Fiberglass Blister Myths?

Jeff Asbury

Principal Partner
Fiberglass Blister Myths?

I have heard from different folks on the docks as well as some professional boat maintenance people that boats with fiberglass hulls that were made after a time in the mid Seventies (74 or 75), are more susceptible to blistering. When I purchased my 1973 E-27 four years ago, she was in pretty rough shape but when i hauled her we only found two small blisters near the prop strut. I have not hauled out for four years now because the paint is holding up quite well. I do plan to haul out this winter because I have read that if you let it go for that long, you are asking for trouble.

This is from: www.boats.com

"The URI study indicates that most fiberglass hulls are vulnerable to blistering or internal water damage as a result of long periods of immersion. It suggests that the hull should be sanded and coated below the waterline every one to three years, depending on water temperature and the length of time afloat each year. If the boat is in cold water for only six months per year and the bottom is carefully inspected every year, renewing the bottom coating every three years may do the job. If the boat is afloat in warm water 12 months per year, the coating should probably be renewed annually."

I know of two identical 1977 Islander 28's that have had severe blistering after less than 3 years in the water. I also have a good friend that has a 1977 Ericson 25 that is very badly blistered after less than three years and has been given a Yard estimate of $6,000. to do the repairs and re gel coat.

Note that all three boats are from the later 1970's and my boat is a 1973.

Is there any truth that the polymer compounds were changed around 74 or 75 for environmental or economic reasons?

Should I send this in to the TV show Myth Busters or does anyone here have a answer for me?:confused:
 
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Jeff Asbury

Principal Partner
I did a little more research on line!

I did a little more research on line and found this article from:
marinesurvey.com*

The Wonderful World of**Hull Blistering by David Pascoe, Marine Surveyor

Not long ago a marine surveyor wrote a letter to the editor of a boating publication. In that letter he indicated that it was his experience that prior to around 1970 he had encountered very few fiberglass boats with bottom blisters. Then, suddenly in the mid 1970's, bottom blistering seemed to blossom into a chronic problem throughout the boat building industry.*
He further wondered if the 1973-4 Arab oil embargo, which dramatically raised the price of oil (and therefore the price of plastics) for a year or so, didn't lie at the heart of the problem. Since then other writings on the subject have appeared, and other surveyors have been heard to make similar comments. Indeed, hull blistering was not a major problem since the first fiberglass hulls were built in the late 1940's, until the advent of mass production on a large scale beginning around 1970.*
Mass production of small boats began in the mid 1950's, larger boats starting in 1960 with the advent of Bertram, Hatteras and Hinckley. The transition from wood construction to fiberglass was nearly completed by 1970, at which time very few wooden boats were being built.*
These comments caught my attention because it had also been my perception that very few boats ever developed hull blisters prior to the mid 70's. This is not to say that hull blisters never occurred prior to this time, because they did. In fact, one of the very first reinforced plastic hulls built in the 1930's developed all sorts of problems, including what has been described as blistering. But those problems have long since been solved and there is no excuse for the wide scale blistering of hull bottoms that occurs today, despite the absolute knowledge of every boat builder of what materials to use to avoid blistering.*
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Note that Mr. Pascoe's opinions may be right or wrong, but he is *never* uncertain about his expertise.
:rolleyes:

Loren
 

rwthomas1

Sustaining Partner
Here is what I have read about fiberglass and polyester resins. Polyester resins contain VOC's (volatile organic compouds-solvents) that evaporate as the resin cures. That obnoxious smell polyester has is the VOC's. Cured polyester is lighter than "wet" polyester. This means that as the VOC's dissipate they leave 'holes" or pores in the finished product. These pathways allow water in and it reacts with the binders in the fiberglass mat causing blistering.

Epoxy resin is almost 100% solids so when cured it weighs the same as when wet. It has no pores or holes in it and is therefore much more resistant to blistering if not completely impervious. Epoxy is also very expensive compared to Polyester and more difficult to work with thats when most boat builders still use polyester resins.

