Perfect bottom paint for a boat, especially for racing, is essential. Unfortunately it is one of those boat jobs for which many shipyards prove inadequate. Used to working mainly with cruising boats, they give a few coats of antifouling without really preparing the bottom properly. Those few shipyards that know how to do a nice job do it at exorbitant costs. In this article we see how you can do a perfect job in total autonomy and obtain a perfect result.
Antifouling a boat: how to get a perfect racing bottom
The first step is obviously the hauling, if you cannot delegate, I advise you to be present. Racing boats such as Mini 650s and Class40s have a hull shape that many crane operators are not used to. Very wide in the stern, they tend to tilt forward during the hauling phase. Armed with patience, you will have to work with the crane operator to ensure that the hoist straps are positioned correctly. Some tilting forward is necessary so that the crossbar does not touch the mast and the swept aft spreaders.
However, depending on the model, it may be necessary to shorten the bow strap. Straps usually have multiple attachment points, and reducing the bow strap may be the solution. But, if the boat comes up too straight, or worse, it tilts aft, you must immediately abort the manoeuvre and try again. In the end you will find the right compromise, with a boat like a Mini 650, light and manageable it is not a big problem. For a Class40s you might decide to go to a yard with a travel lift to avoid surprises.
Many Mini 650s can be lifted with 4 lifting straps attached to the padeyes. But be careful, you must have the right length of the straps and only attach to those padeyes with three bolts and higher breaking load. In any case, if it is the first time, ask the crane operator to lift slightly and evaluate if there are excessive bending of the fiberglass, not all boats can be lifted this way. I happened to have to abandon a lift because, due to some previous repair one of the padeyes seemed to want to tear off the deck.
Antifouling a boat: laying it on the cradle
On racing boats, the yard cradles with 4 or 6 adjustable legs are usually not used. Each boat should have its own cradle with saddles that exactly match the shape of the boat by distributing the weight. If you are using the cradle of another boat of a different model you will need to get some foam blocks to ensure that the weight is distributed. I do not recommend polystyrene because under compression it tends to stick to the boat. You can buy a sheet of insulation material for home construction and cut pieces of various thicknesses.
As soon as the boat is placed on the cradle you will be able to take a first look at what awaits you to antifoul a boat. If you have done the work the previous year you can evaluate which points have been consumed more than others. When you re-apply the antifouling you can give an additional coat in the affected points. The weak points are usually the water line, particularly at the bow, rudders and the keel. The boat can remain with the keel hanging, i.e. on racing boats there is no need to have it rest down on the ground or cradle bottom. However, you can chock it for greater stability of the boat on the cradle.
It seems silly to say this but before the cradle moves always check that no rope has fallen off the deck to the ground. Sometimes the mooring lines are thrown on deck and can fall. I happened to see them get stuck in the wheels of the travel lift and the boat very nearly fell off the cradle. When the boat is finally in the yard, double-check that the loads are well distributed and there are no pressure points – later we will see how to intervene.
Antifouling a boat: sand down to gelcoat
If we start from a boat that has not received the right love in the past we are forced to go back to gelcoat. If there are in fact other layers of antifouling it will be difficult to obtain a good result. On this type of boats we really must always have a perfect bottom. For this we will inevitably have to clean it with a slightly abrasive sponge regularly throughout the year. For this reason we have to choose a hard matrix paint, for example one for motor boats.
Self-levigating antifoulings cannot be cleaned throughout the year. Even if they give good results in many waters, they will never be comparable to a well-painted bottom with hard antifouling. Of all the jobs, antifouling is where racers and cruisers live in worlds apart. In fact, on a cruising boat you simply slap a new coat onto the old antifouling. You can use a primer will prevent flaking and give good grip and give the new antifouling on top of the old one.
If, on the other hand, you have decided to sand back to gelcoats let’s see the work involved. First of all, do not be stingy on sand paper discs, you will need a hundred for a small boat, change them frequently. As for the grain, work with the 120 grade. Only if the type of paint makes it in an impossible task, you may be forced to use a 80 graded sandpaper disks. But be careful with an 80 you have to work with the sander perfectly flat and press on the edges of the disk. Change the discs as soon as they are ineffective and never fall in the temptation to use the sander at an angle as you will end up with an irregular surface.
