Hull Maintenance Special
How to select and use the best anti-fouling paint system for your boat, by Bob Ross.
ANTI-FOULING a boat is expensive. It's hard and dirty if you do it yourself with the labour of heavy-duty wet- sanding before applying a gooey paint by roller or bush.
But cleaning the bottom of a neglected boat is harder and dirtier, involving scraping off the sharp shells of mussels, limpets and barnacles, coral encrustation, weed and disposing of the stinking residue collected on the tarpaulins and drop sheets. That's why I'm not too keen on fish, mother.
Seriously though, there are good products and programs to fend off the critters of the deep that will seriously slow your boat if not confronted.
Let's look at the enemy. First to attach is the layer of green slime, comprising billions of single-celled algae. It will not come off as your boat moves through the water and once established, provides an ideal settling ground for more micro-organisms. Algae slime tends to be denser near the waterline due to higher exposure to sunlight.
The major invasion of fouling organisms feeding on the green slime includes barnacles, limpets, mussels, seaweed, sponges, sea squirts and coral worms. They feed by ingesting passing particles carried by currents and wave action. To resist the turbulence, the animals within this growth anchor themselves to the hull's surface with suction and powerful natural glue-like substances. Once attached, they grow and propagate, creating clusters which in turn capture more passing food to extend the colony.
Besides creating significant drag to a boat's movement, the encrustation of growth on a boat that is continually in the water if left untreated will infiltrate hull openings and seize up moving parts like propellers and rudders.
Growth will be faster in tropical and warm water than in cold. The longer the growth is there, the harder it will be to get off, so regular cleaning is better for the boat and the environment.
It's easier to remove fouling when it is wet but for environmental considerations and because it is illegal in most areas (check with your local authority), you should not clean fouling from your boat in the water because you may be putting live pests and toxic waste back into it. Ideally, you should slip your boat; collect the waste removed during cleaning, bag it and put it in the rubbish bin.
Differences in water quality – fresh, salt, brackish — as well as temperature, can produce different types of fouling. Design of marinas, as well as location, may also be a factor.
Research by Oliver Floerl from James Cook University in Townsville, Graeme Inglis from the National Institute of Water and Atmospheric Research in Christchurch, New Zealand and Vicki Hall from CRC Reef Research Centre (the Cooperative Research Centre for the Great Barrier Reef World Heritage Area), has found that the floating docks and pilings of the average-sized marina provide several thousand square metres of space for organisms to grow on and may be the major source of species that foul resident boats.
“The research shows that vessels moored within a given marina develop fouling communities that are characteristic of the assemblages that grow on pilings and structures in that marina.
“On average, the cover of fouling organisms on the boats increases by about ten per cent every five months that they spend moored and uncleaned within tropical waters. This means that, despite the use of modern anti-fouling paints, marine organisms cover about half of the submerged surfaces of the boat within two years of being painted.
“The longer the boat goes without being repainted, the more species it shares with the surrounding marina and the greater risk it poses for spreading those species to other locations.”
The researchers found that besides the danger of exotic marine species migrating to Australia on cruising boats, like the black-striped mussel introduced to Darwin by an overseas yacht, boats travelling around the Australian coast may carry fouling species that may not occur in the marina at their destination.
They say that the design of some marinas may aggravate the fouling problem. “Preliminary studies on water movement in the different types of marinas show that the breakwalls of enclosed marinas can create circular eddies that retain water for much longer than marinas without breakwaters. This can lead to an entrapment of the planktonic larvae of fouling species within enclosed marinas.
“Rates of recruitment by fouling organisms were found to be between two and nine times greater in these enclosed environments than in unenclosed marinas and between three and 19 times greater than adjacent coastal environments.
“These results have two major implications. For boat owners they suggest that maintenance will be required more often in marinas with poor tidal flushing because fouling is considerably greater in these environments. Second, because water circulation in enclosed marinas appears to trap marine larvae for a significant period of time, the spread of established induced species from the marina may depend more on vessel movement than on larval dispersion by ocean currents.”
