I'm building a Phaeton 90 and am confused by conflicting information i've heard about wing incidence stability.

I contacted Balsa USA and was informed of the following:

For optimum aerobatic performance set it up, top wing 1-2 degrees negative, bottom wing 0.0, tail 0.0 but like this you should only need 0-2 degrees down thrust and I would say 1-2 degrees right thrust. this will make the model real quicker in turns, spins, snap rolls and other maneuvers entered through stalling the model, but will also lead to higher stall and landing speed and possibly tip stalling.

For optimum stability set it up like this, top wing 1-2 degrees positive, bottom wing 0-1 degree negative, and the tail 0.0. with this you will need more down thrust maybe 2-3 degrees and again right thrust should be 1 -2 degrees. This will provide easy going flight with a very gentle stall and lower landing speeds, but will make the model slower in roll rate and less likely to spin.

I've heard from others that the reverse is true, stability would be greater if the incidence is set to negative on the top wing, rather than positive. I'm looking for low and slow stable landings.

Any help would be appriciated,

RickT
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Interesting question. My GP Supersportster has 1 degree neg in the top wing as per plans, but I don't know how pos. would influence it. If you get no answers here, try re-posting in the aerodynamics forum.

Negative in the top wing compared to the bottom is best for low speed stability. With this setup, the bottom wing will stall first because it will always have a higher angle of attack whenever the model is upright. With the bottom wing stalled and the top wing still flying, the fuse will act like a pendulum hanging from the top wing.

As far as aerobatics, the same setup works very well.

If you set the top wing positive compared to the bottom wing, the model will experience increased drag and will not fly as smoothly.

Been there, done that.

The best thing to do is follow the plans. That is how the model was designed and tested. The kit manuf knows what to expect with the model setup this way. Unless you are willing to experiment and possibly change the top wing after you have flown the model a few times, I wouldn't deviate from the plans on wing or tail incidence angles.

John

John

Believe what BalsaUSA said. I've built several of their bipes and all flew best with negative 1.5 to 2 degrees on the upper wing, 0 on the lower and all required about 3 to 5 degrees downthrust and some right thrust to fly at their best. Just a half degree change in the incidence of the upper wing can change a doggy flyer into a nice flying plane. If you can, build it to allow a little experimentation on this, you may need to fine tune it a bit.

I've got a lot of flights on the Phaeton 90 and 1 or 2 degrees negative on top and zero on bottom and stab will give you a very nice flying bipe. Even before I changed the incidence (the plans don't show any incidence, which to me, means zero) it was still as stable as could be, it just flew with a definite nose up attitude.
Believe me, you don't have to worry about this plane. There's NOTHING hairy about it. I trained my son to fly with it when he was twelve years old. It's strictly a creampuff even as heavy as mine was with a 4 pound gasser up front.
Great flying bipe.
I crashed mine eventually when it went dead , low, slow and inverted. I couldn't pull out in time.

Thanks to everyone who helped me out with this. I'll be going with -1 degree on the top wing and 0 bottom, 0 stab, 1.5 right thrust and 2 down thrust for the G26 engine.

Rick Taggart, AMA 23715, IMAA 26601
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The GP Aeromaster 60 has 1 degree neg incidence in the top wing. I built both the Lou Andrews and GP Aeromaster 60's this winter and the LA kit doesn't mention incidence on the top wing. The 2 planes are identical except for how the landing gear, and both wings are attached.