Blisters! Is it Osmosis?

[casual]

Did the same thing on a C&C 36 20 year's ago,Dried laid mat used only epoxy faired No Problem afer 20 years

[boatpoker]

Originally Posted by Dame.n.Jess

Its amazing how much inconsistent advice still floats around on this subject. Can Osmosis be fixed? If so how? We removed half a dozen large blisters (2-6 inch dia) from our keel, they were ground out, relieved of water and pressure and then dried out once this was finished they were filled with glass and resin and faired back then primed and anti-fouled.
Does any one have any experience of this type of repair not working?

I have surveyed hundreds of older boats that had been stripped, dried (supposedly) then epoxied. At least half of the barrier coats fail within three years. Ask yourself why no repair yard will warranty this type of work.

[sabray]

Osmosis on a boat is resin dissolving and mixing with seawater making a reaction and expanding molecules. Bigger molecules make a blister if the expansion can not get out. blister means osmosis no blister means nothing. Applying clear coats of epoxy or preferred vinylester is good if you are not trapping moisture in the substrate. removing matt and laying up with vinylester is really good. Its really pretty simple. I have no blisters: does not mean the resin is not simply rinsing through. I have blisters: something is reacting and causing a chemical reaction. I have seen boats where the the cloth looked like it was layed up dry with no resin. It dissolved and others where the matt at the gelcoat layer was crap and the lower laminates had many years of service. Hope that helps

[boatpoker]

Actually ....resin dissolving in water and creating a bigger molecule is a process called hydrolysis.

Suggest you read Osmosis Mythology

[sabray]

Originally Posted by boatpoker

Actually ....resin dissolving in water and creating a bigger molecule is a process called hydrolysis.

Suggest you read Osmosis Mythology

Okay your right but its a semantic. hydrolysis occurs and then osmosis maybe. In boat terms osmosis is often dispelled by a lack of blisters. Your correct term hydrolysis may occur even though blisters are not prevalent. Water mixes dissolves resin is hydrolysis and then molecules expand osmosis if it can not rinse through the outer layer. Your right we should be asking do I have hydrolysis.I concede you are right. The question we should be asking: Is my hull suffering from hydrolysis? Or I have never seen a blister so I have no Osmosis do I have Hydrolysis? If you have a blister you have hydrolysis and osmosis.

[Seahunter]

[QUOTE=sepeteus;704973]Finished today taking all old antifouling off the bottom (Beneteau 47.7 First). Method of removing the old paint was sodablasting and it worked like a dream. Found 10-20 blisters around rudder shaft and two groups of skinfittings. The blisters were small and were just a circle around the 4 skinfittings. The rest of the gelcoat exposed was absolutely perfect (pls note large hull)! Do I have to be concerned about this and do I have to treat these three group of blisters some specific way before the shipwright puts on the epoxy coats?[/QUOTE

A small amount of small blister is acceptable. If there's the "smell" you'll need to grind out the problem area, but I doubt there's a problem based on your comment. To be sure get a surveyor to check it out.

[boatpoker]

Osmosis is a term that originated in biology. Hydrolysis is a totally different process. Everyone in this business has a different idea of what osmosis is and this is why I never know what is being talked about. As fas as I am concerned FRP is an absorbtive material .... if you stick a piece of bread in water and the water gets absorbed is this osmosis? No.

[sepeteus]

Originally Posted by Tomtom39

Hi all!
Sepeteus! Can you let me know if your repair work to the blisters around the seacocks has proved to be successful.
I have just purchased a beneteau 47.7 and soda blastered the bottom and revealed exactly what you have shown in your pix. Have you just ground back and filled? And was it successful?
Thanks
Nick

Very interesting the fact that you found same defects on your girl. I would be keen to see some pictures of yours to see myself! Look, I am totally in peace with my so called 'disaster' on our 47.7. I simply groung back and washed with soapie water + acetone and fiberglassed the lost surface. Before installed new seacocks, reinforced the fiberglass with marine ply blocks inside. As you asked, was the repairs successful, the time will tell. I will find out the next time on slips. Good luck with your First 47.7. It is an awesome sailing boat!

[sabray]

A block of polyester resin stuck in a bucket of water will dissolve or dilute in the bucket. some molecules get bigger but you would not notice. Some resin mixes are better then others so disolve slower. some boats were saturated in resin so have more to lose.Polyester resin is bad if exposed to water. Barrier coats stop the reaction by baring the water from contacing the resin. You need complete barrier not partial. the better the barrier the better you are protected. If the barrier is breached water is getting beyond the protection and getting into the resin and is dissolving the resin. Bubbles mean bad things No bubbles does not mean resin is insoluble. High moisture in your laminate means bad things and your hull is washing away. Im trying to dumb this down.
I am an idiot that spent several years pealing the layers off of many boats.underside I got to see how bad and good the lay up was. The worst boats never had blisters they lacked resin in the layup and were mushey cloth with the resin rinsed away.

[jewel114]

[Blisters are caused by water penetration. You may consider grinding out, filling, and then sealing prior to putting anything else on. Try contacting a Interlux rep.
It seems the problem is in drying. I have done one blister job on an IP 31 and it failed after 4 years. I let it dry for 5 months in N Florida and I don't think it was enough. If I were to do it again I would peal the gelcoat, tent the boat with black visqueen. install a fan and try to dry the hull like they kiln dry wood.
Harley

[boatpoker]

Sabray, I see no disagreement here, Polyester is hygroscopic as are epoxy and vinylester although to a much lesser degree. It is simply the term "osmosis" I object to as it obscures the real issue and confuses the matter.

[sabray]

Originally Posted by jewel114

[Blisters are caused by water penetration. You may consider grinding out, filling, and then sealing prior to putting anything else on. Try contacting a Interlux rep. Harley

ughhh noo caused by resin dissolving and chemical reaction. Water does not just make a blister by getting somewhere

[boatpoker]

Try contacting an Interlux rep and asking for a guarantee. When he stops laughing, he'll tell you No Way !

[sabray]

Originally Posted by boatpoker

Sabray, I see no disagreement here, Polyester is hygroscopic as are epoxy and vinylester although to a much lesser degree. It is simply the term "osmosis" I object to as it obscures the real issue and confuses the matter.

Thanks you clarified a term and the process in better language then I. Glad to be called out as such. The obscuring is what I hoped to put out and you did better then I. Everything is dissolving . The question is is it slowed down enough or is the rate acceptable.

[MacG]

Meanwhile there are (solid) fiberglass boats aged 50 years and still in good condition.
Worse are the sandwich/balsa constructions from the 70's. Some Bowmans 45/6 are already hammered down with hefty restaurations. Same for some Swedish production boats from that era. Sandwich constructions in combination with FRP are sooner or later bound to delaminate. Do not forget that material does not last forever. Every material save for titanium has its final date written allover.