Determining incedence angle on a symmetrical wing?

[EABiker]

I am designing a symmetrical airfoil foam wing that will be held in place by the opening cut into the fuselage, so once it is installed, it cannot be adjusted. My question is...do I consider the centerline of the airfoil to be the the plane that needs to be parallel to the horizontal stabilizer?? :confused:

Thanks,

Eric

[Sparky Paul]

Yes.

[EABiker]

Thanks for the quick response!

Eric :)

[Salto]

Eric,

I've recently been playing around with various models using the Eppler 479 symmetrical airfoil. They have all been built with zero wing and stab incidence. With a nicely rearward C/G, I've found they fly level with no elevator trim, and fly inverted with little or no down elevator input. They've mostly been 3D type models, so the rearward C/G and neutral or slightly -ve pitch stability have been what was needed anyway.

If the C/G is more forward, to give some pitch stability, then with zero wing incidence you'll need a bit of up elevator trim to fly level. I havn't measured anything on my models, but I would think 1 deg. +ve incidence on the wing, and a corresponding forward C/G would have some useful pitch stability.

A good solution to the problem of building a wing that cannot be adjusted for incidence, is to make the horizontal stab all-flying. I've done this on 3D type models and it takes all the guess work out of setting up the wing - you just correct for required incidence with "elevator" servo centre position.

Hope this helps.

Graham.