Copper Coat and Older Hulls - Is Blistering A Risk?

[Deleted member 36384]

The Copper Coat thread thats running at the moment is of interest to me. I keep the yacht in the water for two years and then lift her out for a winter. This year is a lift out year and I will be removing all the anti fouling with slurry process.

My yacht is from 1974. I believe copper coat is an Epoxy based product that has the copper formulation mixed in. On older boats there are risks associated with applying Epoxy to hulls vis-à-vis osmotic blistering. Would Coppercoat form the impermeable barrier that Epoxy coats produces or does the copper element provide some permeability (not likely I would imagine)?

The hull of my yacht is likely to have moisture readings that are elevated, maybe not, so I guess there is a dryness standard for the hull before its applied. Would Copper Coat be a waste of time on my old hull as the risk of blistering (trapped pressure below the Epoxy coating) be a realistic risk.

Thanks in advance for the comments,

BlowingOldBoots

 

[AntarcticPilot]

The Copper Coat thread thats running at the moment is of interest to me. I keep the yacht in the water for two years and then lift her out for a winter. This year is a lift out year and I will be removing all the anti fouling with slurry process.

My yacht is from 1974. I believe copper coat is an Epoxy based product that has the copper formulation mixed in. On older boats there are risks associated with applying Epoxy to hulls vis-à-vis osmotic blistering. Would Coppercoat form the impermeable barrier that Epoxy coats produces or does the copper element provide some permeability (not likely I would imagine)?

The hull of my yacht is likely to have moisture readings that are elevated, maybe not, so I guess there is a dryness standard for the hull before its applied. Would Copper Coat be a waste of time on my old hull as the risk of blistering (trapped pressure below the Epoxy coating) be a realistic risk.

Thanks in advance for the comments,

BlowingOldBoots

No experience whatsoever - I am in the same position as you - but when I've made enquiries of professionals, I've had two responses:

1) Yes, works fine as long as you strip the hull at the beginning of the winter, have it under cover for the winter so it can dry out, and then do the Copper-coat in the spring. To me, this makes sense.

2) No, it has too high a failure rate to be worth-while on an older hull; it works best if applied on a new hull. This, though, from a company that was suggesting simply stripping the old anti-fouling, then applying the Copper-coat.

I've never heard that epoxy is a no-no on an older hull; indeed epoxy coating is often recommended as a preventative for osmosis. But, of course, the hull has to have time to dry out before application to avoid the problem you mention.

So, my guess, based on opinions from professionals is that the critical bit is to allow time for the hull to dry out, ideally under cover.

If I can ever find the funding, I'd like to do it! Capricious is a bit younger than yours (1989), but I am pleased to say that the hull is in excellent condition underwater, so I think that option 1) would give a very good chance of working.

PS, AFAIK, Copper-coast is epoxy based, and in any case, epoxy coating before applying it is usually recommended. I think the point is that the epoxy is NOT permeable, so only the copper exposed at the surface is actually being eroded.

 

[macd]

BlowingOldBoot's point about the adverse effects of 'sealing' water in is often made and, while I'm no expert on the chemistry involved, warrants caution. I think it's difficult to generalise, since no two (old) hulls are the same. Equally, drying out is not always so easy as AntarcticPilot suggests since the products of osmosis (if present) are hygroscopic: so, perversely, a hull can be best dried by frequent jet-washing (to flush out the hygroscopic elements), although this will have much less effect if the gelcoat is retained.

Equally, epoxies are not completely impermeable. A typical barrier coat epoxy might have a water take-up of up to 0.5%. Coppercoat epoxy is rather different. It's 'water missible' (indeed the resin is 50% H2O, which is why it dries as well as cures). It is not generally regarded as a barrier coat, although it may have some barrier properties.

I'd suggest that the OP has someone test the hull's moisture readings a few weeks after lift out. If they're especially high it might suggest not Coppercoating, although I certainly wouldn't be dogmatic either way -- except to say that if there is evidence of osmotic blistering (as opposed to simply high moisture levels), it would be folly to throw money at the hull without remedial treatment.

I'd also suggest speaking with Ewan or one of his colleagues at AMC (Coppercoat). Clearly they have a vested interest, but I've always found them helpful and straight. And, if your doubts aren't dispelled, you've no need to follow their advice.

Edit:...and along comes Elessar with some real expertise...

 

[Elessar]

The Copper Coat thread thats running at the moment is of interest to me. I keep the yacht in the water for two years and then lift her out for a winter. This year is a lift out year and I will be removing all the anti fouling with slurry process.

