Osmosis Protection

DKnight

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The hull of my Moody 336 has been slurry blasted clean, if it was not for the paint manufactures at the Excel Boat show, I would just prime the bottom and slap some Antifoul on. However they all said that as I was so far I should consider epoxy coating the bottom. ( the only reason I had the bottom cleaned was because of the numerous layers of paint, and there is no sign of any osmosis.)

I am concerned about water entrapment, and have had the hull checked for moisture. Many values are low 3-6 but other areas by water tanks, keel, engine bearers are higher at 12-15 is this dangerously high, and what does it relate to? What misture reading would be regarded as suitable for epoxy coating?
Certainly I can get some heat onboard and ventilate under the floor boards etc. but am I going to achive a low enough reading with a month or so, particularly in the area of the engine bearers?

Your opinions and advice appreciated

D>K
 

capt_courageous

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We epoxy coated our last boat after having it slurry blasted to get rid of anti-fouling just as you have done. It is an easy but longish job - 5 coats or so. Get a pet surveyor to get some 'official' meter readings. He will tell you if all is well and can give you a coating certificate if you do the job. Useful when/if you come to sell.
 

Sans Bateau

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I am doing exactly the same, luckily all my moisture readings are very low. The surveyor suggested epoxy to protect the gel coat.

What I am going to do is use Copper Coat, which will be 4 coats of epoxy with copper antifoul, it totals about 200mic. This will cost about £500.00 for a 35ftr so works out a good deal.

How much was the slurry blasting?
 

oldsaltoz

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G'day David,

As you know it's critical that the moisture levels must be within acceptable limits prior to epoxy coating, or you will create problems that you are trying to avoid.

However with only a month I doubt you would see much change in your moisture levels even with heating and ventilation; a number of techniques have been developed to extract moisture from fibreglass hulls, but this is very expensive and only as good as the operator, so results can vary.

If your high moisture readings are localised you have some options. You mention that you have high readings close to water tanks, keel and engine bearers.

Tanks tend to give high readings even on new installations, interpreting moisture readings is not (as some believe) a simple matter of reading the numbers displayed, so you might like to have one re-assessed.

Engine bearers, not uncommon to have to higher reading here, if they are timber glassed over like most are, then the timber will absorb moisture over time, even if epoxy coated and I doubt these ever were, you can dry them by drilling small holes along the base about 3 inches apart, also cut some holes with a hole saw about half way up; drop in a couple of lamps and run them 24/7 till dry. Then re-glass the holes.

High moisture around the keel, If you have a keel box or a lot of glassed over timber in this area then treat as above with heat and venting.

As the hull is showing no sign of blisters it may have been treated in the past, and needless to say it has all now been removed leaving thousands of raw fibreglass ends exposed just waiting for drink.

Applying the epoxy is a task well within the capacity of an average DIY'er, if you need more information or advice on this aspect of the project run a search on this forum and don't hesitate to ask if you need more.

Avagoodweekend........
 

Birdseye

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The advice given to me by the Blakes tech help line was to epoxy only if readings were 5 or below on the Sovereign meter (can remember which scale B or C but it was the tightest). but he wasnt talking about every reading - he did accept there may be a highspot or 2.

on my boat I found that all the glassed in wooden bulkheads gave a reading in the 10 / 15 area because the meter was capable of responding to moisture on the inside of the hull. Had the same prob with a skeg where I had had salt water inside it. When I washed with fresh and dried out the prob went away.

So its not surprising that you get high readings where you have wood or metal engine bearers, or where you have water tanks. The bilge bit might simply be where there is re-inforcement.

If the boat were mine I think I would wait as long as poss and then epoxy. If water is in the laminate and doesnt come out in 2 or 3 months natural drying, then you may well have the osmosis soup anyway and the moisture will never come out without treatment. so nothing much lost. and areas which do not have the problem will be protected by the epoxy to a large extent.

but the boat is worth a fair bit, so personally I would ignore us semi experts on the forum and cough up to get some specialist advice from someone who really does know what he's talking about! whats a few hundred for the peace of mind?
 

Avocet

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I was in the same situation last year and a local surveyor stuck a meter in it and told me it was pretty good for a 1972 boat - a couple of localised 12s and the rest about half that. he advised me to slap a few coats on. Said it wouldn't do any harm so I did! there were no signs of blisters anywhere except some pinholes round the boot top line. None had anything in them.
 

macd

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If I've understood you correctly, suggest you be wary: Copper Coat is manifestly not an epoxy barrier treatment, since the epoxy is 'water miscible', to quote the maufacturer's bumf. You'll need a proper epoxy barrier coat underneath it. Copper Coat themselves can advise which works best.

Having said that, I've found Copper Coat to be good stuff, albeit in relatively low-fouling areas. But it is just an antifoul.
 
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