The Basics of Fiberglass Repair for Students Pursuing Auto Careers


All classic Corvettes had entirely fiberglass bodies.
All classic Corvettes had entirely fiberglass bodies.

Fans of classic cars will be familiar with fiberglass bodywork. Lightweight and inexpensive, the material—a plastic composite reinforced with glass fibers—became a staple of early sports car design, most famously the Chevrolet Corvette. The Corvette has been manufactured with fiberglass since its launch in 1953, although other materials have gradually been introduced to the bodywork of later models.

Of course, it isn’t just classic cars that use the material, and auto body repair students will come across many models with fiberglass spoilers, hoods, and other parts during their careers. With that in mind, knowing how to properly repair fiberglass damage is important.

While durable and weather-resistant, fiberglass is quite rigid and prone to cracking, and can be challenging to repair when it does.

Preparing For Fiberglass Jobs During Your Career In Auto Body Repair

When performing fiberglass repair, you need to ensure that you have the proper supplies. Most body shops you’ll work in during your career in auto body repair should have all the tools needed. However, you will want to ensure you have a good stock of fiberglass fabric and mat, scissors, brushes, and small containers to mix resin.

Proper assessment is also important. Not all fiberglass cracks are immediately visible, and you should look for unseen damage by tapping the bodywork with a tool and listening for a dull sound. For more detailed inspection, remove the part to look for cracks from the underside.


Not all fiberglass damage is visible.
Not all fiberglass damage is visible.


The Repair Process Explained For Students Pursuing Auto Careers

For a more seamless finish, fiberglass repair should be done from the inside out. The underside should be repaired first, taking care to grind down and remove excess bonding. A dewaxing solvent should be applied to the area around the hole to help the new fiberglass bond. Body repair professionals usually screw a metal backer to the underside of the crack, in order to provide a hard surface to work on.

The fiberglass needed to fill the hole should then be carefully measured and cut, and no more than four layers should be used, as any more will weaken the bond. Once the underside has been repaired, the topside of the crack can be ground down the same way, and filled in with body filler.

Auto Body Repair Pros Know How To Achieve a Seamless Fiberglass Finish

Since fiberglass is quite delicate, students enrolled in auto body repair courses will need to take extra care when finishing this type of repair. A catalyst is usually applied to harden the resin, and many shops will use a halogen light to help to keep the fiberglass warm during this process. A resin roller can be used to smooth out any bumps or cracks.

Auto body repair professionals know it’s important to pay attention to the cut-lines in the bodywork to ensure consistency when sanding. Heavy grit sandpaper is usually used to get the filler level with the surrounding fiberglass. For a really smooth finish, a block sander can be used to sand down the edges of the repair in more detail, leaving the surface ready to be primed and repainted.

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