I have a slight confusion about symmetric airfoils-PLEASE HELP ME CLARIFY THEM
I)In model 3-D aerobatic planes is the symmetric airfoil at a slight angle of attack or else how do they fly?(Actual model owners plz do reply)
II)Is it actually necessary that for a plane to have 3-D aerobatic capability it has to have a symmetrical airfoil?

(a) Not necessarily. Even though sym airfoil doesnt provide lift at 0 angle of attack, you can always fly it adjusting the cg, to give a bit of angle of attack during flight
(b) If you are referring to an inverted flight in 3D aerobatic then flat bottom airfoil fail to do inverted manuvers as their airfoil design force them back to normal position. flat bottom airfoils can do decent maneuvers.