Fiberglass can become weak through distress or disrepair, or if the original fiberglass coat was not thick enough. Either problem can be remedied with a new coating of fiberglass and resin. Applying a new layer of fiberglass strengthens the fiberglass and makes it strong enough to handle most uses and applications.
Clean the surface of the fiberglass with de-waxing cleanser and a soft cloth. Inspect the fiberglass for signs of weakness or damage. Tap it with the back of a screwdriver. If the area sounds hollow, then it is weak.
Grind down any weak areas of fiberglass with a handheld grinder. Wipe the area clean with a damp cloth. Sand the entire surface of the fiberglass with a grinder. This roughens the surface to improve adhesion.
Put on a pair of work gloves. Cut fiberglass sheets to fit over the weak areas in the fiberglass and any other area that you want to reinforce.
Apply resin to the surface with a paint brush.
Press the fiberglass sheets into the resin. Apply a second layer of resin over the fiberglass sheets. Use a metal roller to press the fiberglass sheets firmly against the original fiberglass and resin. Allow the resin to dry for 12 hours.
Add another coat of resin to the fiberglass sheets. Add another fiberglass layer. Coat with resin and allow to dry for 12 hours. Repeat the fiberglass process one final time.
Coat the entire fiberglass item in one final finish coat of resin. Apply the resin with a paint brush. Allow the resin coat to dry for 24 hours.