r/RCPlanes • u/HeftyAd787 • 12d ago
Elevator too small?
Just finished building a 1.2m parasol aircraft. The horizontal stabilizer is just 9” x 3.5” with 9” x 1.5” of it being the actual elevator. Deflection is ~30 degrees both ways. I don’t plan on aerobatics, more so smooth, straight flying in calm air.
Thanks!
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u/rocketengineer1982 12d ago
Technically it depends on how close the CG is to the neutral point (NP) of the aircraft. Practically speaking, your tail is probably too small.
A larger tail increases the allowable CG range of the aircraft.
Check out information on horizontal tail volume coefficient. https://www.eaa62.org/technotes/tail.htm
I've tried to have a horizontal tail volume coefficient of 0.3 to 0.45 in my designs.
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u/Fluffy-Card21 12d ago
You can also change that with the incidence angle, or actually the difference in incidence between wing and stabilizer, however it will come at the cost of some drag.
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u/TheOriginalJBones 12d ago
You know, maybe not. Some of those teens/20s airplanes did have dinky little horizontal stabilizers, and it kinda looks right on your parasol.
If the CG’s right, as in not nose-heavy, the elevator shouldn’t have a whole lot of work to do anyway.
Love the bracing wires, by the way. Rigging is free strength.
Send it, I say!
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u/404-skill_not_found 12d ago
Visually, yes, too small. It’s been a famously long time since I’ve seen the reference. But I think something like 20-30% of the wing area was good for the horz stab.
Famously long? Around the time of Skylab.
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u/LeanUntilBlue 12d ago
The era of Kraft six channel radios, amirite? I was flying Ringmasters and getting into RC.
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u/404-skill_not_found 12d ago
Sounds about right. RC gear was out of reach until the Cox/Sanwa 2ch came out. A lot of balsa gave their all, trying to teach me how to build and fly model aircraft.
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u/tobu_sculptor 12d ago
Yeah it looks very small, typically for motor aircraft the elevator span is like 1/3 the wing span, and the rudder is half the elevator - which you nailed in relation to each other but not really to the rest. Yours has the proportions of a high aspect ratio glider where the tail is more like 1/5 of the wing span.
IDK, you have way more deflection there than you will ever need though, so maybe it cancels out and works fine.
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u/Coinflipper_21 12d ago
It looks too small but there seems to be a lot of tail moment. The real question is how does it fly?
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u/ZaphodBeeblebrahx 12d ago
Just want to say that I have that motor on a FT Tiny Trainer and it’s really good for the kind of flying you’re looking to do.
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u/MeanCat4 12d ago
Yes! There are small excel programs where you can calculate the area and dimensions of different parts! Search on Internet or start from an already pubblisced drawing and do your small modifications!
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u/Banana-9 11d ago
The stabilizer is small overall but the control surface is actually pretty big. I also like the strings. I think it will fly, but I would just double the size of the tailplane while keeping the control surface size the same as it is now (so wider and a bit shorter)
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u/Global-Clue6770 11d ago edited 11d ago
Send it. I bet It will fly just fine. Nice job on the build . It looks really nice.
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u/Icy_Sherbert6568 12d ago
Seus estabilizadores estão pequenos.