Painting a Fibreglass Boat
Many of us paint our boats above the waterline to give them a new lease of life. It could be that colour trends have changed and you wish to modernise the look of your boat, or just that the existing paint is either at the end of its life or just looking a bit tired. Either way, painting your boat's topsides can be a simple and rewarding task, and with a bit of prep the results you get can look quite professional.
Areas we might want to paint
We refer to the boats ‘topsides’, but what does this mean? Well for the purpose of this guide we are basically looking at any exterior surface of the boat that is not below the waterline. Generally we antifoul below the waterline, but if you have a boat that doesn’t live in the water for any length of time such as a sailing dinghy that you just launch to race, then this guide can also apply to the entire hull. It’s worth mentioning at this stage that the paint process is slightly different when painting wood or metal, and an additional primer may be required.
The Paint System
We sell various brands of paint, but the method of application remains largely the same. Essentially we prepare the surface for primer undercoat, prime the hull, then finish with a gloss topcoat. We will work through the process in this order, but it’s worth mentioning that no step will ever be better than the previous one, if you skimp on either of the preparation steps, your final look and finish is doomed before you start, so be prepared to put plenty of time and effort in to the prep work. This guide is aimed at single-component paint systems, but the theory is almost identical for two component paint systems (and their dedicated 2 component primers).
Preparing the Surface
Preparation is the key to all paint finishes, so this step is worth taking extra care over. We are trying to achieve a strong and smooth but abraded finish that will allow the next step, the primer undercoat, to stick to it. If you are starting with bare fibreglass (ie not previously painted) you will need to examine the entire surface carefully and fill any small blemishes with a marine filler or epoxy filler. This filler should then be sanded to give a smooth finish. The entire surface needs to be lightly abraded using around 240 grit paper - just enough to remove the shine from the existing gelcoat, and thoroughly cleaned with a degreaser prior to the next step. If your surface is already painted, you first need to establish how good the existing surface is. If the existing paint is in good condition, then you can treat it in the same way as fibreglass i.e. prep and sand with 240 grit paper, but if it is loose or flaking you will need to remove any loose paint to leave a solid surface. Your new coat of paint will only be as strong as the layers underneath, so take your time with this, and work over the entire surface carefully.
Priming the surface.
If you are working with bare fibreglass, and you have abraded the surface, you will need to apply 1-2 coats of primer undercoat. Choose your primer undercoat colour to work with your topcoat colour - for example a light coloured topcoat such as white will need a light coloured undercoat. Ensure you thoroughly clean and degrease the fibreglass prior to application - you want this primer undercoat to adhere well. Degreasing should be done either with a dedicated degreaser or with acetone on a cloth. You can also use pre-painting wipes too.
If you are working with a painted surface, it is possible to skip this step if you are using the same type of paint that is already on the boat. If you are unsure about the type of paint, then apply a coat of primer undercoat as with bare fibreglass. Either way the surface will still need to be thoroughly cleaned and degreased as above. We recommend applying the primer with either a brush or roller. Make sure that you reduce the chance of dust and dirt hitting your surface - dampen the ground around your boat to prevent dust being kicked up, and ideally paint when vehicles won’t be driving past. You will need to apply at least one coat of primer, but we recommend two for a superior finish.
Applying the paint
Allow your primer undercoat to dry thoroughly before moving on to the final step - applying your shiny new topcoat. You should be completely satisfied with the smoothness of your undercoat before even thinking about applying your final topcoat. This is the time to go over the surface again with a fine-toothed comb to check for and repair any minor blemishes or indentations. Pick your day carefully, not too cold but ideally without direct sunlight. Ensure that no dust will hit the surface - as with priming dampen the surrounding ground with a hose if in doubt. Don’t paint late in the evening - you don’t want a significant temperature drop during the drying process as this can introduce excess moisture.
When you have decided that the time is right, it’s time to clean and degrease again. This should be done almost immediately before application. Stir your paint well, and then do it again for good measure! Don’t apply from the can, this can introduce dirt and debris into the paint, apply from a paint kettle or tray, pouring out only what you need for the area on which you are working immediately. Our preferred method of application is using two people. The first person applies the paint with a roller, the second goes along with a good quality brush ‘tipping off’, which means just gently running the brush over the painted surface to smooth out the paint. We find this system give a great finish if care is taken. We recommend applying two coats of topcat, with a minimum of 24hrs between coats.