A Bad Case of the Pox

demonboy

demonboy

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A week in a boat yard is never much fun, at least not in the tropics, and after hauling Esper our misery was compounded by the discovery of some serious osmosis. The joy of sailing the idyllic Maldives went out the window, at least for a few hours, as we inspected the water blisters covering many parts of the hull. Experts reassure us that osmosis isn’t as bad as people believe, but when you see the pictures of our rudder you might think twice before agreeing with them. Moral of the story? Haul out more frequently than every four years!

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Can't seem to upload pics (not a valid image file (?) and I'm on a crappy connection) so photos and story here: http://www.followtheboat.com/2013/04/09/a-bad-case-of-the-pox/
 
Fortunately there are reams of information about osmosis, its causes and treatment on the Internet, most of it contradictory as you might expect. The main suggestion that most seem to agree with is that repeated fresh water washing and drying is the first step, followed by filling the blisters with epoxy paste. Persistently wetting the surface seems wrong somehow but most agree it is necessary to remove all contaminants, thus enabling good adhesion in the repair.
 
Rudders often suffer from pox. Grind it out and fill for now.

Do it all properly in SA (as you plan to) - it shouldn't be too expensive to do there.

A friend returned to to the UK via SA in his Oyster 43 after 14+ years away. He'd had the boat overhauled in SA inc Awlgripping the topsides. The list of work was quite extensive. The quality looked very good.

When he told me what it had cost him I nearly fell over. Incredible value for money (probably 3-4 years ago now).
 
We're pretty philosophical about it really. If we were here for a couple of weeks I'd grind them all down, wait for them to dry and fill them in, but time isn't on our side this time. Encouraging to hear about the SA connection, Tradewinds, and interesting to hear that this is common with rudders.

Anyway, we have other things to be cracking on with. This one goes on the backburner. Cheers, all.

(I tried again to upload the pics but still can't. Reduced to 700px wide and under 200kb. Is that right, or is that another forum I'm thinking of?)
 
demonboy said:
We're pretty philosophical about it really. If we were here for a couple of weeks I'd grind them all down, wait for them to dry and fill them in, but time isn't on our side this time. Encouraging to hear about the SA connection, Tradewinds, and interesting to hear that this is common with rudders.

Anyway, we have other things to be cracking on with. This one goes on the backburner. Cheers, all.

(I tried again to upload the pics but still can't. Reduced to 700px wide and under 200kb. Is that right, or is that another forum I'm thinking of?)
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Hi Demonboy,

What you describe may not be the pox at all, watery blisters may be just that, water trapped behind the paint, not uncommon.

You may find they disappear in few days when out of the water and pressure is off them.

You van check by removing a bit of the coating and inspecting the area behind the blister.

Good luck and fair winds.

PS. if it turns out to be the dreaded pox, I grind out the area and look for a slight yellow ir brown stain and follow it with the grinder till it,s all gone, sometimes you will see a wandering brownish line, follow it and remove it all.

I find this works better than washing and hoping you have removed any contamination, take it out I say.

Good luck and fair winds. :)
 
The blisters, if sanded down, weep an epoxy-smelling liquid. If I grind them out the fibreglass looks to be in an ok condition. One or two on the hull are quite big (4cm in diameter) but the rest are small. Some don't go back to the fibreglass, just the gelcoat. Quite a few weep though. The rudder definitely got the worst of it. Be interesting to see if they do go down after a few days in this heat. Cheers.
 
Sorry to hear of your woes Demonboy. You describe the smell of the fluid as 'epoxy-like', which is odd. Osmosis usually smells more like vinegar. If it is the pox, don't even think of simply grinding out and waiting for it to dry: it won't. The products of osmosis are hygroscopic, so you'll be waiting funtil Xmas -- 2020. Hence the advise above for frequent washing with fresh water to remove the hygroscopic chemicals. That's why Vyv called such washing counter-intuitive.
 
Rudder? The surprise would be if your rudder isnt wet. Usually they leak down the join between shaft and GRP so they are full of wet foam. And they osmote. Not sure I'd even bother to treat is - I certainly havent treated mine.
 
macd said:
Sorry to hear of your woes Demonboy. You describe the smell of the fluid as 'epoxy-like', which is odd. Osmosis usually smells more like vinegar. If it is the pox, don't even think of simply grinding out and waiting for it to dry: it won't. The products of osmosis are hygroscopic, so you'll be waiting funtil Xmas -- 2020. Hence the advise above for frequent washing with fresh water to remove the hygroscopic chemicals. That's why Vyv called such washing counter-intuitive.
Click to expand...

I used hot water and a garden fertiliser spray. the smell diminished over a few weeks and was as said a vinegar smell.
 
I wouldn't worry too much about it, as said it's mainly cosmetic as it stands. It will need to be dealt with at some time and SA will be a good place to it. Check out our blog for some pics when we got lifted after 5 years in Trinidad, some good blisters there! We were back in the water after 3 weeks!!

I ground them all back to solid glass and then washed them 3 or 4 times a day for a week before filling and fairing - seems to have worked short term. Long term I think we'l need to be out for a few months and dry it all out properly, then assess it and do what needs to be done.

As our surveyor said "no boat has sunk because of osmosis!" It's caused by bad initial build - ours was built in 1981, not a bad run for the old girl!
 
macd said:
Sorry to hear of your woes Demonboy. You describe the smell of the fluid as 'epoxy-like', which is odd. Osmosis usually smells more like vinegar. If it is the pox, don't even think of simply grinding out and waiting for it to dry: it won't. The products of osmosis are hygroscopic, so you'll be waiting funtil Xmas -- 2020. Hence the advise above for frequent washing with fresh water to remove the hygroscopic chemicals. That's why Vyv called such washing counter-intuitive.
Click to expand...

Hi Mac, nice to hear from you. Hygroscopic is a new word for my vocabulary, and Liz reckons the smell IS like vinegar. Anyway, rudder is done and I've just slapped some dabs of epoxy over one or two other blisters to see us through to SA. Hope you're well. Jamie
 
macd said:
Fair winds, Jamie.
Incidentally, if you can't tell epoxy from vinegar, maybe wisest to let Liz make the salad dressing...;)
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The funny thing is that I spent some time under the hull this morning and the vinegar smell was very obvious. I could smell it on our first day on the hard too but thought it was my sweaty t-shirt!

Liz's salads are better than mine ;)
 
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