Gelcoat Filler is an excellent material for carrying out small Gelcoat Repairs to Boats, Caravans and Campers. Gelcoat Filler is essentially a thickened Clear Gelcoat with a smooth Peanut Butter consistency. It can be easily pigmented to match an existing colour and includes MW Solution so that it will cure externally on the surface of your repair. On boat repairs it can be used above and below the water line and is a fairly easy material to use and understand.
Preparation
The project area needs to be dry and clear of any loose material in and around your repair. You should clean out the repair area with a modelling knife or stanley blade removing dirt and loose material. It is a good idea at this stage to mask off the repair area to protect the surrounding gelcoat. After the debris has been removed lightly sand your repair area which will provide a key to the final Gelcoat Filler layer. Clean the area with Acetone to remove any remaining grease or residue.
First Gelcoat Filler Layer
The next step is to fill out the void with Clear Gelcoat Filler. First add catalyst at 2% mixing ratio to your Gelcoat Filler and mix well. Fill your void (using a small brush or mixing stick but remember not to leave the clear gelcoat filler proud of your repair at any point. Leaving a 1-2mm indentation which will be filled with the final pigmented gelcoat filler. If your repair is deep you can build up in layers of 5mm to the required depth leaving 1-2 hours between each layer to allow for curing. Make sure to fill the whole void as any small spaces will be an area of weakness.
Pigmented Gelcoat Filler Layer
Once your first layer is fully cured it is time to apply your finishing coat. This can be done using clear gelcoat filler (if the repair is below a water line and will be covered with anti foul) or you can add the correct colour pigment needed to blend your repair seamlessly with the existing gelcoat colour. Pigment is usually added between 5 and 15% by weight to the clear gelcoat filler prior to the addition of catalyst. For more information and availability of Pigments click the following link - GRP Polyester Pigments.
The final clear or pigmented Gelcoat Filler can now be applied. This should be added so that it is slightly proud of the repair to allow you to sand back to the original profile of your project and should also overlap the edges by 3 - 4mm.
Sanding Process
Once the final layer of gelcoat filler has been applied and cured you are ready to sand back to the original profile of the project to achieve a seamless repair. Anything from 240 grit to 320 grit wet and dry will do the job. Be careful to sand the repair area only and not the surrounding original gelcoat. The earlier application of masking tape will help protect this area but please take care during this process. Once you are happy that you have done a good job in returning your repair to its original profile you can go through the grits to a 1200 to 1500 grit wet and dry before removing your masking tape.
Compounding
The final stage is designed to blend your repair to the original colour and profile of the project to create a seamless and often invisible finished repair. Start with a small amount of fairly course compounding solution. ROAR Compounding Solution 910 or 920 would be ideal and can be applied with a clean microfibre cloth across the repair area and beyond. Work this area evenly until you approach a fairly high gloss finish across and some inches beyond your project area. You will then want to blend in this repair with a less course finishing solution. The ROAR 950 Finishing Glaze would be perfect. To achieve a fully blended repair use a finishing glaze across the whole panel on which your project sits so that the repair and extended area beyond matches to a high gloss finish. Wipe the whole area with a clean damp cloth removing the sanding and compounding / polishing debris revealing a seamless, watertight and pleasing final repair.