As you can see I’m making a Dragon, but I need some advice for the wings. They have a 3D bone structure and originally I extruded one edge to create the thin wing membrane between the bones, but Blender seems to be having problems with the Normals on this membrane, randomly turning some in and some out.
Is it appropriate to create the membrane by extruding only 1 edge, or should I give the membrane 2 surfaces?
If you extrude an edge to make the wing membrane, you create what is referred to as a ‘non-manifold’ object (where three faces share one edge). Although you can technically do this, you may find that it introduces more difficulties than it is worth. Lighting normals will be all jacked up, and you will see weird lighting artifacts along these shared edges.
Bottom line is this: it is probably far better to avoid the non-manifold issue by creating the wing membrane with two sides.