How to Prepare Fiberglass before Apply Gelcoat

You can add a gelcoat surface to your fiberglass boat if you wish to change its color, if you have damaged the outside of the boat somehow, or there are other reasons for replacing the fiberglass shell which the boat came with using a gelcoat resin. If you plan to do this, following a few simple tips can help you to prepare your fiberglass for the application of this coat.

Step 1 - Get Your Fiberglass Clean

The most obvious step in preparing your fiberglass body for a gelcoat is the one which many people miss, and that is simply to give your boat a cleaning. Fiberglass can attract dust particles like paper on a comb, so you need to make sure that the fiberglass chopped strand mat you will be painting is scrupulously clean. You should first sweep the surface with a wide brush, and then clean up the area more closely using a brush with rigid bristles. This will help to remove debris from the corners or between panels. Sweep all of your debris into a dustpan, and then clean out your brush carefully, ready for when you will next want to use it.

Step 2 - Sand Your Fiberglass

Sometimes, the surface will need a new coat of gelcoat because the old surface has become oxidized through contact with the air and salt water. If this is the case, you should strip away the old gelcoat surface using a specially designed planer. This will cut into the pigmented resin and ensure that the gelcoat is completely removed from the surface of the fiberglass boat. You can purchase these sanders from local hardware stores, and it may be possible to rent them from marinas and other boat-specialist stores. Once you have the gelcoat planer working, connect it to a vacuum cleaner or other waste disposal unit in order to ensure that the dust and dirt will not be left on the boat surface, where it can affect the appearance of the new gelcoat.

Step 3 - Wash Your Fiberglass

After you have sanded down the old gelcoat, it is a good idea to give the surface a good wash with some soap and water. This will remove any old gelcoat that is adhering to the fiberglass, and it will also wash away specks and stains from the surrounding surfaces. A good wash will ensure that your fiberglass has a smooth surface, and therefore that the gelcoat will pour or spray evenly onto the boat. Once you have washed the fiberglass, give the area where you will be pouring your gelcoat a good buffing with some sandpaper. This will give your surface a slightly raised edge, which will help the gelcoat cling to the fiberglass.