My yacht is from 1974. I believe copper coat is an Epoxy based product that has the copper formulation mixed in. On older boats there are risks associated with applying Epoxy to hulls vis-à-vis osmotic blistering. Would Coppercoat form the impermeable barrier that Epoxy coats produces or does the copper element provide some permeability (not likely I would imagine)?

The hull of my yacht is likely to have moisture readings that are elevated, maybe not, so I guess there is a dryness standard for the hull before its applied. Would Copper Coat be a waste of time on my old hull as the risk of blistering (trapped pressure below the Epoxy coating) be a realistic risk.

Thanks in advance for the comments,

BlowingOldBoots

Its a good question and there is no easy answer.

Yes CopperCoat is an epoxy. 25x more waterproof than gelcoat. Yes water is its solvent, but that all evaporates, it is an epoxy once cured. What it does do is get microscopically thinner every year which is why some people put non eroding epoxy underneath it.

When water passes through the gelcoat through osmosis, is does so only to pass into something it can dissolve. It won't go though just to make a wet patch, gelcoat is waterproof enough to prevent this (or your boat would sink) The desolveable entity sucks the water through if you like.

This new substance is heavier than water, just like salt water, which is just water with salt dissolved in it, is heavier than fresh.

So the water can pass through the gelcoat, but the newly created hydrolysed solute cannot get back out.

Thus the epoxy won't hold the water in any more than sound gelcoat will. You can see from this that the practice of leaving the boat out to dry is a myth. Yes it is not getting any wetter on the hard but it is not getting drier either. Plenty of people, even some surveyors, will tell you to do it though. So you can see why getting a straight answer isn't going to be easy.......

The exception is when you are in full blown stage 3 osmosis and the gelcoat is actually fractured in places. Then it can dry. I did say sound gelcoat.

I have had a few cases where a bubbling hull was CopperCoated after just localised bubble popping and filling. The owners wanted this against my advice at the time and they have got away with it. They are now part of my advice.

So with just elevated levels and no evidence of stage 3 (bubbling), bearing in mind you are stopping any more water getting in, I would probably go for it.

I had a particularly bad case on a westerly and took advice from AMC.

they said

As you know, Westerly was one of the UK's major boat builders through
the 1970's, 80's and 90's with the Centaur being the most popular model.
Consequently it is perhaps not surprising that more Westerly yachts are
treated with Coppercoat than any other individual marque.

The techniques and products used in the construction of these boats were
clearly less advanced than we are now used to, and it is not unusual to
find elevated moisture levels in yachts of this vintage.

Coppercoat can be applied to the hull of any GRP boat, regardless of the
moisture levels. However, Coppercoat will only follow the contours of
the gel-coat. Consequently if the gel-coat on a hull with high moisture
levels begins to blister, naturally these bumps will be seen across the
surface of the Coppercoat.

If the moisture levels are so high as to cause gel-coat blistering (the
most obvious sign of osmosis) the recommended course of action would be
to undertake an osmosis treatment before applying the Coppercoat. Strip
the defective gel-coat, clean and dry the underlying laminate, rebuild
with solvent free epoxy, and then anti-foul with the Coppercoat.

However, not every boat owner wishes to undertake such an extensive
repair, and many are more than willing to sail in boats with high
moisture contents, some blistered gel-coat and less-than-perfect
laminate. And quite right too - it doesn't affect how the boat sails!
Certainly I have known owners apply Coppercoat to very wet boats - they
know the gel-coat underneath is (and will continue) to blister, but they
do not worry about this. They apply the Coppercoat to keep off the
fouling, and it will do this regardless of the moisture content of the
hull.

In conclusion - in the ideal World, every boat with high moisture
readings would be treated for osmosis and put back to better-than-new
condition. But in the real World many owners are happy to apply
anti-fouling to their damp boats, safe in the knowledge that the
anti-foul will do its job (of keeping the hull clean) regardless of the
osmotic activity.

To give the counter argument, this excellent guide from Nigel Clegg advises against epoxy on elevated moisture hulls http://www.passionforpaint.co.uk/pdf/osmosis3.pdf

I am speaking from real world experience and in summary if it was my boat:

Moisture high, no bubbles, intend to keep boat for more than a couple of years - CopperCoat.
Moisture high, no bubbles, intend to sell soon - antifoul and enjoy sailing till she sells.
Moisture high, some bubbles, intend to keep boat - local repair and coppercoat.
Moisture high, extensive bubbles, intend to keep boat - full repair and coppercoat.
Moisture high, Bubbles and intend to sell boat soon - sell it now.

but you have to make your own mind up from the contradictory advice available.

