Boat Services

The Importance of Boat Fiberglass Repair

Almost every fiberglass boat owner will eventually need to make Boat Fiber Glass Repair. Whether it’s a small chip, a deep scratch, or a gouge, you should always give the job careful consideration and attention to detail.Boat Fiberglass Repair

Before starting your repair, listen to the affected area with the end of a screwdriver handle; solid laminate sounds sharp, delamination dull. Mask the surrounding areas of the damaged area to protect them from inadvertently applied gelcoat or errant sanding.

While not as serious as a hole in the fiberglass, nicks and scratches can quickly detract from the look of your boat. In addition, if left unattended, they may provide a pathway for water to get inside the hull and cause damage.

Fortunately, light scratches and cracks in gel coats are easy to repair with some basic supplies and patience. Start by washing and rinsing the area you want to work on so that all of the dirt is exposed. Then sand the area with sandpaper, making sure to wear a respirator mask, as fiberglass dust is not good for you. Once the sanding is done, you can buff the area to smooth it down using a buffing wheel or sander.

For deeper dents and rough patches, you can use a fiberglass “chop” mixed with filler and gelcoat for the most durable results. This mixture will create a putty-like fiberglass substance that will fill in the dents and patch the rough areas. Apply it to the dents and let it set; this usually only takes a few minutes but can take up to a day to fully cure.

Deeper gouges in the gelcoat are more complicated but still relatively easy to fix. First, sand the area to prepare it for gelcoat. Then mix and saturate the fiberglass cloth with resin and hardener, applying it a small section at a time. Allow it to cure until it starts to gel. Continue this process with progressively smaller pieces of fiberglass until the gouge is filled.

It is important to note that using autobondo or other bonding agents with fiberglass strands in them, or even polyester resin thickened with cabosil, will result in cracks sooner rather than later. These products have no tensile strength, so they will not hold up to the flexing of your fiberglass boat.


Whether caused by normal wear and tear or an accident, holes in boat fiberglass are every boat owner’s worst nightmare. Not only do they let in water, which is bad enough in itself, but if left untreated, holes can lead to extensive damage and detract from the performance of the vessel. This is why it is important to address them early on.

When a hole is discovered, the first thing to do is clean the area thoroughly. This is essential for ensuring the patch adheres properly and prevents further deterioration of the fiberglass. The next step is to back the hole with a piece of lightweight cardboard, which helps to ensure a strong bond and even thickness across the surface. After the hole is backed up, it is time to prepare the patching material. The type of material used will depend on the size and severity of the damage. For example, for small repairs, a fiberglass repair kit may be sufficient; for larger holes, it is best to use a sheet of fiberglass mat or chopped cloth.

The first step in the process is to cut a piece of fiberglass mat that is slightly larger than the hole. Soak the mat in catalyzed resin and position it over the hole. Use a spreader or putty knife to apply the resin and work it into any crevices around the hole. Allow the resin to cure for 24 hours before sanding down any excess and applying paint.

If the hole is in a load-bearing part of the boat, it is best to use core material to reinforce the area. However, if the hole is in a non-load-bearing area, it can be filled with a fiberglass mat. This is a dense material made from short fiber strands held together with a resin binder. It is available in a wide variety of thicknesses, from a light lay-up to a high-strength version that can be used for structural reinforcement.

When laying the mat, it is best to start with the smallest layer possible. This will help to prevent dimpling and other unevenness that can detract from the appearance of the finished product. The next layers should be laid out a little bit more generously, but never so much that the mat is bunching up in some places and thin in others. The goal is a smooth, consistent patch that will be difficult to see once it is applied to the hull.


Fiberglass is beautiful when it’s new and shiny, but like anything else, it can become damaged over time. Sun and water exposure, vibrations from a boat’s engine or waves, and even the simple act of loading a boat onto a trailer can all cause damage to the fiberglass surface. If left untreated, that damage can eventually eat through the underlying layers of fiberglass, leaving you with a soft spot in your boat’s deck or hull (delamination).

Delaminations are a major issue and one that typically results in expensive repairs for your boat. The key is to catch the delamination as soon as possible because if it gets too far, the resulting hole will allow water into your fiberglass structure, which, if not treated, can lead to core failure.

If you are able to catch a delamination early, you can prevent a large repair bill by removing the affected fiberglass surface and replacing it with a perfectly matched piece. Then your technicians can fill the void with resin and apply a new gel topcoat to leave you with a beautiful and functional boat.

While some types of delamination can be repaired with fiberglass cloth and polyester resin, others require a more involved approach. For example, the hull stringers on many boats are made from wood and are very important to the structural integrity of your boat. If an impact occurs and you notice that a section of the hull stringer is no longer attached to the rest of the hull, this is a sign of delamination. You can check the tabbing on a stringer by tapping it with a hammer. Solid, intact stringers will give a crisp tone when tapped, while delaminated stringers will sound dull.

This type of delamination is generally more serious than an impact hole and requires the replacement of the entire stringer section. The process can be complicated and is best done by a qualified fiberglass technician. When it comes to replacing a stringer, always make sure you use proper scarf bevels and properly bond the new section in place. This is particularly important on older boats where the fiberglass and polyester resin have cured and shrunk over the years. This will ensure the new section of stringer is bonded to the hull and will be strong for many years to come.

Hole Patching

Whether structural damage was caused by an impact or weakened by water intrusion, the laminate of fiberglass, resin, and core (whether wood or composite) that makes up the hull must be repaired as soon as possible to prevent rot. It’s also a good idea to keep the area as dry as possible until the repair is complete. This is because broken edges will absorb moisture, which will cause the surrounding fiberglass to swell and crack.

If the hole is small enough, you may be able to use a standard drywall patch for it. If the hole is too large, it must be bridged with a stronger, more rigid material. This can be done with fiberglass cloth, which is available in a variety of sizes to suit your needs.

Start with a piece of the proper size to fit the hole, then cut additional pieces to size if necessary. Lay the new piece of fiberglass cloth over the hole, making sure it is even and flat. Use a putty knife to apply the resin mixture over the cloth, working it into any crevices. Continue this process until the hole is completely filled. Allow the mixture to cure for 24 hours before sanding down the excess fiberglass and filling any remaining holes with an additional layer of the mixture.

For medium-size holes, try a fiberglass mesh patch. These patches come with an adhesive on the back that sticks to the smooth drywall surface around the hole. They also work for holes larger than 6 inches. For a hole that is too large to use this patch, add strips of drywall furring strip on either side of the gap to support the replacement piece and prevent it from collapsing into the wall.

If you’re using the drywall patch, be sure to apply the final coat of joint compound with a putty knife and “feather” it at the edges to help it blend into the rest of the wall. When you’re finished, run your finger over the repaired area to make sure it feels smooth, then sand down any humps and apply another coat of joint compound. When that’s dry, prime and paint the patched area.