Osmosis: Don't Worry, Be Happy !

[bludden]

What about epoxy barrier coats?...If they slow migration to almost nothing why aren't they standard use?...The incremental cost to initial purchase price must be tiny?...Even switching to epoxy resins for laminating hulls can't be as much cost as doing one properly executed peel?...Geoff Cruse at Windspeed Cats in Australia did this in the eighties...I wonder if it was 100% successful at avoiding the pox....Cheers

[Geminidawn]

Originally Posted by bludden

What about epoxy barrier coats?...If they slow migration to almost nothing why aren't they standard use?...The incremental cost to initial purchase price must be tiny?...Even switching to epoxy resins for laminating hulls can't be as much cost as doing one properly executed peel?...Geoff Cruse at Windspeed Cats in Australia did this in the eighties...I wonder if it was 100% successful at avoiding the pox....Cheers

With all the companies I have ever work with this was always an optional extra at the point of purchase, rather than a standard practice.

[Dockhead]

Sorry for the thread drift, but does letting the hull dry out on the hard every year for a couple of months help prevent osmosis, or not? I have heard conflicting things.

[Geminidawn]

Originally Posted by Dockhead

Sorry for the thread drift, but does letting the hull dry out on the hard every year for a couple of months help prevent osmosis, or not? I have heard conflicting things.

Well it wouldn't help prevent it but it will help slow the whole process down, as long as the bilges are kept dry, the less time the boat spends in the water the slower the migration.
Another area of concern if on the hard is the trailer or cradle pads. I'm currently treating a boat for osmosis which has never even been in the water. The carpeted cradle pads absorbed rainwater which found it's way through the hull after being laid up as an unfinished project for a number of years.
The drier you keep your boat the better.

[Weyalan]

I am by no means an expert, so I might well be wrong, but I was under the impression that osmosis was particularly a problem with grp boats constructed using polyester resin, and was far less common if vinylester resin was used and almost unheard of in epoxy resin boats.

[Joli]

I would be real curious to see the layup schedule.

The warranty is also void if you sand the bottom? Wow.

[Geminidawn]

Originally Posted by Weyalan

I am by no means an expert, so I might well be wrong, but I was under the impression that osmosis was particularly a problem with grp boats constructed using polyester resin, and was far less common if vinylester resin was used and almost unheard of in epoxy resin boats.

You are pretty much spot on, both vinylester and epoxy boats are a lot more immune, however they are costly and a lot more tempermental to work with, hence polyester is the main resin for production boats.

[Dragon Lady]

I recently had a 30 ft power boat built using a chopper gun lay up solid GRP no foam.
The builder used vinyl easter resin for the first coat after the gel coat.The reason he gave was that it was too expensive to do the whole boat in Vinyl easter but the one coat would be enough to keep out the osmosis. Hopfully he's right but I have a 5 year warranty and he's been in buisness a long time so I'm quite confident it will be OK.

[bludden]

I'm sure FP have analysed to death the reasons the Lavezzi layup was such a problem. I'd love to know what their conclusions were just to know how isolated the problem is likely to be in their model range. I'm leaning more and more to a Bahia and would like to get as late a model as possible but if I find out Bahias are poxing I don't know what I'll do. I had a preliminary look at the Lagoons but I think they use (or at least used to use) a lot of balsa core; another long term maintenance nightmare. Does anyone know if Fountaine Pajot use composite or plywood bulkheads?...Cheers

[Weyalan]

With the sort of dollar figures that are being thrown around here, you might consider buying a set of plans and having a small yard or builder build the thing for you, allowing you to specify whatever resin type, layup, layout, etc that you want...

[osirissail]

Originally Posted by Dockhead

Sorry for the thread drift, but does letting the hull dry out on the hard every year for a couple of months help prevent osmosis, or not? I have heard conflicting things.

That was the big unknown years ago when osmotic blisters first appeared. Why did boats in New English take twice as long for the blisters to show as compared to boats in the south like Florida. Finally it was determined that total time in the water (like an hourmeter) needs to accumulate - "roughly" about ten years for the problem to become visible. If your boat is only in the water half a year you can expect double the calendar years.

