high moisture after osmosis treatment

[Vire]

I recently bought a GB42 classic 2002.The experienced expert did not notice that the boat had an osmosis treatment several years ago in the pre purchase survey but measured high moisture values in the underwater hull (40-80 scale parts, Skipper moisture meter, but no documentation) and he mentioned to me that this is normal for a GB of this age. After the sale I took a second expert who measured and documented higher values(equal or above 60 scale parts everywhere) after having the boat longer on ground. Do I have to make me worries about premature osmosis after already done osmosis treatment?

Thanks for replying

Sabina

 

[Comodave]

Welcome aboard. What type of treatment did the boat have!

 

[RT Firefly]

Greetings,
Welcome aboard. If you're happy with the boat, don't worry about it. Osmosis that leads to blistering never sank a boat.

 

[Cigatoo]

Welcome. Not sure what an osmosis treatment is? Maybe the hull has been barrier coated? Is the moisture in just one location? The boat must be on the hard now. Have a look for blisters. I would be very surprised if you found one on that hull, barrier coated or not. That’s a well laid up hull. A moisture meter cab be dangerous in the wrong hands. I wouldn’t give it a second thought unless someone pointed out something obvious such as a blister or evidence of prior damage. And even a blister is no reason for concern. Grind it out fill with epoxy, and paint.

 

[psneeld]

Search for info on hydrolysis of laminates.

Blisters may be no worries for many, but whether present or not, and whether considered cosmetic or not, hydrolysis isn't and has sidelined a few boats (admittedly very few) because they were deemed unseaworthy or uninsurable. Maybe not an issue for you but could be an issue if you ever try to sell (and need/want money).

Poor repair solutions and their execution can cause bigger issues than they solve. I personally have experienced after a major bottom job on my last boat and read/discussed with experts/yards that mostly agree just letting a boat with it's gel coat on and deep water issues can not be dried out just by sitting even for years sometimes.

Be wary of "internet wisdom" on this one. I used to be one of those that thought "blisters, no big deal" till I bought a boat with a real problem that many "thought" the boats bottom blisters were no big deal.

You may or may not have a significant issue... you never know if you just brus it off.

Look through this thread to see my experiences.

https://www.trawlerforum.com/forums/s32/blisters-64311-2.html

 

[sunchaser]

Sabina
Just me, but I'd get to the bottom of the concern, for knowledge and peace of mind. As Cigatoo mentioned, moisture meters are problematic themselves. High readings can be backed up by simple percussion testing. A diagram showing areas of concern should have been provided. If concerns remain a few core samples will show nature of problem.

The yard that did the osmosis treatment could offer up what was done and why. Did the previous owner sign a full disclosure document listing known or previous defects and remedial action? How about previous insurance claims?

A decade old GB 42 is not a beater boat, unless it suffered hurricane damage or was a sinker. Thus answers are required if your worries prove warranted. Are the lower hull interior locations bone dry? If not why not? A moisture meter can pick up sitting internal water from shaft or rudder post leakage.

On your nice vessel my recommendation is don't ignore or assume anything. Find out the real story and pursue remedial actions if issues found.

 

[Pete Meisinger]

I have never heard of an "Osmosis treatment".

It sounds to me like the boat did not have the required three or more coats of a barrier paint under the VC 17. Not really a big deal but next time you need bottom paint you should consider taking it down to bare glass.

I did half of my boat by hand, it was awful. I had the other half soda blasted, it was basically painless and not very expensive.

pete

 

[sunchaser]

I have never heard of an "Osmosis treatment".

It sounds to me like the boat did not have the required three or more coats of a barrier paint under the VC 17. Not really a big deal but next time you need bottom paint you should consider taking it down to bare glass.

I did half of my boat by hand, it was awful. I had the other half soda blasted, it was basically painless and not very expensive.

pete

Pete
If one Googles "marine osmosis treatment" dozens of replies and sites pop up. That is why it would be good to hear from the OP what aftermarket, if any, "osmosis treatment" was utilized. Also, there should be some GB factory guys that could assist the OP on what the factory did a decade ago on this specific vessel for barrier coating and layup protocols.

 

[SteveK]

I recently bought a GB42 classic 2002.The experienced expert did not notice that the boat had an osmosis treatment several years ago in the pre purchase survey but measured high moisture values in the underwater hull (40-80 scale parts, Skipper moisture meter, but no documentation) and he mentioned to me that this is normal for a GB of this age. After the sale I took a second expert who measured and documented higher values(equal or above 60 scale parts everywhere) after having the boat longer on ground. Do I have to make me worries about premature osmosis after already done osmosis treatment?

Thanks for replying

Sabina

A search on the net for osmosis treatment, it involves the stripping of all gel coat followed by drying the hull, a barrier coat and bottom paint. Once completed you cannot see that it was done unless you were told. So not expecting an expert to see it was done.

I find my moisture meter very handy in tracing leaks as long as I can see a difference in reading. I have had a high reading on apparently dry materials, don't know why. So I look for differences in reading numbers by establishing a base reading in an area of concern. Then a higher reading suggests the real wet area.
A boat sitting in water probably has a film of wetness which the meter picks up on. Just an opinion.

 

[Vire]

I'm very pleased with the subtle and professional answers in this round. Overall, bad at all no documentation of osmosis treatment available. According to the 2nd investigation, a 7-layer epoxy resin layer with a layer density of 400-500u was carried out.
My fear is that a new osmosis is to be expected sooner rather than later with this high moisture.

Best regards,

Sabina

 

[psneeld]

If the hull was not properly dried or there are very wet, unprotected glass bilges than the best barrier coat system has issues.

My boat was hideous with blisters and delamination from hydrolysis.

After grinding off the hull to no moisture (in places over a 1/2 inch), and a single layer of 6oz cloth and standard Interprotect 2000 system kept my boat blister free for 12 years (as long as I owned it and hopefully the next owner will have the same kind of longevity.