A major fiberglass repair, such as patching a hole, can be a daunting task. Watching a professional do the job can help you get on the right track and be confident in doing the repair yourself. This step-by-step video tutorial produced by Sea Hawk Paints will show exactly what needs to be done when patching a hole in your fiberglass boat.
Note: Before attempting a repair by yourself, get a professional opinion. Always wears Personal Protective Equipment when sanding or working with chemical compounds! Respirator, safety glasses and gloves are always recommended.
Here is a list of products you will need for the repair:
Fairing is process of smoothing out and restoring the damaged surface of the hull. A fairing compound such as Epoxy resin can be used to fill in divots or gouges and then be sanded to a smooth finish. This restores the surface to its original shape and also prepares it for painting.
Note: Before attempting a repair by yourself, get a professional opinion. Always wears Personal Protective Equipment when sanding or working with chemical compounds!
Here are some guidelines to fairing out imperfections in your hull:
Every household should own a Hawk Epoxy Kitlike this. You can use it to repair anything around your home or own your boat. This kit comes with the resin, catalyst and your choice of filler. Just mix them together and you have an excellent bonding, filling, or adhesive paste.
FGCI General Purpose Resin is used for laminating with fiberglass, kevlar and carbon reinforments. It can be tinted with pigment up to 3% and best results are when used at 70-85 degrees F. Hardener varies depending on thickness of fiberglass, the more fiberglass the less hardener as you will generate more heat-never go below 1%. Complete cure needs sanding aid added to resin or PVA while still hot.
Polyester resins are unsaturated resins that are combined with hardeners, such as MEKP.
Polyester resin is used more for fiberglass lay-up or if you’re going to finish a repair with gelcoat, as the polyester resin will bond to the gelcoat better than epoxy. It is also cheaper than epoxy and a great choice when casting deep molds.
Various Types of Polyester Resin:
Boatyard Polyester Resin is a non-specified resin that contains different types of polyester resins and wax. Boatyard Polyester Resin is not recommended for use below the waterline. The material may cure hard and tack-free due to the included wax. If so, the product will need to be sanded prior to adding another layer in order to promote good bonding.
Clear Casting Polyester Resin is used to cast small objects into a mold. This method can be used to create sculptures, crafts, or industrial prototypes.
Surfboard Polyester Resin is Clear & wax free. It is ideal for building & repairing surfboards because it cures to an almost clear color when applied in a film. Also it highlights underlying graphics.
Iso Marine Resin is based on isophthalic acid. This resin is a step above the general purpose polyester resin and that is reflected in the price. Iso Resin is stronger, more durable, and is the best choice when applying in corrosion environments or elevated temperatures.
Vinyl ester resins are formulated with a base of polyester resin strengthened with epoxy molecules (a hybrid form of polyester and epoxy and aiding for gelcoat to bond with epoxy) and also use peroxides, such as MEKP, for hardening. These are cheaper than epoxy resins and more expensive than polyester. Ideal temp for use is 77 F, not applied over 1/8th thickness or it will generate to much heat.
Vinyl esters are more tolerant of stretching, less likely to show stress cracking and more resistant to water penetration. Vinyl ester is the choice when improved resistance to moisture is the goal (like repairing a blistered hull).
Long term water exposure (hull or water tank) or if impact resistance is important vinyl ester is usually chosen.
Epoxy resins are cured with the addition of a hardener. Unlike the polyester and vinyl ester resins, cured with a small amount of catalyst, epoxy resins usually require a lot more, often 1:1 or 2:1. A epoxy resin is the most expensive of these.
Epoxy resin has the best bonding strength as it will bond dissimilar or already cured materials for strong, reliable repair work. This is the most expensive resin but offers the most in its ability to flex, prevent delamination and ease of repair work.
If doing a repair and not overlaying with gelcoat then the epoxy will perform best as it tends to act as a stronger “glue” for the patch to the surrounding surface.
Laminating Epoxy Resin is the correct choice for repairing boats. It is super durable and has high resistance to water. Also, it has very good adhesion to a variety of surfaces including metals, plastics, fiberglass, wood, and glass. Laminating Epoxy is available in 3 different ratios that provide different working and cure times.
A Premium Commercial Grade Clear Epoxy Resin – Klear Kote Epoxy Resin is used extensively in coating surfaces and in table tops where a clear, hard and durable coating is required. Commonly seen on bar tops and restaurant tables. Easy to use 1:1 mixing ratio of resin and hardener. Items coated with it will become permanently preserved and protected for your enjoyment throughout a lifetime. The epoxy resin will not exhibit blushing or sweat out under high humidity conditions.
Epoxy resin kits are sold in two parts, A and B, which should be applied in two stages. The first stage is referred to as the seal coat. The seal coat is brushed on in a thin layer and is used to seal any pores in the surface and prevent air bubbles from forming in the following flood coats. This stage is followed by the flood coat, which will flow and self level, clean brushes or squeeges can be used to help spread the epoxy. Flood coats are applied in 1/8″ layers at a time, as many as desired can be applied, however one to three coats is average for most table or bar coatings. Resin kits are often applied on bar tops and table tops in many bars and restaurants.
Gelcoat and resin spray guns are ideal for large surface spraying, such as new mold construction, composite refinishing and large boat surfaces. Look for a resin gun with a blue die cast body which will ensure a long life. Most HVLP cup guns use nylon flat seal just behind the threads that the air cap attaches to.
If you have used a spray gun with a nylon flat seal just behind the threads that the air cap attaches to and cleaned it with acetone, the seals disintegrate so it is best to use one with a plastic seal.