Copper-bottoming

We've had another productive but exhausting week at the boatyard in Totnes. The stanchions and guardrails are back in situ, which makes working on deck much less risky (the ramifications of a fall from height were too awful to ignore, so this was a priority) and the refitting of deck kit has continued. The big job, however, was to apply the Coppercoat antifoul system.

A yacht (not Maunie) suffering heavy fouling

For those not entirely au fait with the life cycle of the barnacle, boat hulls are perfect targets for the little blighters to set up home. If allowed to do so, they quickly encrust the underwater surfaces and, together with any weedy fouling, cause huge amounts of additional drag as you sail. Wooden vessels can also be afflicted by the teredo worm, particularly in warm waters, which bore into the planking with potentially disastrous consequences, so the battle against underwater invaders has been fought by sailors for centuries. Back in 1761 the Royal Navy first began applying sheets of copper to the bottom of their ships - it turned out to be an expensive but worthwhile process (hence the phrase 'copper-bottomed investment') as the copper repelled barnacles and also prevented the teredo worm from being able to bore into the timber.

Today, most yachts use an ablative antifouling paint, applied annually or (if you're lucky) bi-annually. Containing a cocktail of fairly unpleasant chemicals, the painted surface is soft so it slowly erodes, preventing barnacles and weed from gaining a grip on the hull. The annual cleaning and repainting process is the yachtsman's least-favourite task and, with the cost of a haul-out added to the cost of the paint, it's an expensive process. Also a key driver for our move from antifouling paint to Coppercoat was reducing the environmental impact.

Back in 2011 we had Maunie's hull slurry-blasted back to clean fibreglass, five coats of epoxy sealer paint were applied and then Coppercoat added. As its name suggests, Coppercoat is the modern equivalent of nailing sheets of copper to the hull; very fine copper powder is mixed into an epoxy base which is then applied by roller. The resulting finish is hard and provides effective anti-fouling for up to 10 years with nothing more than a regular scrub to keep the hull clean. After 8 years and thousands of miles, however, the coating on Maunie's hull was wearing thin so we knew it was time to apply a fresh coat. The yard quote for labour to do the job was close to £2,300 so we decided to do it ourselves; the manufacturers provided excellent instruction and videos so we braced ourselves for two and a half days of hard graft:

The first job was to sand back the old Coppercoat - a vacuum cleaner extracted the dust but a face mask is a vital extra as epoxy dust is pretty nasty

The sanding reveals the copper colour

The epoxy base is a two-part mix...

… and a drill-mounted mixer made it easy

The very fine copper powder is mixed into the epoxy - about 2.2 kg of copper per litre

Di at work. We applied an epoxy-only coat onto the hull first then five coats of Coppercoat, each applied when the previous coat was still tacky. You can see the white patches on the keel where the original Copper coat had worn thin

The trick is to apply very thin coats, so the first coat looked fairly patchy

After the third coat things were looking better. 

With just two people the process is hard work. Once mixed, the product has a pot life of only about 30 minutes so we had to work fast to get it all applied in time. One litre of mix was enough for a single coat of one side of the hull and we'd decided, wisely, to do one side of the hull at a time. Once we'd finished the coat, we had about 20 minutes of rest before starting the next mix.

Motivational donuts and coffee between coats

The end of day one, the hull half completed

End of day 2

The epoxy is water-based so didn't give off horrible fumes but it needs good air flow to allow it to dry. When we started the port side we found that there wasn't any breeze in the shed and the coating was taking an age to harden; luckily we were able to borrow a huge industrial fan which solved the problem in a few minutes.

While we were working, Andy the painter came to polish out a couple of minor imperfections in the paint. He has done a brilliant job.

The best bit of the job - removing the masking tape

Done! Well, not quite - after five days to let the surface harden, we need to move the supporting pads to coat the four patches of old surface that they will leave.