Osmosis

[ghilliedhu]

I am considering buying an old ( mid 60`s) fibre glass yacht . She was heavily built and the gel coat was stripped and 7 coats of epoxy applied about 10 years ago. She has been out of the water fo 6 years.
Is is worth appliying more epoxy at this stage?
Can I just strip back to the epoxy applied in 1994?
If so what is the most efficient way of stripping the hulll back to the epoxy?
Will there be an effective chemical bond if I do so?
There is no sign of osmosis on the outside of the hull but is there a possibility that osmosis might in evidence under the epoxy and if so is this a problem? I ask because I noticed a few blisters about the size of a thumb in the bilges.
Any advice greatfully received.
Regards David

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[SimonD]

I take it when you say they are blisters in the bilges, there are on the inside. If so, it may be a simply a symptom of watery bilges for many years.

If there is no evidence of blistering on the hull itself, I wouldn't worry. If she's been out of the water for 6 years, the hull should be dry (so forget getting a surveyor to take moisture readings). As it's dry, you could apply another coat of gelshield or the like, but I personally wouldn't bother. Depends a bit on how long you intend to keep the boat and how much peace of mind you want.

Simon

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[longjohnsilver]

If it's already been epoxied, the fact that's it's been out of the water for 6 years doesn't necessarily mean that it's now dry as the epoxy could have trapped moisture in the laminate. I would recommend that you get hold of a moisture meter and check it out before putting more layers of epoxy on it.

The chances are that it will be dry as Simon suggests, but why take the chance when checking it is relatively easy.

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[ghilliedhu]

Thanks , I am sure that is sound advice.
David

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[Aeolus_IV]

It is worth noting that none of the Osmosis treatements are 100% water impermiable - they are simply much, much less permiable than original gelcoats. After spending 6 years out of the water the hull will have had plent of time to dry out. As explained to me by the people who did our boat - it is not that it is kept dry, it can be in the open and being rained on - it is the fact that it isn't under water pressure (from being several feet under salt water). Also in its favour is the weight of the layup which seems typical of GRP boat from the 60's and 70's - our hull is typically an 1" thick, thicker in places.

Jeff.

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[Guest]

Whilst on the subject of osmosis - I had a surveyor do a moisture test on my 18 year old hull last September when she was lifted out and the readings came back zero.She has not been epoxied.I am thinking of laying her up afloat next winter does anyone have any opinion as to how likely this is to induce osmosis?She will be lifted out the following winter when I will consider having her epoxied.

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[tome]

I kept mine afloat this winter and enjoyed some great sailing. I posted a thread on this some time back and the consensus seemed to be balanced for and against.

Seems the winter layup goes back to wooden boats on swinging moorings which became exposed during winter gales.

Get yourself a decent dehumidifier and you won't even need too strip the upholstery etc. Make sure you run up the engine every couple of weeks.

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[vyv_cox]

I have only spent one winter ashore in the past 6 years. We do have a small amount of osmosis but we did when we lifted out every winter, so there doesn't seem to have been a lot of change. Our boat lives in fresh water where the risk of osmosis is higher anyway.

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[dynamic]

Beware of blisters inside the hull. If found to be osmosis its more difficult to treat, and more expensive.Get it checked out.

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