applying many coats of AF - lasts longer?

[Modulation]

...........or does it?? In theory if I apply say 6 coats of an eroding antifouling it should last for 3 seasons, as it should erode constantly, with a new surface to combat growth. But I guess it doesn't as the mfrs. don't mention it on their instructions. But WHY doesn't if? Has anyone ever tried it? Have you found an approach which avoids the annual drag of antifouling - even for a year?
Thanks

<hr width=100% size=1>Brendan

 

[pvb]

Yes!

Your theory is sound, as far as eroding antifouling goes. I tend to challenge a lot of conventional views, because they are often not based on sound logic. One of the conventions I've always challenged is the annual lift-out for the winter. I leave my boat in the water all year round, and lift it only every 2 years for antifouling. Partly, this decision is down to cost. The marina I'm in has a "summer offer" every year and I can have my 35 footer lifted out, pressure-washed, cradled for a week and then lifted back for about £170 - that's way cheaper than their regular prices in the winter. Also, I find that polishing the topsides is a lot easier in warm weather, and even antifouling seems less of a chore in summer.

Convention breaker number 2 is never antifoul by roller. I firmly believe that the only way to get a reasonable film thickness (which is the secret of longer antifouling effectiveness) is to brush it on. Harder work, but worth it. I apply 3 good coats all over, then add a 4th coat on the waterline, leading edges, rudder, etc. I use Micron Extra, which incidentally does give instructions on the can on how many coats to apply for 1 season or 2 seasons.

I've followed this method for years now. When the boat's lifted after 2 years it's a bit slimy, but generally there's not a lot of nastiness. To some extent, I'm helped by the fact that the boat is marina-based, and so the water probably has a fair concentration of toxins.

Why not give it a try yourself?

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[boatmike]

This assumes the antifouling is 100% effective. Ask yourself if the boat ever comes out of the water as clean as it goes in. It doesn't of course. How clean it is is a function of how much you use your boat and how fast it is (eroding antifoulings usually erode when underway far faster then when stationary) Where you keep it is important too (some areas are high fouling areas , some are less so)
If you use the boat a lot and she is quite fast when underway you are likely to get a situation that will easily mean you can stay afloat for 2 or even 3 years by applying more antifoul. Cruising folk who live on their boats will tell you this is so.
Weekend sailors who keep their boats in marinas, usually need at least a light scrub or sponge down once a year though and if you are going to haul out ashore anyway there is no point in putting more than two coats on. Hauling out is also beneficial in avoiding osmosis as it gives a drying out period.

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[ccscott49]

I apply 4 coats and lift my boat every two years, if she needs it, I dive under the boat and have a look, if the props rudder (metal) look a bit barnacaly! I scrape them off underwater. Maybe twice a year, then she will last at least two years.

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[andy_wilson]

The chemicals in soft anti-foulings leach out. By adding coats you add chemicals but also add thickness which will have to come off at some point.

The lower layers will not leach out effectively if the layers are too thick. Heavy use of the boat will help, but not completely. You notice that A/F manufacturers don't do paint for high and low mileage craft, only fast and slow ones, which is different.

Best strategy is to dry out and scrub once or twice a year with a nylon pad to remove the top layer and expose fresh material.

Slightly wasteful I realise, but it does mean you never end up with mega-thick, flaky, ineffective A/F coatings.

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[pvb]

Eroding antifouling...

Eroding antifouling actually wears away (hence the name) so it doesn't lead to a build-up of paint which needs removing. You're probably thinking of the paint build-up which happens when you use "hard" antifouling.

