Antifouling - whether to strip down old paint instead of painting another layers?

[B40]

I need to decide how to prepare the bottom of the hull of my GRP boat for the next seasons.
The boat’s history is following:
One and half year ago I have bought the Beneteau Oceanis 40, the construction year 2007. Upon buying, the hull was thoroughly checked for osmosis and it was OK. I’ve decided for the anti osmosis check because around 5 years earlier the boat had a major hull repair as a result of hitting an object. After buying the boat, their hull was painted with any International ablative antifouling paint. You can see the hull before painting in 2016 at the enclosed pictures (their names start with 2016 – first 4 ones) https://www.dropbox.com/sh/48you4r1wwveilt/AAB7yr_PSzyLnc5hJ9CVj2Lka?dl=0.

During last 18 months, most of the time the boat was moored close to Athens at the Aegean Sea. The boat was hauled out recently and after pressure washing, I’ve found many patches have appeared as a result of peeling off the paint. The patches look similar to that from the previous year but they have appeared a little bit less frequently. You can see the recent pictures of the hull enclosed (their names start with 2017 – last 6 ones).

For the next few years, I plan to keep the boat as long as possible on water mostly on a permanent mooring with no more than 150 hours of sailing during the year.

What results should I expect after I choose any of the following options:
• Priming and painting with another layer of ablative paint?
• Remove all the layers and prepare the hull from scratch?
• Could Coppercoat be a solution for long-term cost effective solution for the yacht which will be most of the time on a mooring?

 

[lpdsn]

I find wet scouring with heavy-duty scourers the best way to reduce build up of self-eroding anti-foul. It does take two or three days of hard work though on a 40 footer. Don't dry sand.

Yours does look in quite poor condition so might be worthwhile taking it all off. By far the easiest way to do it is to pay someone to blast it.

If you do keep it whatever you do don't use filler to smooth it before the next coat. It is a right pain to remove that if someone has done it.

Also I wouldn't use a primer. A primer sitting on top of layers of self-eroding antifoul is likely to give you craters if it is worn away at any point.

 

[Tranona]

If you plan on keeping the boat for some time, now is the time to clean all that off and start again. Doing it manually is hard work so blasting is the way to go. Then you have a choice. As a minimum if you get back to bare GRP it is worth using an epoxy coating system then either conventional antifoul or Coppercoat. The latter is potentially better in the long run, but expensive and needs careful application. You also have the problem of dealing with the keel, particularly if it is iron. After blasting to the correct finish it nees coating straight away to prevent rust sso you need an experienced contractor to do the job.

If you do want to go down the Coppercoat route then suggest you contact them for advice and recommendations of contractors who can do the work. You can, of course do it yourself and you do have the environmental conditions that make it easier to do it outside.

 

[B40]

lpsdn, please explain what exact process do you mean writing about wet scouring? Rubbing with hands using green cloth for cleaning pots? I hope I'm wrong.

 

[johnalison]

If you can get it stripped this year and do a full job, all well and good, but there is no harm in making do if this is not convenient. Before I had my bottom stripped I had a few years during which I had to cope with areas that had peeled. I found it gave the best results if I painted the patches with Primocon, then carefully sanded the sharp edges to feather them off and putting on another primer coat on the patch. The result was hardly visible after antifouling.

 

[B40]

johnalison, Please confirm: First, Primocon, then sanding, Primocon again and finally antifouling.

 

[peter gibbs]

The practicalities are that no antifoul paint keeps a hull totally clean, especially if the boat is moved too little for water action to shake off growth. With time AF paint patches - as you see- and you will end back where you are now whatever you do.

So a lot of cost and effort now is only worth it if you are a fastidious sailing type and value every nano second of speed. Get the hull blasted down and repaint but with hard AF I suggest, then a light brush removes future excessive growth without removing the AF.

With a modern hull, going to the cost of Gel Shielding is probably not justified. Osmosis is not a threat.

Copper coat is lovely and seems to work well enough - if a near spanking clean hull every time out is your standard.

For myself, I scrape loose flakes, slosh on the primer, and heavyweight regular AF to the top 18 inches of hull - where light percolates and encourages growth. Moving the boat fairly frequently removes intermittent growth which along the E coast of England is a mounting problem.

PWG

 

[wotayottie]

• Could Coppercoat be a solution for long-term cost effective solution for the yacht which will be most of the time on a mooring?

9 years on and its the best thing I ever did to my boat.

 

[ghostlymoron]

Can't see any point in priming,
then sanding - you'll just take the primer off again and Primocon isn't cheap.

johnalison, Please confirm: First, Primocon, then sanding, Primocon again and finally antifouling.

