Damage to the exterior of a fiberglass RV shell is a common occurrence with regularly used recreational vehicles. The constant maneuvering of an RV in and out of campgrounds and tight spots or while storing at home makes bumping into something and causing damage all too likely. Once damage happens to the RV fiberglass exterior, it is important to repair it promptly to seal out moisture and debris. Fortunately, minor damage to the fiberglass exterior of an RV is easy to repair at home. Using a few inexpensive supplies you can patch holes, gouge and scrape marks, and fix cracks.
Remove any splintered fiberglass that is jutting out of the side of the RV exterior. Sand the area to be repaired with 60-grit sandpaper and remove any loose fiberglass bits and pieces. Wipe down the area afterward with a clean dry cloth. Be sure to prepare the damaged area for repair by making sure it is free of dust and debris.
Cut a portion of fiberglass cloth into a size that completely covers the area of the RV that is damaged. If the damaged area is too large for a single piece of fiberglass, cut enough pieces that when used together will cover the damage. Keep fiberglass handy.
Mix the polyester resin and catalyst with a stick. Add just a few drops of the catalyst to the polyester resin so that it does not harden too quickly. The more catalyst used, the faster the polyester resin will set up and harden, so do not use too much, because you will need time to apply the fiberglass cloth.
Paint a generous layer of mixed polyester resin directly onto the damaged fiberglass exterior of the RV and the area immediately surrounding the damage. But only paint as large an area as you can cover with the fiberglass cloth. Work in small stages so that the resin does not dry before you have time to apply the fiberglass cloth, which needs to be laid smoothly across the area to be repaired.
Lay the fiberglass cloth on top of the area where you painted the polyester resin and press it into place to remove all air. Paint another even layer of polyester resin on top of the fiberglass cloth and work out any air bubbles that may be under the fiberglass cloth or in the polyester resin.
Continue applying the polyester resin and fiberglass cloth as described until the entire damaged area is completely covered. Use pieces of fiberglass cloth as large as are workable under the time constraints of the activated polyester resin, but don't hesitate to use multiple pieces of fiberglass cloth if necessary.