Hull Strength After a Peel

[Jim H]

A general question: does a properly done hull peel and epoxy job have any effects on the strength or flexibility of a hull?

I've been looking at some sites that documented hull peels, and the process looks like it can remove a fair amount of material from the hull. This is replaced by the epoxy job, but is the general strength of the hull improved, left the same, or possibly reduced by the process?

Also, I've read that an epoxy job is normally good for ten years. At that point, what is the process for "refreshing" the epoxy?

Thanks for the comments-- we're not in a rush to own a cruiser, but the following ad caught our attention:

http://seattle.craigslist.org/boa/115884905.html

We're impressed by the recent upgrades, but I looking to learn more about pros and cons of peel jobs.

Thanks!

[Richhh]

Peeling involves removing the gelcoat and into a substantial portion of the matting layer. The matting layer is a random oriented layer of glass strand and is not considered to much degree to be a structural layer; it is essentially a cosmetic 'cushion' layer between the gelcoat and the structural roving/cloth beneath. It prevents the gelcoat from being cosmetically deformed by thermal cycling and continual further 'curing' of the underlayment; and, thus allows the gel to remain smooth and flat over the lifetime of the hull.

I dont know if I agree if an epoxy job needs to be repeated/repaired after ten years. If sufficient barrier coat (an epoxy) is applied over an epoxy filled fairing of the peeled matting that it will need additional remediation at ten years. My previous boat that I peeled, added cloth and then faired with epoxy, then double barrier coated. still after 20 years since the application has no signs of hydrolysis nor blisters. My present hull is into its sixth season after such a repair and also has no evidence of degradation - also epoxy and cloth and then 'double thick barrier coated'. I have noted that the barrier coat manufacturers have consistantly recommended increasingly thicker and thicker application coats over the years, my application simply 'got a jump' on their recommendations.

Most peel jobs are the result of a 'moron with an uncalibrated moisture meter' ... and moisture meters only read 'surface moisture'. If you are considering a peel job, I strongly suggest that you take sample corings and send these cores to a composite materials analysis lab to determine IF you 'really' need to do a "peel job" - most do not.

Actually most 'blister/peel jobs' are probably uneeded and unnecessarily expensive 'hype' jobs. Only if the hull is suffering from evidence of extreme hydrolysis (destruction of the polyester molecules similar to a metal 'rusting') should one consider a 'peel job'. Only with the beginnings of delamination or hydrolysis down into the roving/structural layers should one consider a 'peel job'. Go to www.yachtsurvey.com and follow the link to 'blisters' for further discussions on peeling, blisters, etc.

Myself when doing a preliminary survey for a new boat usually consider ANY DIY attempt at blister repair a 'deal breaker' and a cause to reject a boat. Most boat hulls are usually 'ruined' by DIY blister repair and usually need total removal of the DIY repair to gain back to a solid integral hull. Blisters and their repair to me is just expensive 'hype' which creates a great deal of (unnecessary) income for those who support such 'hype'. Rarely do you ever find a boat whose 'blisters' are down into the structural layers. When was the FIRST time you ever heard of a boat that sank because of blisters? If you are not 'racing' or have an obsessive need for a drastically smooth and fair hull then there is hardly a true need for blister repair. HYPE!!!!!

[Euro Cruiser]

I attended two seminars during the 2004-2005 winter, given at the Cruising Association House in London, delivered by individual surveyors who had no relationship to each other. One had been a surveyor for 30 years, the other began his career as a chemist with International Paints and moved into consulting on behalf of both builders and (unhappy) owners of large megayachts. Both presentations abounded in slides & accommpanying longitudinal reports on specific laminate failings and how they ultimately were resolved.

It was a very interesting experience to attend these programs because the two men had very different conclusions in some areas. However, they agreed on the following in spades:
1. Peeling does not remove the cause of the blistering. It removes the blisters.
2. Because the depth of a peel will depend on the depth of laminate damage, when some of the structural lay-up is removed, it needs to be replaced; OTOH this is usually not needed.
3. Barrier coats, properly applied, do not provide an end cure; they do not have an infinite lifespan. This didn't used to be the professional view but, now that more time has passed, it is clear that so long as the cause of the blistering remains in the laminate, blistering will eventually return.
4. An epoxy-based barrier coat will have a lifespan of approximately 10-15 years, after which it will need to be removed and replaced. (Coincidentally, this was demonstrated just a few months later by two boats I know well, both with 13 year-old epoxy barrier coats that had been totally effective). Some boats fair better (the barrier lasts longer) because of course boats are used differently in different waters in different climates, and because the source(s) of the blistering can vary in degree between one hull's layup and the next.
5. Use of Iso gelcoats on newer boats slows down the onset of blistering but it doesn't stop it. Again, if the cause of blistering resides in the laminate, iso gels just slow the intrusion of water into the laminate. Their presence on the laminate's surface does not elminate the cause buried in the laminate.

