How to Repair Fibreglass

repaired fiberglass

Repairing fibreglass is relatively easy. To ensure strength, it is best to match the original material’s thickness, density, and ply orientation as much as possible.

Push around the damage area to feel for any weak spots; these could indicate larger problems lurking underneath that aren’t yet visible.

Clean the damage with an acetone-soaked rag to help the epoxy and fibreglass patch adhere more securely.

Steps to repair fibreglass


Fibreglass is an increasingly popular material choice used in all sorts of structures, vehicles and personal watercraft. This versatile composite offers exceptional resistance against corrosion, cold and heat; yet damage may occur. When this happens, fibreglass repair provides a straightforward, affordable and effective solution.

As the first step to repair fibreglass, cleaning with a mild soap and water solution and then drying thoroughly is important in creating the necessary conditions for repair materials to properly adhere.

Once the fibreglass surface has been properly cleaned, it must be sanded down and ground to remove any damaged areas and provide a smooth, even surface to work with. A coarse grit between 36 to 80 may suffice, though higher grades may be necessary if deeper damage exists or you need to grind rounded areas.

When sanding the fiberglass surface, be sure to wear a respirator to protect yourself from resin fumes and eye protection as well. A variable speed buffer, wool buffing pad and chemical-resistant gloves are key tools in this step of your project.

Bristle rollers can be an indispensable resource when working on fibreglass projects, helping remove air bubbles and spreading resin evenly. A flexible rubber squeegee can be used to spread and saturate fibreglass fabric as it’s being placed. A plastic applicator can then apply epoxy resin while having a drop cloth ready to protect work surfaces from resin drips is advised. Finally, having some acetone handy can clean off any contamination on its surface.

toolkit used to repair fibreglass

Once the fibreglass has been cleaned and sanded down, it must be prepared for epoxy and fibreglass patch to adhere. A dampened rag with acetone may be used to wipe down its surface to eliminate contamination or residual surface residue; you can find this solution at most hardware or big box stores under their nail care section as it’s commonly used to take off polish.


When undertaking a fibreglass repair project, it’s essential that all necessary materials are on hand. An epoxy resin kit provides all of the tools and supplies you need for getting started, while you may also require fibreglass cloth that matches the damaged area along with basic items like nitrile gloves and sandpaper.

Crack repairs on fibreglass panels are most often handled using epoxy as it provides an effective, quick, and cost-effective method suitable for most applications. Unfortunately, it doesn’t compare to full replacement as its strength may weaken over time leading to further structural issues and possible additional damage down the road.

Before beginning work on any fibreglass repair, it’s essential to first clean the area with mild soap and water solution to wash away dirt, oil, and grease from its surface. In addition, consider using an alcohol pad on cracks in fibreglass before drying it completely before beginning again.

After cleaning and clearing away debris from the area, use 80-grit sandpaper to sand it down using multiple passes until all rust, paint, primer and gel coat has been removed from damaged areas. Sand both sides of each damage patch to strengthen them more.

When sanding damaged areas, it’s essential to taper or scarf the sanding angle to increase patch strength by increasing surface area bonded with primary structures. A common scarf angle ratio for fibreglass repairs is 12:1, meaning for every unit thickness repaired you should sand at an angle 12 units from where damage was caused.

fibreglass material

Before using epoxy resin, make sure that you read and follow all safety information found on its package and are working in an area with adequate ventilation. As some supplies used in your project may contain hazardous fumes that could pose health hazards to yourself and others, be sure to wear appropriate PPE.


Preparation of the bonding surface is of primary importance in any fiberglass repair, and should include cleaning the damaged area with mild soap and water solution to remove contaminants, while drying it out as part of this preparation process. Furthermore, pressing on damaged areas to detect weaknesses is advised.

Depending on the extent of damage, you may need to sand fibreglass. While this task is unpleasant, it will help make repairs look better and last longer. When performing this work, use a respirator or dust mask as to not inhale glass dust that will be produced.

After you have sanded a damaged area, it is wise to disinfect it using acetone or methyl alcohol as soon as possible to eliminate contamination that might enter cracks in the bonding surface and weaken bonding strength. Even if damage appears minor, cleaning with these solvents should always be performed to ensure optimal bonding surface performance.

As the next step, cut pieces of fibreglass cloth that are at least an inch larger than the damaged area to give yourself some room when applying resin. Mixing the kit’s resin and hardener may include disposable mixing containers, applicator tools, brushes or spreaders and brushes; additionally various grits of sandpaper may also be provided so you can sand and smooth your repaired area afterward.

Before applying the fibreglass to the damaged area, lightly wet it with water using a brush to allow resin to adhere properly and fill any cracks or voids. After wetting down your surface with water, lay the first piece of fibreglass cloth onto it ensuring it resides centered over your repair site. Continue adding layers, always soaking each one with resin between applications.

Sanding and buffing is a messy task that will require plenty of cleanup. To protect yourself while working on this repair, wearing a respirator, dust mask or wet/dry vac is recommended as this will prevent inhaling fibreglass dust which could potentially harm your health.


Fiberglass is an extremely useful material that has numerous applications across numerous fields of application. It is lightweight, durable and resistant to various chemicals; yet still vulnerable to damage; therefore regular maintenance must be conducted to keep it in good condition. However, there are various repair methods available ranging from patch kits to compounding putty that may help restore fiberglass’ original state. Ultimately the best approach will depend on its size and nature of damage being addressed.

repair fiberglass

No matter the type of fibreglass repair needed, it is vitally important to first clean and clear away all potential contamination sources from the area before proceeding with repairs. A rag soaked in acetone should be used to clear away debris or contaminants from damaged areas before using grinder and sandpaper tools to smooth and prepare surfaces in advance for application of fibreglass resins.

Once the surface has been thoroughly cleaned, it is crucial that any crack or hole be veed out so as to facilitate fibreglass and epoxy resin application. A piece of cloth should also be placed within the crack if possible to strengthen it further.

When repairing fibreglass, it is crucial that its thickness and density closely match that of its original laminate. Doing so will eliminate stress points that could compromise or even break the fibreglass itself, and also recommended is using identical ply orientation between new and existing laminate.

For exterior applications of fibreglass repairs, polyester resin may provide maximum strength and longevity to repairs. This will give them maximum strength and longevity as a repair method.

Next, create “peanut butter resin.” This mixture of resin and thickener should have the consistency of peanut butter for easy application onto any areas that have been damaged – this will fill any voids that need filling while providing an ideal surface to place fibreglass patches over.

Share the Post:

Related Posts