 

[AntarcticPilot]

Its a good question and there is no easy answer.

.............

Thus the epoxy won't hold the water in any more than sound gelcoat will. You can see from this that the practice of leaving the boat out to dry is a myth. Yes it is not getting any wetter on the hard but it is not getting drier either. Plenty of people, even some surveyors, will tell you to do it though. So you can see why getting a straight answer isn't going to be easy.......

Just to say that the advice I had wasn't just to leave the boat out on the hard, but to have her under cover, in a dry building with temperature control. I suppose you could rig something up with greenhouse heaters and tarpaulins if a suitable building was not available. It happens that the marina I am in does have a very large dry building available, and it is not alone in these parts; Fairlie has one too.

Of course, if there is serious osmosis present it won't do any good, as you clearly demonstrate; osmotic pressure will see to that. But we are talking about normal moisture levels in GRP, not cases where there is free fluid.

Never mind the drying out aspect, it has obvious advantages for applying the epoxy as well.

 

[PeterWright]

Elessar's advice is excellent in all but one respect. Coppercoat, although epoxy based, is not as effective as plain epoxies at preventing water penetration through osmosis.

The reason is quite simple. Coppercoat is an epoxy loaded with as much finely divided copper as they can get into it while still retaining enough strength to provide a stable film (i.e one which won't disintegrate or fall off). The consequence of this is that leakage paths exist aong the surface of each copper particle which will allow water penetration. Indeed, some water penetration along the surface of the copper particles is actually required to give the biocidal properties for the paint to work as antifouling.

Despite this, I don't believe applying Coppercoat to an old hull will make it any more prone to developing blisters than applying ordinary antifouling, which is even more porous.

Once a grp hull has taken up some water through osmosis, it will not surrender that water unless the affected areas are peeled and washed thoroughly with fresh water, regardless of whether blistering has started or not. The osmotic pressure generated by the hydrophyllic properties of the chemicals in the grp will make sure the water stays in there until those chemicals are washed away. If some water has penetrated, but blistering is not evident, preventing further water penetration (from outside or inside the hull) will preclude blistering. Water trapped in there cannot, by itself, create the addtional water needed to cause blistering.

If you have a dry hull, with no water uptake (either new or just after osmosis treatment) it is worth putting a barrier layer of epoxy on the grp first before applying Coppercoat. This will keep the big O at bay for many years to come.

Last thought for those worried about osmosis - keep your bilges dry. Although the pressure of bilge water is lower than that outside the hull, the bilge frequently has no gel coat at all or sometimes a simple gel wash of very low film thickness. On occasion, you even see unwetted strands of glass sticking out, providing an ideal wick to suck bilge water into the grp.

Hope this helps.

 

[Elessar]

Elessar's advice is excellent in all but one respect. Coppercoat, although epoxy based, is not as effective as plain epoxies at preventing water penetration through osmosis.

The reason is quite simple. Coppercoat is an epoxy loaded with as much finely divided copper as they can get into it while still retaining enough strength to provide a stable film (i.e one which won't disintegrate or fall off). The consequence of this is that leakage paths exist aong the surface of each copper particle which will allow water penetration. Indeed, some water penetration along the surface of the copper particles is actually required to give the biocidal properties for the paint to work as antifouling.

Despite this, I don't believe applying Coppercoat to an old hull will make it any more prone to developing blisters than applying ordinary antifouling, which is even more porous.

Once a grp hull has taken up some water through osmosis, it will not surrender that water unless the affected areas are peeled and washed thoroughly with fresh water, regardless of whether blistering has started or not. The osmotic pressure generated by the hydrophyllic properties of the chemicals in the grp will make sure the water stays in there until those chemicals are washed away. If some water has penetrated, but blistering is not evident, preventing further water penetration (from outside or inside the hull) will preclude blistering. Water trapped in there cannot, by itself, create the addtional water needed to cause blistering.

If you have a dry hull, with no water uptake (either new or just after osmosis treatment) it is worth putting a barrier layer of epoxy on the grp first before applying Coppercoat. This will keep the big O at bay for many years to come.

Last thought for those worried about osmosis - keep your bilges dry. Although the pressure of bilge water is lower than that outside the hull, the bilge frequently has no gel coat at all or sometimes a simple gel wash of very low film thickness. On occasion, you even see unwetted strands of glass sticking out, providing an ideal wick to suck bilge water into the grp.

