Is Osmosis Prevention a Good Idea?

[sailorboy1]

Originally Posted by neilpride

Don, its a 2002 sun odyssey, barrier coats are ok in new or old boats , and yes lots of folks strip the old antifouling to barrier coat and renew the antifouling, boatyards are full of boats striped of old antifoulings...

I didn't say there was anything wrong with a barrier coat, I bet that Sun Odyssey came with 1 already.

And in 6 years in the same winter storage yard with lots of boats I have never seen anyone strip thier hull just to barrier coat. Even for the old boats because they all did this years ago.

[neilpride]

Well , to barrier coat a hull you need to get rid off antifouling anyway, barrier coat epoxy primer over antifouling is a no no, maybe you dont see anyone doing that, but trust me is a regular job in many boatyards, and the sun odyssey come from factory with just gelcoat , no fancy barrier coats, unless we talk about some exotic hull aka vinilester resin, CF, or epoxy , gelcoat alone is a poor waterproof layer against water intrusion..

[Robin3]

Originally Posted by Don L

To me this falls into the "don't fix what isn't broken" world. You barrier coat IF you strip the hull paint for something else, but you don't strip the hull just to barrier coat (on a modern boat).

We have just had all the bottom paint removed (much had worn off anyway) from our new to us Beneteau Oceanis 36CC and we had 4 coats of interprotect 2000 Barrier paint applied then followed by two coats + of new MICRON 66 antifoul paint The interprotect is there a) as a primer to aid adhesion to the bare hull and b) for some protection from water ingress as well. On our last boat back then in the UK, a 1988 Jeanneau Sun Legende, it came to us at 12 years old with 2 coats only of international barrier paint and a thin remaining level of antifoul, so we asked International Paints (Interlux) should we remove the remaining antifoul paint and add more barrier coats and they said, the paint removal would need to be complete and would be much as work/cost as for doing a full blister repair, so just leave it and see, and only if a problem arises later do the full job. WE did just that and the boat was sold ten years later with no need to do anything except bank the cheque.

IMO Be wary of bein panicked into excessive work/cost especially by those with a potential commercial interest in doing or supervising the work.

[psneeld]

I personally know dozens of boats that have been sand/soda/dry ice blasted to get barrier coated and switch anti-fouling paint. That's at just one yard...I have personally done 3.

[Factor]

What resin was it built with? If Poly then may be worth at least a barrier coat, if Vinyl then leave it alone.

[Idle]

Thanks to all!
Up to my knowledge the sister boats off 2002 don't have the problem of osmosis.
Second specific message I got is whether the boat has a vinylester layer
or similar.
I will check it with Jeanneau sending a message with my hull number.
If I get a satisfying answer I will post it also.
Idle

[sailorboy1]

Originally Posted by neilpride

Well , to barrier coat a hull you need to get rid off antifouling anyway, barrier coat epoxy primer over antifouling is a no no, maybe you dont see anyone doing that, but trust me is a regular job in many boatyards, and the sun odyssey come from factory with just gelcoat , no fancy barrier coats, unless we talk about some exotic hull aka vinilester resin, CF, or epoxy , gelcoat alone is a poor waterproof layer against water intrusion..

I think you need to read what I wrote and not what you wanted it to say so you could attack.

[neilpride]

Old jeaneaus got a hull feature called Kevlar energized! its basically a layer of kevlar in the bow area , not sure if your boat is built like that, 2002? no idea,, but could be nice if you ask this to...

[Robin3]

Originally Posted by neilpride

Old jeaneaus got a hull feature called Kevlar energized! its basically a layer of kevlar in the bow area , not sure if your boat is built like that, 2002? no idea,, but could be nice if you ask this to...

Our 1988 Jeanneau Sun LEGENDE 41 and a friend's 1985/6 Sun Fizz 40 were both laid up with Kevlar reinforcing but that is for strength and stiffness not osmosis protection. some models were locally reinforced I think but I Heard they found it easie in practice r to do the entire hull than quality control workers just doing it in selected areas,

[Robin3]

Originally Posted by psneeld

I personally know dozens of boats that have been sand/soda/dry ice blasted to get barrier coated and switch anti-fouling paint. That's at just one yard...I have personally done 3.

Nobody said it cannot be done did they?? IN my case the paint company experts said don't do it because it will remove what epoxy is already there and then the whole process has to start again.

By the way the UK osmosis expert Tony Staton-Bevan says you need 80-100 microns of dry film thickness epoxy to be an effective barrier, yet most solvent based epoxies like interprotect only apply at about 50 microns per coat dry film thickness so you need 20 coats to be effective mayb the paint company experts said any more than 4-5 coats of the solvent versions risks getting solvent entrapment between layers that can cause other problems . We did one of our boats when back in the UK with a solvent free epoxy (Blakes SFE200) which goes on at around 200 microns per coat (we did 5 coats) I painted a layer each coat we did on the boat on a panel of Formica plastic and when dry measured the thickness overall each time with a digital micometer to confirm how much we had managed to put on the hull, in all one millimeter of epoxy after which we applied a single primer coat and two coats of antifoul This was purely as a preventative measure not an osmosis repair and we had a qualified surveyor oversee the whole job. Nowadays I am not so paranoid and recognizing the inadequacies of the simple slap on a solvent based barrier coat method lean more towards the if it ain't broke don't fix it school.

[psneeld]

Originally Posted by Robin3

Nobody said it cannot be done did they?? IN my case the paint company experts said don't do it because it will remove what epoxy is already there and then the whole process has to start again.

