Roof patch causing warp / oil canning

[mongocanfly]

Robert...great explanation of gap vs no gap....

[nsb29]

I think the idea of using metal bond would be my choice. The idea of cutting a hole in the inner cab is only going to create more work, if the backer is kept to a minimum amount of overlap and you use slick-sand as your high build primer chances of having ghost lines would be slim to nun.

[ItWillBeSlow]

Thanks for the continued discussion. After some more research on the metal bond, it does seem this would be the simplest solution. This brings me to a few new questions as I plan to explore this direction further:


- Should I stick with my current ~2" square patch, or open the hole to be circular if using metal bond?

- Do I need to leave a small gap around the perimeter of the patch for the material to bond the edges, or do I want it as tight as possible?

- When placing a backer, do I want "space the backer" down toward the inner roof, so that there is a small gap between the backer and my patch for the bond material to fill? Or does it need to be completely flush? It seems if it is flush I will not get the patch completely flush with the roof line without pushing 100% of the bond material out of the joints. Clamping the backer in place first will also be a challenge, a tiny C clamp should do it but I am open to recommendations if anyone has tried a similar application.

- Can anyone elaborate more on the ghost lines, and why these are a risk? I planned to sand/grind all the joints, skim coat with bondo, epoxy, high build, then paint. Im not understanding how this patch would be different after it is prepped like the rest of the cab.

Thanks again everyone