Vinylester resins have some of the qualities of epoxy and some from polyester. They are much more resistant to blistering and some manufacturers are using them exclusively or at least for the first few layers of a hull to prevent blistering. Vinylesters are about halfway between polyester and epoxy in price.

My experience with blistering is limited to a few boats but what I have seen leads me to believe it is not that big a deal. A friend has a 48ft Hatteras that has pretty significant blistering. After letting it dry out for 3-4 months we sandblasted the bottom and then filled the blister depressions directly or ground them out and then filled them with epoxy filler and sanded smooth. The bottom was then treated with epoxy barrier coating. Yes it was quite a bit of work but not impossible. The barrier coat needs to be reapplied periodically. Some boats seem to blister, others don't. I know Valiant had some very bad years I think 78-80? as they tried a "flame retardant" resin and this proved especially blister prone. I would not worry about blisters untill you know you have a problem. Haul the boat and take a look. I am guessing that you will have few or none. RT
 

Steve

Member III
Was pleased not to find any blisters

Hand scraped and sanded to the original gel-coat on our 84 35-3 this spring. Likely after 15+(?) years of abuse from (cheaper) hard bottom paint build up. Didn't find a single blister, thought for sure we would... Barrier coated with four coats (gray-white-gray-white) for safety, then two coats of micron extra... I would not wish this job on anyone! .. very time and physically consuming not to mention the mess! (never again!)

Steve
 

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CaptnNero

Accelerant
where is your snorkel mask ?

Jeff, since you're going to haul out in a few more months anyway you might want to just dive the bottom now and take a look. If things are ok down below then when it's on the hard leave it to dry out the bottom paint at least a few weeks and get a good surveyor who really knows how to use a moisture meter to assess hull moisture levels and take it from there. You've got plenty of time to find a good one.

Jeff Asbury said:
Fiberglass Blister Myths?

I have heard from different folks on the docks as well as some professional boat maintenance people that boats with fiberglass hulls that were made after a time in the mid Seventies (74 or 75), are more susceptible to blistering. When I purchased my 1973 E-27 four years ago, she was in pretty rough shape but when i hauled her we only found two small blisters near the prop strut. I have not hauled out for four years now because the paint is holding up quite well. I do plan to haul out this winter because I have read that if you let it go for that long, you are asking for trouble.

This is from: www.boats.com

"The URI study indicates that most fiberglass hulls are vulnerable to blistering or internal water damage as a result of long periods of immersion. It suggests that the hull should be sanded and coated below the waterline every one to three years, depending on water temperature and the length of time afloat each year. If the boat is in cold water for only six months per year and the bottom is carefully inspected every year, renewing the bottom coating every three years may do the job. If the boat is afloat in warm water 12 months per year, the coating should probably be renewed annually."

I know of two identical 1977 Islander 28's that have had severe blistering after less than 3 years in the water. I also have a good friend that has a 1977 Ericson 25 that is very badly blistered after less than three years and has been given a Yard estimate of $6,000. to do the repairs and re gel coat.

Note that all three boats are from the later 1970's and my boat is a 1973.

Is there any truth that the polymer compounds were changed around 74 or 75 for environmental or economic reasons?

Should I send this in to the TV show Myth Busters or does anyone here have a answer for me?:confused:
 

Jeff Asbury

Principal Partner
Thanks for all the feed back guys.

Thanks for all the feed back guys. I did dive the boat Neal, it was in the very clear waters at Catalina Island. I looked all over the hull and found no blistering or peeling paint. I couldn't believe how good it looked. I use a monthly dive service and they keep telling me the paint is in very good condition. I will probably haul out in mid November and I will defiantly have it surveyed. It just seems strange that others in my Marina have had so much trouble with the later 1970's boats and I seem to be doing fine. It was interesting to read that it is important to keep the inside of the boat dry with a dehumidifier. I do, during the wet months. It must help.

Thanks again all but I guess my Myth has no definite answer yet.:confused:
 

hcpookie

Member III
Mythbusters - LOL!

