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Old 12-11-2004 | 03:55 AM
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NFOOTE
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From: Issaquah, WA
Default RE: canard flap location..??

ORIGINAL: Johng

Nate is correct about needing the canard to stall first and still provide lift when the wing is at zero lift. There are other ways to achieve this besides airfoil selection or modification(flaps). You can play with the canard loading (cg location) to get the canard loaded higher, so it must function at a higher angle of attack, closer to stall. This could impact maneverability in aerobatic flight though. Also, a higher aspect ratio wing will stall at a lower angle of attack. And, remember that reynolds number is a big consideration at model sizes - as Mike j can tell you first hand from his long-ez experience. The canard chord can be so small, that it won't provide enough lift to get off the ground. While this can be a headache, you could also tailor it to be a feature that provides stability at approach speed while still being manueverable in up-n-away flight. Of course, this figures into the aspect ratio equation as well. All of these things involve a real balancing act that would take some serious tweaking and forethought.

I might suggest that you consider NACA leading edge droop on the main wing, or even LE flaps to allow it to function at a higher angle of attack. Then use flaps or even slotted flaps on the canard to drive the angle of attack higher. The LE flaps don't add much drag themselves, but they allow the whole plane to get nose high which will be draggy in itself.

Yep: right on. I should have mentioned it but wasn't thinking. Re plays a huge factor on the characteristics of an airfoil depending on the size and speed of your plane. Good luck finding low speed data... There is some but not a lot and computer programs only go so far.

By the way, with computer radios these days, it makes mixing the flaps between the canard and the main wing a breeze if you go that route.

Good luck on your project,
Nate