Zero lift occurs at what angle of attack for positive camber

Zero lift occurs at what angle of attack for positive camber airfoil?

Solution

Zero lift occurs at negative angle of attack for positive camber airfoil.

If the camber line lies above the chord line, then an asymmetrical airfoil section results. (Upper surface is not a mirror image of the lower surface.) When the free-stream velocity is alined along the chord line (a = 0°), a positive lift results. The chord line must be negatively inclined with respect to the free stream to obtain zero lift (that is, the angle of zero lift a_L=0 is less than 0°.