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Scratch jet design

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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.


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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.
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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 .
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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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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.
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