The Different Types of Composites Used in Boat Construction

Written by James Hughes on May 21, 2023 in Boat Repair with no comments.
Composites Boat Repair

If structural damage to your composite boat occurs, it is likely a cumulative effect over time. It could also be a result of unrecognized damage or fatigue. Structural CV Composites Boat Repair is often made to restore stiffness and strength to the hull. Typically this involves patching damaged areas with fiberglass cloth.


Fiberglass is one of the most commonly used materials in composite construction. It is used in ships and submarines; automobile body and engine compartment liners; electrical insulation tape; textiles; and reinforcement. It is also used as a thermal and acoustical insulation material. It is strong, lightweight, and inexpensive. The resins used in fiberglass production are often volatile, so safety precautions should be taken when working with them.

Before doing any repairs to a fiberglass boat, it is important to make sure that the damage is not structural. To do this, you should identify the area of the boat that is damaged. You can do this by using a screwdriver to tap the surface. If you hear a dull sound, it means that the area is delaminated and may cause problems later on.

The next step is to prepare the area for repairs. This can be done by sanding the damaged area until it is smooth. It is important to use a respirator when doing this. This is because fiberglass particles can irritate the eyes and upper respiratory tract. In addition, the vapors from the resins can be irritating.

You can buy a fiberglass repair kit at your local hardware store or online. The kit contains everything you need to repair your boat. It comes with gel coat filler, powdered fiberglass, and resin catalyst. You can choose the size of the kit according to your needs. The fiberglass is available in different thicknesses, and the gel coat filler is available in a variety of colors.

After preparing the surface, you should lay the fiberglass patch. Then, you should saturate the patch with resin. You can use an epoxy, polyester, or vinyl ester resin. After saturating the patch, you should let it dry for 1 to 2 hours.

After the patch has dried, you can apply a gel coat finish to it. This will protect the fiberglass and keep it looking new. A good finish will last longer and will look better than a paint job. You can find a quality gel coat finish at your local hardware store. You should use a high-quality product, and you should follow the manufacturer’s instructions for application.


Even with proper care and maintenance, fiberglass boats will suffer from nicks, dents and scrapes over time. Some of these will require only a quick fix, while others may need to be completely rebuilt. If a repair job is going to be extensive, it can be a good idea to consult a professional fiberglass repair company that can provide an expert solution for your needs.

A key aspect of the repair process is the selection of the correct type and style of resin. For fiberglass, epoxy resin is recommended. It forms stronger primary and secondary bonds than polyester or vinyl ester resins, and it provides better abrasion resistance and flexibility.

Woven fiberglass mat is available in several weights, ranging from 4 to 10 oz per square yard. The choice depends on how much strength is needed and the size of the area to be repaired. In general, 6 oz fiberglass cloth will work for most repairs, as it has a relatively fine weave and conforms well to hull curvatures. Heavier weights, such as 10 to 12 oz fiberglass, offer greater stiffness and abrasion resistance.

The woven fiberglass material is usually held together by a styrene-soluble binder. The binder dissolves in contact with a liquid, such as polyester or vinyl ester resin. This allows the fabric to be saturated and laid on a surface such as a boat or mold in a process known as wet layup.

The wet layup method of making and repairing composite parts involves using a combination of reinforcement materials and liquid resin to saturate the fabrics and adhere them to each other. The process is used for both new and existing composite parts, and it can be used to create a range of shapes and sizes. The most common application is the fabrication of fiberglass boat hulls, which use either ortho- or isophthalic polyester resin to sheath the fiberglass. However, it is also used in a wide variety of other applications, including aircraft construction and marine construction.


Kevlar is a very strong, lightweight fiber that has excellent impact and abrasion resistance. It is used in bullet proof vests as well as composite boat construction, but its most common use is in conjunction with fiberglass to produce high performance boats. Kevlar is also available as a fabric, and when used alone it produces structures with very high stiffness.

Composite fabrics are sold in a variety of weights, and they can also be found in different types of fibers. The most basic fiberglass cloth is called e-glass, and it’s adequate for most repairs. S-glass is heavier and stiffer but has higher abrasion resistance. Some kayak manufacturers use it as the outer layer on their kevlar or graphite canoes.

Regardless of the type of fiber used, it’s important to use the right resin for your repair. Polyester resin is sufficient for most repairs, and it bonds well with any resin that may have been used in the original construction of your boat. For serious damage, you’ll want to switch to vinylester or epoxy resin for added strength and durability.

When using kevlar to mend your boat, it’s important to lay the cloth in as flat and consistent a pattern as possible. If you don’t, the resulting patch will be weaker than the surrounding area of your boat. The most common weak spots in composite boats are at the seams and where there is a step in the deck, such as around the cockpit. These areas tend to bend when the boat is loaded, and if not patched immediately will become worse over time.

Once you have your kevlar laid in, brush resin over it until it’s thoroughly saturated. Then use a stippling motion when you apply the resin to the surface, to avoid trapping air bubbles under the kevlar. It’s also a good idea to put some peelply, which is thin cloth sold for children’s craft projects, over the top of your kevlar patch to smooth it down and stop the resin running down the boat in drips. Once the mending is done, the boat should be thoroughly sanded down to ensure a clean finish.


Graphite is much tougher than fiberglass or any other composite but it is also very expensive. This is why it is used in aerospace and other high performance applications where weight is critical. Graphite can be formed into complex shapes using a variety of methods but it is most often made from a matrix of resin and carbon fiber. This matrix is consolidated with heat and pressure to form the part. A matched male and female mold is used for this process.

The resulting composite is extremely strong and light, but it must be carefully handled to avoid stress cracking. It can be machined or hand sanded to remove rough edges and contours. It is important to use the correct tools for these processes to prevent damage to the fabric and the matrix. The tooling should include a sanding block and a sanding disc, and the work area should be covered to protect it from dust or epoxy vapors.

Repairing a graphite composite structure starts with inspecting the damage and preparing the surface for bonding. This preparation involves mechanical and chemical treatments to ensure the epoxy resin will adhere properly to the damaged surface. Once the preparation is complete, multiple layers of glass and carbon fiber reinforcements are laminated to the surface with epoxy resin and cured. This produces a strong, fully repaired patch.

Many boaters use graphite coating on their bottoms to reduce friction and to block ultraviolet rays. It is important to note that coating the surface does not increase the strength or stiffness of the boat but it may make it easier to sand and fair the bottom. It also does not increase the abrasion resistance of the bottom. Powdered graphite can be added to epoxy to increase the hardness of the coating but the abrasion resistance of the coated bottom will still be less than that of a plain gelcoat or fiberglass. To get the best result from a graphite coat it is advisable to apply only a thin layer.

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