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Each season, The Green Blue will be posting a new topic. If you have a topic you would like to see covered, or can share advice with others, get in touch.
This season’s article comes from David Parker of Warsash, Hampshire and reports of trials of
Seajet 036 Shogun-Eco on Green Blue supporter, Mike Bailey's 27ft sailing cruiser
Check out our Tried and Tested section for more antifoul reviews!
If you have ever been sailing at night you may well have seen phosphorescence streak by the hull underwater as it is lit up by the moonlight. It’s always a captivating site – your own little marine aurora borealis around the boat. The beautiful phosphorescence you see is marine plankton, the drifting organisms of our oceans. It’s a shame to think that the coating of the boat you’re on is designed to kill it and other marine life.
Because if your boat has antifouling on it, that’s what antifouling does.
Antifouling is a marine paint which typically contains a biocide or poison held in the coating itself. When it is on the hull, the poison leaches slowly from the paint coating straight into the marine environment. The antifouling is there to stop marine fouling by poisoning settling organisms and preventing larvae, barnacles, mussels and seaweed spores etc attaching themselves to your hull. Such growth will not only slow the boat down and produce unsightly ‘beards’ of weed around the waterline; in the case of wooden hulls for example unprotected hulls can be destroyed by marine worms such as Teredo and Gribble.
However, although traditional antifouling paints protect the hull and prevent drag, they can have a harmful effect not just on the organisms trying to foul your hull; they can also have an impact on other marine life unconnected with the boat. The toxins from the paint can settle in the sea and riverbed affecting a host of tiny creatures which make up the vital marine food chain. Sediments in low flushing waters such as river estuaries and bays are particularly vulnerable to an accumulation of toxic residues.
This is why in 1987 there was a Europe-wide ban on the use of tributyltin (TBT) in antifouling paints for use on boats under 25 metres. It had become apparent that this biocide was causing severe damage to shellfish communities. Elevated levels of TBT have also been found in other marine mammals such as dolphins and otters. The International Maritime Organisation started a similar ban on commercial shipping using TBT in 2003 and all TBT based paints are to be phased out by 2008.
The ban on TBT has resulted in a shift back to antifouling paints which contain copper as the main biocide. It is difficult to generalise about the toxicity of copper to marine organisms but there are now restrictions on the use of copper content in antifouling in the Netherlands, Denmark and on the east coast of Sweden. Sweden and the Netherlands have introduced an outright ban on copper based antifouling for pleasure craft below 25 metres.
To comply with this and other possible future legislation paint companies have been working hard to come up with more environmentally friendly coatings to protect hulls from unwanted colonisation by micro-organisms i.e. fouling. One such coating is the new Seajet 036 Shogun-Eco which is a biocide free antifouling. It is manufactured by the Chugoku Marine Paint Company of Japan which apparently supplies coatings to a fifth of the world’s shipping. This new product is distributed in the UK by Marine and Industrial and the makers say Shogun-Eco is suitable for all hull types. From their tests they say it will perform well in all fouling conditions and is particularly effective against barnacles.
So Mike Bailey, lifetime member of the RYA and supporter of the Green Blue has agreed to try it out on his 27ft sailing cruiser, a Hunter Horizon 273. Previously a conventional antifouling had been used on his boat. But Mike, like many sailors, is keen to do as much as he can to live an ecological lifestyle. In fact during the summer he heats all the hot water used in his home using a solar panel on the roof.
Preparation for the new coating is basically the same as for antifouling any GRP hull and the first job is to make sure the surface to be coated is as sound as possible. To do this you need to remove old flaking and loose antifouling with a scraper and then sponge and rinse it with water and allow it to dry. Do the rest of the preparation with wet and dry paper; never burn off or dry sand old antifouling because the dust and vapours are toxic. Collect and dispose of all debris, old antifouling and rinse water in the appropriate waste area. The manufacturers of Shogun-Eco recommend in their product literature using high pressure fresh water as a pre-treatment. However, avoid hosing down or using a pressure washer where you cannot collect the water because old antifouling may end up in the drains and/or as run off into a river next to a boatyard.