Antifouling a boat: precautions before sanding
Sanding is a tiring, dangerous job that requires the right precautions. First of all, check with the regulations provided by the yard. In many yards, even if you are allowed to antifoul, you will have to use a sander with an aspirator. In other places they are more tolerant, with a small boat ask to be put in a corner of the yard where you will not get dirt on other boats. At least you won’t create too much dust for the neighbors, although aspirators should be mandatory for obvious reasons.
Protect yourself first, remember that you are sanding a toxic antifouling. A paper mask is not enough, make yourself a gift and take a serious mask with filters. Wear a protective suit and try to avoid exposed skin, at the end of the day it affects your health. I have never been a very good at health and safety but over time I got used to it. I remember blowing my nose and realising that I was literally breathing antifouling, that’s not good and that’s when i stopped using simple paper mouth and nose filters.
The boat also needs to be protected, this is simply because it will save you a lot of time later. If you get all the sides dirty while you are antifouling you will have to spend a lot of time cleaning afterwards. The 1.8 meter high protective plastic sheet is perfect for a Mini 650. You can protect the whole boat with a single roll which comes with an adhesive edge. A small investment that is worth every penny.
Antifouling a boat: the primer
Having sanded back to gelcoat you will necessarily have to apply a coat of primer. This is because the antifouling applied directly on the gelcoat will tend to peel off. If you want to protect the boat from humidity you can choose an epoxy primer. This is more difficult to apply well and obtain a perfectly smooth bottom. Be careful because the epoxy primer drying becomes hard like epoxy resin. If you give it with a roller it will create a hard and rough surface and you will have to re-sand everything!
To apply the primer with a smooth finish with a roller you have to dilute it. For perfect results dilute more than recommended. Always prepare a little primer at a time in your tray and mix well. Otherwise you will have areas with very thin primer and others where the thinner has evaporated and the paint is thick. Knowing how to apply the primer smoothly without spikes, orange peel effects etc requires the right amount of practice but it’s not rocket science.
If you have a painting awning or are able to make it with canvas, I recommend that you spray paint. In many shipyards that allow you to do boat maintenance, you can ask to be put aside to have room for manoeuvre. Especially with a small boat you can find a place. After applying the primer I advise you to let a day pass. Then with 120 sand paper, by hand, give a light once over that levels slight imperfections before applying the antifouling.
Antifouling a boat: spray painting
Spray painting allows you to obtain results that are unthinkable of with a roller. Many think it is difficult or impractical in some situations. Maybe you don’t have a suitable compressor or you have the inconvenience of taking it to the yard. From the compressor you will need an air line long enough to allow you to work without constantly moving the compressor.
An alternative, which only requires a hose with suitable connections, is to use scuba tanks. The hose requires on the one hand a gun attachment and on the other hand one that will go onto the scuba tank. I had it made by a local company for 30 euros. I recommend that you then add a pressure regulator between the cylinder and the spray gun. The regulator of the diving bottle gives you air at 6 bar but you need a maximum of 2, with an additional regulator you will triple the life of each bottle.
With two full 18 liter air bottle you will be able to prime and give three layers of antifouling on a small boat like a Mini 6.50. If you have a diving license you can rent the bottles or if you have your own you you can fill them with your compressor or go to a diving shop and have them filled. Obviously, if you have a compressor life is easier. In my case I needed to be able to paint even in places without electricity, hence the bottle. In fact, the portable air bottle was very versatile for all sort of small paint jobs.
Antifouling a boat: applying the antifouling
If you work with spray paint, you will have to dilute it much more than indicated for use with a roller. Each layer will therefore be rather thin so I recommend a minimum of three layers. A fourth for the whole water line, the bow, the keel, the rudders. Having protected the boat with film you will have no problems with dirty sides. Needless to say, when spraying a toxic substance you have to use a serious mask with filters and no there must be no people standing by. Paint on a windless day and fit temporary paint sheets properly – these are not visible in the photos as i couldn’t otherwise take the photos.
It should be said that if you do not use a protective tent spray painting is not allowed. If the yard has sufficient spaces and tanks for the collection of sanded particulate matter, it could tolerate sanding without aspiration, but not spray painting. More importantly when spray painting make sure the paint does not come out of the painting tent.
