Fiberglass can crack, indeed. These cracks are holes caused by UV rays, scraping, or brittle epoxy resin.

You need to repair your fiberglass if it has cracked. Even frozen water can cause these cracks if it expands in the holes.

You need to know how to repair it, and that’s what this article is all about!

Whether you want to repair the fiberglass on your RV, boat, or pool enclosure, you can do it all the same with a good adhesive.

Please keep reading to find out which adhesive I recommend for specific requirements!

What Is Fiberglass?

Fiberglass is a complex material made from glass fibers woven into a mesh.

Think of clothes’ fabric bonds, and you’ll understand what fiberglass is.

You can use it for almost anything, including boat hulls, building insulation, RVs, etc.

The material is very lightweight, resilient, and fairly inexpensive. That’s why constructors favor it over other materials when building stuff.

You can make roofs, windows, and boats using fiberglass. Fiberglass is also easy to use and cost-effective.

But fiberglass isn’t indestructible, as it can form cracks on its surface. That’s when you need to repair it.

Fortunately, most home improvement stores sell resin kits that you must mix manually before applying them to the cracks. You can also buy pre-mixed adhesives.

They often come with caulking gun tips that help you bond the fiberglass together easier.

Why Does Fiberglass Crack?

Fiberglass cracks for several reasons, not limited to excessive humidity, physical impacts, improper installation, or lack of ventilation.

The lack of ventilation, for instance, causes condensation and a difference in pressure between the inside and the outside of the fiberglass.

The temperature difference will create moisture on the fiberglass, and as we already know, moisture is bad for fiberglass.

With an epoxy resin kit, you should finish the repairs fairly quickly but don’t use chemical cleaners like acetone and ammonia. These will dissolve the adhesive!

You don’t need to replace the entire fiberglass surface if it’s cracked. Get a good adhesive and apply it to the surface.

Please wait for it to dry and cure, and you’re done. This method is inexpensive and simple.

Best Glue for Repairing Fiberglass Cracks

Here are the best glues for fiberglass repair.

1. TotalBoat Polyester Laminating Resin

This glue is durable and easy for anyone, even those inexperienced in working with adhesives.

It forms long-lasting protection and a durable bond thanks to its tough resin nature. Even though it’s a bit expensive, TotalBoat Resin is perfect for laminating applications and steel bodies.

You can use it to mend fiberglass, wood, and metal. Thanks to this versatility and fairly strong bond, TotalBoat is perfect for boat repairs and more!

2. True Composites Hardener Polymer Resin Fiberglass Repair Kit

If you want to finish the repair fast, I recommend True Composites Hardener Polymer Resin Fiberglass Repair Kit.

After application, the glue will cure in about four hours, which is quite good compared to other glues in its class.

It uses the best resin polymer to deliver a tack-free and ultra-fast curing process.

You don’t need any wax or covering to speed up the curing process either. Anyone can use it, beginners and veterans alike, as the adhesive can repair boat hulls incredibly fast.

True Composites Fiberglass Repair Kit is toxic, so I recommend extra caution when working with it.

3. Fiberglass Warehouse Polyester Laminating Resin

This glue is used by most boat builders when they need a tough adhesive. Its holding strength is over the top, as it can hold fiberglass cloth and any composite fabrics in place.

Even if you’re building or repairing it, Fiberglass Laminating Resin is a great choice for a good job!

It’s easy to use, dries quickly, and you can apply it by hand. Use an MEKP catalyst to preserve the tackiness if your project takes longer.

After that, you can wait and apply another layer to keep the materials tight.

You can bond composites, fiberglass, FRP parts, car components, boat components, and more.

How Do You Repair Fiberglass Cracks?

Depending on the severity of the crack, from a superficial scratch to a deep crack, you’ll need to apply a solid amount of glue.

Temporary measures don’t work for deeper cracks, so don’t even consider filling up the spaces between the glass pieces with caulk.

Instead, use quality adhesive to bond the glass pieces together and mend the cracks naturally.

After it dries and cures, the glue will form a permanent bond that will stand strong against the test of time.

First, you need to use a heat gun or a blow dryer to warm the fiberglass surface.

You’ll want to remove old paint or glue residues from the surface. Then, you should use painters or duct tape to mask the areas you don’t want to glue.

With acetone on a rag, clean away the excess goop from the fiberglass cracks, and apply a new resin filler.

You should also use sandpaper with 220 grip power to smoothen out the sides of the crack.

Now, manually mix your epoxy resin using the instructions on the label. Alternatively, apply pre-mixed glue to the crack until you even it out.

But don’t make the glue layer too thick because it’ll take too long to cure.

Use glue instead of resin if the cracked piece of fiberglass contains any sharp edges or metal parts.

Resins will melt the metal parts and sharp edges, making the surface uneven.

When using glue, you should wait for the fiberglass texture to become tacky before putting everything together.

When you’ve applied the glue, press the two surfaces together in a clamping position.

This will disperse the residual oxygen between the two sides, aiding in drying.

After the glue has dried and cured, you can sand down the rough edges and smoothen it out. It’s not hard at all to repair fiberglass using glue or fiber.

You just need patience and lots of knowledge. It’s only natural to make some mistakes at first, but once you become experienced, it’ll become easier.

Check out my guide on how to glue PEX to CPVC for more tips.

Wrap Up

Fiberglass is one of the strongest glass composites in the world. It’s a material best used for industrial applications, thanks to its incredible durability and strength.

However, even fiberglass cracks from time to time. When that happens, you should glue it back together with regular glue or resin.

It’s not worth replacing the entire thing when you could repair it in a couple of minutes.

It’s not hard, and with this guide, you should have no problems repairing your boat hull, RV, or other fiberglass items!