) in 1/72 scale.

The parts fit well. Very simple model.

If you shrink it you will need the wood spars or else, the fit may be an issue.


You can build it in one evening.

Isaac

[Isaac]

Since this aircraft never made it off the drawing boards, I will have to assume the simple cockpit. I am still not sure how it would have fitted above the engine and still allow the pilot to seat up right.

For now, I am still evaluating how it may have looked.

Isaac