I should add that this whole issue (laminate blistering) is taken much more seriously in the UK than here in the USA. Some sailors view it as the onset of the death of the vessel. One message emphasized by both UK surveyors was that UK boat owners should chill a significant amount about this topic; neither had seen more than a few examples of boats being structurally compromised due to laminate blistering. (They had a total of 50 years surveying experience). Still, it obviously presents problems insofar as how we view the desirability of a boat.

Jack

[Jim H]

This is an interesting subject.

Both of your replies seem to suggest the following:

1) Most blistering is not a structural problem.
2) Most peel jobs are not necesary.
3) A DIY repair job, or a poorly done yard job can do more damage than the blistering itself.
4) The blistering is caused by the laminate itself, and the peel only removes the blisters.
5) Epoxy coats, even if done right, can have a lifespan of 10-15 years, and then blistering can return.
6) Even new/newer boats may develop blisters, but after a longer period of time.

This makes me think of the informaiton I've heard about Valiant sailboats built during the "fire retardant" resin period. Some reviewers recommend seeking out these boats, because their selling prices will be significantly affected by the blisters, yet the boats may be prefectly fine other than the cosmetic issues or relatively easy ongoing blister repairs (unless poorly done...).

However, I've been on a Valiant where even the deck had small blisters, and owners have even called their boats "blister factories." If the problem accellerates, perhaps when a cold water boat is moved to a warm/humid area, it seems like the matter could get out of hand even for someone who knows the blisters aren't a structural problem.

There's a local Valiant that had both the hull and decks epoxy coated (though I don't think a deck can peeled?) after being allowed to dry for two years. Obviously, significant investments are being made to combat this issue (with solutions that may not last).

Given this, in most cases, is a blistering boat (light to moderate) an opportunity or a morass to run away from?

[Jon D]

Jim H once whispered in the wind:
This is an interesting subject.

Both of your replies seem to suggest the following:

1) Most blistering is not a structural problem.
2) Most peel jobs are not necesary.
3) A DIY repair job, or a poorly done yard job can do more damage than the blistering itself.
4) The blistering is caused by the laminate itself, and the peel only removes the blisters.
5) Epoxy coats, even if done right, can have a lifespan of 10-15 years, and then blistering can return.
6) Even new/newer boats may develop blisters, but after a longer period of time.

Given this, in most cases, is a blistering boat (light to moderate) an opportunity or a morass to run away from?

Jim our 85 Moody 47 developed lots of very small blisters after 19 years. We had a laminate profile done and it showed that the blisters were primarily in the gel coat and just into the first layer of glass. Moisture went from >25% to less than 4% as they peeled back layers. They did a peel and took of less than .25" total. Added back a layer of glass with vinylester resin and the hull is probably stronger than new. I expect that this will solve the issue for another 15 years or more. As i understand it blisters are caused by water being trapped in the laminate and interacting with the resins to form acids that then begin to disolve the glass and form blisters. Couple of good write-ups on the web talking about the process. In fact one of the worst things you can do is put epoxy barrier coat over a damp hull, will blister faster than no treatment by orders of magnitude.

Would I stay away from a boat with non structural blisters - probably not as long as priced right to account for the repair. Will the boat be harder to sell in the future -- depends on the boat and buyer. Anb educated buyer should not sweat it if repair done right...

[Euro Cruiser]

What we seem to now know with certainty is that there are a number of ways in which a lay-up can be done poorly, each of which can result in water absorption & blistering. I have seen not only huge (bumblebee e.g.) insects laid up in laminates but even small birds.

However, assuming some level of environmental protection within the laminate shop, a major cause of future blistering seems to be the hygroscopic chemicals the laminate shop intentionally uses, most notably Propylene Glycol. By definition these are water-absorbing chemicals and I think this is usually as close as it gets to 'water being trapped in the laminate'. It's actually a chemical in the laminate attracting water.

This is why hulls may not 'dry out' or why a 'dry' hull seems to be okay, yet eventually reblisters. The glycols themselves are still resident in the laminate and, either immediately or after a barrier coat eventually is permeated, absorb moisture.

Jack

[Alan Wheeler]

The contaminations in the GRP make up is NOT the cause of water being drawn into the hull. The contaminants are what cause the chemical reaction AFTER that water has got there. It is Osmosis that draws the water into the hull material. It take time for the water to get in there. Years infact. The water can go in both directions, in and out of the material. But because it is so slow in coming in and thus going out, any pressure build up due to atmospheric pressure, heat of the day, etc etc, cuases an internal pressure and with the chemical reaction creating an acidic nature, the material starts to form a larger void. And eventuall a blister is formed.
A hull peel does not get rid of blisters and voids and what have you. It only removes the membrane that stops water from exiting the blisters and aid sin a faster drying time.
The hull MUST be dry before the epoxy barrier is applied. This does not take two years to do so. Infact, two years outside in uV, would be totaly destructive to the unprotected glass that was exposed and would create a surface open to being a playground to blisters once again.
The entire idea of hull peels is to get the job done much much faster than if you were just allowing the hull to dry under it's own means. The hull should be peeled and dried under heat sources and then sealed as soon as dry.
Epoxy barriers are just that. They are a non-porouse membrane. Water can not migrate through the Epoxy barrier. The only way for a blister to appear again, is there had to have been moisture trapped under the epoxy when it was applied.

