Sealing larger holes in roof

Agree completely with Jon. TIG would tend to warp the top. I have tested the flamability of the foam with an acetylene torch. It'll burn but self extinguish when removed from open flame. I hear that when burned, it gives off hydrogen cyanide gas. This was when I was working with it way back in the 70s so might apply to this particular compound.

Aluminum patch is what I'd do.
 
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If it were me I'd find some good thick aluminum, cut out a patch 1" bigger on every side, bend it, shape it to the curve and pop rivet it down, then Dicor over the top of it. Never silicone.
 
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Thanks for the note - Just today I cut out patches from rolled aluminum and just used auto panel bonding adhesive & bag of sand to cure. I forgot; I also used a rubber roller & extensive preparation of the surfaces. I first start with mineral spirits, then scuff both surfaces, acetone then mix the 2 part epoxy. I start with mineral spirits because acetone doesn't strip the tar and other crud as well. A thermonuclear bomb couldn't get that patch off. I doubt I even need to seal the edges. I'll take and post a photo if I think of it tomorrow.
Thanks Again
JFK
 
Thanks for the note - Just today I cut out patches from rolled aluminum and just used auto panel bonding adhesive & bag of sand to cure. I forgot; I also used a rubber roller & extensive preparation of the surfaces. I first start with mineral spirits, then scuff both surfaces, acetone then mix the 2 part epoxy. I start with mineral spirits because acetone doesn't strip the tar and other crud as well. A thermonuclear bomb couldn't get that patch off. I doubt I even need to seal the edges. I'll take and post a photo if I think of it tomorrow.
Thanks Again
JFK
Please post a few photos if you wouldn’t mind. I have two antennas on my roof that I would like to remove and I’m sure the holes will be similar. Thanks!
 
Ok - here goes - The very first thing I did was hammer down around the hole with an auto hammer & dollie to make it flat. Then a lite sanding wheel with dremmel tool to get it absolutely flat. Anytime we drill a hole (Especially self tapping screws) the rim around the hole gets pushed up above the level of the roof. It might not seem like much but it's enough to keep the patch metal from completely touching flat. IMG_9473.webpIMG_9474.webp
 
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Then cut aluminum patch to about an inch larger that the whole. Scuff both aluminum patch and around hole followed by a thorough cleaning with acetone & clean microfiber cloth. Mix the 2 part epoxy - I've always applied the epoxy to the patch leaving it not quite to the edges. When you use a roller it will spread to the sides. After applying the patch, I put some plastic over it (the epoxy will not stick to the plastic. This keeps the roller from getting nasty & keeps what ever weight you use from sticking.
 
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IMG_9481.webpThis is actually a different patch on my coach AND hasn't been cleaned up or painted. The alluminum can be thin. This is rolled alluminum thats used in gutter repair and flashing. A little sanding and rattle can you'll hardly notice. You'll definitely not notice it from the ground.
 
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Holes in the fiberglass are a little more complicated. This is the former antenna location. IMG_9466.JPG
The gel coat must be sanded off for good adhesion. Again, Acitone/clean microfiber. To make it stronger I also put fiberglass on the underside held in place with a balled up paper towel. Before I put the top sheet of glass I apply the resin/hardener onto the bottom piece so I know it gets soaked completely. Then put the top glass on then squeegee resin around the patch - done. In the next couple days I'll lightly sand & rattle can some paint. I figure it's on the roof it doesn't need to be perfect just be strong and water proof. I'm sure you guys know all of this but I thought I'd be thorough. Cheers
 
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Additional sealing will not be needed. Dino-mite wouldn't loosen that bond. Again you guys know this but for the benifit of somone that might read this that doesn't; It's all about the 95% preparation and 5% application. Prep Prep Prep,