It sounds like you didn't cut a notch for the hinge knuckle to go into. If you are going for extreme 3D throws then you would bevel the leading edge of the moving surface and the trailing edge of the fixed surface. Then you would notch both surfaces such that the hinge pivot is right in the middle.

For normal aircraft I usually bevel just the moving surface about 35 degrees which will allow about 30 degrees of movement after the covering is applied (if you put the surfaces tightly together with almost zero gap.

Oh, and when I say bevel, I mean double bevel. The apex of the bevel is on the center of the hinge line.