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Old Dec 20, 2014, 10:34 AM
Declan R.
Joined Nov 2014
9 Posts
Question
Does this look like a decent airfoil for what I want?

I'm building a skywalker-like fpv platform out of epp, and I built the wing pictured below. I want to know if this is airfoil will give me a good glide slope, and I also want to know how well this airfoil will do inverted. It looks a bit like a NACA 4 digit 2413 or 2415 to me.
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Old Dec 20, 2014, 01:34 PM
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whitecrest's Avatar
Orleans, MA
Joined Feb 2007
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If you are shooting for a shallow glide slope, wing loading will be more important than the airfoil used. Anything less than 10oz/sq.ft. should produce a reasonable glide. Also, a lifting airfoil (like a Clark Y) will help the glide. Yours looks somewhat symmetrical so it should do fairly well inverted at the expense of better glide capability. You could produce a more precise airfoil if you cut a foam core.
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Old Dec 20, 2014, 01:47 PM
Declan R.
Joined Nov 2014
9 Posts
Thank you. I don't want to cut a wing core because my hotwire isn't long enough. When I mount the wing on the plane, at what angle should I mount it relative to the tail? I know the skywalker uses a clark-y tilted about two degrees upward.
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Old Dec 20, 2014, 02:15 PM
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Orleans, MA
Joined Feb 2007
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I would set the wing and tail at zero incidence to start. See how it flies and adjust for better flight characteristics if necessary.

I've had good luck with scratch builds using a built-up Clark Y airfoil (balsa construction) set at zero incidence for wing and tail. I can get the flight characteristics I want by adjusting CG, elevator trim (not incidence) and motor thrust angle.
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Old Dec 20, 2014, 02:41 PM
Declan R.
Joined Nov 2014
9 Posts
What about the thickness of the airfoil? Is it ok for medium speed flight?
Is a semi-symmetrical airfoil a good choice for high winds (In that it doesn't get affected by the wind)?
I mean, this plane isn't going to be a glider, but I still want typical/better than typical glide performance.
A NACA 2415 is the closest I can get to this airfoil.
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Last edited by Decroxx; Dec 20, 2014 at 03:21 PM.
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Old Dec 20, 2014, 03:10 PM
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Orleans, MA
Joined Feb 2007
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A thicker airfoil is generally more suitable for slower flight, and a heavier wing loading will generally do better (better penetration and less twitchy) in higher wind speeds.

I have a small park flier (Clark Y foil) with just 210 sq.in. wing area and 7.5 oz/sq.ft. wing loading that does fine in 10-12 mph winds. It also has a very shallow dead-stick glide.
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Old Dec 20, 2014, 08:35 PM
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Joined Apr 2013
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I don't know what span you're doing, but if it's anything up till around 60 inches then I agree with whitecrest that concentrating on lowering wing loading will be the most important factor in improving glide ratio. Of course, having ridiculously low wing loading in strong/turbulent conditions can make things challenging. So as always, there's a trade-off.
The second most influential factor (for glide ratio) at this scale is drag, and your wing looks pretty un-draggy. Just don't add a whole lot of draggy structure to the rest of the plane.
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Old Dec 20, 2014, 09:35 PM
Declan R.
Joined Nov 2014
9 Posts
Thanks guys! I'll try out this wing, and, if it doesn't provide the characteristics I want, I'll modify it. But, based on your feedback, I think I can achieve what I want with this wing.
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