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Old Nov 29, 2010, 03:12 PM
jackerbes is offline
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USA, ME, Ellsworth
Joined May 2008
18,098 Posts

It does make sense. And I don't think there will be remarkable differences in the way that plane would fly with either the Clark Y or the KFm3. My impression after having had and flown a couple of Clark Y wings is that the KFm3 might have better slow flight performance and a more gentle stall.

If you want the best aileron performance, I recommend building flat or with very low dihedral. The combination of dihedral and ailerons can work together OK, it may need the use of some differential control on the ailerons to satisfy some of us. So all thing considered if I want to fly with good aileron action/roll rates I will surrender the inherent stability of the dihedral to get it.

The Clark Y's I had were bigger heavier high winged planes (64-72" wings and 6-7 pounds in weight) and both wonderful fliers but had characters that were very different than the foamies.

Essentially the test is simply "If I move the wing from top to bottom, how will it fly?". With the ease and speed of building these KF wings, it sure makes it hard NOT to implement them for testing. Then again, I could make a built up wing AND KF wing to contrast and compare but perhaps Im getting a little ahead of myself.
If there is a danger in this is might be that you'll find yourself losing interest in Clark Y wings and become a "foamaholic" or "KFm addict." I love the building but also like it to be simple and go pretty quickly. And the FFF foam and KFm wings have certainly fed that process.

There are a number of KFm variations with the steps varying in number and location. There is a figure at the start of the thread that shows some of the step configurations.

If the goal is to build a low winged plane it would typically be a higher performance and more aerobatic plane. That has been done KFm wings too and the KFm4 variation, with steps top and bottom at 50% of the chord has proven itself to be the best performing KF wing in that configuration. A foamie called the Piranha is a good example of a low winged KFm4 foamie. Again there is a link to that plane in the list of planes at the start of this thread.

The KF foils have given rise to a number of great flying wings too (Zagnutz, SpaFFFnutz, Divinity, The Nifty, KESL, etc., etc.) and nearly all of those were built as KFm4 wings. The KFm4 seems to a natural choice for flying wings because the KFm4 really adapts itself well to the maneuverability and speed many expect from flying wings.

But the interesting thing is that if you compare a KFm4 flying wing to a Clark Y or flat bottomed Clark type airfoil on a flying wing you'll find that the KFm4 flying wing will be much easier to fly, it will be able to slow down to a crawl in most cases, doesn't seem to know how to stall and fall out of the air, and it easily built and flown by relatively new fliers. If you have mastered a high wing RET trainer and are making most of the stick movements in your subconscious, you are rprobably eady for one of these gentle KFm flying wings.

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