I have a situation with some 'oil-canning' occurring on the bottom of the wing tips. I mounted the wing tips and as best I could determined where the oil-canning was occuring and the size of the area. I marked the extents with a pencil. I thought about several ways to fix the problem, but settled on adding an internal partial rib to each tip that spans the area affected. I have some 1/4" foam left over and measured and cut a piece just big enough to fit the area. Some slight sanding got the contour to match the wing tip. I then layed-up 2 plys of 6 oz cloth between a heavy duty trash bag segment, and then cut/trimmed the lay-up to the same dimensions as the foam plus 2 " (to allow for attachment to the wing tip. Applied expoxy to the form rib and the wing tip sides, then removed one side of the trash bag plastic, and put the lay-up in position on the rib, used a squeege to remove air bubbles, and stippled it with the brush. repeated for the other rib following same procedure. Remounted the wing tips and it seems to have solved the problem. I painted 4 coats of smooth prime on the hinge covers, then sanded them w/ 220 grit and remounted them. I also rounded the edges of the routed out area where the covers will sit so that when painted they will look better than a sharp edge.
