The drwing is ok the directions are wrong, #2 picture is the rib and leading edge, #1 is the top view of the whole assembly, #3 is the side view of the rib,leadin edge,and trailing edge w/wing tip. The A part in the top view is the remaining wood piece used to make the trailing edge/wing tip assembly that is shown in the side view as assembly "A". I have one of these in the closet and could check the plans to help you out if you want.
E-mail me.
Ray