lifting out a liveabourd

[capel679]

how long should liveaboards leave their hulls in the drink ?
and if you need to "dry" her out where would you live ?




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[Anonymous]

>>how long should liveaboards leave their hulls in the drink ?<<

They say that unless you leave GRP hulls out for at least three months a year then, over time, the hull moisture content will inevitable keep rising. At some stage this might cause problems such as osmosis or delamination.

>>if you need to "dry" her out where would you live ?<<

Mixture of cheap holidays and staying with family. Some people live aboard out of the water but that's not for me.

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[ccscott49]

Mine comes out a max of one to two weeks every two years, I am working on her, so either stay aboard, if there are good washing and toilet facilities, or bed and breakfast it.

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[ChrisE]

Very difficult to dry out a liveaboard, in my experience they tend to be permanently pickled.

Seriously, I believe that if you have the hull coated in one of modern non-water permeable resins, there is no need to haul out other than for maintenance.

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[Anonymous]

>>Seriously, I believe that if you have the hull coated in one of modern non-water permeable resins, there is no need to haul out other than for maintenance.<<

One yacht I nearly bought this year was gelshielded by the manufacturer as new but had a very high moisture reading on survey. The surveyor said that's what he'd expect given that it has spent most of its life in the water as a virtual live-aboard in the Caribbean and the Med. Another well-known surveyor said much the same. Having said that, high moisture is treatable and need not be unduly expensive if carried out at the stage when the yacht needs a refit (mast down, rigging, winches off, deck, etc.).

But then maybe there are newer resins - does anyone have any suggestions that have stood the test of time?

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[PaulS]

At the risk of starting an argument...
Anecdotal evidence suggests that osmosis was not a problem during early yrs of GRP construction. That it was not until less expensive resins and "more efficient" mass production techniques were introduced that it became something other than an occasional phenomenom. So, in that respect, the answer would be for manufacturers to start using better quality resins, stop using chopped strand, and actually invest in a little research into the chemistry and physics of the raw materials used in the products they sell.
Your message seems to imply that you believe the gell coat should provide some sort of barrier. In fact gell coat IS water permeable and there is where the problem begins. That's why people are resorting to stripping of the gell coat and recoating with epoxies. Epoxies being less permeable.

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[Anonymous]

>>Anecdotal evidence suggests that osmosis was not a problem during early yrs of GRP construction. That it was not until less expensive resins and "more efficient" mass production techniques were introduced that it became something other than an occasional phenomenom.<<

The 45' TSDY that my parents had built by Beecham Marine, Tewkesbury, in 1971. She was the first GRP boat that Beechams had built and they spared no expense - the GRP was all hand-laid. My parents were live-aboards and ten years later they had bad blistering which was treated by grinding-out the blisters and epoxying. A few years later the blisters re-appeared and they had to remove the gelcoat. After that, all was fine. In those days there was controversy about the cause and best treatment.

>>Your message seems to imply that you believe the gell coat should provide some sort of barrier. In fact gell coat IS water permeable and there is where the problem begins.<<

Absolutely right. Gelcoat is permeable so if you leave your boat in the water year-round the hull moisture will rise over time. Whether this will ever cause a problem is less certain and seems to be down to luck, in part. However, if one has an eye to the resale value of the yacht, it is worth remembering that a high moisture content on survey is justification for the purchaser to back out or re-negotiate. On that subject, I suggest that if one knows that one has high moisture, that fact is best declared before survey as it will be discovered and you might get a survey failure. Word gets around when a yacht has 'failed' on survey and it can be harder to sell.

>>That's why people are resorting to stripping of the gell coat and recoating with epoxies. Epoxies being less permeable.<<

Not many people strip and epoxy purely because of hull moisture. Most people wait until there is visible evidence of the consequences of high moisture - i.e. blisters.

Once you have high moisture, if you want to reduce it you'd need to keep the boat out for a very long time - maybe years - unless you strip the gelcoat. Putting epoxy over the gelcoat of a moist hull will reduce the further ingress of water (though not stop it) but the moisture will never fall, in or out of the water.

The yacht I mentioned in my previous posting, a Bowman 40, was built in 1986 and gelshielded from new, by Bowman, the manufacturer. I saw the original Bowman invoice and my surveyor showed me the gelshield layer when he made his survey patches, so there is no doubt about this. I don't know exactly what proportion of the time she had been in the water but I suspect most of the time since that would be typical of that sort of user.