By the way the UK osmosis expert Tony Staton-Bevan says you need 80-100 microns of dry film thickness epoxy to be an effective barrier, yet most solvent based epoxies like interprotect only apply at about 50 microns per coat dry film thickness so you need 20 coats to be effective mayb the paint company experts said any more than 4-5 coats of the solvent versions risks getting solvent entrapment between layers that can cause other problems . We did one of our boats when back in the UK with a solvent free epoxy (Blakes SFE200) which goes on at around 200 microns per coat (we did 5 coats) I painted a layer each coat we did on the boat on a panel of Formica plastic and when dry measured the thickness overall each time with a digital micometer to confirm how much we had managed to put on the hull, in all one millimeter of epoxy after which we applied a single primer coat and two coats of antifoul This was purely as a preventative measure not an osmosis repair and we had a qualified surveyor oversee the whole job. Nowadays I am not so paranoid and recognizing the inadequacies of the simple slap on a solvent based barrier coat method lean more towards the if it ain't broke don't fix it school.

Funny...NONE of those boats and none of my 3 was there ANY epoxy already there prior to bottom paint removal.....

I don't disagree that the whole mess is misunderstood by many...but I can assure you it's not misunderstood by me.

And if you are referring to "coats" you need a bit more instruction because the experts and paint companies never rely on "coats" to determine the amount of material applied.

[onestepcsy37]

as a previous poster said -

"IMO Be wary of bein panicked into excessive work/cost especially by those with a potential commercial interest in doing or supervising the work."

when i hauled my 1979 csy 37 last year i decided it was time to sand off ten years of hard bottom paint and start fresh. i asked a contractor in the yard what he would charge me for a 'heavy' sanding. he said he didn't do that anymore. he only peeled and barrier coated. then he tried to convince me that the remains of barnacles i had knocked off were actually osmotic blisters. when i asked him if he'd ever scraped barnacles he decided to look elsewhere for a sucker.

i hard sanded the boat myself - not a pleasant job but nobody else would do it. then a surveyor happened to be in the yard checking the boat next to me and i had him measure the water content at many places around the hull and he found little to none. i never saw any signs of osmosis. so i put two coats of trinidad on and splashed.

the contractor, meanwhile, had found himself a mark. it's been eight months now and he's still working this guys morgan 382. i'm guessing he's over $5000 and still running the bill up.

i guess what i'm saying is, don't panic. unless you've got a boat that's known for serious osmosis - like some of the valiant 40's - just check the boat each time you haul. fix any blisters you find and move on....

[Idle]

Originally Posted by onestepcsy37

as a previous poster said -

"IMO Be wary of bein panicked into excessive work/cost especially by those with a potential commercial interest in doing or supervising the work."

when i hauled my 1979 csy 37 last year i decided it was time to sand off ten years of hard bottom paint and start fresh. i asked a contractor in the yard what he would charge me for a 'heavy' sanding. he said he didn't do that anymore. he only peeled and barrier coated. then he tried to convince me that the remains of barnacles i had knocked off were actually osmotic blisters. when i asked him if he'd ever scraped barnacles he decided to look elsewhere for a sucker.

i hard sanded the boat myself - not a pleasant job but nobody else would do it. then a surveyor happened to be in the yard checking the boat next to me and i had him measure the water content at many places around the hull and he found little to none. i never saw any signs of osmosis. so i put two coats of trinidad on and splashed.

the contractor, meanwhile, had found himself a mark. it's been eight months now and he's still working this guys morgan 382. i'm guessing he's over $5000 and still running the bill up.

i guess what i'm saying is, don't panic. unless you've got a boat that's known for serious osmosis - like some of the valiant 40's - just check the boat each time you haul. fix any blisters you find and move on....

I am confused with " bottom paint " is it the original paint or antifouling?
I am at the point of sanding all the accumulated antifouling by the years to the level of original paint/gelcoat. Several patches of antifouling has started to drop off.

[Robin3]

Originally Posted by Idle

I am confused with " bottom paint " is it the original paint or antifouling?
I am at the point of sanding all the accumulated antifouling by the years to the level of original paint/gelcoat. Several patches of antifouling has started to drop off.

Coming From the UK we call the paint paint to keep growth away 'antifoul' it is usually applied on the bare new grp from i1st launch, often with a coat of primer to promote better adhesion to the grp. in subsequent years more such antifoul paint is applied and consequently a build up of old innefective and probably now flaking paint in places stuff occurs over time, after which most people will decide to take it back to the bare hull and start again. It is at this stage owners often think of putting on a barrier coat of epoxy to help delay or prevent water ingress and later possible osmotic blistering. All good reasoning but in my opinion not worth doing unless done properly as in removing all traces of old antifoul paint and then putting on enough coats(as in dry film thickness) of a good epoxy paint to build up a thickness that will do the required job, a quick application of two thin coats is not sufficient but I have heard that idea put about here in Florida by those seeking to do somework and make a quick buck. If the hull is already wet and a moisture reading is required to properly show the extent, then it needs to be dried first before any barrier is applied as it cannot dry out through epoxy applied on top which would simply be a waste of time and expensive paint.

That is my opinion and no doubt I will (again) be told I don't know what I'm talking about, but hey it isn't my money being spent nor my boat so my opinion can be thought valid or simply ignored, who cares,?

[barnakiel]

It is interesting what you say about Kevlar.

I always somehow imagined Kevlar was added for impact resistance. I thought stiffness came from adding carbon fibres.

But sure, things are connected and why not Kevlar may have this use too.

THX for sharing.

b.