Is it worth epoxying a sound GRP hull, or is it just fashion?

[MeaCulpa]

A Vinylester boat that’s dry, I don’t SE the point of an epoxy treatment. IMO a lot of epoxy treatments are of dubious value, and often accompanied by dubious workmanship. Gelshield, IMO and all that, is a pretty poor epoxy product as it contains loads of solvents that will evaporate when the paint is drying/curing leaving the surface somewhat porous, to eliminate most of the pors something like five layers is required. I’ve seen layers of gel shield drop from hulls, I don’t know if it’s been due to poor workmanship or a poor product but it doesn’t inspire confidence. A professional epoxy product could basically be straight epoxy but would also require more precise combinations of temperatures, hardener and epoxy to work well.

 

[MapisM]

Now, that's an interesting feedback, thanks.
Pretty much confirms what I was told by those folks in the "don't epoxy" camp.
By chance, have you ever experienced similar problems also with Coppercoat?
I understand that it's also based on an epoxy resin, where the copper powder is mixed, but it's a water (rather than solvent) based epoxy.
If and how that makes a difference, I'm not sure.

 

[superheat6k]

I think it's fashion more than science. You have good laminate with vinylester, so just apply gel coat. People talk about permeability but does it really matter if a few water molecules get through? Selling these epoxy coatings seems to use a business model with a few things in common with the RC Church: instill a fear of what will happen if you don't. So I'm gelcoat all the way. But you will also be ok if you use epoxy and you'll be fashionable :encouragement:. Or just use good quality paint

+1

 

[MeaCulpa]

Now, that's an interesting feedback, thanks.
Pretty much confirms what I was told by those folks in the "don't epoxy" camp.
By chance, have you ever experienced similar problems also with Coppercoat?
I understand that it's also based on an epoxy resin, where the copper powder is mixed, but it's a water (rather than solvent) based epoxy.
If and how that makes a difference, I'm not sure.

As I’m a Swede That lives on the East Coast and boats in the baltic and lakes where marine growth is not especially bad copper coat is not something i’ve seen on a boat out of the water. I do suspect that the ones licensed to apply CC might be a bit better than the average marina or DIY.

 

[PowerYachtBlog]

The International Epoxy Gelshield has about 60% Epoxy matrix and the rest is solvents. Hence why you need the four/five coats.

There is other makes which offer a higher content I think Nautix from France has just lined a Gelshield type product with a 90% content.
The best system would be to cover the hull in Epoxy.

I think it was daf to remove the gelcoat. The yard should have gone this direction; antifouling removing product, and orbiter sanding to leave the gel intact.
Using soda blasting on a sound hull is just lazy. But yes that is what 99% of yards suggest nowadays.

 

[MapisM]

I think it was daf to remove the gelcoat. The yard should have gone this direction; antifouling removing product, and orbiter sanding to leave the gel intact.
Using soda blasting on a sound hull is just lazy. But yes that is what 99% of yards suggest nowadays.

Well, if you're accusing myself of being daft, of course I am: there's no better living proof of anyone's daftness than owning a boat, if you think about it!

But I think that calling what was done a "gelcoat removal" is a stretch to say the least.
As I said previously, I understand that the above enlarged pic can give the impression of a ruined gelcoat surface, BUT:
- First of all, as I previously said, you struggle to feel the difference if you swipe a finger on the hull bottom vs. the much more shiny sides above the w/line.
- Besides, afaik there's only one way to keep the very superficial, uber-smooth and shiny gelcoat finishing which you can see on a brand new hull, and it's to never antifoul the hull, period. A preparation for antifouling the bottom which doesn't remove the very superficial gelcoat gloss surface is a poor preparation, where the a/f is bound to peel off in no time.
- So, leaving aside the fact that I had contrasting views also on the effects on gelcoat of a/f removal with chemical products, there's no way that such method could make the miracle of bringing back the gelcoat to as-new conditions. Those conditions were forever lost upon the first antifoul.

In fact, it's interesting to see here the pics that Hurricane posted after coppercoating his P67, which back then was only 2 years old.
The previous a/f layers (which were bound to be much thinner vs. my 14yo boat, obviously) were removed with wet slurry blasting, which is widely recognised to be more gentle than dry blasting - though the operator hand/expertise remains the most critical component, afaik.
Unfortunately, Hurricane didn't post any very enlarged pic, so it's hard to evaluate exactly the superficial gelcoat conditions - though a proper evaluations can only be done in flesh anyway, touching the real thing and looking at it, possibly with a magnifier lens.
But it's clear from his pics that the bottom didn't have the glossy superficial finishing of brand new gelcoat anymore.
Would you call that "gelcoat removal" for this reason alone...

