CLEAN BOTTOMS

Veteran offshore cruisers share their research into Coppercoat antifouling and some useful tips for applying it.

Suzanne Hills and Chris Cromey recently antifouled their 43-foot cruising yacht Whanake using Coppercoat. Experienced cruisers with plenty of offshore sea miles, the couple chose Coppercoat because it claims to offer up to 10 years’ hull protection against fouling.

After doing a fair amount of research online, Suzanne found some stories about Coppercoat to give her pause, but further investigation revealed good reasons for the product not performing to expectations, so she has shared her tips for applying the product to ensure the best possible result.

APPLYING COPPERCOAT

Application went well with no dramas. Temperature inside the shed (12-17°C) was perfect for applying with just the two of us, so we got the whole hull done in a day, five coats in all. It took almost 12 hours from start to finish.

I think if it was any warmer than the peak of 17° Celsius we would have needed a third or even a fourth person, but as it was, cooler temperatures gave us plenty of pot life and enough application time.

We applied Coppercoat as a continuous process, so by the time we got to the end it was good and tacky for the next coat.

The first coat went on really well, but then the second coat was a bit difficult as we did not use thinners and it was too thick on the roller. We got the odd run, but nothing much.

For the third, fourth and fifth coats we thinned with 5% propanol and this gave a perfect consistency for rolling, so we would advise everyone that thinning every coat is essential.

We used 11 litres of Coppercoat for the five coats, but still have our rudder and patches under blocks to paint. That should take another litre and we plan to keep a litre for any repairs, so 15 litres in total for the job.

WHAT COULD GO WRONG?

I did a lot of trawling on the internet for people’s experiences with Coppercoat because, like many people, we had heard a few bad stories. But, delving deeper, in every case there was a good reason the product didn’t perform properly.

Here are some typical online complaints, along with why I think they had issues.

Many people make a DIY mix by adding self-sourced copper powder to epoxy and then refer to it as ‘coppercoat’.

Most likely the surface was not abraded enough – we used 80-grit sandpaper – or else wax residues/fillers/paint remained on part of the hull. Cause was pinpointed to adding propanol to the roller tray where it cannot be properly mixed, trapping alcohol. We added 5% thinners to the mixed epoxy before adding the copper.

Probably copper settling out in the roller tray during application. We stirred the mix in the pot every time we added more to the roller tray, but we also frequently – every second roll – stirred the mix in the roller tray. It is clear it needs mixing as it goes a little bit streaky.

Probably not abrading the finished antifouling sufficiently to expose the copper before it first goes in the water. With insufficient copper exposed barnacle growth can start and

once the white residue from knocked-off barnacles is left on the hull it becomes hard to control. Ensuring enough copper is exposed in the first year appears critical to prevent growth; in subsequent years natural weathering exposes more copper.

We spoke to a few Coppercoat users and they advised getting in the water every six months and giving the hull a light scrub with a green scouring pad to expose the copper. Other people said the boat still needs to be taken out of the water every 12 months, but there is only slime to remove, followed by a light sanding. Either way, the hull does need some attention every 6-12 months.

For an older boat like Whanake, it was a lot of work to remove decades of antifoul paint to get back to the original primer, but it was well worth the effort as it exposed all the imperfections, dings, damage and problems. Treating with Coppercoat is a great opportunity to repair everything properly and get the underwater hull sections perfectly fair again, including the underside of the foot which often gets neglected.

We have been full-time cruising sailors for the past six years and have antifouled every 18 months to two years by slapping on another two or three coats of traditional antifoul over the existing coats. That’s because we usually had to work while drying against a wall in a tidal area and could not remove old antifoul. This makes traditional antifoul even less effective, since much of the active ingredient gets absorbed into the hull by the old chalky antifoul. We got away with it as we cruised mostly in cold water, but in temperate and tropical waters it did not even give a few months of protection. This is one of the main reasons why we have gone to Coppercoat – to avoid having to antifoul in foreign countries.

Coppercoat was a pleasure to work with compared with nasty traditional antifoul. Plenty of interested boaties around the yard were curious about it, as many had never heard of it. Hopefully this article will help. B

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EDS is a not-forprofit organisation established in 1971. Bringing together the disciplines of science, law and planning, it is one of New Zealand’s leading environmental think tanks.