An airfoil doesn't need camber (the arch you mentioned) in order to generate lift, it just needs an angle of attack.

For aerobatic airplanes, you want to look at symmetrical airfoils because in aerobatics you will want an airfoil with right-side-up performance equal to (or at least similar to) upside-down performance.

What exactly are you trying to learn about airfoils?

Ken - www.litkoaero.com
R/C Aircraft Laser Cutting and Design