 

[oldgit]

Some uneducated observations.....
The most ardent worriers and spenders on this problem appear to be yachties, which is curious as most yachts would appear to spend exactly 50% of their lives high and dry on the hard.
In the real world of motorboating. UK Craft spend 99.99 % of the time in the water and osmosis is seldom a topic of conversation in our club with 100 odd boats on our tidal moorings some over 50 years old.
As for Copper coat can give examples of CC being applied and very quickly being over coated with traditional A/F.
My boat being one of them.
Perhaps CC less effective in salty rivers with constant tidal flow.

 

[PowerYachtBlog]

Yes in Hurricane method with wet sand blasting the gel coat looks still very much intact. Reading some posts I think you said you removed the gelcoat or not?
You need the gel to become a bit rough for it to stick something to it or else nothing bonds.

Following ones dreams if that entails to own a boat is never daf.
But I know how some Italian moaners say the best day in a boaters life is the day you buy it and the day you sell it. I am sure you are not one of them.

 

[Hurricane]

Well, if you're accusing myself of being daft, of course I am: there's no better living proof of anyone's daftness than owning a boat, if you think about it!

But I think that calling what was done a "gelcoat removal" is a stretch to say the least.
As I said previously, I understand that the above enlarged pic can give the impression of a ruined gelcoat surface, BUT:
- First of all, as I previously said, you struggle to feel the difference if you swipe a finger on the hull bottom vs. the much more shiny sides above the w/line.
- Besides, afaik there's only one way to keep the very superficial, uber-smooth and shiny gelcoat finishing which you can see on a brand new hull, and it's to never antifoul the hull, period. A preparation for antifouling the bottom which doesn't remove the very superficial gelcoat gloss surface is a poor preparation, where the a/f is bound to peel off in no time.
- So, leaving aside the fact that I had contrasting views also on the effects on gelcoat of a/f removal with chemical products, there's no way that such method could make the miracle of bringing back the gelcoat to as-new conditions. Those conditions were forever lost upon the first antifoul.

In fact, it's interesting to see here the pics that Hurricane posted after coppercoating his P67, which back then was only 2 years old.
The previous a/f layers (which were bound to be much thinner vs. my 14yo boat, obviously) were removed with wet slurry blasting, which is widely recognised to be more gentle than dry blasting - though the operator hand/expertise remains the most critical component, afaik.
Unfortunately, Hurricane didn't post any very enlarged pic, so it's hard to evaluate exactly the superficial gelcoat conditions - though a proper evaluations can only be done in flesh anyway, touching the real thing and looking at it, possibly with a magnifier lens.
But it's clear from his pics that the bottom didn't have the glossy superficial finishing of brand new gelcoat anymore.
Would you call that "gelcoat removal" for this reason alone...

Just to add my comment.
I WOULD use slurry blasting in favour of sand blasting even if there were lots of layers of old a/f.
As to the final finish after slurry blasting, the process had left the gelcoat intact but had taken the shine off.
This left a rough surface which was an excellent base for the Coppercoat.
And, yes, we applied the Coppercoat without an initial epoxy coat.
Now, several years since, the Coppercoat is still in good condition - well it was when we last looked!!

 

[Portofino]

There’s obviously been some “ osmotic “ events on MapishM s boat.

Blistering is in a nut shell from a chemical reaction .Seawater + “some others “ .
The exact “ some others “ does not matter cos you can,t do ought about them .They are in your hull lay up .The whys and where fores are wasting oxygen

Said to be un cured resin(s) react with the chemicals in the seawater produce a byproduct that via osmosis attracts water through and its the excess water that causes the blister of the outer Gelcoat layer .

Let’s not beat around the bush .

Back to JFM,s point if there’s no chemical reaction ,ie the layup is inert then who cares about the moisture content - gel coat may as well be a sieve .Thats a different issue .

Here we have blistering

That leaves seawater as the only thing you have any control over .

In theory the gel coat supposed to minimise the chances of the seawater getting through to the underlying lay up .
Minimise not 100% waterproofing.

So as said in a none reactive layup who cares apart a buyers surveyor ?

Blasting it has thinned down the protective layer , Sanding it has smoothed it a bit and also thinned it down .
“Finger smoothness “ with all due respect means nothing. It’s the permeability to water that counts and you can,t tell that running your finger about !

So if it’s blistered with full thickness then surley it’s more likely to leak more than ever and more so if blast it again and again .

So the requirement to re seal in this instance is more than say a none blisters boat like Hurricane,s ?
Does not really matter how much water gets in Hurricanes none reactive boat .