Hope this helps.

I see where you're coming from with the water up the grains system but I'm going to attempt to disprove it

Copper corrodes very quickly in salt water.

There are 2 basic copper antifouling systems that use cuprous oxide as their only biocide - the CopperCoat copper in resin system (which has been copied) and the Cuprotect system (which has been copied)

In the latter system all the metal is sprayed dry onto the tacky epoxy. The copper would last just a few months, so the corrosion rate is controlled by nickel. Thus copper nickel, not pure copper is used.

In CopperCoat the corrosion rate of the pure copper is controlled by slowly eroding the epoxy. If the water could pass along the copper labyrinth as you suggest, the copper on the inside would be wet and corrode so it would last less than a year.

Furthermore, for water to travel from copper grain to copper grain as you suggest the copper grains would need to be touching each other. They do not as evidenced by an ohm reading with a multimeter, which reads infinity.

I think of the copper grains in coppercoat like the bubbles in an aero bar. The chocolate is the epoxy, and is contiguous.

So I think you'll find it is more waterproof than gelcoat as I suggested.

 

[Deleted member 36384]

Thanks for the comments and good advice.

Regards,

BlowingOldBoots

 

[RobbieW]

I cant add to the technical expertise above - however, having the same hull as yours (slightly newer at '83), I did CopperCoat it in the summer of 2009. The boat had been on the hard for about 18 months prior.

I ran a moisture meter over the hull following the blasting. I cant remember what meter readings I got but they seemed to indicate a fairly dry hull except on the rudder and to a lesser extent in the area at the back of the keel where the deep sump is (subsequently found some water in there).

She's been in the water continuously since except for a 4 day lift out in May this year. There was no sign of anything amiss at that stage, the only place the epoxy layers hadnt adhered was on the bronze shoe of the skeg/rudder. It was also the first proper scrub she'd had in 12 months - good result, just slime but I think there is less growth in the seas down to Gib than often found around the UK.

 

[OldBawley]

