DIY Osmosis treatment

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Is there a company who will hire you all the kit required to do a decent job of Osmosis treatment? The process is reasonably well documented now and many of us DIYers are capable of doing it- it's only another time consuming and grubby job after all! I have been quoted nearly £6500 for a proffessional treatment on my elderly 38 footer. There must be scope for a big saving in there.
 
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I am currently in the process of DIY Osmosis treatment on a Roberts 34. I have not had a need to hire equipment. If you are near Swanwick marina at the weekends you can come take a look. (So far, I've ground off the starboard side. Port side yet to do. It is very tedious.)
 
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How have you ground off the gelcoat? Having looked at various treatments the best seems to be the Gelplane to remove gelcoat, a slurry shot blast to remove chemicals and further etch the surface, drying using an enclosed skin and dehumidifier (unless you live in hot, dry climate) and all this needs to be monitored using a special moisture meter.(If you don't check the moisture you will end up with what I now have. A previous owner did all the work but failed to check the hull moisture content and neatly sealed it in when he epoxied the hull!) I make that at least four bits of kit which I don't want to buy but would happily hire. Did you remove skin fittings?
 
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The hull is slightly different to production boats in that we used a male mould when we first made the hull about 20 years ago. Consequently, the gelcoat is not of the traditional gelcoat. Having said that, the surface layer was removed with flapdiscs. (You need to scrape of as much anti-fouling as possible first as soft antifoul tends to clog.) The skin fittings were left on. The moisture meter is the cheapest part to hire or buy. (I've not bothered yet but maydo when I'm ready to apply the gelcoat (gelshield 200). The next step for us (depending how bad your Osmosis is) is to lightly screed the hull and sand off with a belt sander to a smooth finish. Temperature is important for the screed. The new surface will be painted with solvent free resin and then the 6 coats of gelshield applied. Finally hard-antifoul within 24 hours of last coat of gelshield. Nothing hard about the whole process but preperation and waiting for the right conditions are everything.
Interestingly enough, when you grind off the hull you can see any wet spots as the dust absorbs the liquid. The conditions are really no different from when we first built the hull and the boat has been in the water for 20 years until now. However, I do remember weeks of sanding and they are not happy memories.
 

billskip

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sounds as though your getting to involved ...you need good breathing gear and clothing protection...an angle grinder and a good eye ..grind it off...let it dry and apply epoxy..sounds simple ...its hard work...I have done it ...and then I asked ...WAS IT REALY NECESSARY????..
 

tony_brighton

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As I recall there was an article in one of the mags about 2-3 yrs ago - some company would come around and strip the gel coat for you with a robot with a grinding head. Don't know if they still exist/perform the service.
 
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I couldn't agree more, people go way over the top with Osmosis repair. Grind it all out and epoxy has worked wonders for my boat. None of the original 50 or so blisters I did a year or so ago have reappeared. I did let it dry out for a month though, but I am not sure even that was necessary, it was a month of lost sailing. The actual work wouldn't have taken any more than a day or two.
 
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the key issue is getting the hygroscopic salts out of the laminate. dont fall into the trap of drying the hull with heat / dehumidifier because whatever coating you apply is slightly porous (inc epoxy) and if there are salts in the laminate remaining to be dissolved you will get a repeat of the problem. so wash, wash and wash again until the laminate dries reasonably quickly and without heat.

remember that the moisture meter measures the dielectric constant of the laminate and if you have an air gap between meter and hull (like on a sharply curved surface) you will get a false dry reading.
 
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