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Hull shapes on motor boats | Gel Coat Blisters on boats |
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Blast off the gel coat? In spite of what others may say, that might be too drastic explaines BoatsExplained.com IT'S MY BELIEF that many gel coats are removed unnecessarily usually on the recommendation of someone who hopes to profit by the work. Could there be an alternative, perhaps something which the owner can tackle himself? The answer is often 'yes', though I know this contradicts current wisdoms. Ask yourself this: . How extensive are the blisters isolated, in patches or spread all over? . How large are they - pimples, 6mm, or 25 mm or even more? . Spacing - wide apart or close together? . Are there dozens, hundreds, or thousands? . Are they wet, dry, cracked or broken? . How deep are they - between layers of gel coat, beneath the gel coat, or within the laminate? . And their shape - are they round or elongated? Basically if the blisters are widely spaced and comparatively few, in the dozens or hundreds range, it may be possible to save the gel coat and do the job yourself. Only when the blisters are closely spaced, fIlled with fluid and appear all over should you consider the drastic step of replacing the gel coat. I know this is contrary to the views of many experts but my own experience has taught me otherwise - and I've been involved with such matters since 1958! But what exactly is gel coat? It's not a coating in the normal sense, but an integral part of the boat, applied during moulding, and made of polyester resin like the rest. The gel coat is cured at the same time and therefore melded into the moulding, becoming part of it. And, because it's actually part of the hull it makes sense to retain it for as long as possible. Except when fairly new, say less than three years (when blistering is a matter for a lawyer not a repairer), practically all blistering is caused by the quality of the moulding beneath. The gel coat itself often remains sound and only blisters because it's in the way. Diagnosis is the key factor. There's no single disease called 'osmosis' (which, anyway, is a commonly misused word). There are many causes of blistering. I know over three hundred and I'm still fmding more. Unless the precise cause can be established, any premature treatment is simply bodging. So be warned. Never agree to gel coat removal until the true cause or more likely causes - has been established and you're absolutely convinced there's no alternative. Get an independent diagnosis first and perhaps a second opinion too. Dry before repairing Whatever your method, good drying out is essential. And the only way to really ensure that is by giving it time - months at least. This will need advance planning, especially if you're on a long cruise or based in distant waters. And, of course, you must choose a time when money is available because even minor treatment can prove expensive. But if there simply isn't time, just piercing, draining and treating deep blisters is beneficial because it will take a year or two for them to fill and build up again. It'sJ\ot essential to remove the gel coat to dry out the hull. Water got in through it and can get out the same way, though it might take longer. Removing antifouling will help, but don't shave those smaller blisters. How dry should it be? In theory completely dry - or below 0.5% which is about 5% reading on the Sovereign meter scale. In practice we must be realistic. The dryness you'll settle for will be dictated by economics as much as by meter readings - a matter of how long you can afford to keep the boat ashore! So forget about moisture meter readings. The practical aim is to get the hull as dry as possible in the time you can afford. This will take at least three months under reasonable drying conditions. Six months is better which, in northern Europe represents a winter laid up ashore. Keep the rain from the underwater areas of your hull and allow plenty of air to blow through. Air and time are your friends. These methods are cheap, simple and something most owners can do themselves. I'm sure there will be howls of disapproval from experts indeed on purely theoretical grounds I would disapprove myself. But that's not the point. If you can't afford professional care or are far away from specialists who can help, these are practical and relatively inexpensive measures which will help preserve your boat. And painting the hull with epoxy will help to reduce the permeability of the gel coat but it's not the magic protection so often claimed. The permeability of epoxy is, at best, only three times less than polyester. Moreover that assumes two critical things: (a) that it is as thick as a gel coat and (b) it is applied under good conditions and properly cured. A gel coat, at about 0.5 mm, is ten times thicker than a coat of paint so just a couple of coats of epoxy are not effective. Only thickness will decrease permeability and with pennies tight, (more likely £s with noughts on the wrong end) that's likely to be skimped. Application and cure, when used in the open, won't be comparable to an original gel coat applied under moulding workshop conditions, and certainly nothing like the laboratory samples on which the claimed comparisons were made. Faith in epoxy alone is useless. |
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