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Gelcoat Repair

Author: Karen Connolly
Categories: Gelcoat
Sand Paper for Fibreglass Preparation

Gelcoat repair is inevitable for the vast majority of boats after a sustained period of time on the sea. Common gelcoat repairs are often applied for spider web cracks or eroded gelcoat to the point where the base laminate is starting to show.

The good news is, the vast majority of gelcoat repairs are easy to undertake and will save you lots of money by repairing them yourself.

Prepping the damaged area for repair

To ensure a successful repair the area must be prepped accordingly.

The first step is to chip or grind down any damaged material and finish feathering the edges with a course sandpaper such as 240-grit. This will give the new layer of gelcoat a suitable are to bond with. Care should be taken to not sand down too far and reach the glass.

Once the area has been sanded down, it should be wiped with Acetone to remove any contamination.

Gelcoat application

FibreGlassDirect supply 6 standard gelcoat colours; White, Black, Dove Grey, Dark Olive, Bright Blue and Clear. The clear gelcoat may also be pigmented if required. One or more mixes of pigment may be required to achieve an exact match to the rest of the boat.

Gelcoat must be mixed with 2% catalyst based on an average room temperature. This will give a working time of approximately 20 minutes. In colder conditions, more catalyst may be added but generally no more than 3% should be used. Likewise, in warmer conditions less catalyst may be needed to slow down the curing time, but no less than 1.5% should be used. If the gelcoat is allowed to cure too quickly, it will create air bubbles that will appear when sanding takes place after the cure.

Depending on the depth of the repair, apply the first layer with a brush (for very shallow repairs, a match stick may be used to apply the gelcoat) so that it is thick enough to cover the damaged area and overlapping the masking tape. Remove the masking tape before the gelcoat fully cures. This will leave a clean edge without disturbing the hardened new layer of gelcoat. After applying the gelcoat to the repair, cover the repair with sandpaper, ensuring that there is no trapped air. This will help reduce sanding when the repair is dried.

If 2 layers are required it is important to sand the first layer once cured to allow the new coat to stick.

Finishing touches

When the Gelcoat has fully cured, the area should be sanded. We recommend using wet and dry sandpaper. Wet sanding the cured area will reduce sanding time and stop the sandpaper from clogging. We would also recommend to start with a course sandpaper such as 240grit and work up to 1000 grit. Work to sand the area so that it becomes flush with the untouched area and blend edges accordingly finishing with the 1000 grit sandpaper.

To add shine and to remove any of the finer scratches from sanding, a handheld, motorised polisher may be used with a lamb's wool pad. Farecla compounding pastes work particularly well for adding shine.

Contact FibreGlassDirect

To purchase any of the gelcoats mentioned, accessories such as wet & dry sandpaper or compounding pastes, visit our online shop FibreGlassDirect. We offer fast, nationwide delivery across the UK and Ireland.