How many layers of Antifoul Paint?

[oldbilbo]

Like many, I'm almost ready to slap on antifoul paint. In my case, after stripping back by soda blasting to the original layer of VC Tar - which is well stuck on. A top paint pro who came by reckoned that would now be 'an A-OK' substrate, and I followed his recommendation with a good layer of Jotun Vinyguard Silvergrey 88 ( which is 'a quick drying, modified vinyl primer' ) which he personally guaranteed would chemically bind to the subsequent antifoul layers.... or the first one, at any rate.

Now, it so happens I have acquired enuff of this AF stuff for four+ layers and not simply the two that most of use slap on. So the question is, do I gain anything, or lose, by painting on more than two layers? Should I use it all up and not expect to do more than a quick hose-brush down a couple of times a season, for ever afterwards?

I've asked said expert - indeed, I've asked more than one - but they're all so hidebound by company H&S and potential liability dogma that all I got was "Yes, but....No, but...!"

So, does anyone here have a view-from-experience of the merits of putting on more than two coats of quality AF?

 

[Iain C]

If it were me, I'd be going for a self polishing AF. Yes, it's a bit more, but it's much easier to scrub mid season in a wetsuit, and it takes no time to prep for next year's coat. You don't get that horrible build up of layer upon layer of heavy, pitted, speed sapping, creepy crawly crevice attracting AF.

If you do go for self polishing, it's worth 2.5 coats...with the .5 being around your leading edges, keel, rudder, and around the prop. Basically, where the water is most turbulent and the AF will erode quicker.

 

[LadyInBed]

2 coats this year & 2 next year, you will then see how it stands up to your local conditions.

 

[pvb]

Eroding antifouling ("self polishing" if you like) is the stuff to use for sailboats, as it doesn't build up an excessive thickness over the years. Indeed, a lot of the old stuff can be washed off easily with a hose and a plastic scouring pad, before re-coating.

As for how many coats, the real answer is to use the volume of antifouling recommended by the makers. I use Micron Extra, apply the amount recommended by International, and it lasts a full 2 years in the water. The boat's only lifted for a week every second summer for antifouling.

Talking about "coats" is difficult, as some people use a cupful and roller it over half the hull, whereas others whack it on thickly with a brush. It's the volume which is important - and that could, for example, be 4 coats by roller or 2 coats by brush.

 

[NormanS]

Best to put on just enough for your expected time afloat. Our boat is only in the water for the "summer" six months, so having spent good money a few years ago getting her slurry blasted, I'm not keen to build up a thickness again. I find one coat applied by roller to be perfectly adequate. I also prepare by rubbing down (wet) using one of these universal jointed sanding pads meant for doing ceilings, with a gauze abrasive, which also helps to avoid a build-up.

 

[William_H]

2 coats this year & 2 next year, you will then see how it stands up to your local conditions.

yes I agree. A/f will be fine for use next year. (I think) That on the assumption that you will lift the boat for next winter. If you want to leave it in cmmission over several years then put it all on.
I use Jotun and have done for some years. fouling is terrible here with warm water and a lot of sunshine. I find that after 4 weeks from painting it has developed a slime. By 6 weeks I am inm the water wiping it down firstly with a soft cloth then later with scotch brite then wet and dry sand paper. The soft a/f comes off pretty easily. Such that after 3 months I am cleaniong fouling off where there is no a/f paint left. Yes perhaps 4 coats would do better but I do like the fact that I have not had a big build up in 30 years of being moored with clean and repaint each winter. Oldbilbo will soon find out what suits him and his location best. Rememeber whatever you do is only till next winter. olewill

 

[jwilson]

Best to put on just enough for your expected time afloat. Our boat is only in the water for the "summer" six months, so having spent good money a few years ago getting her slurry blasted, I'm not keen to build up a thickness again. I find one coat applied by roller to be perfectly adequate. I also prepare by rubbing down (wet) using one of these universal jointed sanding pads meant for doing ceilings, with a gauze abrasive, which also helps to avoid a build-up.

+1 for the minimum - on a bare hull I'd put on two thin coats, but thereafter only one thin coat per year, with an extra coat just 6" down from the waterline and on the leading edges of keel and rudder. My idea of a thin coat is 2.5 litres of AF does a 35 ft broad-sterned AWB for the year. Seems to do well in a high-fouling area for 8 months afloat - Shogun 33.

AF makers like you to use lots - but they are selling the stuff, so they just might have a certain bias.