There may be some relevance to a mysterious change in the magic forumlae that were in use during the mid-seventies. However, I would submit this humble opinion:

I read an online article that had some write-up about the material itself, and concluded that sloppy "assembly-line" construction can plague any boat design. It may have been that self-validating surveyor's site, I don't remember now.

The point of the online article was that they observed many poorly-mixed (read: heterogenous) coatings that had dry areas, wet areas, etc. where the hired hands didn't mix the goop enough to reach a good consistency. That led to a hull where some areas are more prone to wicking water into the fibers, causing the gelcoat breakdown and blistering.

Personally, I'm satisfied with that observation since that seems to make the most sense... because even *IF* you were to buy the most expensive goop that money could buy, and still not mix it properly, you'd have a crappy outcome! Something about reading those directions...



There are some rumors that some subcontracting took place in Mexico (pre-NAFTA days!) and the contractors either didn't know, didn't understand, or didn't care about the quality control levels needed for use as a gelcoat. The rumors concluded that some of the "made in Mexico" hulls are more likely to blister... but only sometime. Search this forum and you'll find some of those posts. Some have the problem, others don't...

Again, the inconsistency of the QA makes the most sense, because intermittent problems are a sign that the "unchanging" factors such as materials, shape, etc. are not a problem. In other words, if it WAS a mystic formula change, then "ALL" of the mid-seventies hulls would have some sort of gelcoat issue, even after factoring in different topcoats, environmental conditions, etc. etc.

All IMHO. My '75 -27 has the small blisters about the size of quarters and silver dollars, so I'm interested in hearing more authoritative responses! I think the conclusion that some of these articles reach is spot-on... "why" it happened is not nearly as important as "how" to correct the problem.
 
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Emerald

Moderator
Loren Beach said:
Note that Mr. Pascoe's opinions may be right or wrong, but he is *never* uncertain about his expertise.
:rolleyes:

Loren


Thank you for the chuckle Loren. I long ago reached the same conclusion after reading many of his articles (which are often interesting, to say the least) - couldn't have summed up your observation better :devil:


-David
Independence 31
Emerald
 

maggie-k

Member II
No boat has sunk from blisters part 1

Here is the definative artical on blistering by the old man him self Jan de Groot

