How to Fix Cracks in Fiberglass Panels: A Step-by-Step DIY Guide

How to Fix Cracks in Fiberglass Panels: A Step-by-Step DIY Guide

Got a crack in your boat, RV, or fiberglass panel?Don’t worry—it happens. The good news is that you can fix it yourself with a little patience and the right tools. In this guide,we’llwalk you through how to repair a structural fiberglass crack soit’s strong, smooth, and ready to go. 

What’s the Big Deal with Cracks? 

Not all cracks are the same. Some are just on the surface (cosmetic), while others go deeper and can weaken your panel. If the crack moves or flexes when you press it—or if you’ve noticed leaks or soft spots—it’sprobably a structural issue that needs a bit more attention. 

What You’ll Need 

You don’t need fancy tools, but you will need a few key items: 

- Fiberglass cloth or mat (usedifferent sizes and thicknesses) 
- Resin 
- Sandpaper (80 to 220 grit) 
- Mixing cups,brushes or rollers 
- Safety gear: gloves, goggles, and a mask 

Let’s Get Started 

- Clean It Up 

Wipe the cracked area with acetone to remove grease, dirt, and anything that could get in the way of a good bond. 

-Open Up the Crack 

Use a rotary tool or sander to make a small V-shaped groove along the crack. This gives the repair area more surface to grab onto. 

- Sand the Area 

Rough up a few inches around the crack with sandpaper. This helps the fiberglass stick better. 

Time to Patch 

- Cut Your Fiberglass 

Cut 3–4 pieces of fiberglass cloth. Start small—just enough to cover the crack—and make each one slightly bigger. This helps the patch blend in smoothly. 

- Mix and Apply the Resin 

Mix your resin according to the label. Brush some onto the crack, then place your smallest piece of cloth on top. Soak it with more resin. Repeat with the other pieces, layering from smallest to largest. 

- Let It Dry 

Let the patch cure.Don’t touch it untilit’s fully hardened—usually overnight. 

Smooth and Finish 

- Sand Again 

Once dry, sand the area smooth. Start with rough grit, then move to finer grit for a smooth finish. 

- Add Gel Coat (Optional) 

If your panel had a shiny top layer, youcan apply gel coat to match it. You may want pigment to get the color right. Apply thin coats and let each one dry. 

Keep Cracks Away 

 - Check your panels often for signs of wear. 
- Add support if certain areas bend or flex too much. 
- Keep your panels clean and protected from sun damage. 

Final Tip 

Fixing fiberglass cracks might seem tricky, but take it one step at a time—anddon’t rush the drying process.You’ll end up with a clean, strong repair that lasts. 

Need materials? Check out our full line of fiberglass cloth, resins, and repair kits at https://truecomposites.com