How to repair Gelcoat Part 2

How to Apply and Finish Gel Coat for Fiberglass Repair (Click here to see Part 1)

In part two of our gel coat repair series, we will cover how to apply and finish gel coat for a seamless and durable repair. Whether you're fixing a fiberglass boat, jet ski, camper shell, or trailer, following these steps will ensure a high-quality result.

Color Matching Gel Coat

• If your surface is white, stock colors will be easier to match. For colored surfaces like red or blue, custom color matching may be required.

• Old gel coat fades over time. When sanding or grinding, you will expose the original color underneath—match your new gel coat to this shade.

• Unlike paint, gel coat remains the same color when wet and after curing, allowing for accurate color matching before adding the catalyst.

Preparing and Mixing Gel Coat

1. Work in a well-ventilated area and away from open flames.

2. Wear safety goggles and gloves to protect against harmful fumes and contact.

3. Thoroughly mix the contents of the gel coat can, as ingredients tend to settle over time.

4. Measure and mix:

   • For small repairs, mix about one ounce of gel coat.

   • Add 20 drops of MEKP catalyst per ounce of resin and stir thoroughly.

   • Maintain a working temperature between 70°F and 85°F, which allows for 10-20 minutes of working time.

Applying Gel Coat

1. Use a disposable brush to apply gel coat to the repair area.

2. Cover the crack completely, ensuring the gel coat sits slightly higher than the surrounding area.

3. Avoid applying excessive gel coat, as the excess will require additional sanding.

4. Curing and Tackiness:

   • Gel coat cures with a tacky surface, which can clog sandpaper. There are three ways to address this:

     • Heat treatment: Use a hairdryer, heat lamp, or place the repair in direct sunlight to reduce tackiness.

     • PVA mold release: Spray the gel coat with PVA mold release after it has gelled. Once cured, wash the PVA off with water.

     • Plastic film method: Press a flexible plastic sheet (such as cellophane or Mylar) over the fresh gel coat to eliminate air exposure. Peel it off after curing.

Finishing the Repair

1. Sanding:

   • Start with 150-grit sandpaper to level the gel coat with the surrounding surface.

   • Always use a sanding block instead of your fingers to ensure even pressure.

   • Power sanders can also be used but require careful handling.

2. Fine Sanding and Polishing:

   • Use 220-grit wet/dry sandpaper with a trickle of water to remove scratches.

   • Progress to 400-grit and then 600-grit wet/dry sandpaper.

   • Wipe the surface clean between sanding stages.

3. Buffing and Waxing:

   • Apply a rubbing compound (e.g., 3M Fiberglass Restorer) with a clean cloth, rubbing in circular motions.

   • Use a power buffer for a smoother finish.

   • Wax the entire area for final protection.

Final Notes

• Initially, the repaired area may appear slightly lighter than the surrounding gel coat, but with sun exposure, it will fade to match.

• Completing a gel coat repair yourself can save hundreds of dollars compared to professional services.

• This entire repair process can be completed in under three hours.

By following these steps, you can achieve a professional-quality gel coat repair with minimal cost and effort!