Auto body repair & detailing: Body repairs, polyester filler, dodge challenger

Question
I have a 71 dodge challenger that I'm "restoring". It is not going to be show quality, but I want it to look good. I'm reusing a lot of the old body panels and the person doing the body work for me wants to use a Spray on Polyester filler over the plastic he had to use. I've never heard of this and wanted to
make sure it's not something that's going to crack and fall off in a year of
two. Any thoughts on this?


Answer
I'm not sure, it sounds like he's using marine gel coat over the body filler as a final fill on the body work. I personally have never done this, but I know it's how they repair fiberglass on boats. I don't have enough information. Find out exactly what product he's using. I suppose one good thing about it, is the gel coat should be weatherproof. It would help stop water intrusion into the body filler if the paint gets cracked. The down side, will the gel have the same expansion and contraction characteristics as the body filler it's being sprayed over? How good is it's adhesion to bare steel? These things I don't know. I personally don't like to stray from time proven products. I use a skim coat body filler called USC Icing as a final fill, and then primer with a quality catalzed primer surfacer. (not Lacquer primer-it's outdated stuff.) The surfacer can be blocked to remove imperfections and low spots, then reprimed. Then the car is ready for wet sanding. Get me the name of the product, and I'll have a more definite opinion for you. I think he is using a product that allows for lazy body filler work, and he is just pounding the repairs full of gel coat. It sands easy, and its high build, so he doesn't have to do the extra work of skimming a coat of bondo on the repair spots. I would also be worried about longevity. Bill