- - Epoxy barrier coats are very very good at preventing water migration to the FRG. But there are two problems with epoxy - it is very expensive compared to polyester resin; and after it sets virtually nothing will stick to it. So for mass production of FRG hulls the better company uses Vinylester resin for the first few layers of laminate and the "price-point" company continue on with polyester resins and a barrier coat when the bottom paint is applied. Power washing can dislodge or remove that barrier coat which is why I suspect they void the warranty if it is used.

[Joli]

Why are you afraid of balsa? We've owned many balsa boats and if they have a problem they can easily be repaired. I think they are easier to repair then the foam boats actually.

Originally Posted by bludden

I'm sure FP have analysed to death the reasons the Lavezzi layup was such a problem. I'd love to know what their conclusions were just to know how isolated the problem is likely to be in their model range. I'm leaning more and more to a Bahia and would like to get as late a model as possible but if I find out Bahias are poxing I don't know what I'll do. I had a preliminary look at the Lagoons but I think they use (or at least used to use) a lot of balsa core; another long term maintenance nightmare. Does anyone know if Fountaine Pajot use composite or plywood bulkheads?...Cheers

[bludden]

Originally Posted by Joli

Why are you afraid of balsa? We've owned many balsa boats and if they have a problem they can easily be repaired. I think they are easier to repair then the foam boats actually.

In my (so far) one year search for the perfect yacht (which is rapidly becoming a search for a yacht I won't slit my wrists over owning!) I've looked at a wide range of production and one off cats, seeing many levels of skill in building and maintenance. Occasionally I came upon a balsa cored boat with a soft spot on the decks and wondered how you'd repair the damage without cutting back one side or the other and routing out the rotten core...It just seemed to me that if a foam core had delaminated there would be more chance drying it out and injecting resin into the damaged area without all that destruction. Same thing with plywood bulkheads (or plywood transoms on power boats for that matter)...I inspected a cat with rot in the plywood bulkhead under the mast; to properly repair it you would have had to gut much of the fitout of the boat...It's a personal choice; I'm sure you've had good service from your balsa boats but I'll buy plastic...

[Geminiguy]

Originally Posted by bludden

I'm getting ready to spend perhaps US$300,000 on a used catamaran of 5 to 10 years age and some of them have already been peeled to their core because of osmosis ??!!...What's going on here? Temperature, humidity and dust controlled factories turning out hulls that pox in just a few years !! My personal favorite is a Fountaine Pajot Lavezzi 2005 model the broker told was in "new condition" which spent 8 months per year on the hard; sounded perfect but when I eventually asked whether it had had any repairs I was told it had already required a full peel !! I love the FP designs, reasonable performance and accommodation, exactly what I want, but why do I have to be worried about structural integrity...motors, rig, sails, nav gear etc. can all be replaced or upgraded but the hulls and bulkheads, the essential structure can't be. We seem to know more and more about osmosis in fibreglass boats and doing less and less about it. Indeed many articles I read on the internet tell me all fibreglass hulls will pox and I should just get used to it !!...You spend $30,000 on a Toyota and if they stuff up they recall your vehicle and repair it at their expense...You spend $300,000 on a 5 year old yacht and take your chances !!

Hi Bludden, I just came across this link which you might like to check out: Fountaine-Pajot Lavezzi court case - osmosis

Also, I believe osmosis (hydrolysis) is a problem only associated with polyester resins as opposed to vinylester or epoxy resins. I could be wrong but it may be woth checking out.
Cheers.

[miami privilege]

Hey its just the way it is when it comes to Resin. A few of the posts were accurate in stating the glycol, a hydrophobic action creates blisters. This is true on all fiberglass hulls. Its the extent that this happens and how noticeable it becomes. I wouldnt get overly anxious about this matter. Water inside the hull and outside will create this affect. My older boat sat in water for 20 years before it needed to be repaired. Fiberglass technology has been around for quite some time. If your around boat yards enough you see it every where on older boats. It a little like rust on metal the older it is the more you find
In my case I needed the antifouling done so I bit the bullet and stripped the gel coat and replaced it with 15 gals of epoxy. I didnt have it peeled but in retrospect would have gladly paid the 2500 in the states to have this done. Truely its not as big of a deal as many make it out to be. After 10 years of having fun on your new cat, have it hauled peeled and be happy. My waterline jumped up 4 inches after I finished mine. Its about 2-3 days for peel then roll on epoxy, hot coat is the best. If you want more details private message me.