According to my surveyor, the epoxy overcoat, 'gelshield' is not completely impervious so even if you gelshield a dry hull the hull moisture will rise if you leave the boat in the water 12/12. Whether that will ever cause a 'problem' is uncertain but it might reduce the value of the yacht on resale, or make her hard to sell. Having said that, we plan to stay in most of the time and I have budgeted on rectifying any high moisture when we come to sell.

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[ChrisE]

At the risk of continuing this beyond what it is worth. It was the early boats that had severe osmosis, attributed to bad layup techniques such as not expelling all of the air between the layers of matt and attempting to cure the resins in too high a moisture content atmosphere. Early American GRP hulls had voids that led to a seive like result. That said, the anecdotal evidence is that no boat has ever sunk through osmosis. Modern phenolthalic (sp?) resins are water impermeable, I believe.

Osmosis was a big deal in the early 1990s when we bought our boat and it had a high moisture content (wicking) but we were advised that this a non-strucutral weakness. We eventually had the gel coat removed and replaced with a modern resin four years ago, five years after the boat had successfully completed a 15000 mile transat and had been all over the place before that. The point I'm making is that whilst there may be moisture in the hull does it matter (other than when you sell the boat, perhaps)

I'm sure there are some surveyors/boat builders on this forum who know better but my own view is that if you buy a modern boat laid up in a factory in controlled techniques then have the hull covered in said modern resins then you have the best of all worlds. When looking at older boats I'd be happy to buy a high moisture content hull provided that it wasn't covered in large blisters that are indicative of severe osmosis.

If you really want to dry a boat out you need to take it out of the water ideally in somewhere warm like the Med or Caribbean, pell off the old gell and leave it to air cure for 3-6 months. In the UK this is acheived by putting the boat under cover and applying heat lamps all round but this costs a load more and can give variable results.

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[PaulS]

Coincidentaly, or not, the early 70's seems to be the time when blistering reared it's ugly head in any quantity. That also coincides with a time when manufacturers moved to less expensive resins. There were few reports of blistering prior to that time.
I agree with you regarding the fact that presence of moisture would appear to be no indication of present or future problems with blistering. But I do believe blistering has to be attributed to quality of either material or workmanship since you can find boats manufactured the same year by different manufacturers exhibiting vastly different degrees of damage from osmosis despite sailing and berthing under virtually identical conditions.

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[PaulS]

I personally think the whole "hull moisture content" thing is for the most part a bogey man. One might almost suggest that a boat with high moisture reading which exhibits no signs of blistering has proven itself as being of sound layup. If it hasn't blistered then it's unlikely to. Personally I wouldn't put too much faith in these readings.

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[Anonymous]

>>I personally think the whole "hull moisture content" thing is for the most part a bogey man.<<

I've never heard of blistering on a hull with low moisture content.

As for being a "bogey man" it's a very expensive bogey man if you are selling a yacht. The purchaser gets a survey report with all the usual minor defects and the final blow is the high moisture content that nobody will give any guarantees about. My surveyor effectively said "you might be lucky and have no problems or you might get blistering at any time". Which, translated into plain English = dunno.

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[cliffb]

Ok you guys. You clearly are the experts... so do indulge me if you will.
I thought osmosis only occurred below the water line. Is this not the case? and as such I thought that annual application of anti foul would avoid it.
Do, please, enlighten me.
Thanks

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[ccscott49]

Not an expert, but I know antifouling is porous/semi-porous, so wouldnt stop osmosis.

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[charles_reed]

My boat always used to be out for 4 months out of 12.

There was no evidence of retained moisture when it was time to put her back, though readings were high immediately after lift-out.
This last year she was only out for 12 weeks, after 22 months in the water and there was a far higher water content than previous readings when I came to put her back in again.

The layup happens to be isopthalic resin, with an additional layer of copper-impregnated polyester on top of the gelcoat so I hope to avoid blistering but in future she will be dried out every July/August which in the Med is far better drying than other times of the year.

Whilst I've been working on the boat I've usually slept and lived on board but it's uncomfortable in a well-equipped marina and frankly squalid in many.
About 4/12 months in temperate climes and 2.5/12 in sub-equatorial temperatures will dry a boat out. Otherwise you have to learn to live with the adsorption factor.

My own opinion is that there is no truly impermeable coating (including epoxies) and to keep your boat-structure dry you have to have out for long periods.

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