The best approach in a major repair is to replace the panel along the factory seams. If possible, the factory bonding strips should be retained and remain in place to provide a guide for the placement of the panel. The old panel is simply cut off short of the flanges and then the bonding areas are ground back to remove the original panel adhesive, and the new panel is bonded in place. The key here is to carefully fit-up the panel prior to bonding until it shows perfect alignment when screwed and clamped in place. Grind, trim, and adjust until the panel falls into place perfectly before reaching for the panel adhesive. Once everything is confirmed to be perfect, the panel is bonded in place using a specialty Corvette body panel adhesive, or a panel adhesive rated by the manufacturer for use with fiberglass. When the panel is clamped and screwed into position, spread and feather the excess bonding adhesive using a putty knife or plastic spreader where it squeezes out to the outer surface. After the adhesive is cured, remove the clamps and screws and apply a layer of panel adhesive over the length of the bond line to act as a filler, and then fill and finish with conventional filler as required.
Primer and Blocking
Difficulty: 3 Wrenches
Once all of the body repairs have been made, getting a Corvette's body ready for paint requires the tedious process of using a primer surfacer and "blocking" the car smooth. The primer acts as a filler material, helping to level the surface and filling small imperfections. Primer surfacers come in a wide range of formulations, depending upon the brand or product line, including urethanes, epoxies, and polyester resin based products. All of these utilize an activating catalyst which creates a more stable cured product in comparison to older air-dry lacquer-based primer surfacers. Again, we'll issue the warning to make sure that the primer product being considered is rated for fiberglass use, and advise that the primer should be a part of the product line system from the manufacturer of the intended finish top-coats.
The idea in using a primer surface is to build a layer of primer as filler material on the surface of the body, and then sand the surface back in a way that allows the primer to remain in the lower areas, bringing the entire body up to an even, smooth, and level surface. This is done by "blocking" or block-sanding the body by hand. Block-sanding simply means sanding the surface with the paper backed-up by a backing pad or sanding board, and using a technique to enhance the leveling action. There is real skill involved here, and the choice of backing blocks depends upon preference. Some can work the curved body of a Corvette to perfection using a hard, rigid sanding board, while others prefer a flexible sanding block. Generally, blocking is done using long strokes following the lines of the body panels, and the "breaks" of the panel's curvature. A criss-crossing motion is often used in multiple passes.
An aid to successful blocking is using a primer guide coat. Here, a contrasting color of primer or basecoat is lightly dusted or fogged over the primer before sanding. The guide coat will provide a visual reference to the sanding progress, since it will be sanded off the high spots, and remain in low areas or those that need further sanding. The guide coat will help identify areas that might require further filling, since those areas will not "clean" with sanding even though the adjacent areas have been virtually sanded through the primer layer.
The blocking process will usually require more than one go around, and may actually end up taking several, meaning that the car will need to be blocked, and then re-primed, and sanded again, until the surface will block-sand to perfection. Often a painter will prefer to use a coarser sandpaper for the first go-around with block-sanding, such as 180-220 grit, to aggressively cut the primer level, with finer paper such as 400-600 grit used in the later block sanding go-around (or whatever grit is recommended as the final surface for the paint being used). This is definitely a time consuming and tedious process, but it makes all of the difference in the final outcome of a paint project.
Difficulty: 4 Wrenches
After the intensive effort in bodywork, prep, and block-sanding, the final painting is just the icing on the cake. The work in the paint booth will vary, depending upon the materials being used and the type of paint. A basic single stage paint job will just require two to three coats of color to be sprayed, and it's all over. An involved custom candy or pearl effect paint might take eight hours of spray gun time in the booth. The key to success is to become familiar with the material being used. The manufacturer will have the product data, which will include the recommended application technique, and recommended spray gun specifications and air pressure.