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Old 07-03-2016, 03:21   #1
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Osmosis prevention for oldboat

1970 boat, heavy hand layup (almost 1" thick throughout the hull), life spent in cold Northern waters, hauled each Autumn for inside storage.

No osmosis, and might not even get any. But prevention is better than cure, right?

So I did a search of the forum, and came across a recommendation for Sherwin-Williams two part barrier coat, and looked into it, and it seems they do some really good stuff (quite a range, in fact).

Epoxy Coating Comparison Chart - Sherwin-Williams Protective & Marine Coatings

So anybody used it? Which one did they use? How many coats? Where did they buy it?

If no info available, I'll contact the Company (though first hand user info is best) and update if I get a response.
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Old 07-03-2016, 04:23   #2
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Re: Osmosis prevention for oldboat

I would suggest you use the proven go-to products like Interprotect2000.
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Old 07-03-2016, 04:53   #3
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Re: Osmosis prevention for oldboat

Did my bottom a couple years ago, I used the Interlux product line from start to finish coats of bottom paint.
Was easy enough to work with all the products and I knew everything would be compatable, great instructions and videos available.
Doing the top sides this spring, had such good luck I'm using all Interlux again.
One of the main reasons I used that product was it was all available and in stock, did all my shopping in two stops, Home Depot for stuff like rollers, tape etc, Boat shop for the " wet stuff".
Heard good things about Petite but not carried where I shop, & most boats at the marina shop at the same place I shop.
If Sherwin Williams has a full line of products I imagine it would be OK, pretty well known name. Personally never seen it used, doesn't mean much though! Lot's of stuff I've never seen.....
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Old 07-03-2016, 07:24   #4
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Re: Osmosis prevention for oldboat

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Originally Posted by s/v Jedi View Post
I would suggest you use the proven go-to products like Interprotect2000.
Believe it or not, I don't think you can get a more proven range of products than Sherwin-Williams (they have very extensive offshore experience with a range of well proven products).

It was a recommendation here (CF) which mentioned a two part barrier coat of theirs (but not a specific one), that got me looking.

As this could open up some new options for us all, and as competition is good (as well as much needed in the boating sector), I don't mind looking, and the right one would be risk free.

I agree Siberianhusky, they have a very good name.

PS. Just emailed them, we'll see what they say (also told them that Coppercoat will be going on top of it).
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Old 07-03-2016, 07:43   #5
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Re: Osmosis prevention for oldboat

Be sure the hull is really, really dry first.
My old boat had lots of tiny blisters, about 1/4", just in the gel coat, PO had the boat hauled, stripped, barrier coated and splashed all in a couple of days.
I speculate that the barrier coat sealed some moisture in causing the little pox in the gel coat.
Interesting at last haul last year, there were far fewer of them?
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Old 07-03-2016, 08:40   #6
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Re: Osmosis prevention for oldboat

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Be sure the hull is really, really dry first.
My old boat had lots of tiny blisters, about 1/4", just in the gel coat, PO had the boat hauled, stripped, barrier coated and splashed all in a couple of days.
I speculate that the barrier coat sealed some moisture in causing the little pox in the gel coat.
Interesting at last haul last year, there were far fewer of them?
Having been in heated storage over the winter should help, so I would like to get the barrier coating done before launch (along with any through hull and seacock servicing/replacement, etc - all originals were bronze and proper seacocks apparently). Also with CopperCoat on top, it will need at least a week on the hard to cure properly. I don't mind extra days beyond that to make sure all is ok.

If I can get it done within the first week of signing on the dotted line, then there's at least two weeks for everything to properly cure before launching and exiting stage left beyond the 3 mile limit.
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Old 07-03-2016, 09:08   #7
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Re: Osmosis prevention for oldboat

Much of the FG resins used in the early 70s have exhibited little or no inclination to allow for water absorption. If it ain't broke why in the world do you want to fix it? There must be other great projects on your boat on which to throw your time and money.
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Old 07-03-2016, 09:19   #8
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Re: Osmosis prevention for oldboat

I agree with Seasick. Not likely will never develop osmosis on this vintage boat.
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Old 07-03-2016, 09:32   #9
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pirate Re: Osmosis prevention for oldboat

True.. osmosis is the result of mass production and 'modern' technology..
IE; Cheaply built & over priced.. trouble is there's so few.. if any yards that turn out the quality lay-ups of back then folk think osmosis is a norm..
Automation is expensive.. and I've yet to see prices drop on anything once initial costs are recovered..
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Old 07-03-2016, 09:46   #10
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Re: Osmosis prevention for oldboat

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Originally Posted by Ribbit View Post
No osmosis, and might not even get any. But prevention is better than cure, right?
Odd one out here - but I wouldn't do a thing to prevent something that is unlikely to happen from happening, especially because it's not a big deal if it does happen.

I mean, you take care of your boats, right? You'd notice blisters before she'd delaminate right in front of you

I'm aware we are supposed to fear the Disaster that is Osmosis and spent lots of money on products to prevent it, and panic & peel when we see one blister.

