DIY Osmosis treatment?

[Dave_Snelson]

As you know from a previous post, I have some small (6mm) blisters in a confined area on CI's hull. I'm not bothering about it this year but I am seriously considering a DIY approach to fixing this at the end of next season. Given that I was quoted £3k minimum, and I think a lot of this is just emporers new clothes...

Here's the plan...

1) Haul out one month early
2) Plan to stay out on the hard longer, say to March.
3) Strip off all the AF right back to the gelcoat as soon as the boat is out
4) Dry the hull forcibly by tenting up and using a space heater
5) Apply something like THIS in order to form a permanently impervious barrier.
6) AF again

What does the panel reckon?

 

[rickp]

Get hold of the West System's "Gelcoat Blisters - a Guide to Osmosis Repair" (you can borrow mine if you want - pm me) as its a good guide. Wessex Resins do the West System epoxy in the UK and are very good for advice over the phone.

Rick

 

[Bergman]

Not sure I would do that.

If you only have a few blisters then probably best to treat them individually.

Get your Dremel out and grind the blister out back to the glass mat.

Wash it with lots of clean fresh water ( If you have osmosis you will be able to smell the acetic acid from inside the blister)

Let it dry thoroughly, really thoroughly.

Once dry, line the hole with epoxy. When thats dry mix epoxy with some filler and level and fair to the match the rest of the hull

Antifoul.

Trying to dry the whole hull with the gelcoat still in place is unlikely to succeed. If you then apply a complete coat of epoxy you will be effectively sealing in the moisture.

 

[Pete7]

Dave, why not just strip the antifouling off at the end of a season and leave it inside somewhere, farmers barn perhaps. Don't forget to dry the inside too. As for stripping the antifouling, I used Inernationals paint stripper last year (£75 worth) on a 6.5m rib. Never again. Took 4 days lying upside down over Easter, was a horrible job and even then wasn't really happy with the result. I would pay for slurry or sand blasting type of treatment next time without question.

Pete

 

[Dave_Snelson]

Thanks Pete - good points, well made. I hadn't thought of slurry blasting. Seems like a good alternative to me.

 

[burgundyben]

Be cautious of using space heater that burns gas, that will put lots of moisture in the air. Better with a dehumidificator!

 

[Dave_Snelson]

Thanks Ben - I had wondered about that. Interestingly on the stupid price scale of wonder-works for osmosis, there is the "steam pad". They drill a million holes in the gelcoet and hold a steam-heated pad (1M sq) against the hull to dry it out.

Que?

 

[fisherman]

My view is there's a lot more gelcoat attached than not, so just repair the spots

 

[Pete7]

Dave, it might also be worth getting to grips with those moisture meter thingies. Do they really work and give consistant results? no idea, but it would give you an idea if the hull is actually drying out over the winter.

I have a few bubbles on the rib (1981 vintage), but they are between the 2 pack paint and the gelcoat at the waterline rather than in the gelcoat / grp. Decided to leave them alone for the moment and see what happens.

Pete

 

[bendyone]

the steam is not to dry it out but to wash out the bad bits you still need to dry it out 100& maybe using IR heater.

 

[Cliveshep]

Re: DIY Osmosis treatment? - Dave_Snelson

The Epoxy Bitumen was as far as I recall first used commercially as an osmosis treatment by Meakes of Marlow (JGM) who would in the 70's do a 30ft hull for about £1k. They told me that the product they used they discovered in South African diamond mines where, due to high temperatures and humidity the pit props corroded away in no time. This type of product stopped all that.

JGM's method was to sand-blast the hull and then apply 2 coats. They offered a 10 year guarantee.

I've been past Marlow 3 years running - they seem to have gone! Whether that was due to the recession or too many guarantee problems - who knows!