Each year, over two billion pounds of plastic auto parts roll off of assembly lines worldwide. With time, many of these items, such as bumper covers, body panels, dashboards, and interior trim pieces, become damaged and need to be repaired.
Last month, we showed you how to fix your C5's semiflexible plastic bumpers. This time around, we'll tackle the job of mending the car's sheet-molded compound (SMC) body panels.
There have only been two different construction techniques used to manufacture Corvette body panels since the car's inception. When the Vette made its debut in 1953, the new FRP (fiberglass-reinforced plastic) body was a major innovation. FRP was a construction method that could be used to make lightweight fiberglass panels. These body panels were built much like a fiberglass boat hull. A "chop gun" was used to blow fiberglass strands and resin into a mold. This technique was used through the first part of the '81 model year.
Most SMC repairs can be accomplished in around three hours using 3M products. The process begins with cleaning the damaged area using soap and water, then drying with unoiled compressed air. Finish with 3M General Purpose Adhesive Cleaner to remove all oils and waxes.
In many respects, 1981 was a transition year for the Corvette. The Corvette Assembly Plant moved from St. Louis, Missouri, to Bowling Green, Kentucky; fuel injection made its return; and computer controls were installed to manage engine functions. That year also saw the advent of a revised body-panel-construction method: SMC. SMC panels are thinner and lighter because their composition is more plastic and less fiberglass. This foundation alone necessitated a completely new method of repairing damage. Fortunately, the techniques available today are considerably improved over those employed 27 years ago.
Repairing your Corvette's damaged SMC body panel will involve grinding, sanding, sculpting, and painting, using products specifically designed to adhere to the SMC material. Having achieved excellent results from 3M products in our last installment, we decided to rely on the company for this month's job as well. Remember, no matter what brand you use, it's a good idea to stick with the same manufacturer for the entire repair to ensure compatibility.
In this article, we'll also show you how to fix a broken bumper-mounting tab. This repair will enable you to reattach the original bumper rather than replacing it. The work is uncomplicated and should take less than an hour.
3M Product List
* General Purpose Adhesive Cleaner (PN 08987)
* Polyolefin Adhesion Promoter (PN 05907)
* Automix (PN 5885)
* Duramix Super Fast Plastic Repair Adhesive (PN 04247)
* Duramix Semi-Rigid Plastic Repair Adhesive (PN 04240)
* Roloc Sanding Disc (PN 01396)
Prepare the front of the area using a pistol-grip die grinder with a 50-grit Roloc sanding disc to "U" grind and cut away any excess material. Next, examine the area to make sure the panels have relaxed and line up correctly. This will ensure a proper repair. | 
Apply a coat of Polyolefin Adhesion Promoter and allow five minutes to dry. The adhesion promoter will also aid in feathering when sanding. | 
When using any two-part material, it's important to hold the dispensing tube vertically and remove all the air from the tube. This will eliminate most of the pits caused by small air pockets forming in the finished product. |