The fear of osmosis is something I'll never understand, to be honest, but the marketing is working cos people are spending a LOT of money on prevention, even when there is no reason to think the boat will have any issues at all ...
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Old 07-03-2016, 10:05   #11
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Re: Osmosis prevention for oldboat

The osmosis issue began just after the Arab oil embargo when resins became very expensive. There was a lower quality of resin that began use at this time. The older resins were more like the vnyilester resins the higher quality builders now use for the outer layers.
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Old 07-03-2016, 10:46   #12
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Re: Osmosis prevention for oldboat

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Much of the FG resins used in the early 70s have exhibited little or no inclination to allow for water absorption. If it ain't broke why in the world do you want to fix it? There must be other great projects on your boat on which to throw your time and money.
When going from short season cold water environments, to warm water long season environments, some of these early boats do get afflicted.

If I am going to prepare the hull for CopperCoat anyway, by default it will also then be prepared for a barrier coat in the process.

It seems too good an opportunity to miss, and an ounce of prevention is better than a pound of cure.

I am hoping this boat will see me out.

Plus I've been reading this:

"We may as well begin the discussion of poor workmanship with the statement that the boat never should have been made of GRP in the first place because all polyesters eventually decompose in the presence of water. The short reason for that is that an ester is made by reacting two things together and eliminating water as a reaction byproduct, or waste. When put back in the presence of water, the reaction goes the other way, although it may do that very slowly. This will be discussed in MUCH MORE detail later.

The hull should have been made of some epoxy resin system, as they are inherently stable against reversion from excess water exposure. Why, then, are polyesters used? The simple answer is cost. Epoxy resins cost $1.50-$2.00 (U. S.)/pound, whereas polyesters cost fifty to seventy-five cents per pound, roughly a third the cost.

So, there we are. The boats will be, are and have been made of polyester resin for all except the most wealthy, and that is the beginning of poor workmanship.

Why, exactly is it that polyesters are not stable in the presence of water, and why do GRP hulls have all those problems?

The word "polyester" means "many esters" and an ester is a chemist's name for something made by reacting an organic acid with an organic base and eliminating the resulting water. When you put esters in water the reaction goes backwards, with ester-plus-water disassociating back into acid-plus-base.

It's just chemistry. It's the way things work. "

http://www.smithandcompany.org/GRP/GRP.html
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Old 07-03-2016, 10:57   #13
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Re: Osmosis prevention for oldboat

I replaced the Interlux 2000 Barrier with Sherwan Williams. The Interlux was applied by the builder and failed on the entire hull in less than 8 years. It actually resulted in increasing the hull blistering because it tended to trap moisture. Word at the yards around here is that it generally fails in about 5 years. It's been 9 years since the SW was applied and not a single sign of moisture in the hull. The SW product identifiers on the 1 gallon Part A & B cans are: Epoxy-Polyamide, Type III, Formula 150, N1V00350, 640182580 (Part A), 640182168 (Part B). It also has a mil. # Mil-DTL-24441D/20A & 20B Paint. You can get it at your local SW store or they can order it for you. Just make sure that the hull is dry and any blisters have been rectified. Hope this helps.
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Old 07-03-2016, 11:13   #14
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Re: Osmosis prevention for oldboat

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Originally Posted by Lizzy Belle View Post
Odd one out here - but I wouldn't do a thing to prevent something that is unlikely to happen from happening, especially because it's not a big deal if it does happen.

I mean, you take care of your boats, right? You'd notice blisters before she'd delaminate right in front of you

I'm aware we are supposed to fear the Disaster that is Osmosis and spent lots of money on products to prevent it, and panic & peel when we see one blister.

The fear of osmosis is something I'll never understand, to be honest, but the marketing is working cos people are spending a LOT of money on prevention, even when there is no reason to think the boat will have any issues at all ...
Only partly correct.

I have a 1988 Trawler that lived all it's life in warm water with few haulouts for short periods.

With no blister problem indicated by the pre-purchase surveyor...or even delamination from hydrolyzed resin...when I went to barrier coat the boat (ground off paint and gelcoat) I discovered the entire matt layer on the bottom of the boat could be pulled off almost by hand and had a 6 foot by 6 foot area of delamination 1/2 inch deep in a 1 inch thick hull. It may have been deeper but I stopped knowing what I was going to put back would be better than before.

Common issue? No but it is there more of this than people know...several fairly in depth white papers discuss this issue and bottom line is until you look for the problem...it is well hidden from most buyers and even surveyors.
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Old 07-03-2016, 11:21   #15
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Re: Osmosis prevention for oldboat

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Originally Posted by Scrimshaw4 View Post
I replaced the Interlux 2000 Barrier with Sherwan Williams. The Interlux was applied by the builder and failed on the entire hull in less than 8 years. It actually resulted in increasing the hull blistering because it tended to trap moisture. Word at the yards around here is that it generally fails in about 5 years. It's been 9 years since the SW was applied and not a single sign of moisture in the hull. The SW product identifiers on the 1 gallon Part A & B cans are: Epoxy-Polyamide, Type III, Formula 150, N1V00350, 640182580 (Part A), 640182168 (Part B). It also has a mil. # Mil-DTL-24441D/20A & 20B Paint. You can get it at your local SW store or they can order it for you. Just make sure that the hull is dry and any blisters have been rectified. Hope this helps.
Utter BS....

While I think Sherman Williams stuff is fine (probably made by the same company that makes a lot of Interlux stuff)...so is Interlux 2000.

Interlux 2000 doesn't "fail" on any schedule. I have applied it to several boats from 5-15 years and all are still perfect. And know probably dozens more with varying ages...all still perfect.

Sounds like it was applied incorrectly in the one case and of course it might fail. If you usually have bilge water in a boat, and don't barrier coat the bilge...any barrier coat can accelerate blistering.
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