[speedoo]

If the bottom has a lot of blisters, that is usually a sign that the problem has to be addressed ... there is potential for serious damage to be done to the structural laminate. Going after the individual blisters is not at all cost effective, so peeling is the appropriate action to be taken. Followed by drying and barrier coating.

I do not agree that a hull that has a serious blister problem (called "pox" is some of the literature) is simply a cosmetic issue.

[Jon D]

I agree with what Wheels just said only difference I would have is that a peel can get rid of the blisters, voids etc to the point where the peel stops. In many cases a well built boat may only have issues in the very surface layers and a proper peel etc can fix the issue.

[delmarrey]

Here's an artical that might be of interest!

Blisters & Laminate Hydrolysis

And as for the Cal 2-34, Cal's seem to have a pretty good rep.

My first boat, a Cal 2-27, was excellant. Strong and fast!..........._/)

[Jim H]

Delmarrey,

Thanks for the link-- the process they use is explained well, but their prognosis seems rather bleak. They may be right, but the article suggests that all hulls are in trouble, and even the older hulls end up with "severe hydrolysis but no blisters." And "hydrolyzed laminates are not redeemable." This suggests that even pre-72 boats with no blisters may have decomposing laminates (leading to more flex and fatigue failure). Thus, we need their process that replaces the laminate with new cloth and uses vinylester resins. (They advise against simply using an epoxy barrier coat.)

If it's true that what they claim is inevitable, then the $300 to $500 per foot process (possibly more to get the faired and repainted topsides that match) could put lower cost older boats into the realm of not worth owning. (I'm not saying I fully believe their argument, of course.)

This thread has provided a lot to think about-- but there does seem to be a range of opinions and beliefs about what is necessary or advisable. For example, one could opt for a boat that has already been peeled and treated, but then could worry about the quality and longevity of the work. Alternatively, the boat could be purposely bought having not been peeled yet, with the consideration it may be needed later but done well at significant cost.

[GordMay]

Some excellent online articles:

Thanks to Capt Lar:
“THE CAUSES OF BOAT HULL BLISTERS”
By
Thomas J. Rockett, Ph.D. and Vincent Rose, Ph.D.
Department of Chemical Engineering; University of Rhode Island; Kingston, Rhode Island
http://www.daviscoltd.com/nams/Docum...er_Report.html

Thanks to Rick:
”BLISTERS & LAMINATE HYDROLYSIS” ~ by Craig Bumgarner
http://www.zahnisers.com/repair/blister/blister1.htm

”To Buy or Not to Buy - A Blistered Boat, That Is” ~ by David Pascoe
http://marinesurvey.com/yacht/BuyingBlisterBoat.htm

”Failed Blister Repairs - A Case History and Solutions” ~ by David Pascoe
http://marinesurvey.com/yacht/BlisterRepairFail.htm

[Euro Cruiser]

Well, at least we can see where we disagree. E.g. epoxy barrier coats are not only porous but even pass water faster than some resins.

Also, when I read "The contaminations in the GRP make up is NOT the cause of water being drawn into the hull" I wonder if terminology is getting in the way of clarity. Laminate builders intentionally use hygroscopic chemicals, so it's probably neither fair to label them as 'contaminants' nor to deny their existance. If we can get to that common ground, then a claim that a water-absorbing element in the laminate does not contribute to water aborption thru a permeable laminate is probably not a reasonable expectation.

Jack

[AllAboutMe]

I'm glad I ran across this thread. While there are alot of "expert opinions" around re:delamination and repair, there are very few sources of information that aren't sites trying to sell their "fix" .
I recently acquired a CS27, a boat famous for it's hull pox problems. The hull was peeled a couple of years ago, but there has been no repair to date. The exposed laminate seems to be dry, and solid. One of the posts above mentioned possible UV damage from extended exposure. How would one determine the extent of this damage? The surface is solid, not powdery, there is no flaking of the glass. There are no obvious cracks in the hull, and the area around the keel attachment is solid.
The peel thickness is approx. .25" or less. I will fill the remaining blister craters with Interlux waterproof filler, and I plan to epoxy two layers of 15 oz woven glass,using West epoxy and slow hardener, and then barrier coat to bring the surface to the same height as the original gelcote. Do any of you see any fault with this plan of action?
While I'm not a professional glass worker, I have done enough glass work to feel confident that I can do an above average repair. What specific concerns are there as far as diy repairs of this type?