Gelshield/moisture

[Memphis_Chung]

I have seen a yacht for sale that has recently had 4 coats of gelshield applied. A survey has shown that there is some moisture trapped behind the gelshield.

My question is: 1. How concerned should I be?

thanks


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[jerryat]

Hi M-C!

I would be very concerned personally, unless I could talk to the surveyor (if there was one) who looked at the boat prior to the present Gelshield application. Once moisture is trapped, it can only be the basis for future problems unless you are very lucky.

There's a hell of a lot of rubbish talked about osmosis, and many people (myself in the past) have been panicked into doing work that was at best premature, and at worst unnecessary. One factor that is essential as far as I'm concerned, is that the substrate must be properly dryed out. All the paint manufacturers cite this as a basic requirement.

Of course, your surveyor will be able to advise you far better than I, and you don't say what readings your proposed hull has shown, but I think in your place, and if you want the boat, I would allow in your price negotiations for removing the existing Gelshield, drying the hull and re-doing the work properly. That doesn't necessarily mean you would have to do the work for a year or so (or even longer) but you will need to do it.

The alternative is to get the present owner to do the work to a proper standard.

I do not suggest that is the case here, but the application of a couple of coats of epoxy to cover up a potential problem prior to selling is not unknown.

Sorry I can't be more cheerful about it, but hope it all works out ok in the end.

Good sailing!

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[Rigger]

How do you know there is moisture beneath the gelshield.As I understand it,one of the problems with gelshield is that unless yoy remove it you dont know what is going on underneath as moisture meters dont get an accurate reading.If the hull was not prepared /dried out properly before application then moisture could have been sealed within.I had a similar problem on a Westerly 12 years ago.When I bought her the surveyor recommended removing the gelshield so the hull could be properly assessed.I didnt do this and some 8 years later she suddenly developed widespread blisters (through the gelshield) and needed full osmosis treatment.(whether one actually needs to worry about osmotic blisters is of course a whole new debate!!) I think you just have to consider this as one factor in buying a second hand GRP yacht. If she is otherwise tidy and cared for and the price is reasonable,I would not be too put off.Good luck.

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[Memphis_Chung]

Thanks - I think you have answered question. The gelshield was applied in the last 2 weeks which immediately set alarm bells ringing with the surveyor. I understand the reasoning for doing it - successive years of antifoul had been sandblasted off and the gelcoat was slightly pitted as a result (there is a survey from last year giving the hull a clean bill of health) The difficulty (particularly as this will be my first boat) is making the judgement on what you can live with and what you cant. people definately seem to have the view that all boats of circa 20 years of age will have some moisture related problem in the hull and that I should be pragmatic about it - but with moisture locked in behind new gelshield, it would seem to be an unecessary risk (there are other boats in the sea!).

Thanks again.

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[Dave1258]

Moisture retention is tested with a 'Tramex Skipper' or similar electronic device,
The scale of measurement is 0-100 which is a relative scale and does not express a percentage of moisture.
Readings of up to 60 are considered acceptable. a high moisture content is as you say expected on older GRP boats, but may not neccessarily mean a structural problem.
Is the boat trailered, or on moorings, a trailered craft would show low readings'
Regards Dave /forums/images/icons/smile.gif

<hr width=100% size=1> A man should have two things in life, a boat and a wife willing to let him have one.

 

[Memphis_Chung]

It has been out of the water since last season. I am still waiting for the full surveyors report to get the precise readings.

<hr width=100% size=1>Quit the job, sell the house, sell the kids, sell your wife, go sailing.......

 

[Birdseye]

For what is is worth I had my last boat treated for osmosis. Before they applied the coating, I personally measured the moisture readings with a sovereign meter at 3 to 5. After coating with West epoxy, which includes something in the resin to aid waterproofing, the readings went up to 8 to 10. This was before the boat was put in the water! West couldnt explain and neither can I. Clearly the resin cannot have introduced moisture so I can only speculate that the readings were wrong, some fault in the meter, or the meter (which doesnt directly measure moisture at all) was being deceived by something in the coating.


Whats more, bulkheads where the wood is up against the hull will give higher readings since wood holds water. So will any dampness on the inner hull surface - for example where sea water came in as someone freed off a stuck impellor.

Your surveyor might be brilliant. Some of the ones I have seen have no scientific background and no clue how a measuring instrument should be used.

Personally, even if the moisture reading is correct, I dont see how a boat with an epoxy coat can be any worse off than it was before it was sandblasted. Certaily its better than my situation where the muppet who previously owned my boat had it blasted then coated with primer (into all the little dimples left by blasting) and then anti fouled.

So in my view, decide on the basis of the whole package

P S The West system proved to be a good product.

 

[Avocet]

If it's been epoxied so recently could the epoxy itself be giving a false reading? I don't know a great deal about this but I wouldn't be surprised if the last of the solvent evaporating out of the epoxy was responsible for the readings! I'd be inclined to get a second opinion and maybe talk to the surveyor whilst he's doing it if possible. For what it's worth, I put a few more coats of epoxy on ours a few years ago and asked the local boat yard to stick their moisture meter in a few places before I did so. they came back with an average reading of 12 and said that was fine for applying the epoxy. (mind you, they were selling me the epoxy!)

 

[Guest]

a) Readings through Epoxy - especially 4 layers of it are unreliable and will not show reference to prior to epoxy coating.
b) Trapping in moisture is worse than leaving the hull free to dry. (Do not confuse with lifting boat over winter and drying out - which doesn't actually happen ...)
c) The epoxy coating could eventually prove to have been a wasteful exercise.

I would negotiate a price reduction based on probability of having to strip and do the job properly later ... And of course you have the option to leave it and see what happens over the next years ...

It is not often mentioned - but the meter used also is important .... Soveriegns - which are recc'd - are certanily NOT what they are cracked up to be and do not actually show DEEP moisture ... but the Tramex is far more sensitive, a better machine all round etc....... (Now I will be the target of all those who have invested in Soveriegns !!)