I have just applied Coppercoat on a very old wooden yacht.
Explanation :
The boat been build 1946, a sort of Bawley yacht. Total rebuild 1970, sheeted in fibreglass on new wood. In fact two hulls in one, hence the 8 tons for 8 meter length.
When I bought the boat, it was working as a semi professional shrimp fishing boat.
The fibreglass sheeting under the waterline was very rough, so back in 1987, I worked for three months to put some extra layers on it and smooth-en the surface a bit. Also applied a gelcoat.
Since liveaboard, Belgium Holland and France, cruising the Med for 13 year.
Taken such an old heavy yacht out on land is a pain in the ****, working on a yard even more, so after some problems on the shipyard in Rhodes I kept the hull clean by snorkelling in summer. At the end of winter we ware a bit slower, not a real problem, small as the yacht is, we are always the slowest. An old long keeled boat as ours needs to be taken out with the weight resting on the keel. A travel lift is OK, but on a lot of yards they move the boat by wagon so the yacht fits in a smaller space and that is no good at all for old boats.
Getting older, my nose grows huge, no diving mask fits, so I had to think of a way to keep the hull clean for our last ten years together.
Last summer I discovered a shipyard that pleased me. Made me think of the old days back home. Even the smell of sheep grease and old wood. In the middle of nature, a one way dirt road along the beach. Local fishing and taxi boats been hauled on sledges. Sheep, two guard dogs, chickens and Greek cats off course. Two brothers running their faters-grandfathers yard. Just a nice dingy sail to town for shopping. A ( Museum ) shed full of old wood and machines. I liked the place, for once had no “ Have to go “ feeling, so decided to take the boat out for a month and Coppercoat it.
First of May was the best time but safety and language problems made it middle May before the boat was taken on the brothers biggest sledge. They took the biggest because they hate it, needed the smaller easy handling ones for normal business. They left the boat standing on that huge sledge, the deck almost 4 meters above the ground.
The work was absolute horror. Thirty square meters of underwater ship had to be scraped. I used a Sandvic 3/4” blade scraper because the hull is so uneven. Had to take of 2 mm of old anti fouling and gelcoat to have a clean surface. Then sanding. Had been scratching trough the gelcoat so had to apply a new one. Four coats of gelshield. Could only manage half a hull a day, then lifting the boat, moving the keel supporting blocks, and on to the other side. Rolling on Gel coat for 12 hours to cover half a hull, most of it above my head. Was completely covered in green and grey sprinkles, My body had never been so valuable.
Made yacht legs out of 4 meter long scaffolding planks, then the Meltem came so I secured the boat by tying the halyards of the head sails to solid wharf. Eye height standing on deck 5,5 meters, the whole boat shaking, eight tons of boat standing on the keel and some scaffolding planks.
Living on board was no fun with that Meltemi. We had the wind blowing from behind, which is the wrong way. Imagine living on a open truck for weeks, the truck doing 35mph. All the time.
The new gelcoat had to dry for a week, so I painted the topsides, placed some new sea-cocks, ec...
By the time I was ready to apply the Coppercoat, May had gone, now mid June. Hot !
Knowing how long it took me to roll one half of the hull, curing time of the coppercoat with 26° C, doing some thinking ( To late ) I realised we needed 6 man to roll, and my wife for mixing the stuff. No way, so I mixed half a litre of Coppercoat at the time, reducing manpower to three.
In the end three of us rolling for 8 hours ( No breaks possible ) could do one half hull. Four days of curing, then lifting the boat again, moving keel timbers, coppering the other half hull. A total of 16 hours of rolling almost pure metal above your head. Three man, total 48 hours! Have to admit that one of my rollers was a Swiss guy ( Thanks Jean Pierre) who rolled extremely precise, and I am not used working any more. In total 47 kilo of epoxy paint went onto that old hull.
Another four days curing, then we could launch.
The huge sledge, weighing 20 ton according to Kώσtαζ, had been drying for a month and a half. It took the brothers three hours to get it moving, and then, by Murphy, the sledge had more floating power than our eight tons of boat, so the yacht stood firm onto that huge swimming raft, the waterline half a meter above the water. Theoreticley we just had to wait a few days, let the wooden sledge soak up water and free us slowly.
Panic, because if one of the dozens of ferry’s passes, making big waves, the old boat would be holed by the struts holding the yacht straight up.
I was on board, keeping the rudder strait during the launch, saw my dear old boat floating on top of a raft and flipped out. …....Mental hospital nearby.
Don’t know how but we got off, some nasty scars in our beautiful copper.
Decided not to worry about it, life is to short to grumble about something that cant be changed.
The day after, with the new sails set, towing the dingy, we ware doing six knots hard on the wind. Guess force three, not even white caps. What a boat.
Osmosis ?
We have some, about 3 inches above the waterline. The gelcoat ends 6 inches above water, from there on its plain ordinary paint on glass fibre. Guess the water wicks in from there, day and night been wetted in 20 cm waves. I do not care, it is a working boat, not a yacht.
Would I do it again ? Yes, it was absolute horror, despite the beauty of the scene, but now, it is over for ever. No more lifting, no more yards. With every bath some gentle caressing of the precious copper should do the trick.
Hope we are OK for the next, last ten years. Will let you know.

 

[srm]

A bit more practical experience, not with Coppercoat but a copycat product that turned out to be less effective. (Now have the real thing on my current boat).
2003 bought a catamaran, low moisture readings during pre-purchase survey so surveyor suggested epoxy coating. Cleaned off old antifoul by hand (never again), applied 5 coats West Epoxy then 3 coats copper epoxy. Rudders however were found to have water in them so dried as best I could before epoxy etc.

Within 3 years slight blisters evident on rudders.

When I sold her in 2010 there was no sign of osmosis found on the hulls, but the rudders had quite big blisters lifting the epoxy off the gel coat and some blistering in the gel coat. Have been told of similar blisters occurring on a hull after epoxy coating.

Much will depend on the hull's moisture content.

Hope this helps.

 

[Deleted member 36384]

... not with Coppercoat but a copycat product ... 2003 ... low moisture readings ..... applied 5 coats West Epoxy then 3 coats copper epoxy. Rudders ... found to have water in them so dried as best I could before epoxy etc. .... Within 3 years slight blisters evident on rudders. .... sold her in 2010 ..... no sign of osmosis found on the hulls, but the rudders had quite big blisters lifting the epoxy off the gel coat and some blistering in the gel coat. Have been told of similar blisters occurring on a hull after epoxy coating.

Much will depend on the hull's moisture content.

Hope this helps.

Thanks SRM. This is my fear. Based on nothing more that an amateurs research on the web it would appear that older hulls that subsequently get Epoxy coated have an increased probability of blisters appearing where they might not have if the Epoxy had never been applied. My hull was laid up under Lloyds Register supervision, so I assume it was as good as they understood in those days, but it was along time ago and much water has passed across the hull since then.