Wherever they are, boats should be checked every month for fouling. If it's evident, have the hull slipped and cleaned as soon as possible and definitely before you change locations, liable to spread pests to other areas.
Even if fouling is not visible, boats need to be slipped at least every year to check propeller shafts, rudder bearings, skin fittings and sacrificial zinc anodes for deterioration. This is a convenient time to re-coat or replace the anti-fouling.
Warding off the critters
Anti-fouling paints, developed over many years with good research driven by the needs of commercial shipping, provide the traditional answer. They repel the invading organisms by creating a constantly toxic boundary layer of water next to the hull surface.
They're expensive with copper, which is used in most anti-fouling paint as the main repellent, hitting record high prices in recent years and most have an effective life of only 12 months before replacement or re-coating is needed.
There are basically two types of anti-fouling paint, hard and eroding (sometimes called ablative). They use biocides, like cuprous oxide, that slowly release to repel the underwater pests. Some of them have additives like a biocide that resists slime and Teflon for an ultra-smooth surface.
Hard anti-fouling paints release the toxins through the paint film, without any significant reduction in film build. This is the solution for racing yachts because the surface can be wet-sanded smooth and the algae slime can be scrubbed off readily by divers.
After a few seasons, the film build-up will not retain sufficient internal strength and will have to be removed before repainting.
The eroding coatings, which are less expensive, shed part of the paint/binder toxins in layers through friction, like a cake of soap wearing away, eventually leaving no anti-fouling on the hull. They were developed originally for shipping. If a commercial vessel had to undergo frequent slippings for survey inspection, it could be replaced by a new coat, without buildup. They work best if the boat is used regularly, ideally weekly.
The current generation of eroding paint does not continue to provide protection until it totally wears off, warns Keith Ryman, the technical manager Asia Pacific Yacht Coatings of International Paint. “As the paint film starts to get thin, the biocides are preferentially washed out, leaving paint that is essentially not antifouling paint. This is the time to apply new product.”
Popular hard choice option is International's Longlife, which at Whitworths' stores costs $225 for four litres ($240 for tinted colours), a high-strength copper-oxide based product, suitable for all surfaces except aluminium.
International's VC Offshore ($210 for two litres) is especially formulated for racing yachts. It incorporates Teflon with the copper oxide for an especially smooth finish. It's a two-pack product and applying it is a two-person job with someone having to stir the pot all the time to keep the copper in suspension.
This is the favourite anti-fouling product of Sean Langman, managing director of Noakes Boat and Shipyards, which has facilities in Tasmania, Nelson Bay and Newcastle, as well as on Sydney Harbour, who is also a successful inshore and offshore sailor. “VC Offshore is designed for racing yachts but I have used it on powerboats and my gaff-rigged veteran boats because they perform better.
“It comes with a Teflon base; it's two-pack and you actually tip the copper into the product to keep it suspended. I get two years out of VC but I do keep wiping the boat to keep the slime off.”
For the cruising boat or club racer, the ablative Altex No 5 ($180 for four litres) copper-based anti-fouling, is recognised as a good, well-priced product by boatyard proprietor Jerry Hendrey of Careening Cove Boat Brokerage and Slipway.
Altex claims that two coats properly applied will give two years of anti-fouling protection. The New Zealand-based manufacturer says that this “soft” anti-fouling works because the salt in the surrounding water “hydrolises” or softens the outer surface of the anti-fouling. This outer layer then becomes unstable and marine organisms find it hard to get a grip.
Every 18-25 days, depending on the salt levels in the water, the boat's usage and the amount of tidal flow, this unstable outer layer falls away, taking any fouling with it. This self-cleaning, self-polishing action keeps the hull smooth while reducing the thickness of the film build.