 

[GrahamM376]

A few years ago, after many years of coats, our antifouling was very thick and flaking off previous coats, applying new coat loosened even more as soon as the solvent hit it. I stripped it by hand using scrapers and power chisel which, on a 38 ft boat, is not a fun job. Yours seems to be flaking in patches down to gel judging by the photos. My inclination would be to strip it all off and apply a coat or two of primer before new antifouling. Applying primer over antifoul isn't the way to go as it won't stop the underlying stuff coming loose and make future stripping harder.

 

[Pye_End]

If you decide on antifouling:

Scrape off loose stuff with decent scraper or chisel.

Wet sand using sanding mesh (hose - sand for a few seconds - hose) gets a decent finish for antifouling will relative ease.

 

[Homer J]

Hand sanding and chiselling the hull of a 40 ft boat?

Mmmm, sounds like an unenviable task. I wonder how far through the job you will get before you begin to wish that you had paid someone else to soda blast it? May as well get them to do it from the outset - money well spent in my opinion and probably a lot better for you health.

 

[neil_s]

If you decide on a 'just keep it going for another year job' use thinned antifoul to prime the bare patches, not primocon. This seems to seep under the adjacent edges and 'glue' them down. Been doing this for 15 years, now!

 

[laika]

lpsdn, please explain what exact process do you mean writing about wet scouring? Rubbing with hands using green cloth for cleaning pots? I hope I'm wrong.

Unfortunately you're right. You get a plastic handle thingy that you stick one of those green scourers on then scrub with water. Depending on whether it's blue or red antifoul you end up looking like a smurf or a serial killer.

 

[GrahamM376]

Hand sanding and chiselling the hull of a 40 ft boat?

Mmmm, sounds like an unenviable task. I wonder how far through the job you will get before you begin to wish that you had paid someone else to soda blast it? May as well get them to do it from the outset - money well spent in my opinion and probably a lot better for you health.

Easy to spot those in the yard doing it, they look like Smurfs Unfortunately, nature reserve so no blasting here but powerwash residue drains into Ria

 

[vasant]

i guess its clear what the best is if the money is there. soda blast - epoxy prime- AF.

In my case where i didnt have 1,5kEur at hand i sanded down until i reached a layer that was solid. Then i applied some primer and AF. Ever since and every year i water blast it and its almost clean. I then wet sand it with grit 120 and 180 and apply ONE coat of AF. My boat stays in the water only 10 months.

 

[NormanS]

Unfortunately you're right. You get a plastic handle thingy that you stick one of those green scourers on then scrub with water. Depending on whether it's blue or red antifoul you end up looking like a smurf or a serial killer.

No no. You can do a lot better than that. House decorators use a long handled device with a pad attached with a universal joint, for sanding ceilings. Made of alloy, it weighs very little. Then Google gauze sanding roll. Add one to the other, and use with plenty of water. It's a lovely job to do on a miserable day..

 

[lpdsn]

lpsdn, please explain what exact process do you mean writing about wet scouring? Rubbing with hands using green cloth for cleaning pots? I hope I'm wrong.

Apologies for the late reply, been away for a while.

Yes, basically. Except you need the heavy duty scourers that say not to be used on pans. As you rub it it'll start to build up momentum - you'll know what I mean when you do it. Then just use a sponge to remove what you've scoured. Using a bucket you collect most of the stuff and can pour it down teh same drain the yard uses when pressure washing.

 

[lpdsn]

Depending on whether it's blue or red antifoul you end up looking like a smurf or a serial killer.

Not if you're using enough water. You rinse your hands in the bucket everytime you wet the scourer or squeeze the sponge so there's only traces get on your hands and arms. Worst thing is wet cuffs, so you need your arms bare up to the elbows.

 

[vodzurk]

Great thread . About to hit my first joy-of-antifouling job too .

My mobo was antifouled with what I believe is hard paint, then sat on a dealers courtyard for 6 months... then this time last year she met the water and has been chilling out in the marina since (in the lovely brown waters of the UK / Bristol Channel.

She needs some wear+tear bits sorting on the hard over the next month ready for mid-march, so I've just had some Cruiser Uno Antifou arrive today, as it was on offer (1/3 off - Link for those in the UK).

I think my bottom will be slightly less pocked than yours. I figure whilst she's out, give it a light all-over touch with a power sander, then get the antifoul rolled on. Hopefully just a one day job . As it's not utterly critical, I reckon I'll not even bother asking the yard to move the chocks once its dry (though mayyybe i'll have a brush ready when they're lifting her back in, I think it's rapid-dry).