Also +1 for the sanding pad on a pole for rubbing down the old AF: you come home after doing the job only slightly blue-spattered instead of deep blue all over.

 

[GrahamM376]

Seaforce 30, I use 5 liters on a 38ft boat. That does one coat all over and then a second around the waterline, rudder & skeg and leading edge of keel and stem, using a short pile 71/2" roller. Haul annually for a month and find some areas eroded down to previous years coat so minimal buildup.

 

[pvb]

AF makers like you to use lots - but they are selling the stuff, so they just might have a certain bias.

But they also want the stuff to work, otherwise they get complaints. The actual cost of the antifouling paint pales into insignificance compared with average marina haul-out costs. That's why I apply enough antifoul to last 2 full years, and also only lift out in summer (when marinas have cheap lift-out offers). It saves hundreds!

 

[Bobc]

yes I agree. A/f will be fine for use next year. (I think) That on the assumption that you will lift the boat for next winter. If you want to leave it in cmmission over several years then put it all on.
I use Jotun and have done for some years. fouling is terrible here with warm water and a lot of sunshine. I find that after 4 weeks from painting it has developed a slime. By 6 weeks I am inm the water wiping it down firstly with a soft cloth then later with scotch brite then wet and dry sand paper. The soft a/f comes off pretty easily. Such that after 3 months I am cleaniong fouling off where there is no a/f paint left. Yes perhaps 4 coats would do better but I do like the fact that I have not had a big build up in 30 years of being moored with clean and repaint each winter. Oldbilbo will soon find out what suits him and his location best. Rememeber whatever you do is only till next winter. olewill

Wow. You should try International 77. It's not cheap, but my boat was last antifouled in 2010 with 2 years in the Caribbean, and 2 years in the UK. Apart from a quick waterline scrub every couple of months it's stayed pretty clear, and it's still working (although I'm going to re-coat it this year as I don't want to push my luck).

 

[J Neeves]

But they also want the stuff to work, otherwise they get complaints. The actual cost of the antifouling paint pales into insignificance compared with average marina haul-out costs. That's why I apply enough antifoul to last 2 full years, and also only lift out in summer (when marinas have cheap lift-out offers). It saves hundreds!

I'd agree - the cost difference between the most expensive AF and the cheapest really does not come into the equation - by the time you add in the cost of slipping, power and acid wash, new anodes, labour (or time if you do it yourself) then the AF is not such a big feature.

We have just completed an ablative AF trial here, almost irrelevant to the UK as formulations are different here, but three generous coats should last 24 months in the water, double up each coat at water line, leading edges and trailing edge of rudder. But from 12 AF we trialed only 4 of them would last the 24 months - the others no way. There was no relationship between copper content, biocide and performance - there is more to it. But you do need to keep the slime under control as once it is left it simply forms the basis for hard fouling and once you have had fouling you have lost the battle. Getting hard fouling off is hard work and you take off too much paint.
If you wipe off the slime with a soft sponge you'll prolong life.

But for most AWB here 24 months is too long as the anodes do not last and the prop and sail drive fouls too quickly so we would recommend 2 good coats and look for 12 months. If we ever get something that will stop fouling of props/saildrive and have anodes that last for 2 years (I dream) things would be different.

Ablative AF performance depends on the way you use your yacht, how fast it sails, whether you wash/wipe off and how salt (or how much fresh water) is your mooring and of course temperature. Some AF do not work in freshwater (and you seem to be getting your share of fresh water just now). So best to monitor your neighbours to find out what might work.

Most of the international paint coy make one good AF, or at least International, Jotun and PPG (Sigma in the UK?) but they also make some pretty average products.

Jonathan

 

[JumbleDuck]

I think it depends very much on where you are and how bad the fouling is there. I use one coat of Akzo-Nobel "Nautical", for which 2.5 litres is exactly enough for my 26' and long keel. On haul out last year there was no significant fouling whatsoever. There simply wouldn't be any point to my putting on another coat.

 

[J Neeves]

I think it also depends on how you coat - working a tea cup of paint over a whole keel is going to produce a different result to the 100 micron film thickness for each coat suggested by some suppliers. So one man's 'coat' might be as much as 2 coats by someone else. We can spread 4l over our 38' cat, but its very thin and even 2 coats of the best, at this loading, will not last 12 months - here.