Sean Langman prefers the hard anti-fouling coatings for all boats, including his own 77-year-old classic gaff rigger Maluka of Kermandie and his powerboats. “The smoother the surface, the better the anti-fouling will perform, hard or soft,” he says.
“One of the drawbacks with most of the soft types of anti-fouling coatings is once they've ablated they can end up with quite a rough surface. So my preference is well-maintained harder finishes for all boats if you want to enjoy better sailing ability or better fuel consumption.”
However, International's eroding Micron 66 does smooth as it polishes, so helping to reduce surface friction.
For all types of anti-fouling, Jerry Hendrey recommends repainting every 10 to 12 months. “If you get something that lasts longer than 12 months and you are hopeful that it gives 18 months because of the cost of doing the job, I think that can be false economy because other problems, like electrolysis, can occur in the meantime.”
Sean Langman sees nine months as the magic time to renew anti-fouling in Sydney, to coincide with water temperature patterns, with late autumn the best time to do it.
Soft copper anti-foulings can only have more soft copper paint applied over them. If you want to use a hard type, you must completely remove the old soft copper. Hard anti-foulings are generally compatible, irrespective of brand.
Australian paint manufacturer Norglass warns that removing anti-fouling from fibreglass with chemical paint strippers can affect the integrity of the gelcoat. If a slow-reacting paint stripper is used, only small areas should be coated at a time so that the paint residue can be removed before the stripper has time to react with the gelcoat surface.
Because the toxins in anti-fouling paint are potentially hazardous, dry sanding is not an option. In wet-sanding, make sure that the entire residue is captured before it can reach the water.
If the paint already on your hull is in good condition and compatible with the anti-fouling you are going to apply, you still need to give the surface a good wet sand with 80-grit paper, says Keith Ryman of International.
This will remove the layer of paint that is depleted in biocides and which contains salt and calcium deposits. Failure to remove this layer will result in blistering or poor anti-fouling performance, as biocides in the new paint permeate the old depleted layer.
If the old paint is of an unknown product, after sanding and washing and when it is thoroughly dry, apply a sealer/tie coat compatible with the new paint to prevent interaction between the new and the old paint.
Sean Langman sees preparation as the most important factor in the success of the anti-fouling paint; especially reducing the build-up of previous coats. “After the boat is water blasted, it should be progressively wet rubbed to remove as much of the paint as possible; otherwise the poisons in the new anti-fouling leach inwards towards the old remaining coat instead of outwards.”
Carefully calculate the area to be painted before you buy the anti-fouling, and then apply all of it. It's expensive, remember and does not last well in a part-empty can.
Make sure that you stir the paint thoroughly to keep the heavy copper particles in suspension and keep stirring as you apply it; before each refill of the tray if you are using a roller. Anti-fouling can be applied by airless spray, roller and/or brush. For roller application, International recommends using a short mohair roller of either radiator or larger size and for brush applications a large width, like five-inch, brush because the finish will not be as smooth as a topside paint so the type of brush used is not critical.
Wear the protective clothing and eyeware recommended by the paint manufacturer. Even when washing down old anti-fouling, avoid splashes in the eye or on skin. Never dry sand anti-fouling of any type.
It's important to apply the recommended film thickness. Two coats are needed. A third coat around the waterline to ward off the sun-loving slime and weed is a good idea. The leading edges of the keel, rudder and the prop-wash area might also welcome an extra coat.
Follow the manufacturer's recommended overcoating and immersion times carefully. “Read the can and whatever the space of time is recommended between coats stick to it, because if you don't, you will get solvent entrapment, which later on will cause blisters and flaking,” says Jerry Hendrey. “Putting two coats on in one day and putting the boat back in the water is not on; it's going to bring you undone.”
Most if not all anti-foulings are best put into the water as soon as they are dry. They are not formulated to sit around exposed to the air for long periods. Some anti-foulings like Micron Extra are far more stable on exposure to the air, but the right place for an anti-fouling to be once it's on a boat is in the water.