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[William_H]

You will get lots of often contradictory guidance on antifouling. Its almost as if every boat is different. I am very leary of the build up of A/F especially at the waterline. I suspect that it will build up despite it supposedly being intended to erode. A/F here seems to be mainly available in 4 litre containers and I have a lot of friends with boats in the 20 to 25ft class who reckon they should put all of it on being often around 4 layers. I don't beoieve it lasts any longer and still requires scrubbing about once per fortnight. (warm water lots of sun) I put two thin coats on my 21fter and this lasts about one month before it needs scrubbing and 3 months until there are patches with no paint at all being scrubbed once per week. By the nd of the season there is not much to scrape off before new layers.
I am not suggesting this regime would suit you just thought you might be interested. currently SWMBO does the in water scrubbing takes about 10 mins with a rag. She has too much bouancy and has trouble geting to the bottom of the keel so I stand on her shoulders to sink her down. (thought you might get a laugh) 30 degrees today hoping the wind will hold out for a night race.
regards will

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[ccscott49]

Thats fine, but I wouldnt want to scrub my 57 footer every two weeks. Thats why I put at least 30 litres of antifoul on every two years, thats three coats. Seems to work for me in the meddy. But I've seen some real messes coming out of the water six months, from around the ebro delta, that is a real bad fouling area! Whole forests of weed and all kinds of weird and wonderful fauna!

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[Anonymous]

Don't mean to nit-pick but in one post you said four coats and then you said three. Which antifoul do you recommend for the western Med?

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[Modulation]

thanks for the replies. Really useful. That's why I like this forum even though it irritates me by occasionally going all anti-EU.
I think I'll try 4 coats and see what happens over 2 years if I leave the boat in the water for the winter. I'll give her a scrub at the end of the 1st year to "refresh" her and then see how things go for year 2.
Anybody got any views on an eroding antifouling which actually DOES erode? I've used Veneziano Rafaello, Titan, Int. Cruiser, that Plastimo cruising stuff and a home made brew from a boat jumble. Hugely variable performance - the Venez...... - way best - but all a bit loath to erode, thus causing build-up. Never used Micron. Is it worth the extra cost? Boat is Marina -based in northern France behind a lock so limited water changes. Used most weekends and sails at around 6 knots.

<hr width=100% size=1>Brendan

 

[pvb]

Give Micron a try...

I've found minimal build-up with Micron after 2 years in the water. It seems to erode quite well. Most of what's left can be fairly easily washed off with running water and a pan scourer.

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[Jules]

Re: Eroding antifouling...

So, if I use Seajet eroding lightish blue antifouling, and when I lift out at the end of the year, pressure wash off the slime and still see plenty of fresh antifouling why would I need to apply another coat?
Is what I'm looking at still good AF or is it a "holding substance", ie the "Glue".
If not, then leave on until the gelcoat appears!
I think this is what the poster is getting at.
Any ideas, or are we being conned to re-coat annually by the manufacturers. Am I brave enough to try it? Probably not!

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[andy_wilson]

Re: Eroding antifouling...

I don't think I stated my case overly well. Soft A/F does erode, but not at the same rate as the chemistry leeches out.

The evidence for this is clear, after a period of time the A/F is still clearly present by evidence of the pigmented thick layer, but it's A/F properties are all gone so the coating becomes ineffective.

I have a feeling (nothing more) that most erodable A/F is optimised for fairly heavy use, ie the substrate erodes at almost the same rate as the chemistry.

The average leisure yacht (non-chartered) loses the chemistry far quicker than the substrate.

In my experience a nylon-pad scrub mid-season does revive things a bit by removing the top layer to expose chemicals trapped in lower layers. The bonus is it prevents the inevitable build up. A scrub a year between tides is a relatively easy couple of hours work. A complete scrape back every few years is a filthy, noxious, back breaking, thankless (unless you are paying) task.

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[ccscott49]

Re: Give Micron a try...

Pity it's so expensive. Try buying 25 litres every year!

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[ccscott49]

It's actually 3 1/4 to 3 7/8 coats! Dependa how thick I put it on and how many coats on the waterline!! If you dont mean to nit pick, then why do so? Can't you control your fingers?

Any eroding antifoul, Jotun, Blakes, seajet, whichever is cheap, because it will only last about two seasons and I need a lot of it, last lot fell off the back of an armada lorry!

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