What is Antifouling?
Anyone who’s ever seen the sorry remains of a car or shopping trolly dredged out of a river or harbour will know it doesn’t take a lot for marine wildlife to quickly move in and make itself at home on man made objects.
Exactly the same thing applies to your boat, especially if it lives on the water. Barnacles, algae, seaweed, it’s all a nuisance, and you can either choose to clean it off; which involves the hassle and expense of lifting your boat from the water and pressure washing it every few months; or you can coat the hull with antifoul.
Antifoul is basically just a special type of paint that contains copper compounds and ‘biocides’ to kill off any small organisms, and encourage larger ones such as barnacles to look elsewhere for a home.
How does it Work?
The basic principle behind conventional anti foul paints is that the resin in the paint gradually degrades over time releasing the biocides and copper compounds into the water and deterring marine life from setting up camp. This is why all antifoul products must eventually be replaced, being sacrificial in nature.
A few other variations exist, with some taking advantage of ‘non-stick’ materials such as Teflon to prevent algae and barnacles from being able to stick to the hull in the first place; or formulations which leave a ‘furry’ surface finish made up of small fibres, again so that marine life can’t adhere to the surface as continually moves with the current.
Don’t get me wrong, antifouling isn’t some magical formula that stops marine growth for good. Typically it degrades over time and needs to be reapplied every year or so depending on how often you use your boat, and the quality of the product you choose, but it’s sure as hell easier than breaking into a sweat scrubbing barnacles off the hull every year.
The Main Types of Antifoul
Hard Antifoul
This type of antifoul works on the principle of ‘leaching’ copper and biocides into the water, however the paint itself does not wear away. It has the advantage of being possible to wet sand to achieve a fairer finish to your hull, which is especially important for racing boats.
On the downside it is more maintenance heavy than the other widely used antifoul type ‘eroding’ antifoul, because you are left with more of a residual layer to sand back when you come to reapply the antifoul.
Eroding Antifoul
As the name suggests this type of antifoul erodes more or less entirely over time, with the biocides, copper compounds AND substrate resin all eventually finding their way into the drink.
For this reason eroding antifoul paints are easier to paint over and replace once they’ve worn away, however your hull will still need some cleaning and preparation when it comes time to repaint.
If you’re really looking for peak performance out of your boat, there are premium variants or eroding antifoul paints known as ‘Self Polishing’ antifoul. As these erode the surface film of the paint actually gets smoother rather than pitted as you might imagine. In theory this actually improves the performance of the boat over time, well until the paint is fully eroded anyway.
Do I Need to Antifoul my Boat?
You might think you can live with a bit of grime on your hull; after all if it’s below the waterline you won’t see it, so it’s out of sight out of mind right?
Wrong!
A fair hull is everything in boat design, and for good reason, it improves performance, speed, and fuel economy. It doesn’t take a lot to create drag and slow your boat down, and by the time a hull is a collage of barnacles you’ll really start to notice a reduction in performance.
You may have also wonder whether the need to apply antifoul depends on the hull material (ie aluminium, wood or GRP). Unfortunately all materials and their respective surface finishes are not immune from developing a build up of marine growth without additional treatment.
What you will find is that specific products exist for both materials, so you’ll need to be sure you buy the correct type for your vessel.
Considerations For Selecting The Right Antifoul
Unfortunately selecting the right antifoul for your boat is a little bit more involved than just choosing the right type to suit you hull material. There are a lot of other factors that require thought and research including:
- Whether or not you will be transporting your boat by trailer – some antifoul paints are more rugged than others, with some falling foul (sorry!) to the beating of being repeatedly loaded onto the pads of a trailer, whilst others are more hard wearing
- Whether the boat will be kept on the water or not – many antifoul paints are chemically designed to work in a submerged environment, so much so that they will even degrade and become ineffective if the boat is stored on land
- Whether or not there are any local laws you need to be aware of that disallow certain products from being used. This is likely to be more of an issue in freshwater environments, so always check with the relevant local authorities if in any doubt
- Whether there are any likely compatibility issues if you are painting over an old antifoul layer with a new paint.
So it’s important to be aware that you’ll need to check the full product specifications of a product you might be considering. Otherwise getting just one vital piece of the puzzle wrong could cause unforeseen issues further down the line.
Having said that you’ll find there are so many choices of antifoul on the market that it’s impossible to ever really find the ‘perfect’ solution. The important thing is to apply a reasonable level of diligence when selecting a product, but beyond that it comes down to simply doing a good job of preparing the surface and applying the paint.
Do I Need to Antifoul if I’m Only Using My Boat in Freshwater?
Whilst the growth from freshwater might not be as extensive or aggressive as that from sea water, it most certainly is still an issue, so I would recommend protecting an exclusively fresh water vessel with antifoul.
You might hear stories of some people who claim to get away with not doing so, but this is only really the case if they lift their boat clear of the water for storage, otherwise they’d still likely have issues.
Will it Ruin the appearance of my boat?
Whilst the end result might not be as good as the rest of the boat, you’ll find the appearance of antifoul on the hull will still be a million times better than a hull that hasn’t be antifouled after just a few days in the water.
Apart from the really heavy duty products which are typically designed for the rigorous conditions that work boats face, you’ll find most antifoul paints come in a reasonable range of colours that match the typical hues of most small craft (think white, navy blue, black and so on)
With one important exception…
Copper coat
Seen as the gold (or should that be copper?) standard among many in both the commercial and private boating communities, copper coat is as the name suggests a heavily copper infused surface coating that provides a hard wearing and longer lasting barrier against the build up of marine life.
