Buy used sailboat that had osmosis treatment?

[Ryan_cruiser]

Hey fellow mates,

I am interested in purchasing a used 2003 Jeanneau Sun Odyssey 49.

The advertisement mentions that the boat has undergone a professional osmosis treatment and includes a warranty for the work.

Should I refrain from buying immediately ?

Best
Ryan

[dlj]

Why? The boat was fixed...

dj

[boatman61]

If its been treated it should be fine.. Osmosis never sunk a boat as far as I know..

[boatpoker]

The subject hull is quite thin. If there was any hydrolysis ... I'd pass.

I dislike the word "osmosis" because it gives no indication of the extent of the issue.

If the issue was limited to a rash of blisters in the gelcoat, repair is is quite simple.

If the blisters extend into the skinout mat, repair is more difficult and there is a slight increase in failure rate of the repair.

If hydrolysis occurred with resultant delamination of the structural laminate a lasting repair is very difficult and failure over time is not uncommon if the job was not done to a very high standard.

[Ryan_cruiser]

I thought that once osmosis there is risk it comes back like a disease…
Apparently, I am wrong?

[boatman61]

If it was peeled.. the gel coat back to the glass it is then usually coated with epoxy which is waterproof.
It forms a strong and durable barrier against water, making it an excellent choice for sealing surfaces and protecting them from moisture-related issues.

[Bowdrie]

In a nutshell, without getting to deep, osmosis is a process of equalizing concentrations on both sides of a semi-permeable membrane.
Without resin, it's obvious that fiberglass products, mat/roving/cloth have basically zero resistance to the passage of water.
We add resin to make a relatively impermeable hull, and the different types of resins have different degrees of permeability, epoxy being quite low.
Gelcoat is actually pretty good at keeping the outside water from getting to the fiberglass/resin matrix, but it does nothing to keep the inside water from trying, (by osmotic pressure,) to penetrate the matrix.
The exterior gelcoat surface is thin and weak and has a lower bond strength to the matrix than the individual matrix particles do to themselves.
Interior heat speeds up the process, the heat in the warm wet bilge wants to transfer to the cold outside water, this accelerates the transfer of molecules thru the fiberglass matrix until it reached the more impermeable gelcoat.
Result, the gelcoat bond breaks, and a blister of water forms.
So, we grind out all the blisters or do a gelcoat peel and add lots of low permeability/high bond strength epoxies.
Much of this phenomenon can be prevented by making sure that the whole inside of the hull is well coated with a high solids/low permeability coating.
You don't want raw fiberglass under the waterline, and a simple sprayed on thin coat of paint, while better than nothing, cannot match a good thick coat of a two-part product.
I worked on a 34' sailboat that was hauled into a heated building, the gelcoat was peeled, tarps were taped around the waterline and small heaters set-up under the tarps.
The boat sat there like that for one whole year.
When it left the building and went over the scales it was a few hundred pounds lighter, all in the weight of the water that came out of the hull.

[Tin Tin]

Ask to see a copy of the invoice to see exactly what was done when and by whom and what materials were used.

[Pete7]

Originally Posted by Bowdrie

Much of this phenomenon can be prevented by making sure that the whole inside of the hull is well coated with a high solids/low permeability coating.

Plus keeping the bilges dry perhaps?

Pete

[Fore and Aft]

Tin Tin has the right answer. Tell us what is on the invoice and then we can offer a proper opinion.
With any luck the hulls been peeled, some double bias fiberglass cloth has been laminated on the hull and then faired. Hopefully it's all been done in vinylester or epoxy resin. Fingers crossed there's also been a surveyor involved and he's taken moisture readings as well so you know there's been some effort to dry the hull. I have personally seen a hull peeled then glassed before drying. Then a few years later the fiberglass could be pulled of the hull.
Cheers

[barnakiel]

I think quite the opposite.


If the job has been done well, and it nearly always has been, then the hull is better than original.


Some owners do the osmosis barrier long before there are any bubbles.


I would actually prefer a boat with osmosis job already done. (vs. a same 2004 gelcoated hull).



b.

[Bowdrie]

There were some earlier causes of blistering, but they predated the boat the OP was referring to and they didn't apply to all boats, but the underlying causes were similar and overlapped each other in time frame.
In no particular order:
1, The early fire-retardant resins took much more labor to get them to wet-out the mat. As a result, wet-out and lay-up procedures had to be changed, this led to some boats having hulls that were prone to blistering.
2, The "gas crunch" of the early '70s about doubled the price of resin/acetone seemingly overnight, so some companies "cut corners" so to speak, and produced boats that those in the industry would call a "dry layup".
That also showed-up in many of the Tiawan boats of that era.
3, The fiberglass mat of that time used a "binder" that needed a goodly amount of Styrene in the resin to dissolve it and allow the resin to fully wet-out the strands.
When the EPA reduced the amount of allowed Styrene it caused problems until the fiberglass companies got the binders changed.
It was a relatively short-lived problem, but a lot of boats were produced during that time.
All of these problems kind of "ganged up" together over a few years right when the U.S. boatbuilding industry was going full-bore, when a score of SoCal companies were cranking out boats on a non-stop basis.
Anyway, the bottom line was that there were lay-ups that were more easily "attacked" by osmotic blistering.
Ah the glory days,,,,,.

[t-3400]

I’d ask what the treatment was and have your surveyor evaluat for you.

The treatment could be sand, fill and epoxy or vinyl ester coat. It could also be remove, dry, fair, layup mat with contested, barrier coat.

Both or similar treatments might have been effective. If yes, it is one potentially dignificsnt thing not to have to worry about. Intead, if blisters were popped, sanded, filled and faired, the treatment may not have addressed the issue. Find out more and use a surveyor.

[Pat Ross]

Originally Posted by boatpoker

The subject hull is quite thin. If there was any hydrolysis ... I'd pass.

[Nicholson58]

Originally Posted by Ryan_cruiser

Hey fellow mates,

I am interested in purchasing a used 2003 Jeanneau Sun Odyssey 49.

The advertisement mentions that the boat has undergone a professional osmosis treatment and includes a warranty for the work.

Should I refrain from buying immediately ?

Best
Ryan

We treated ours after repairing thousands of gel coat blisters and several larger delamination failures 16 years ago. The treatment I feel ALL hulls should get is Interprotect 2000E water barrier or equivalent. We applied 6 coats and have never had a single blister of any kind or size since.

Ask for details about what was done and why. Ask also what materials were used. If there was hull damage you prefer that epoxy was used rather than polyester or vinyl ester.

A good and proper repair should be fine. Water barrier is important. Get the boat surveyed and ask that your questions are addressed.