The gelcoat topsides of a GRP boat can be pampered and restored to their former glory relatively easily when it is ashore. Gelcoat is only a very thin outer layer of the hull, often less than 1mm thick, so you should avoid cleaning it with highly abrasive cleaners, or anything that could potentially damage its surface.
Below is a step-by-step guide to keeping a boat’s topsides in good condition:
The first step is to clean the hull thoroughly with fresh water to remove any loose dirt and grit. If you have access to a fresh water hose, then this is best – be prepared to get a bit wet!
If there are some obvious marks that won’t come off using water, then a boat shampoo may suffice. Don’t be tempted to use a domestic cream cleaner as these are very abrasive, even if they cost a fraction of the price. Wear protective gloves if advised by the manufacturer.
- Stain removal
Stains can be formed by fouling and environmental pollutants. These tend to build up along the waterline if a boat is left unattended. Such chemical stains can be treated using a variety of products, most of which contain acids including oxalic, phosphoric, sulphuric and even hydrochloric acid, which is very strong and caustic and perhaps best avoided.
Suitable cleaning products include liquid cleaners, sprays, powders and gels. Gel products containing oxalic acid are generally the most popular and considered the most effective and safest to use, as they are easy to apply and do not drip. You simply brush the gel over the stain, leave it for 10 minutes and then rinse it off thoroughly with fresh water.
However, oxalic acid is harmful to humans and wildlife in concentrated forms, so it should be used with caution in the boatyard. Wear rubber gloves and safety goggles when using any of these stain remover products.
After the gelcoat is clean, it should be degreased before polishing. Use a soft rag soaked in acetone, but go carefully as you don’t want acetone flying all over the place, especially if working above your head. Also wear rubber gloves.
There are many brands of hull polish available, but broadly speaking they all do the same job, which is to remove surface imperfections and the oxidisation – note that polish is not a coating. The critical difference is how abrasive they are. If your hull is in pretty good shape then there is little point in using a highly abrasive, coarse grade polishing compound, when a fine grade polish will do the job perfectly well and not wear away the gelcoat.
Hulls in poor condition may require two or three polishing compound treatments, using different grades. If in doubt, test a small area of the hull with a fine grade rubbing compound first and see how it looks.
Hull polishes are applied using a soft cloth or foam pad and allowed to dry. Then buff with a soft cloth using a circular motion until you have a high gloss shine. If this sounds like too much hard work, then there are electric powered polishing machines that make the task easier. The pros tend to use these. The good machines are usually quite pricey but are better than cheaper alternatives as they are lighter, vibrate less and generally easier to use. Those with variable speed settings and orbital type movement are best, as they will leave fewer swirl marks on the surface. High speed machines produce too much friction and can damage the gelcoat. Once the polish is applied then start the machine at a low speed and keep it moving slowly from side to side and then up and down, but not in a circular motion.
The last all important step is applying the wax, which needs to be done to protect the gelcoat and provide a lasting gloss finish. Waxes can be in liquid or paste forms – which of these is best really comes down to personal choice.
Paste waxes are a bit more physically demanding to use but they tend to leave a harder protection and last longer than liquid waxes. But if you are hand polishing your boat (which I tend to do) then a good quality liquid wax is much kinder on the wrists and elbows. Mechanical polishers can also be used with paste or liquid waxes, using the same up and down, side to side slow movements as are used with compound polishing.
As ever, if in doubt, ask around the boatyard for advice from other boaters and the pros.