When did osmosis start ?

In 1982 I bought a 1973 Nauticat 33. The entire hull had been repainted 3 years before because of osmosis. So when the boat was only 6 years old osmosis was present. Mind you when the hull was painted in 1979 Two Pack Paint was not available for boats and no disrepect to International Paints but at that time you may as well have used paint from Woolworths.
 
I had an Arpege by Dufour new in 1970. By 1774 it had developed bad osmosis. In those days it was a death knoll. I had neither the money nor the time to do the remedial work myself and sold her very cheaply.

Our present Moody 42, from 1978 had epoxy treatment before we bought her in 1995.
In about 2000 we found blisters. Very small ones and for the next 7/8 years I picked them out, washed them and filled them with epoxy. 3 years ago we stripped her down to the old epoxy layer filled the blisters again and gave her 4 coats of International Gelshield epoxy. We will be coming out of the water soon and will wait with interest to see if we have any problems.

Keep you posted :D
 
Orthophalic as opposed to isophalic resins were one of the main causes of osmosis.

People tend to forget that the gelcoat is just a finisher and not a structural part of the yacht. Most manufacturers now put in a "barrier " matt between the gelcoat and the chopped strand matt to stop the fibres puncturing into the gelocoat. Gelcoat is a permiable layer and high moisture content maybe present even without osmosis. The key is to ensure it is as dry as possible prior to adding an epoxy or similar coating.
 
The hull cost is only about 1/3 of the total boat cost and the resin cost only makes up a fraction of the hull cost so the extra cost of epoxy should only be relatively small.
Premium boat bulders sould be encouraged to stop building expensive boats out of inferior resins.
 
Osmosis the real reason

Osmosis started the first day they started to use a chemical called Styrene in the resin during the laying up process
This chemical was used to free up the resin and was used for years in different quantities in most nearly all fibreglass hulls
Styrene as a by-product of its properties absorbs water
So it sits in the resin in the hull and slowly over the years starts to pull moisture through the gel coat and also from wet bilges
This is why you sometimes just get high moisture content and not bubbles
Gel coat is the osmosis part that everyone hears about because the moisture that the styrene pulls through gets trapped behind it and then combines with the styrene to make that nasty smelling goo that comes out of the blisters when you burst them
It’s no one’s fault as such but more an inherent problem with the resin with the styrene in it
Different layup thicknesses and processes, Weather conditions, where the boat is kept, how long it sits in the water, and a number of other variables affect the length of time before high moisture content and or bubbles start to appear
Also the amount of styrene that was in the particular batch of resin that the boat builder used will make an obvious difference


Hope this helps to clear some of the myths
Joe
 
I was offered a Reliant Robin in PX against one of my cars. I walked round it and noticed some bubbles in the body. Its got Osmosis I told him. He asked what that was and I replied "Delimination of the Gel Coat". He obviously did not believe me and we did not do a deal. So its not just sea water that causes it, rain can too.
 
noelex said:
The hull cost is only about 1/3 of the total boat cost and the resin cost only makes up a fraction of the hull cost so the extra cost of epoxy should only be relatively small.
Premium boat bulders sould be encouraged to stop building expensive boats out of inferior resins.
Click to expand...

How many premium boats within the last 20 years do you know of that have had osmosis?
 
Apart from the higher price of epoxy compared with GRP, the work is almost ten times more. Temperatures, mixing the components, all much much more difficult than with GRP which is now an stone age technology. Also the working with epoxy is dangerous, people get sick, once you have an allergy to epoxy, no more working with that stuff. Toxic as hell. Between layers, always sanding. Ask a pro, he will refuse epoxy. And for most jobs, epoxy is inferior to GRP. To brittle, and the sun and light is its enemy.
 
noelex said:
The hull cost is only about 1/3 of the total boat cost and the resin cost only makes up a fraction of the hull cost so the extra cost of epoxy should only be relatively small.
Premium boat bulders sould be encouraged to stop building expensive boats out of inferior resins.
Click to expand...

You also need to consider the fact that CSM is sprayed into the mould and takes very little time, Epoxy cloth goes on one layer at a time and the cost of the cloth is also a lot more expensive than CSM.

The time and labour to bild an all epoxy hull would be at least 2 thirds more than a standard chopper gun built hull.

Manufacturers of hulls build what the market will buy and most buyers will not pay the extra for better materials, so let's not blame the builders or regulate them into bankruptcy.

Good luck and fair winds.
 
How many premium boats within the last 20 years do you know of that have had osmosis?

I have seen quite a few. It's more common in say Australia due to the warm water and tendency for people to leave their boats in the water all year round.
 
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