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Scratch jet design

Old 09-16-2018, 11:55 AM
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nilsreinert123
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Default 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.


Old 09-16-2018, 02:26 PM
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speedracerntrixie
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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.
Old 09-16-2018, 09:25 PM
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nilsreinert123
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Yes it is a V-tail , and wingspan is 2 metre .
Old 09-17-2018, 02:41 PM
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Art ARRO
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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.
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Art ARRO
Old 09-17-2018, 11:18 PM
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nilsreinert123
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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 glassed

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Old 09-18-2018, 02:08 PM
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Art ARRO
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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
Old 12-20-2018, 03:06 AM
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Old 12-20-2018, 03:18 AM
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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
Old 12-22-2018, 06:14 AM
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Old 06-18-2019, 02:22 AM
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I have glassed and painted the plane now , so next is building canopy and installing all the gear.



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Old 06-20-2019, 02:33 AM
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Building the canopy
Old 07-12-2019, 07:01 PM
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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
Old 08-03-2019, 12:43 AM
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The plane is almost finished now , so i will try to fly it as it is now and see how it fly
Old 11-27-2020, 12:03 AM
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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



Old 01-07-2021, 11:45 AM
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nilsreinert123
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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.
Old 01-07-2021, 09:28 PM
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I think that you need a larger elevon surface,and a forward balance.
Originally Posted by nilsreinert123 View Post
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.
Old 01-07-2021, 09:31 PM
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bring some stability by using a bigger spine fin through the vert axis to the turbine

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