A tip I’ve used with fiberglass cloth is to put a clear dry cleaning bag (or grocer’s clear fruit/vegetable bag) on the driveway, lay the (already cut) fiberglass cloth on top of it, then mix the fiberglass hardener and resin in a plastic cup and pour it over the cloth. Smooth the resin into the cloth with a body putty spreader. Then peel the cloth off of the bag and lay it over the rust hole (which you already sanded), using the spreader to smooth out the edges. The resin won’t stick to the clear bag and the cloth will have the right amount of resin when you peel it up. After everything dries you can sand it and apply more resin, if necessary. Use plastic gloves, of course, when working with the cloth and resin. And make the patch’s diameter several inches larger than the hole if you can.
Fiber glass does absorb water. Epoxy paint will fix that. What the heck. It the car is valuable, install a sun roof. But, cutting out the rust and brazing in sheet metal from the outside is doable. It it’s a junker, use a rubberized roofing cement over a metal patch like you would roof flashing.
Depending on the size of the holes, you could benefit from using galvanized steel sheet metal stock. It won’t sag while curing. Cut slightly larger diameter patch than hole. The flat anvil part of a vise is a good place to do the next step but any flat, hard surface will work. Work (pound) around the outer diameter of the patch to thin it out and feather the edge so it will blend better into the existing roof structure with less filler operations, if any. Once you are satisfied with the piece, spread a small amount of JB Weld around the outer edge and place it over the hole. Put an appropriate weight on it and immediately remove any excess squeeze out. Wait for 15 minutes (JB Qwik is awesome), then sand the edges to finish smooth and prime/paint. Viola!
Well I didn’t read the “glue metal over the hole”. That might have worked.
I used the fiberglass resin and hardener after I sanded and scraped out the rust. A lot more rust than I thought. A dime size hole became about half inch by 3 inches. I put two sheets on there. Big mess but I think I did a good job. I removed some of the headliner to look at the underside. No real rust there but I could spray some primer on there.
When the bondo stuff dries I have spray paint primer and spray paint.
There is some globs of resin goop on the roof next to the fiberglass. Not sure if I’m supposed to get that off or how.
I’m typing on a phone. Hopefully it won’t put this all in one paragraph.
Thanks for help. Fingers crossed.
Congratulations. Ask a question and you’ll get 20 different answers. About the only thing you can do with drops of fiberglass is either try and scrape it off or sand it down and paint over it. If you have the headliner opened, it wouldn’t hurt to add some fiberglass underneath too to add support. One word of caution with the primer though is that it is porous also and will allow moisture througn it. It needs to be coated over with paint for any protection. Spend some time sanding the patch smooth and add more filler if you need to to blend it in. Sandpaper wrapped around a paint stur stick or something can help keep the dips and high points out. Also after painting it, rubbing compound can be used to remove the overspray and blend it in to the other paint.
that should hold you til the rest of the car slowly reaches the end of its life span
This might be a good application for a vinyl roof.
I wonder if I need to sand before painting. Or if I even need to paint at all. It says it’s waterproof. Reluctant to screw it up.
Yes. You need to remove all the loose rust and any part that is rusted through.
I did sand before applying the fiberglass. The question is does the fiberglass need to be painted.
I would always paint a Bondo patch to help keep water away from metal. The Bondo can have tiny holes.
You’ve gone this far so paint it to make it look nice. It’ll help protect the fiberglass from the sun and weather too. It might be waterproof but it will still deteriorate in the weather, just like an unpainted boat.
yeah, sand and paint. it ll help the water run off, and that’s always good