The antifouling given in this way is perfect, shiny like a mirror, an enviable finish. From experience, it tends to be thinner so if you have time give more coats or you will have a slightly shorter lasting antifouling. Once in the water, however, before each race and training, I imagine you are already used to giving the bottom a good clean. If you do it regularly, the hard matrix antifouling lasts all season. Do not leave too much time between each wiping, because if you find yourself having to scratch off nastier growth of algae you will inevitably take away the paint.
Antifouling a boat: The cradle problem
The boat resting on the cradle leaves two huge sections to be painted. Fortunately, a Mini 650 weighs less than 1000 kilos, depending on the model. Let’s say 1500 at the most. Now I used a DIY technique which worked fine but it should come with all the appropriate risk disclaimers! Spray painting your antifouling and then leaving two large strips to be painted before launching on the old paint without even sanding is a shame.
The alternative, in safety, is to ask the shipyard to move the boat a little along the cradle with the crane. Just move the boat forward or backward by 30-40 centimetres and adjust the thicknesses and continue with the work. Before moving the boat allow at least 24 hours for the antifouling to dry. Otherwise it will stick to the cradle and at the time of launch you will see what a crappy job you’ve done.
I created temporary supports with adjustable building sites tubes. Used upside down, the adjustable leg could be turned to lift the boat as a support point for this temporary cradle. With a support at the bow one at the stern I lifted the boat by hand by turning the adjustable legs in turn. I just had to lift it just enough to make the cradle slide and then lower it down again. The cradle with the saddles always remained under the boat a just a few centimetres away. Let’s say that the risk was minimal, the boat could fall on its saddles at the most.
Antifouling a boat: finish by polishing the topsides
Once the painting work is finished, we can remove all the protective material around the boat. The boat will not be dirty, but a good polish will bring it back to looking new. If there are any rust spots you can buy a rust remover at the hardware store for a few euros instead of using a product like Star-Brite. Put the product on a piece of cloth and rubbing the gelcoat it removes rust stains in no time. Rembember, with the rust remover don’t touch any metal surfaces, because it is corrosive and you have to re-polish them.
Then continue with a car waxing paste to clean the top sides. Continue a few metres at a time, I paste polish than liquid ones. The abrasive component of the liquid ones was too low and would not bring tired gelcoat back to a good shine On the other hand, with a good waxing paste and elbow grease and a polisher a perfect result can be obtained easily.
The moment the boat is lifted, if the straps are not properly placed, the boat will lean forward. In doing so, however, the boat risks slipping on the cradle and scratching all the paint given with so much care. It may be necessary to forcefully hold down the cradle at the stern as this will tend to rise. Prepare a line at the bow and one at the stern to handle and turn the boat during launch. If you are in a yard with a travel lift, everything is obviously simpler. But many yards sites do not like to turn on the travel lift for a small boat and use the crane with cross bars.
Hull: maintenance once in the water
As anticipated, you will then have to regularly keep the hull clean with a sponge. At first, the least abrasive of the scotch-brites will suffice. Towards the end of the season you will need the more abrasive one. This will erode the paint and eventually it will be time to antifoul the boat again. From the point of view of racing, however, you will have a perfect bottom all year round.
In these photos you can see an unorthodox but certainly functional technique for cleaning a hull with a boat in the water without diving. By tying the halyard to a fixed point and pulling the winch, you can bring the boat even to heel at 90 degrees. This is done regularly in many classes during the measurement process, there is no reason to think that this will damage the boat. With a pressure washer you will save yourself a dive that is either forbidden or at least not well tolerated. I don’t know what they will say if they see yo messing around with a heeling boat but technically I don’t see the problem.
How much does it cost to antifoul a boat
To calculate the effort required to antifoul a boat, you need to think by surface and not by length. A Mini 650 has about 10-12 square meters of surface to be painted. A Class40 30-40 square metres, including keel and rudders. Costs are not linear with the length of the boat, but are proportional to the square of the length, or nearly so.
If we exclude the operations of hauling and launching and site handling for a Mini 650 you will have to take into account materials and labour. For an accurate job like the one described you have at least € 300 of materials and 3-4 days of labour. Of course, doing things in the right way can be done even in an afternoon, but we’re not talking about the same job.
In fact, yard estimates can be surprisingly low. For a Mini 650 they ask for as little as €600, but I assure you that you will be lucky if the boat receives even the slightest bit of sanding. For a job like the one described, a shipyard could not ask you less than 1500€, which is why DIY is so widespread in the world of boating. Also remember that with a little practice you can get excellent results even with a roller.