The actual condition of the hull with regards to moisture readings and the effectiveness of natural drying would have to be very clearly understood. Again from the internet, natural drying of a hull, after which the hull exhibits low moisture readings from pre drying highs, might not reduce the risk of blistering after epoxy coating on an older hull.

The correct conditions and preparation are everything as others have said. If I can't guarantee this then its a life of anti fouling for me. However, we shall see.

Thanks,

BlowingOldBoots

 

[Elessar]

Thanks SRM. This is my fear. Based on nothing more that an amateurs research on the web it would appear that older hulls that subsequently get Epoxy coated have an increased probability of blisters appearing where they might not have if the Epoxy had never been applied. My hull was laid up under Lloyds Register supervision, so I assume it was as good as they understood in those days, but it was along time ago and much water has passed across the hull since then.

The actual condition of the hull with regards to moisture readings and the effectiveness of natural drying would have to be very clearly understood. Again from the internet, natural drying of a hull, after which the hull exhibits low moisture readings from pre drying highs, might not reduce the risk of blistering after epoxy coating on an older hull.

The correct conditions and preparation are everything as others have said. If I can't guarantee this then its a life of anti fouling for me. However, we shall see.

Thanks,

BlowingOldBoots

You're right to have the caution, but remember rudders are differnt. When you epoxy them you don't stop the water getting in, they are almost always wet as the water gets down the stock.

So it's blistering, but not strictly osmosis, which is the passing of fluid through a semi permeable membrade (the gelcoat), but I guess thats a pedantic irrelevance.......

 

[wotayottie]

Thanks SRM. This is my fear. Based on nothing more that an amateurs research on the web it would appear that older hulls that subsequently get Epoxy coated have an increased probability of blisters appearing where they might not have if the Epoxy had never been applied. My hull was laid up under Lloyds Register supervision, so I assume it was as good as they understood in those days, but it was along time ago and much water has passed across the hull since then.



BlowingOldBoots

My boat is a 96 build and has coppercoat. Works well but on the leading edge of the rudder it blistered. The rudder is wet ( bad seal shaft to grp) as indeed are most rudders, and we knew this before coating. I patched the blisters when the boat was out this last winter but tbh I expect them to re-appear.

But the blisters themselves dont matter. They are cosmetic unless very deep within the laminate. If your hull has enough water in it to trigger blisters when epoxy coated then it already has osmosis and the structural laminate is degrading. It also has a duff gelcoat that allows moisture to pass without blistering.

The common misunderstanding comes about because the problem is described as osmosis whereas the osmotic blisters are one symptom of the problem and not the problem itself. The real problem is the formation within the structural laminate of pockets of a concentrated solution of chemicals which then degrade the laminate itself. This can and does sometimes happen without the formation of obvious blisters particularly if there is a bad / porous / micro cracked gel coat on an older boat.

In an earlier post someone gave a matrix of actions depending on how long you intended to keep your boat. made sense to me.

 

[IanCC]

A 2012 thread.
Conclusions anybody nearly 10 years on?

 

[CAPTAIN FANTASTIC]

Blistering is a big possibility, to reduce the risk of blistering, the surface has to have low moisture levels, as per or below copper coat instructions. However, in my opinion, the blisters are cosmetic. The real benefit is that you will not have to antifoul the boat every season; this is a big plus to me.

 

[IanCC]

But you do have to sort out each years blisters?

 

[CAPTAIN FANTASTIC]

But you do have to sort out each years blisters?

No, blisters are formed in certain areas but dont get worse nor they increase in numbers. I see many yachts in boatyards with pitted hulls with multi layers of antifouling that look much much worse than a yacht with few blisters due to osmosis or coppercoat. I am not suggesting that blistering is normal, but some people get hysterical about blisters in the same way as Japanese knot-weed in gardens

 

[AntarcticPilot]

No, blisters are formed in certain areas but dont get worse nor they increase in numbers. I see many yachts in boatyards with pitted hulls with multi layers of antifouling that look much much worse than a yacht with few blisters due to osmosis or coppercoat. I am not suggesting that blistering is normal, but some people get hysterical about blisters in the same way as Japanese knot-weed in gardens

From a sample of one and a lot of anecdotal evidence, blistering is not usually a problem if the hull is properly prepared. I did mine after the boat had been out of the water for the winter, so the hull had plenty of time to dry out.

 

[IanCC]

I was just hoping by now that it wasn't an opinion thing and that there was settled knowledge.