Complete Removal of Antifouling Paint

[Goudurix]

My Jeanneau 37 ft is nox 19 years old.
I had it treated against osmosis 4 years ago, complete stripping of the gelcoat, rinsed, epoxy filling and coating, the works...and still with good effect.
I haul out the boat every year for antifouling application. I usually power sand it to remove the old antifouling, but this tends to slightly reach the top layer of the 5 layer epoxy paint coating from the osmosis treatment.
I usually apply 2 layers of antifouling paint. The previous af paint coating is still in good shape.

My question: is it OK to only LIGHTLY sand/roughen the old af paint instead of removing it for approx. 85% as I did in the past? I want to avoid damaging the epoxy caoting, and hope to have to apply only 1 layer of fresh af paint until next haul-out 9 months later.
I am a scuba diver and do an inspection and light cleaning of the hull 2-3 times times during the boating season (although this seems to be a bad idea since it releases quite a bit of the active copper into the water...)

Thanks for any advice/opinion,

Jan

[jdoe71]

Why not use a self - polishing ablative? If you do it right, using different colours per coat, you will only need to touch up yearly in the spots where the colour change is showing through. Little if any sanding necessary on a fairly clean bottom. You're doing a lot of work and spending a lot of money for little reason.

[barnakiel]

At all costs avoid damage to the epoxy barrier.

Check out if your paint manufacturers if they offer a chemical paint stripper.

Ourselves here use soft paint and apply new one over the old one. After rigorous power-wash there seems to remain very little lose paint to be removed prior to each repainting.

b.

[Goudurix]

I was hoping indeed that the "barnakiel" option is what I can apply...here in belgium people usually sand down the old antifouling vigorously untill previous color or even gelcoat or sealing coating becomes visible....

Therefore this time I have only sanded the old antifouling (which is still in good shape without any loose paint) very lightly.
I will now try to limit myself to just one new layer of soft paint except the rudder which gets a lot more of water turbulence..

I'll see how that looks after one season.

Maybe within a few years, if I want to remove all old layers of antifouling I will remove it with chemical stripper. I always use the same brand of antifouling paint (AWL Grip).

Jan

[David M]

Unless the old anti-foulant paint is delaminating then why bother removing any of it? The pressure washer already removes anything that is loose or close to being loose.

[Goudurix]

A good cleaning with detergent and slightly sanding is always good to have a good adherence of new paint no?

Jan

[GordMay]

You certainly do NOT have to strip the antifouling down to the barrier coat.
Even sanding may not be required.

From the AwlGrip Antifouling instructions
➥ http://www.awlgrip.com/MPYACMDatashe...9+A+eng+A4.pdf

Renewing Awlstar: High pressure water wash as soon as the boat comes out of the water, allow to dry.
Sanding (80 grit) / removal of old coating is not normally required but is advised under any of the following conditions:
- Any time the cleanliness of the surface is in doubt. - Fast boats which have ablated to a very smooth surface.
- Sailboats which were recently burnished. - The surface was not power washed immediately after hauling.

[David M]

I have always had good luck just with a pressure wash. But then I am not necessarily using the same bottom paint.

I would definitely go by the preparation recommendations of the manufacturer of the new paint and check the new paints compatibility with the old paint.

It's an easy thing to call the paint manufacturer and get the information directly from the "horses mouth".

[David_Old_Jersey]

Sounds a bit OTT to me.

- Power wash / scrub / a gentle scrape of anything that scrapes off easily
- sand down / fair anything lumpy or bare patches......if fussy.
- slap a coat of antifouling on

Repeat every year. or so

probably find that a good scrape / sand will be needed every 5 years. and maybe every 10 years a scrape / sand down to bare - or nearly. Maybe

[MarkSF]

Originally Posted by Goudurix

My Jeanneau 37 ft is nox 19 years old.
I had it treated against osmosis 4 years ago, complete stripping of the gelcoat, rinsed, epoxy filling and coating, the works...and still with good effect.
I haul out the boat every year for antifouling application. I usually power sand it to remove the old antifouling, but this tends to slightly reach the top layer of the 5 layer epoxy paint coating from the osmosis treatment.
I usually apply 2 layers of antifouling paint. The previous af paint coating is still in good shape.

My question: is it OK to only LIGHTLY sand/roughen the old af paint instead of removing it for approx. 85% as I did in the past? I want to avoid damaging the epoxy caoting, and hope to have to apply only 1 layer of fresh af paint until next haul-out 9 months later.
I am a scuba diver and do an inspection and light cleaning of the hull 2-3 times times during the boating season (although this seems to be a bad idea since it releases quite a bit of the active copper into the water...)

Thanks for any advice/opinion,

Jan

Around here the norm is hard anti-fouling paint, and a light sand before applying new paint. This has the effect of the paint building up over time, but it might take a minimum of 10 years, and 28 years in my case, to build up to the point where it needs stripping again. The real need to strip is when adhesion begins to fail.

A claimed advantage of ablative paint is that it doesn't build up like the hard paint.

[Goudurix]

OK guys thanks for all reassuring replies.

I know that over the years I was doing too much....

Since the original antifouling, after the anti-osmosis treatment was white, this is the colour I see appearing when sanding (too much) and probably not the epoxy sealing layer.

The AWLGrip site was instructional.
My antifouling is AWLGrip Gold.

As indeed the old antifouling was in "good shape" and the boat was power-washed immediately upon hauling, I will limit to:

- have a good wash with detergent and rinse well
- slight sanding on slick looking areas
- no application below 13°C
- a double layer on rudder, bow attack area, keel attack area.

- a thorough sanding/scrub only after many year when there is a real buildup of AF coats.

Thanks!
Enjoy the off-season for those lying in cold waters and may spring come soon!

Jan

[pupuce]

I did the same job, last year, on my boat... you're in Belgium and I think you'll find easily these products:
Dilunett (Owatrol): it removed at least 70 % of old painting (several applications needed)
D4V1 Simab (peintures et vernis SIMAB
Carban + (BP) to clean other parts of gel-coat (rinse copiously)

[nigel1]

Have you considered Coppercoating. Its something I'm thinking about, and doing the sums, it seems to be the best option. Will involve slurrey blasting the old A/F off, and maybe the need to apply one more coating of epoxy before applying the Coppercoat.
The benefits is that the A/F properties are good for 10 to 15 years.
For me this would mean having to haul the boat every two years, not one, and the period out of the water is limited to the need to change aniodes, pressure wash the hull, and very lightly abrade the coppercoating.

[Viking Sailor]

If you can't knock the old paint and marine growth off the bottom with a 2000 lb/sq-in pressure washer -- what makes you think that it will fall off while sailing at less then 10 knots. Pressure wash at haulout and do a light touch up with 80 grit sandpaper and a hose where the straps were and what the yard missed. Paint it and get back to sailing.