Things You'll Need
Apron or coveralls
Fiberglass resin jelly
Jigsaw with fine-toothed blade or other appropriate cutting tool
Soft lint-free cloth
Touch-up paint (optional)
Fiberglass resin jelly is a thick, viscous gel made available commercially by several different major manufacturers. You can find it in department, auto part, and watercraft specialty stores. This gel is commonly used with fiberglass cloth for repairs on not only fiberglass items, but for minor rust damage to metal, and holes in plastic, wood, cars, farm equipment, boats, snowmobiles, motorcycles and campers. This is an easy technique to use and is especially effective for damaged fiberglass items. A good fiberglass resin jelly won't run when applied to a vertical surface, and can be sanded smooth after only about 20-30 minutes of curing time.
Put on your disposable gloves and eye protection. Fiberglass products are very harmful to eyes and skin. It is highly advisable that you also wear an apron or coveralls to prevent any fiberglass fibers from coming into contact with your clothing, because they are not easily removed by everyday laundering methods. These fibers will also "spread" to other garments in the wash load.
Use the jigsaw to remove any rotted, cracked, or otherwise weakened fiberglass fragments surrounding the hole. Gently rap on the adjacent area with a solid object to see if it is vulnerable. Any compromised fiberglass will crack when tested, and should also be removed.
Use a dampened soft, lint-free cloth to remove dust, dirt and any other debris from the hole and the surrounding area so that the fiberglass resin jelly will adhere well to the area. Make sure that the section is completely dry.
Use a ruler to measure the dimensions of the hole. Then use scissors to cut out a piece of fiberglass cloth about an inch bigger than the hole.
Hold the fiberglass cloth in place over the hole. Apply fiberglass resin jelly to the area with a stiff-bristled paint brush, covering the entire piece of cloth. Allow the jelly to dry, or "cure," completely before proceeding further.
Refer to Steps 4 and 5, and create several more layers of fiberglass cloth and jelly until you have built a patch that is even with the rest of the surface area. Allow each layer to cure in between applications. Blend a final coat of fiberglass resin jelly into the section that you have repaired.
Sand and paint the repaired area as desired.
Always work in a well ventilated area when using fiberglass products. Wear eye protection and disposable gloves.
Wear an apron or coveralls to keep fiberglass fibers off of your clothes. Do not launder clothing that has been exposed to fiberglass fibers with any other garments, or you will be "sharing" very itchy fibers with someone else.