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

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

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.

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

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