Hi guys, have a car other than my third gen which had huge rust problems in certain area of the rocker panels. Caused a big hole on each side. The integrity of that area is still good but was impossible to get all rust out. So I had no choice but to use por-15. Now the question is, if I want to keep water out of the hole, should I use fiberglass over it or am I just asking for trouble? When using fiberglass, I know you're suppose to remove all rust and paint. But since that was impossible, that's why por-15 was used to make sure every inch of rust was covered. Thanks!

You will have to rough up the pro 15 to get the glass to stick to it. After your glass work has dried you can put the pro 15 over it.

Thanks for the reply. Now, when you mean "rough up", I'm assuming you mean to sand down the area or a portion of the area that can be sanded?

Oh man this sounds like a disaster in the making. If you are fiberglassing over holes that were rusty and have rust paint over them, this is definitely not a fix that is going to last. But I understand cutting and welding isn't in the cards for everyone either. Is this just a temporary repair? How big is the hole, and is this the area that is going to get covered over by the ground effects anyway? I guess doing it this way is a lot better than leaving it un treated.

Well, would like to make it last as long as possible, it's actually the worst thing on the car, yet actually cutting the parts out and replacing would take some crazy crazy *** welding skills which I do not have, and also take the whole car part which I do not have the proper facilitiy to do (in a condo underground parking). So in my opinion, using por 15 was the next best thing.

by roughing up, he means to give it some texture. you dont want it sanded smooth. Use a heavier grit sandpaper and lightly rough up the surface so it doesnt feel smooth. Don't sand it down past the POR 15, but just enough to make it rough to the touch.

You can use a screw driver to rough up the surface, but as stated before don't go through the por 15. It's not that hard to weld rocker panel patches, as it's fairly flat. But not in underground parking.
Alex

Ok, see I know that fiberglass needs some texture so the way I painted the outer edges was very rough so the brush left the paint extremely choppy and wavy. I know I wouldn't be able to make it rougher with sandpaper. I did a good job in that aspect. I was just wondering if it was do-able? Is this a wise idea? Am I going to prevent rust by patching fiberglass or am simply going to hide it and not notice it get worse?

I understand where your coming from. Welding isn't in the cards for all of us. For one reason or another, we just can't do it. In my case, I've used quite a bit of fiberglass to repair holes in my firebird, in the hopes it'll last long enough for me to move somewhere with a garage and take the whole thing apart and do it right. Till then, I've not got the money, skills or place to do any of it.

There you go, you got it. In my case, I moved 2000km away from a nice out of the city spacious house with detached working garage, compressor, medium welder to the IN BUTT *** MIDDLE of a 5.5-6 million person populated city. Simply finding another place to even have the space to park my car without having to pay an hourly fee would need me to travel about 35 minutes out of my area, lol. The reason I also want it fixed to last is because I have a BAD feeling that despite the fact that city living is NOT for me, my job will require me to stay around the area for a few years. So it may be that long till I get to touch this car in such detail.

I also used fiberglass to fix some holes. I didnt have the tools or skill to fix it with sheetmetal. I figure fiberglass wont do an harm to the area and can be removed fairly easy when the time comes to fix it right. I did it differently though and used the POR 15 with the fiberglass cloth instead of waiting until after the POR 15 was dry. I basically used the POR 15 as resin. Worked great and the POR 15 took care of the rust. POR 15 sells a piece of mesh similar to fiberglass cloth so I figured it couldnt hurt to try. You might be able to rough up the dried POR 15 and used some more POR 15 to soak the fiberglass cloth and attach it. POR 15 to POR 15 might stick better. Good luck on the repair.
Sean

If the POR 15 is applied correctly, it should prevent rust. What your doing is sealing off the metal from the elements, and it should at least work better than simply leaving the rot alone. I'd say fiberglass is a good option for a "long term temporary" fix, if that makes any sense.

My quarterpanels behind my rear wheels have fiberglass covering holes. No, its not great, but it keeps the rest of the car from rotting, and the fiberglass and POR 15 seal it away from the water and salt that started it in the first place. I'll go back and redo it in a few years when i have the time/money/place.

POR 15 is not a ghetto fix, this is what its made for. as was said before, use it as a resin w/ fiberglass. if its done properly, it will last forever.

the problem in this case, if i understand correctly, is that you have already done the por 15 w/out the fiberglass. POR 15 doesnt stick well to anything but metal, including cured por 15. it can be coated, but it must be completely roughed up, not just scuffed. ideally, por 15 should be layered before complete cure, while there is still a little finger drag to it. this also applies to paint or filler applied over por 15.
depending on the location, ou may want to considered blasting or cutting off the por 15 you have already applied and putting new por 15 w/ fiberglass at the same time.

Im not clear on whether the spots you are talking about are visible or not, so not sure what the best way to go for you is.