Fiberglass cloth and resin repair kits can be excellent tools to repair minor rust or collision damage on your car, truck or boat. Proper use of the kit will ensure the best looking and soundest functioning result, and save the cost of hiring a professional to complete your minor repair job.
Major repairs that cover structural or load-bearing areas are best left to welding, as the integrity of the crash-zone of your vehicle is dependent upon the frame or structure, which will be significantly compromised without sufficient metal to support it.
Tip 1 - Kill the Rust!
The most common applications for fiberglass vehicle repair are rust and collision damage. It is necessary to completely remove any rust and treat any vulnerable areas before applying the fiberglass cloth and resin. If rust lingers beneath the surface of your repair, it will resurface and demand more time, attention, and money, destroying more of your vehicle's structure in the process.
Use a metal brush to remove loose rust, and a rust converting primer to treat exposed clean metal and scraped rusty metal. The primer converts rust to black rust, a hardened material that is resistant to further oxidization and rust damage. Without this step, all repair attempts on rusty or exposed metals will eventually corrode.
Tip 2 - Make a Mold
If you are repairing a panel that isn't load bearing but has lost a significant amount of integrity, create a plastic or cardboard mold to place under the fiberglass. Creating a mold ensures that the shape of the new patch matches the shape of the existing panel.
If there is a large hole that needs repair, and it's accessible from the back side, try placing tape over the back end of the hole to provide structural support for the fiberglass repair while the resin is setting.
Tip 3 - Cut the Cloth Before Applying Resin
Fiberglass cloth becomes flexible after the resin is applied, but it also becomes more difficult to cut, and the clock is running as soon as the resin is applied; the hardener must follow soon after, while the resin is still wet. It's best to cut the fiberglass cloth before beginning the resin process.
If you can't get the cloth into the exact shape you need while it's dry, that's ok—just cut a piece of fabric that is slightly larger than what you think you'll need prior to applying resin, and complete the finishing touches on shaping the fabric once the resin in on, but before the hardener is applied.
Tip 4 - Have an Acetone Solvent Handy
Resin is messy business, and can make a mess of your hands, clothes, and workplace, as well as areas of the vehicle where repair isn't needed. Make sure to wear clothes you don't mind ruining, keep plenty of rags around, and have an acetone solvent on hand to take care of the mess afterward.
Use proper caution when handling any solvent, as many of them can be very harmful to skin, eyes, and lungs. Follow any safety recommendations listed on the container.