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Building Tips and technical articles. => Building techniques => Topic started by: RknRusty on December 31, 2016, 01:44:25 PM
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There is an unlikely looking trick to create lift on an otherwise flat plank airfoil. I've seen it on 1/2A and Jr. planes. It's usually a strip of material that is attached along the LE span and is tall enough to affect air flow and on a small plane can give it some more lift, maneuverability, and possibly glide.
Here's a picture I drew to illustrate the end-view as if you are looking straight at the wingtip. Seems like the name is the initials of the person credited with making it popular.
Thanks,
Rusty
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seen it on park flyers, clever
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There is an unlikely looking trick to create lift on an otherwise flat plank airfoil. I've seen it on 1/2A and Jr. planes. It's usually a strip of material that is attached along the LE span and is tall enough to affect air flow and on a small plane can give it some more lift, maneuverability, and possibly glide.
Here's a picture I drew to illustrate the end-view as if you are looking straight at the wingtip. Seems like the name is the initials of the person credited with making it popular.
Thanks,
Rusty
Kline-Fogleman KFm- Airfoil.
https://en.wikipedia.org/wiki/Kline%E2%80%93Fogleman_airfoil (https://en.wikipedia.org/wiki/Kline%E2%80%93Fogleman_airfoil)
(https://upload.wikimedia.org/wikipedia/commons/2/22/KFm_Family_of_Airfoils_Ver_3.png)
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Thanks, Brent, that's the cat's ass. Just what I wanted.
Rusty
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In spite of Kline and Fogelman's successes with it on paper planes, it's never proven itself in practice. It does make for a stronger wing, but it doesn't really add much to the performance.
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seen it on park flyers, clever
From what I've read the park flyers do it so they can use cheap, office max foam board. Thin light foam is very non-stiff, so the multiple layers make it less likely to flap. The molded planes almost all use small carbon fiber spars for the safe effect.
Even for park flyers almost any "real" airfoil works better than flat foam. Dick Sarpolus and I did some experiments which showed that. After that he switched 100% to an airfoiled foam wing.
Phil C
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Thanks, guys, I'll pass your comments along to my buddy the builder and determined experimenter. If he makes a project of this, I'll report back with how it turns out for him. I already sent him the Wiki link and pictures.
Happy New Year to all of you! I hear the fireworks ramping up now.
Rusty
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Theres a ancient book on Whyte , or Grahame white ?? aircraft , pre WW1 , on the Isle of Wight ?? Floatplanes and suchlike .
Part of its on Airfoils , Some Multi stepped on top , similar to the stepped one in the drawing . No luck on google pics on it .
Cant remember which library had it .
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There is an unlikely looking trick to create lift on an otherwise flat plank airfoil. I've seen it on 1/2A and Jr. planes. It's usually a strip of material that is attached along the LE span and is tall enough to affect air flow and on a small plane can give it some more lift, maneuverability, and possibly glide.
Poor? As noted, it's close to a variant on a Kline-Fogelman, but that might be a coincidence. To me, I would imagine that some tried to make the airplane with a flat plate, found it wasn't strong enough and got dinged too easily when you ran it into something, and added the top and bottom parts as a combination of spars and toughening up the LE. The fact that it looks like a crude symmetrical Kline-Fogelman doesn't mean they set out to do it that way.
Note also that these airfoils are generally not very good. These (and flat plates) work less poorly at model airplane Reynolds numbers where you are flying through "honey" vice full-scale where you are flying through "alcohol", but they aren't as good as real airfoils.
Brett