So far too many variables to be definitive, coating thickness, location, speed of vessel, how long the vessel sits idle, the effectiveness of the AF, whether you allow a sensible time between each coat, is the new AF compatible with the substrate - endless.

We can only give our experience and hope the OP can sort out which is applicable to him

Jonathan

 

[jwilson]

But they also want the stuff to work, otherwise they get complaints. The actual cost of the antifouling paint pales into insignificance compared with average marina haul-out costs. That's why I apply enough antifoul to last 2 full years, and also only lift out in summer (when marinas have cheap lift-out offers). It saves hundreds!

I WANT the boat out in winter - after years in the tropics winter sailing in UK is not my preference. I also want a boat that sails well, so don't want more paint on the hull than absolutely necessary. If one thin coat does 8 months why put on more. When in warm waters I used to dive and scrub regularly: nice to cool down in hot sun, could go 3 years between AF painting, but that was with TBT.

 

[pcatterall]

I like the 2 coats now and see how you go idea !! (a coat being the amount suggested on the tin!!) putting 4 on in one go seems excessive. I can use up the rest for you if you wish!!

 

[ParaHandy]

Like many, I'm almost ready to slap on antifoul paint. In my case, after stripping back by soda blasting to the original layer of VC Tar - which is well stuck on...... So, does anyone here have a view-from-experience of the merits of putting on more than two coats of quality AF?

With a clean epoxy 2 coats is enough. I would sand the epoxy - just a light sand to form a key.

What puzzles me is why you think the VC tar is still intact after blasting. According to claims made by proponents of soda blasting the process is very efficient.

If it were me (ha ha!) I'd sand, epoxy and follow with the first coat of antifoul. The a/f goes on just at the point when, if you stick your thumb on it hard, you can just move the epoxy. Of course, you need temp greater than 5 and better 8 c.

Best roller for a/f are the foam, not fluffy, rollers which are sold to paint behind radiators. Quite small diameter in other words.

 

[oldbilbo]

What puzzles me is why you think the VC tar is still intact after blasting. According to claims made by proponents of soda blasting the process is very efficient.

Thanks for that. However, we've moved on and the Jotun Vinyguard intercoat has been applied some time ago. The deeply-experienced Jotun tech specialist who dropped by was asked about this VC Tar specifically. He had a thorough 'inspect' and declared that it was soundly attached and intact. His advice was to apply the Vinyguard, as per data sheet, over the top. That is now, as per the original post, where we're at.

I now have several full days' experience of soda blasting, as well as quite a lot of guidance from individuals who have considerably more, and while the process is certainly a good 'un, it is not foolproof. There is some skill involved in both choosing the right bits of kit and in operating it 'optimally'. It does, however, clean up rusty anchors and soiled Bath stone rather well. While still effective, it is not now the process of choice in stripping layered old varnish from cockpit hardwood.

I remain awaiting a coherent explanation why two coats of AF paint is - as seems to be common practice - the norm, and not ONE or THREE or more..... I have enough of the stuff for four coats, and will dispose of whatever I don't use.

So I ask again, is there a down-side to coating the darned hull with more than two coats and, if so, what is it?

 

[JumbleDuck]

I remain awaiting a coherent explanation why two coats of AF paint is - as seems to be common practice - the norm, and not ONE or THREE or more.....

Because it's enough? Because putting on more than you need is just giving yourself more work when/if you need to strip it? Because it's a waste of time? Because it's a waste of money?

I have enough of the stuff for four coats, and will dispose of whatever I don't use.

Any reason why you can't save it for the next time?

 

[alahol2]

So I ask again, is there a down-side to coating the darned hull with more than two coats and, if so, what is it?

Because ablative/self polishing antifoul doesn't ablate/self polish more than one coat in the average yachtsman's season. Leading edges ablate a bit more, the waterline gets scrubbed off during the season. So after a few years you end up with a rather thick layer of A/F that will start to craze and need removing.
Personally I put on two coats after going back to gelcoat. I now annually do one coat plus a second layer on leading edges/waterline.

 

[oldbilbo]

So... if I read this right, the number of coats/amount plastered on is dictated by the decision of when 'to haul out'. Which may be when others around are doing it. Now that may be valid enough, for other reasons, but it is 'cart before horse' i.r.o. the effectiveness of the thick/thin AF coating.

So what if one is content to dry out alongside a wall, or on legs, a couple of times in a season, and wipe off slime? What if one seeks to avoid the cost of 'hauling out' by staying in the water?