Barrier coating behind the gel coat tell me please !

Look in the Netherlands. When they peel a boat, mostly what you find behind it is a total disaster. Lot of air in the laminate, sometimes you can see complete patches that have been missed by compacting rollers. Next time I will try and make some photos (if the prime minister lets me take the camera with me. Usually she needs to take photos of the newborn...)

 

You are describing voids. That has nothing to do with osmosis.

 

Please explain?

 

Bad lamination happens at the shop. It is the result of poor workmanship. Osmosis is the penetration of water in the gelcoat and/or laminate.

 

...collecting in the voids, dissolving the salts and other materials that are present there, thereby raising osmotic pressure. The gelcoat and perhaps a bit of laminate acts as a semi-permeable barrier, allowing water in to equalise osmotic pressure, but not allowing salts to get out. Pressure in the filled voids raises, causing a blister.

Another effect is the hydrolysis of uncured polyester, breaking it down into the base chemicals it was made of: maleic acid (or other acids) and glycols. Which cause the acid smell.

Voids speed up osmosis big time. They create the base principle.

 

Yes, there are several causes of osmosis; usually they are combined. Bad lamination may help spread osmosis, but is not the cause. If the gelcoat or other moisture barrier is in good condition, a void would not be a problem (except structurally)

 

Yes, you need a couple of things to get osmosis:

-water on the outside (there is plenty)
-semi-permeable layer (gelcoat. Better gelcoats are less permeable, thickness is a factor also)
-water with higher amount of dissolved salts on the other side of the layer

The higher the difference between the concentration of dissolved salts, the higher the osmotic pressure. The semi-permeable layer also has a "treshold" above which it gives in. (there is an amount of resistance against water penetration, which can be measured in pressure. As long as the osmotic pressure is below this resistance, not much happens. The higher that threshold, the better. Adding more material, or better material (vinylester, epoxy) all helps.

 

ok just asking !
What about infused boats do they have the same problems ?
Supposedly its taken the human element of rolling resin and glass away from the process. Theres enough companies doing infusion to be in the survey cycle by now !. They use Barrior coats as well ?? :?:

 

Small air pockets or voids are only a convenient places for the liquids to start collecting, they aren't actually needed for blisters to occur, so yes, infused boats can suffer from the same problems of water migration. Infused parts need a barrier coat even more than a hand laid part for a couple of reasons. One is with the higher fiber content near the gel coat the surface profile can be worse, a barrier coat will help to keep the fibers from showing on the surface. Second, since fibers can be a great very good place for blister to form, and there is a higher fiber content near the gel coat, it can be worse.

There are many sites for the water to collect and start to breakdown the resin. It can wick down the glass fibers creating a void next to the fiber, the binder can be the issue, a combination of binder and resin (poor wetting out of the glass and an incomplete dissolving of the binder). Catalyst droplets, this can be from actual drops from the gun, or a poorly adjusted fan pattern, catalyst hitting the chop before the resin does creating over catalyzed areas near the fiber. Poor resin choice, incorrect catalyst %, temperature either too cold or too warm in the shop, contamination from the roller cleaning solvent, bad glass, glass that got wet, contamination from dirt and dust, oil or water in the air lines, a poorly waxed mold. And there are many more causes.

Most methods of preventing blisters or laminate breakdown due to corrosive chemicals or water, have something to do with increasing the resin content near the surface so there are fewer glass fibers, sometimes a layer or two of synthetic fibers are used. Of course using better resins helps also.

Marine gel coats normally survive fairly well below the water line and you’ll not normally see blisters forming in the gel coat itself, although they can, and if they do its typically because something was done wrong in the application process.

 

I would like to say personally a great big thank you to the people that had contributed to this thread . I feel it is a wealth of good material and because i have not used Barrier coating personally my self it has given me a lot of satisfaction to read from the people that have and know a lot !!!
The company im working in has a bunch of dinosours working there and even a new day is almost to much for them to cope with , trying to introduce new laminating rollers has been a major and i find them back in the store and they have reverted back to there old hand made prehistoric equipment !
Almost had a stand up with one guy this morning that thinks he know it all voicing his opinion about th fully reconditioned chopper gun i have fitted everything new into over the past months . Its a beautiful gun to use and is a smooth as . but he dosent think its right !!. Has never used one before mind you, always the same when theres a ordiance of more than two people .

I took a classic photo yesterday to post when i can sort my new photo program . This is typical of asian contempt and blazaa attatude !!! was the same in Japan and Korea and china is no differant !!.