Prepping For Show-Quality Paint
It has long been said that a paint job is only as good as the prep, but that leaves out the answer of just how to get there. A decent paint job will take a fairly intensive amount of prep work-undeniably hard and skilled work. Raising the bar and going for the ultimate glamour finish seen on a show-car takes exponentially more of the same. For the paint work on our project Corvette, we substantially disassembled the car, stripped off all traces of the old finish, and primers. We were fairly well invested in effort before even lifting a spray gun. We were well past the point of no return here, and there was no way we'd compromise the job now with a hurried prep job. No, the goal here is to make the car's body as straight and sharp as a pin, for a flawless look once the color is applied.
Although the bare fiberglass looks great after stripping, getting a show-quality paint job
The Fill Is In
Our project car had never suffered any accident damage, and the fiberglass below was in exactly the condition it left GM-no better, no worse. The fact is that these cars weren't built as showpieces in terms of body prep, and virtually every one of them will exhibit minor flaws under heavy scrutiny. Our car was no exception, and the bare, stripped body panels told the tale. The relatively smooth No. 220-grit wet sanding given to the surface as the final stripping stage makes it fairly easy to pinpoint these surface flaws by feel. A minor dip here, a little rise there, we could discern the kinds of flaws that separate a stock body from custom show-quality bodywork. Some guys will cake on heavy layers of primer to deal with all but the most flagrant defects, but this isn't the best approach. The only real choice here is using polyester filler in a very light skim wherever we could feel a defect.
Working with filler, like most paint and body tasks, is an acquired skill. The filler coat must be skimmed on in just enough quantity to fill the flaw, without excessive buildup. It also helps to taper the application all around, avoiding laying down a hard edge that will be difficult to feather later when sanding. Working a fiberglass body takes more finesse than a steel car, where a rough cut with No. 36 grit or files can be applied without worrying about the adjacent surface. Fiberglass is easy to gouge, so the best approach is careful application of the filler to very close to the needed shape, keeping the heavy sanding with rough grits to a minimum.
All the filler on this car was worked with No. 80 grit on a long, rigid sanding board. While some suggest that the highly curved body of the C3 Corvette makes the flat long board useless, there is actually no area of the car that cannot be worked successfully with this tool, once the technique is mastered. The result will be superior to what can be achieved with flexible rubber hoses, foam pads, stirring sticks, and a multitude of other sanding aids.