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Antifouling


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I have my H28 in drydock awaing a new prop.

At this time last year I put on two rolled coats of International Awlcraft onto the bottom which was completely stripped of the old antifouling. At this drydocking the boat had a degree of fouling and a dozen or so small barnacles. She lives on the piles in Whangamata which is an area legendary for excessive fouling so I think its not too bad. Most of last years coating is still there so do I apply one new coat or two? In other words, with an ablative type antifouling is it the more the better or does the stuff run out of grunt after a year or so anyway?

Two years between haul outs would be nice!

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Most of last years coating is still there so do I apply one new coat or two? In other words, with an ablative type antifouling is it the more the better or does the stuff run out of grunt after a year or so anyway?

Ablatives employ two interacting methods of keeping the Hull clean. Firstly there are the two main components, being the Copper and the Biocide. These act separately, the Copper on Plant life and the Biocide on the animal life, like the little worms and shellfish etc. The second component is the eroding. This allows fresh Copper and Biocide to be exposed as the old stuff is slowly washed away. Many people get quite upset when their Marina Berthed Boat gets growth on it in just a few months of sitting doing nothing. What they don't understand is that is quite normal. The Hull must move regularly to help wash off the algae and any surface of the paint that needs washing away. However, if the Hull has sat for some time and severe growth has accumulated, the surface is kind of protected somewhat from being washed away and it takes a bit of speed and time to get it clean again.

If you want extended time between haul outs, then yes you need a thicker layer and that comes from several coats. Two coats per year is the normal if you want a good clean Hull all the time. Two coats can be extended to two years in many area's, but if you are in a high growth area, then three or even four coats may be required to get two or even three years out of it.

Remember that your Anode will last 12months and you need to replace that, or hang a "fish" anode over the side.

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Whangamata harbour has an ebb and flood of around 2 - 3 knots. I had thought that this should have kept the boat a bit cleaner than it was. Perhaps we need more in the vicinity of 5 knots for antifouling to ablate?

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Yes to both questions.

But it also depends on how dirty the water is, where the boat hangs out, as well I have found. My boat is up the "creek" at Hobsonville and there can be a huge flow speed at times, yet the water is so dirty, the gunge that accumulates on the Hull seems to coat the antifoul and seemingly renders is non ablative. But after three years between haul outs, there was almost none of the coating left. The previous, which was a different colour, was in full glory. So the later coat had worked as far as ablative is concerned. The faster the water flowing over the Hull, the better the cleanliness. However, because it is a controlled surface renewal, it doesn't matter too much(for the slower moving Keelers), whether it is 2 knts or 5kts or even 7kts. Leading edges and rudder area directly behind the prop tend to get a hammering and it is good practice to double coats on and around those areas. For the speed machines that can see above 12 kts, they should be looking at a hard antifoul.

For Hulls that spend a greater amount of time sitting in calm waters, like an enclosed Marina, or slower moving tidal area and only get a few weeks a yr out sailing during Holiday periods, they should consider the Self Eroding coating, like Micron 66. That self erodes away and in doing so, it takes the growth with it. Expensive stuff though and you get 12months full stop.

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Pwederell, I'm really keen to know what happened re the yacht back in Fiji that had the issue with the Hempel Antifoul. Did that get resolved? and any ideas what may have been wrong?

By the way, in case you don't know, our Mutual friend is no longer owner of Hempels NZ. Hempels themselves bought it off him.

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Hempel basically told me tough luck, they didn't want to know. I tried unsuccessfully to get hold of Alan but he was busy with the Rena and pretty unreachable. I'm actually hauling the old girl for the first time in 3 years. Have been getting away with regular cleans as hauling here is such a bitch.

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