When I say long lasting I’m talking at least 10 years per application, and I don’t know of any other product that can compete with this. Whilst a full coat might cost you anything between a few hundred to a couple of thousand dollars, the cost per year actually works out cheaper than other antifoul products.
The major disadvantage to coppercoat is that its heavy copper content means it cannot be manufactured to be any other colour than… well copper coloured. After a few months your hull will then take on the familiar oxidised green colour that you often see on statues, roofs and other outdoor copper installations.
Not especially attractive, but like I say for cost effectiveness and longevity you can’t beat coppercoat.
How Much Does Antifouling Cost?
There’s no easy answer to this question as it’s dependant on many factors, from the size of the vessel to the brand and quality of paint you choose. Then of course there’s the cost in man hours to do the job, which can be quite extensive especially with cleaning, sanding and surface preparation.
Nonetheless let’s look at one example just to give you a feel for the cost of the paint, not including the cost of other prep work. For an average 40’ full bodied motor yacht:
Length Over All = 12m (40’)
Beam = 3.9m (12.8’)
Draft = 1.19m (3.9’)
Total Surface Area to be Coated = 48m² (516 square foot)
International Paint’s Cruiser 250 is a popular eroding type antifoul paint, and with a recommended 3 coats covering this surface area, the total amount of this paint required is approximately 16 litres (4.2 gallons).
This stuff retails at about £85 ($115) for a 3 litre tin, so we’re looking at a grand total of about £540 ($715) to do the whole job.
How do I Apply Antifoul?
Marking Out The Waterline
How far above the waterline you wish to extend the antifoul paint is a matter of personal preference as much as anything, but I would aim for at least a 5cm (2”) to account for the regular waves and wash when the boat is moored up, effectively raising the waterline, albeit intermittently.
On an older boat the waterline is probably a fairly obvious mark, but on a newer boat it can be more difficult to know exactly where it is, or will be.
The easiest, most obvious way to determine a reasonable indication of the waterline is of course to put the boat in the water moored up against a pontoon, laden to the maximum allowable payload (including full tanks of fuel). You can then mark on the hull where the boat meets the water, putting a mark every few feet or so along the entire length of the boat. This will give you a good indication of the waterline to work from later.
Alternatively of course you can leave the boat in the water for slightly longer and wait for a natural tide mark to emerge, although you will of course have a more rigorous cleaning job to do afterwards.
Once you’re happy with the waterline you can then mark out a line 2” above it to indicate where your antifoul will extend to. To make sure you get the straightest line possible it’s useful to use a laser level to mark a straight line above the waterline. If the floor of your work shop or boat cradle isn’t level you might need to either jack up one corner of the boat slightly or change the angle of the laser level on its stand to ensure the two lines are parallel.
Once you’re happy with your line you can use a strip of masking tape around the perimeter to mark it off ready for surface preparation.
Surface Preparation
Like most painting jobs, preparation is the key to success with antifouling. Failure to prepare the surface to be painted will shorten the life of the antifoul for the simple reason that it won’t adhere to the hull surface properly.
The most important thing to remember is to follow the antifoul paint manufacturer’s instructions to the letter. It will contain all the specifics with regard to what chemicals/cleaning agents can and cannot be used prior to the application of the antifoul, as well as the specifics on surface preparation.
In general however…
Make sure you have taken all necessary safety precautions, as a minimum before doing any work you should have:
- Industrial grade dust mask to protect against paint and GRP and old antifoul paint dust, which is extremely hazardous.
- Goggles
- Gloves and overalls (with hood for when working under the hull)
If the boat is new, the first thing to do is remove any wax or mould release agents that might still be present on the hull. Depending on what mould release or wax is present you’ll either be able to clean this off with soap and water, or you might need to use acetone. Either way, you need to make sure all traces of mould release agent are absent before you begin sanding, or else you risk rubbing it into the keyed surface you’re about to create. It then becomes 10x harder to remove, and will once again prevent the antifoul from properly adhering to the hull surface.
Next comes sanding. Trust me, I know how painful it can be to take a sander to a nice shiny gel coat that you’ve just paid thousands for, which is all the more reason to make sure you do the job properly if you’re doing it yourself.
The most important thing is to make sure you achieve an evenly keyed surface that removes all the sheen from the gel coat. Once again, failure to do this will prevent the antifoul from adhering properly.
Applying Epoxy Primer
Before you do however, another useful tip if your boat is new is to take the opportunity to apply an epoxy primer to the keyed surface prior to applying antifoul. This acts as an additional protective seal against water ingress over time. Don’t forget, by sanding the hull you’ve just reduced the integrity of the laminate, so anything you can do to toughen it up again is going to be worthwhile in the long run.
If on the other hand your boat isn’t brand new and you’re simply sanding down the old antifoul layer you’ll have a much bigger job on your hands to take it back far enough to successfully apply an epoxy primer, so you might want to cut your losses and simply skip straight to the antifoul in this case.
Applying Antifoul
Given the large amount of ‘solid’ content in antifoul paints, you’ll need to be extra thorough about mixing it before you begin painting or else be left with an ineffective end result.
How you apply the antifoul obviously comes down to the manufacturer’s guidelines, depending on the product it can be sprayed or rolled on. Spraying typically requires special facilities to contain and protect against breathing in the toxic paint fumes, so is best left to professionals only.
The effectiveness of some paints are governed by how many layers are applied, while for others the objective is to simply use the right amount of paint for a given surface area. Either way it’s a good idea to apply more layers to leading edges such as the bow or keel, as these experience a greater level of wear.