Many hard stands seem to be situated close to a motorway and given the high level of vehicle use, the effect of the pollution settling on the anti-fouling paint should not be taken lightly.
Once you have finished painting, protect the anti-fouling from the sun as some ingredients can oxidise. When the boat is launched, the anti-fouling will not start working straight away unless you give the surface a good scrub for hard types or light wet sand with 400 grade paper on eroding types. And remember, the true colour of the antifouling will develop about four weeks after immersion.
While there are no problems using copper-based anti-fouling on bronze, they cannot be used on aluminium propellers or saildrives. Only hard type anti-fouling should be used on bronze, with several coats on the outer edges of the blades, recommends Norglass. Longer drying times are also worthwhile.
International's Trilux 33, a a non copper-content anti-fouling especially formulated for aluminium hulls, is effective on props and sail drives, while expensive at $399 for 3.8 litres at Whitworths. “It's by far the most superior anti-foul we've seen, lasting up to two years,” says Sean Langman.
Also suitable for saildrive units in the International range, at about half the price of Trilux 33, is Interspeed 2000, while the eroding is suitable for slower boats.
A relatively recent product finding favour in Australian boatyards for propellers is Propspeed, made by New Zealand-based Oceanmax International, which is a silicone-based, copper-free coating that prevents the attachment of marine growth by low critical surface tension on non-ferrous metals.
“If you put the boat into gear regularly, barnacles won't stick to the pure silicone film,” says Sean Langman.
The propeller is cleaned back to bare metal, two coats of two-component etching primer is applied followed by a clear coat of Propspeed. “We find that when we pull the boat out up to 12 months later, virtually nothing has stuck to it,” says Jerry Hendry. “You shouldn't have a diver ever touch that surface because it works a little bit like skin when you're sunburnt. If you break the edge of it, it will start to peel off.”
Ultrasonic algae control devices, which produce a precise frequency of ultrasonic waves that disrupt and destroy the cellular functioning of algae, are being marketed for boats, as well as swimming pools, ponds, reservoirs and lakes.
Sure Systems, of Tullamarine, Victoria, distributes throughout the southern hemisphere an ultrasonic system named Boat Sure, made in the Netherlands through a company called Flexidal.
It says that Boat Sure works in conjunction with traditional anti-fouling to protect the hull from algae, biofilm and barnacles and extend the period between hull cleaning. It's suitable for fibreglass and metal hulls. Sure Systems says that in some instances it can negate the need to use anti-fouling paints altogether.
The unit has to be installed by one of Sure Systems' approved marine electricians. It emits ultrasonic sound waves through the hull from a transducer attached to it. It operates on 112/24 volts with 0.9 to 1.2 amps current draw. A dual installation for bigger boats is also available.
Reinforced heavy plastic baths, supported by flotation tubes, pulled around boat hulls and dosed with swimming pool chlorine, have been used in Australia for more than 30 years. Sailmakers and even amateurs have made them.
Most innovative products recently have come from specialist manufacturer Boatbath Company, established by former Melbourne Dragon-class skipper Paul Mellody at Narara, NSW.
Mellody, who has an engineering background, has devised solutions for varying hull shapes, including boats with transom-hung rudders, which on previous bags were always prone to dig holes in the bath drawn up around them.
He offers seven options, including different versions for boats on swing moorings, fixed and pontoon marinas with devices to keep the bag open to facilitate entry and exit.
You can expect an effective lifetime of four to five years from a Boatbath, depending on the situation of the mooring or marina and the roughness of the water. Boatbath Company gives a 12-month warranty on quality, stitching and fabric breakdown due to weather conditions.
A swimming pool tablet placed in the bath every fortnight in the cold-water months and weekly when it's warm, keeps algae from forming on the hull. Answering concerns about placing chlorine in the waterways, Boatbath says that after a short period, the only residual from chlorine is salt and that the toxic effects from anti-fouling paint is more harmful.