Of course which ever method is used to put back what’s been removed in an attempt to reseal is highly technique sensitive ,

If you don,t thicken up the external integumentary layer properly then any areas nearly about to blister will now have greater chance for water contact .

Why did you do it —- have it blasted ? I,am with PYB on this

I think you are not appreciating the gravitas of an NONE intact integumen - with potentially reactive chemicals in your hull .

Re smooth bottom s ——- boats

We are not in the America’s cup

Your diesel bill has far too many variables imho in the Med

For me I would just if blistered - *** like yours s localised repair if a few .

Smooth / gently sand the existing AF to improve the surface ( not harming the gel coat ) and reapply AF .

Or if for what ever reason I thought total removal was necessary then chemically strip it ,with the associated hassle .

*** Did you have a hull survey ? When you bought it - just trying to piece together the history of these blisters .

 

[jfm]

Ref your first sentence, the blisters are not osmosis.

 

[PowerYachtBlog]

In theory the gel coat supposed to minimise the chances of the seawater getting through to the underlying lay up .
Minimise not 100% waterproofing.

I do not agree here since gelcoat is one of the most water pouring painting products out there. Even the paint in your car is better to gelcoat.
The advantage of gelcoat is it bonds with resin like nothing else.
The blister that Mapis showed is not an osmotic event because no resin popped out. It is how he says trapped air which when the soda blasting was made left a 6mm hole.
Your real osmosis protection is the resin behind the gelcoat, and after that the glass and stratification used.

If I was him I would cover that hole (and others that popped out) with Epoxy resin, and then if not enough of gel left Epoxy resin the hull and then do an Epoxy based primer.


Over ten years ago I used to take care of a new Fairline Phantom and in the first season out of the water and after power wash (no soda blasting) the boat had chunks of dozen gel-coat bits (largest about 5in squared) falling of the hull. After speaking with local GRP experts they said it was nothing and this was not a case of delamination, since the resin behind them was full intact. Anyways we covered these bits with epoxy, and primed the hull.
In 2003 and 5 this was happening in a lot of new boats since resin companies changed the matrix of the resin to be less polluting and also had a new fire retardant element introduced into it.

 

[Portofino]

I don,t buy into trapped air threory after all these years .

There’s been a chemical “event “ under the waterline .

The pressure of the products of that particular event caused the blister .

Therefore it makes logical sense if possible to protect the underwater parts from what seems the common denominator seawater .
Above the WL has been spared blistering how does this “ air “ know exactly where the WL is ? —-

So if it’s not air or any other gas that doesn’t leave much else .
It’s not a product of any further polymerisation of resins , the only thing left that pushed out these blisters under the WL is what ?
Irrespective of what you want to name it I think restoration of the integumentary layer is important under the WL .

 

[Portofino]

Over ten years ago I used to take care of a new Fairline Phantom and in the first season out of the water and after power wash (no soda blasting) the boat had chunks of dozen gel-coat bits (largest about 5in squared) falling of the hull. After speaking with local GRP experts they said it was nothing and this was not a case of delamination, since the resin behind them was full intact. Anyways we covered these bits with epoxy, and primed the hull.
In 2003 and 5 this was happening in a lot of new boats since resin companies changed the matrix of the resin to be less polluting and also had a new fire retardant element introduced into it.

Below the WL ? Only

I rest my case

 

[PowerYachtBlog]

Below the WL ? Only

I rest my case

Yes and in that same year I saw a Princess, an Azimut, and a Sunseeker with the same problem.

 

[MapisM]

Yes in Hurricane method with wet sand blasting the gel coat looks still very much intact. Reading some posts I think you said you removed the gelcoat or not?
You need the gel to become a bit rough for it to stick something to it or else nothing bonds.

Following ones dreams if that entails to own a boat is never daf.
But I know how some Italian moaners say the best day in a boaters life is the day you buy it and the day you sell it. I am sure you are not one of them.

I don't think I said that I stripped the gelcoat - I did mention a "complete a/f removal" in post #7, maybe that's the reason for the confusion.
Anyway, all clarified & agreed. :encouragement:

PS: Ref your last sentence, LOL, I don't think to be a follower of that old saying, after keeping the old lady for 17 years, and hoping to keep the DP for about as much...
...I must admit that there's some truth in that, though. I wasn't aware that it's an IT-specific wisdom, btw. Is it?

 

[MapisM]

I don,t buy into trapped air threory after all these years.

There’s been a chemical “event “ under the waterline .

The pressure of the products of that particular event caused the blister .

