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-   Scratch Building, Aircraft Design, 3D/CAD (https://www.rcuniverse.com/forum/scratch-building-aircraft-design-3d-cad-174/)
-   -   Scratch jet design (https://www.rcuniverse.com/forum/scratch-building-aircraft-design-3d-cad-174/11654195-scratch-jet-design.html)

nilsreinert123 09-16-2018 11:55 AM

Scratch jet design
 
I need your opinion on my own designed jet, does it looks like it has too short tail moment ? What do you think.


https://cimg2.ibsrv.net/gimg/www.rcu...69132dbf64.jpg

speedracerntrixie 09-16-2018 02:26 PM

I wouldn't say the tail moment is too short but IMO being a V tail as it appears to be I think the tail area is a bit small.

nilsreinert123 09-16-2018 09:25 PM

Yes it is a V-tail , and wingspan is 2 metre .

Art ARRO 09-17-2018 02:41 PM

Nils, I designed a similar scratch built jet several years ago for glow ducted fan. I built several profile sub models to determine the tail angle and area. These were made from thin ( 2-3 mm) balsa and hand launched from my house deck. I determined that a 70 * included angle on the tail worked, ie, glided, the best. Also, made several tails and experimented with the different sizes and areas. The sub-models were scaled up for the flight model which flew very well. It was powered by a Turbax fan unit driven by a Jett 50 DF motor. I'm currently thinking about enlarging it 125% for a 2.5 or 3 m wingspan to be powered by a Wren 44K turbine. Good luck on your project.
Regards,
Art ARRO

nilsreinert123 09-17-2018 11:18 PM

Thanks Art . What do you mean by 70 included angle on the tail ? Is that the V angle ? I have 120 degree on this . I will use my simjet 1200 on it. I have started to build so i can roughly see how it will look , the wings will be balsa sheeted and the whole plane glassedhttps://cimg4.ibsrv.net/gimg/www.rcu...df6fd32a6e.jpg

Art ARRO 09-18-2018 02:08 PM

Nils,
The included angle is the angle on my jig/fixture to set the incidence of the tail. This is 1/2 of the angle between both tails or 140 degrees. Sorry for any confusion. .There is a direct relationship between the angle and the projected areas of the horizontal and vertical stabilizers. I did a lot of research
and ended up making various tails out of balsa sheet to experiment on my sub-scale models. It worked out just fine.
Regards,
Art ARRO

nilsreinert123 12-20-2018 03:06 AM

https://cimg9.ibsrv.net/gimg/www.rcu...5516aacc17.jpg
https://cimg3.ibsrv.net/gimg/www.rcu...c17e45c2a7.jpg

nilsreinert123 12-20-2018 03:18 AM

Finished covering the wing and parts of fuselage now with epoxy and 22gsm glass cloth. Next will be to paint and install equipment and turbine. I have drawed the canopy on the picture for visual reference. Wonder how this will fly . It will be light , balances ok with the Simjet 1200 in the tail and batteries in front hatch. Also i have some lead in the nose tip. Very exciting project :)

nilsreinert123 12-22-2018 06:14 AM

https://cimg0.ibsrv.net/gimg/www.rcu...6468b7722e.jpg
https://cimg2.ibsrv.net/gimg/www.rcu...35f86b35dd.jpg
https://cimg3.ibsrv.net/gimg/www.rcu...150964ff9f.jpg
https://cimg9.ibsrv.net/gimg/www.rcu...107e239114.jpg

nilsreinert123 06-18-2019 02:22 AM

I have glassed and painted the plane now , so next is building canopy and installing all the gear.

https://cimg3.ibsrv.net/gimg/www.rcu...70a7c15b92.jpg
https://cimg7.ibsrv.net/gimg/www.rcu...a0e86a0493.jpg

nilsreinert123 06-20-2019 02:33 AM

https://cimg8.ibsrv.net/gimg/www.rcu...d418fbfb54.jpg

Building the canopy

alex5 07-12-2019 07:01 PM

three fighter jets have a similar profile,except they use a standard tail config...perhaps you should consider the proportions,of the canuck,c100,F104 starfighter,and the Tutor,to get moment correct

nilsreinert123 08-03-2019 12:43 AM

The plane is almost finished now , so i will try to fly it as it is now and see how it fly

nilsreinert123 11-27-2020 12:03 AM

It flew nice , but i stalled it by flying too slow so it crashed on first flight,but it is already repaired and ready for a new flight :)

https://cimg6.ibsrv.net/gimg/www.rcu...6f4d622f57.jpg
https://cimg7.ibsrv.net/gimg/www.rcu...ff87180d21.jpg

nilsreinert123 01-07-2021 11:45 AM

Flew it again today on a frozen lake, it did not crash so it was a success :) Since last lesson learned i mixed in 5mm up aileron following the elevator and it seem to help on the bad flicking tendencies. But today it was very unstable in pitch ,sensitive on the elevator . I hope i can cure this problem by adding some nose weight..and that i dont have too little tail volume on my plane.

alex5 01-07-2021 09:28 PM

what I see,
 
I think that you need a larger elevon surface,and a forward balance.

Originally Posted by nilsreinert123 (Post 12655580)
Flew it again today on a frozen lake, it did not crash so it was a success :) Since last lesson learned i mixed in 5mm up aileron following the elevator and it seem to help on the bad flicking tendencies. But today it was very unstable in pitch ,sensitive on the elevator . I hope i can cure this problem by adding some nose weight..and that i dont have too little tail volume on my plane.


alex5 01-07-2021 09:31 PM

bring some stability by using a bigger spine fin through the vert axis to the turbine


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