Antifoul gas bubbles

[doublebubble]

Hi all, looking for some advice on why we would be getting bubbles, blisters or what ever you want call them on the bottom of our yacht which only show up after we have Antifouled the bottom, it only seems to be in the paint, when the boat comes out of the water there are no sign of any blisters what so ever, no Antifoul ever comes off even with water blasting, we sand the hull quite heavily everytime with no signs of any blisters, bubbles, they only appear after we have finished antifouling and the sun heats up the paint, when we are put back in water they just disappear, any advice would be appreciated.

Cheers Rod

[tkeithlu]

Hypothesis. There actually is water in pores in the fiberglass, and they are evaporating/making bubbles when heated.

That's a long shot, because evaporation requires air, and there isn't much under your bottom paint. I'm still with a temperature phenomenon, because they disappear when you splash.

How old is the hull? How big are the bubbles? Do they only occur on fiberglass, or do they appear on metal fittings as well?

Hypothesis. The wet bottom paint is expanding in the sun. It contracts when you splash, and then dries. That suggests putting on a thinner coat and drying thoroughly between coats.

Do they appear only on the sunny side of the hulls? How warm does it get? Outback hot?

[doublebubble]

Thanks for the reply, the boat is 25yrs old, the bubbles can be up to 5 - 8mm in diameter, yes it only happens when the sun is directly on the side of the hull being a 50ft multihull, the other day the side of the hull was that hot you could cook an egg on it, Far North Queensland, before it's antifouled it could be up to ten days sitting while we polish the topsides and other things and there is no sign at all of bubbles its only when the sun is on a fresh coat of antifouling, in the morning when it's cool no bubbles at all.

Rod

[JPA Cate]

Well, it could be the solvents in the bottom paint bubbling because it is so warm up there..... If the bubble gets a pinhole, the gas will come out. Or you could put a pinhole in and smell what comes out. If it's solvents, it will smell different from water.

On the other hand, you might also just say it's nothing to worry about, if it reverts to normal in the water, and there's no other problem with the antifoul.



Ann

[doublebubble]

Thanks for the comments, we did prick a couple and nothing came out and no smell of any kind, we are back in the water and they have disappeared, we'll see next haulout and see if if it happens again.

Cheers Rod

[Kastaway]

What brand antifoul ? Some don’t like sitting too long before being splashed.

[doublebubble]

Altex No.5 in black.

[Kastaway]

I also use Altex number 5 and have always left the antifoul until last on the advise that it oxidises doesn't like to sit around dry. But reading the product information it should be fine. There goes my theory.


Dry Times (75 µm DFT / 25°C / 50% RH):
To Recoat - Minimum 4 hours
- Maximum Not critical
To Launch - Minimum 8 hours
- Maximum Not critical