Therefore it makes logical sense if possible to protect the underwater parts from what seems the common denominator seawater .
Above the WL has been spared blistering how does this “ air “ know exactly where the WL is ? —-

So if it’s not air or any other gas that doesn’t leave much else .
It’s not a product of any further polymerisation of resins , the only thing left that pushed out these blisters under the WL is what ?
Irrespective of what you want to name it I think restoration of the integumentary layer is important under the WL .

L, you are free to not buy anything that was said of course - not just by myself, but also from others - including PYB in his post #32, which is absolutely spot on.

But your question about why trapped air bubbles happen to be only under the w/line, well, that doesn't take much more than common sense to be sorted...!
The answer is that they don't, and there might well have been some anywhere else, also in the top deck mould, right upon lamination of each and every GRP bit.
And mind, that is absolutely not specific of my boat, but is true of any GRP boat.
Otoh, anything above the w/l is not constantly exposed to water (let alone at some pressure), and that makes a world of difference, because as PYB correctly said, the gelcoat ain't waterproof by any stretch of imagination - contrarily to what most boaters believe, including yourself, as I understand.
Therefore, any tiny air bubble left in the hull bottom between the gelcoat and the first GRP layer is a void which, in the long run, is bound to be filled (and to some extent enlarged) by seawater under pressure.
Above the w/line, what happens is exactly the opposite, i.e. that any void is much more likely to self-cure in the long run, with the air bubble progressively flowing through the gelcoat.
Remember, we are talking of microbubbles here - absolutely not visible and impossible to identify, initially.

So, unless you have some very peculiar situation, like awfully poor construction with bad materials, and/or gelcoat above the w/line which stays "trapped" for some reason, you will never find blistering above the w/line. A couple of examples of blistering above the w/line that I'm aware of are:
- in boats where cushions (typically foredeck cushions) are left in place 24/7, possibly also in the winter, the constant humidity trapped inside can in the long run blister the gelcoat underneath. I witnessed that personally on an Azimut 58 which I evaluated during my search - and btw, that was MUCH worse than in my hull, go figure...
- in decks covered with teak, whenever the seams loose their adhesion to the planks and let rainwater find its way between the teak and the GRP (obviously getting trapped inside, potentially forever), it's not unusual to find a blistered deck upon teak removal.
No first hand experience on this second case - and luckily it wasn't the case in my boat, in spite of the fact that the OEM teak which I recently stripped did have worn out rubbers, hence a lot of humidity between the GRP and the wood, in places.
But I have it on good authority that this can and does happen.

Btw, taking of authoritative sources, just for the records, it's not like I didn't make my homework before removing the a/f, evaluating what to do now, etc.
I can see why you felt entitled to sentence that finger smoothness “with all due respect means nothing", but there's one thing I didn't mention, i.e. that one of those "fingers" was of a specialist from this company.
Sorry if you can't find Itama among their references - maybe it's just because they are a bit far from Rome, and Amati preferred to have his hulls laminated by someone closer to his home.
But hopefully Riva, Benetti, CRN, Wally, and all others can make up for that...

 

[Portofino]

Reminds me of this parable

Frog Research

Take a healthy frog put it on the edge of table and ask it to jump . Measure and record the L of the jump .
Next ,amputate one front leg , repeat the experiment. measure and record the L of the jump .
Repeat this after amputation of the other front leg measure and record the L —— note the L stays the same
Now amputate one back leg , ask it to jump , measure and record the L ——- note the L is now getting shorter .
Finally amputate the remaining back leg - repeat the experiment - ask it to jump - Result you note down = it does not move !

Conclusion you publish

To make a frog go deaf - amputate ALL it’s legs

Happy to agree there’s a lot of Frog research flying about on the interaction of grp and water .


Do tell what you going to do next with the hull ?

 

[MapisM]

Do tell what you going to do next with the hull ?

I'm happy to tell, but only if you'll explain me how exactly my reasoning reminded you of frogs.
Not trying to pick a fight, mind.
But if you think that what I wrote is plain BS, by just stating that it reminds you of a silly joke you are not helping anyone to better understand anything. :ambivalence:

 

[Portofino]

I'm happy to tell, but only if you'll explain me how exactly my reasoning reminded you of frogs.
Not trying to pick a fight, mind.
But if you think that what I wrote is plain BS, by just stating that it reminds you of a silly joke you are not helping anyone to better understand anything. :ambivalence:

No not you personally

The subject - inaction of water and grp and what to do ( if any ) is full of “ frog research “

Hence the divergent and various approaches to diagnosis and treatment of the same condition, back up by “ research/ evidence “