Painting my bottom: non-antifoul for fresh water

JumbleDuck

JumbleDuck

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I've just slathered paintstripper on the bottom of my Hunter 490, so with a bit of luck and a lot of work I hope to have it nice and clean within a few days. I've had to strip it because of an odd osmosis. Loads of blisters in the paint driven, apparently, by acetone-smelling fluid emanating from tiny pits in the gel coat.

So painting time approaches ... but with what? She has a mooring on a fresh water loch where fouling is not an issue. I put Trilux on before, but that was because I found some cheap and her bottom was patchy red when I got her. There is enough left of that for a couple of coats, I think, if necessary. or do I use standard paint and, if so, what can I use under water? Two pack? Standard topsides paint? Or do I go for Gelshield?

All suggestions welcome.
 
When we were sailing on Windermere for a few years, there was a fashion for painting bottoms with International VC17 - very thin coating antifoul with copper that's said to make the boat go faster. Looks pretty and very easy to apply.
 
The osmosis is exacerbated by the boat being moored in freshwater. Ideally you should put one of the epoxy paints on the hull once you get it dry. After that it sounds like the paint system is likely to be cosmetic so I, personally, would probably put a coat of hard antifouling on.
 
Been on Ullswater for a year with cheap "Flag" antifouling and was pleasantly surprised - absolutely nothing whatsoever on the bottom when we came out.
 
Or Hempel Broads antifoul. It used to be cheap, bit more expensive now. Or hard antifoul. I've used both on Windermere. Just a powerwash when you slip the boat and it's pretty clean again. I found a dark colour better for reducing the green slime.
 
I would advocate a 2 pack polyurethane paint brushed on. This will have a similar effect as epoxy but is UV resistant and actually intended as a paint. If you have been fixing osmosis it is likely the surface is now less than perfect so brush marks won't be a great concern. good luck olewill
 
Many thanks for all the advice. I have just spent a cheerful six hours on my back getting about half thebottom reasonably clean with a combination of paint stripper, hot air gun, scraper, chisel and frenzied swearing. When it's all stripped and prepared, I think my plan is ...

Four coats of Gelshield Plus or five of Gelshield 200 (whichever works out cheaper)

Two coats of Trilux 33 (doesn't seem to need primed over Gelshield) if my half used tin is OK, or maybe VC17 otherwise

I had a look at the data sheet for Perfection 2-Pack, and it specifically says it's not for continually immersed surfaces.
 
Hugh Foulis said:
So what would happen if the OP just painted the whole hull top to bottom with Toplac?
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I'd be interested to know. However, stripping the hull is a horrible job and I really do NOT want to do it again, so I don;t want to take any chances. I fear that Hunter did not use the best materials back in 197whatever ... the gel coat is rather soft and porous. It will definitely benefit from an epoxy layer!

Easticks28 said:
+1 for VC17 - over International VC -Tar 2 primer.

Low build and easy to apply.
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Reasonably opaque? I think the choice of antifouling will depend on how horrible the hull looks after the epoxy has gone on. I'm going to smooth it a bit by sanding, but it may still be a bit rough, in which case something matt like Trilux is probably the way to go. Of course no one sees it when she's afloat, but I'd know it was there.

I'm very grateful for the advice, and if anyone else wants to lob ideas at me, please go right ahead.
 
Totally opaque. Its a watery liquid to which you add the supplied amount of metallic copper powder and sir. It goes on like water, dries to a copper hue which, a couple of weeks after immersion turns black.
You will probably never have to lie on your back scraping off old antifoul again, since TEN coats of this is the equivalent film thickness of ONE coat of conventional AF.
 
Easticks28 said:
Totally opaque. Its a watery liquid to which you add the supplied amount of metallic copper powder and sir. It goes on like water, dries to a copper hue which, a couple of weeks after immersion turns black.
You will probably never have to lie on your back scraping off old antifoul again, since TEN coats of this is the equivalent film thickness of ONE coat of conventional AF.
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Thanks. Is that VC-17m, which comes in "graphite"? I see there is also VC-17 which comes in "blue", "red" and "original". I'm feeling tempted.
 
Many thanks for all the advice. Here's how it turned out ...

I got the bottom stripped. It was a wee bit pitted, but the effort to fill and smooth it would have been enormous and it's underwater anyway, so I went ahead with the Gelshield.
Luckily I found a supplier with some old-but-good stuff which he let me have for a tenner a tin, so she got six tins (the first three were full price, alas) which gave eight coats.

I was then relieved to find that the 2.5l tin of red Trilux I bought cheap to paint her bottom five years ago was (a) half full and (b) still good, so two coats of that went on today. I splashed out on some new white Trilux for a boot-topping, and she looks nice and smart.

All ready to launch but the forecast is strong winds tomorrow and heavy rain on Sunday, so she can stay in the barn another week. It gives me a chance to touch up some dings in the topside paint.
 
I sail the baltic sea and in my opinion the antfoul are just humbug. You still need to scrub the bottom to keep it fresh and clean.

Myself it all started with leaving the rudder completely fresh with naked expoxy resin as the outer layer. That was way better than the VC17 ocean on the rest of the hull both in smoothness and in keeping the growth away. So after two years I removed the anti fouling on the hull and redid the epoxy protection.
This is working as well as VC17 but not really as good as the epoxy resin on the rudder. However it is really hard to paint with epoxy resin since it is something in between a paint and glue. The rudder was made when I had down for maintenance.

good luck!
 
ghostlymoron said:
Make sure you treat the blisters before you up any epoxy on or you'll have to do it again.
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The blister were all in the old paint. The gelcoat had pockmarks in it, mostly, 1 - 3mm across, but not a hint of a blister. I still don't know what's been going on there - something has squirted out of the GRP and lifted bits of paint, but that's all I can tell. I left her ashore with her pimples popped for almost two years and no more appeared in that time, so preventing any more water getting to the GRP seems like a good first approach. Certainly no cause to peel the gel coat. Yet.

Edit: I have seen some suggestions that these sorts of blisters can appear if two-pack paint is used over damp (ie previously immersed) gel coat without a suitable epoxy barrier layer. The second layer of paint was a sod to remove, so may well have been two-pack ...
 
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