ORIGINAL: aerowoof
common mistake of using the flat section of a flat bottom airfoil such as a clark y etc, as 0 degree incidence,as the true incidence runs from the center of the le to the center of the trailing edge and is usually 2-3 degrees positive if the flat portion is at 0
I understand what you are saying aerowoof. On my particular set of plans as they have drawn the wing outline, if you use the center of the LE and TE as the reference line (as you would with an incidence meter), I end up with 2 degrees of
negative incidence in the top wing, and 1 degree
negative for the bottom wing.
Negative incidence did not seem right to me??? That is I why I looked at the flat bottom of the Clark Y. I was afraid that the wing outlines may not be drawn correctly on the plans???
Now that I have measured more closely the flat portion of the wings is close to 0 for both the top and bottom wings as per your post, and the stab is + 2 degrees.
In summary, according to my plans:
Using Incidence Meter (center of LE and TE): Top -2, Bottom -1, Stab +2
Using Flat portion of Wings as drawn on plan: Top 0, Bottom 0, Stab +2
NOTE: On the 1/5 scale Pica WACO plans it states the incidence as 0 for both top and bottom wings and +2 degrees for the stab. Using the flat portion of the wings as your reference line this would give the same numbers for the 1/6 scale WACO.
I hope I’m not confusing everyone.