Phil Davis of Marine and Industrial advised Mike on how to apply the antifouling. For a steel or aluminium hull a Seajet epoxy primer is required but with Mike’s GRP boat the first job was to prime the hull using Seajet 036 Binder Coat. Colours available in the primer are white, blue, navy blue, black and red and the choice of colour here is important because the final coating is clear. “The red primer I chose was a joy to put on and because the previous coating had been blue you could of course easily see coverage areas,” commented Mike. “Phil advised me that the roller I was going to use from a DIY shop wasn’t suitable so he got me a shorter mohair roller which was ideal.” The primer should be left a minimum of 8 hours and a maximum of 7 days before the Shogun-Eco top coating goes on.
Using the roller
"When the primer was dry the first coat of the clear antifouling went on quite nicely because it creates a shine,” Mike continued. “ It has a smell and a texture a bit like the dope varnish I used to use on model aircraft. However as it dries it goes ‘stringy’ so it is best to go over it just once.” The first coat of the 036 requires 8 hours to dry but Mike admitted that because it is clear, judging equal coverage with the second coat was a bit trickier. “I found I was struggling at times to find out where I’d got to,” he said. “In the end I found the best way to do it was to roll a slow stripe down from the masking tape around the waterline so then I could see where it was wet because of the tape.” Mike changed the waterline masking tape with each coating application.
When applying the top coat with a brush more layers may be required to achieve the specified film thickness as Phil Davis explains: “With the Shogun-Eco you need quite a thick coating. It should be about 50 microns thickness per coat which goes on wet so we end up with 25 microns thickness per layer of the antifouling when it is dry.” Once the top coat is applied the hull should be left to dry for 8 hours and the maximum interval before launching is 6 months. Over coating and drying times are temperature dependent so the product literature should also be consulted before application. When antifouling you should also apply an extra coat on leading edges, waterline, rudders and stern gear.
Primer on the hull
It took Mike about 2 ½ hours for each coating of his boat and one thing he did comment on was the vapour due to the VOCs (volatile organic compounds) in the coating formulation. “Because there was no wind I had to take a break now and then to get a breather because of the vapour, although they do recommend you wear a mask.” For cleaning his brushes Mike found that standard paintbrush cleaner worked. He used disposable rollers rather than try and clean them with thinners which again put more chemicals into the environment when you dispose of them.
Applying first coat over primer
The biocide free Seajet 036 Shogun-Eco relies on hydrolysis to work; this is more commonly know as ‘self-polishing’ as opposed to the eroding antifoulings which use hydration. Hydrolysis is a chemical term which means the splitting of polymers into smaller molecules – put more simply that means the surface of the coating slowly dissolves in a controlled manner in salt water. As the surface gradually dissolves over a season whatever is hanging on to it in the form of marine growth will get washed off. Because this is a relatively fast eroding antifouling it is not envisaged that it will be used in commercial shipping and the makers are mainly focusing on the leisure boat market.
Last year Mike, who keeps his boat on the River Hamble, said he had quite a lot of fouling both of slime and weed. Many weed species thrive in a mixture of salt and fresh water on river estuaries so Mike will naturally be interested to see how this new biocide free alternative performs. The effectiveness of antifouling can depend on regional variations and how they perform often varies from year to year depending on local conditions.
So far this product has not been widely used in this country so we’ll be watching keenly to see how it performs. At £81.29 for 2.5 litres for the Shogun-Eco and £25.03 for 2.5 litres of the primer it is slightly more expensive than traditional antifouling. However the good news is that major paint companies are now developing products with the environment very much in mind. In the long term of course this benefits us all. If we do have to pay slightly more for antifouling who would begrudge that for the benefits of a cleaner, healthier marine environment.
The finished product
www.seajetpaint.com
www.ybw.com/seajet
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