Gelcoat Blisters
by
Jan de Groot
Copywritten, All Rights Reserved
I'm going to say this right here, right now: "Gelcoat blisters don't matter!" There, I said it, at the risk of being called an opinionated, stubborn Dutchman!
Probably, I inherited those terrible qualities from my Grandfather who built two fiberglass boats in his shipyard in Holland in the early fifties, This he did, despite predictions of doom and gloom, forecasted by numerous experts. Until that time, the yard had been using respectable materials such as wood and steel.
I remember those first two plastic boats because they created quite an upheaval amongst the workers in the yard. "The old man has gone off his rocker", they said. The boats were named after my two aunts, Cornelia and Josephine. They were (the boats, not my aunts) 37 foot, full keel sailing yachts, designed by Sparkman and Stephens.
But, I do not want to blame my Grandfather, rest his soul, for my blister problem. My problem is that gelcoat blisters do not appear to be a problem. Yet, everyone says, "They are!"
Many articles have been written by experts about their destructive qualities. They are referred to as the pox, cancer and all sorts of other horrible diseases which will cause certain death when inflicted upon a human being.
"Don't buy a boat with the pox", they say, "it will delaminate" - another scary term.
Some say blisters should be repaired by removing layers of laminates from the hull and then to be laid over with new layers of glass. Peeling machines are now being marketed to strip the layers from the hull. As a result, thousands of dollars are being spent on blister repair. I have seen figures as high as twenty thousand dollars for a thirty foot boat.
Why are gelcoat blisters considered to be such a disastrous problem? Based on what research and by whose authority?
To answer that question we have to examine the business of pleasure boating as a whole. In North America, pleasure boating and almost everything that is related to it, is pretty much a wide open, non regulated and uncontrolled industry.
As opposed to the building of a house, you don't need building permits, there is no building code, there is no building inspector. Anyone can build, use any type of design, any kind of material. Cardboard? Why not? No one will stop you, as long as you have the appropriate amount of life jackets, fire extinguishers, navigation lights and baling devices, you will probably pass the voluntary Coast Guard inspection, providing the boat doesn't sink before it reaches the Coast Guard dock.
Anyone can sell boats, no license required [in most states]; hang up a shingle and you are a boat surveyor - again no license required. And then, anyone, no age limit, no experience required, can take that eighty foot cardboard boat, powered by twin super charged one thousand horse power engines, out for a spin on the beckoning wild blue yonder.
You think Star Trek is the last frontier? No way, the boating business is. Isn't it wonderful? Yes, most definitely, it is. Pleasure boating is probably the only ungoverned pastime left on this polluted earth. No helmets, no license, no seat belts, and you're allowed to smoke on your boat too! You can even have a sip of brew while driving, although, that is pushing it a little bit. But, you can get away with it as long as you don't hit anybody.
I'm all for it! However, because of this, the boating industry attracts a lot of self appointed experts. The government doesn't appoint, so we do it ourselves. So, the experts are where the boats are. The number of experts closely equal the number of boats. Ask one question and you're bound to receive a multitude of answers and opinions. Most of the experts cast spells of doom and gloom and readily relate some tale of woe that has happened to so and so to add credit to their advice. Bear in mind that a gloomy view of something demands more attention and sounds more impressive. There is always a knowledgeable answer, let's face it, a reply such as "Gosh I don't know", or, "I have to read up on that", just doesn't cut it!
Now let's get back to blisters. I have also formed an opinion about blisters, just like all the other experts. I will back up that opinion by reasoning. Here is my case:
The first time I had to deal with a gelcoat blister problem was in the late sixties. Until then, I had not encountered it before, most certainly not to the extent as in that particular case. As a result I did a lot of research and talked to a lot of people in the fiberglass trade. I did not get any deeply researched scientific answers other than the fact that the gelcoat was blistering, as in 'paint blistering from wood or steel'. In other words, it's coming off! Perhaps it was because the surface underneath it was not prepped properly, or it was not dry when the gelcoat was applied or, it is just plain tired and worn and needs to be done again.
Since that time I have seen a lot of boat bottoms. These busy days, through my Company, I see or hear of and deal with as many as close to a thousand per year. Therefore, I think I can safely say that I see more 'bottoms' than most and that includes boat yards. It is therefor, I think, safe to say that it is likely that I have seen, tapped, probed, dug into and caressed more blisters than most.
Yet, after having had a working part in the boating industry since the days well before fiberglass, I have never encountered a fiberglass boat that was in any way structurally damaged or unsafe to operate as a result of gelcoat blisters. To silence any critics of this statement I suggest they produce or point out a boat of normal solid fiberglass construction which has become structurally unsound and unsafe to be operated for it's intended service as a result of gelcoat blisters. If they can, I'll eat it!
Gelcoat blister problems can occur due to three basic reasons:
1. The use of type of resins, such as fire retardant resins. In this case blisters are generally also apparent above the waterline of the hull and on the superstructure. It is not caused by water. It can not be fixed because the problem is within the composition of the hull laminates.
2. Poor building procedures. The fiberglass cloth is not stored properly and has become damp prior to layup. The result is intermittent and generally poor bonding of the resins with the cloth and the gelcoat. The blisters may appear above as well as below the waterline. As a rule the vessel will have internal delamination of the fiberglass layers and may or may not have any gelcoat blisters. The delaminated areas may show up as very large blisters and the outer layer of the blister will be thick since it may contain several laminates. This is a structural problem and is difficult if not impossible to repair.
3. Water migrates through the gelcoat. Blisters are located under the water line and sometimes located along the water line only. When punctured, the blisters contain a colorless liquid which is acidic.
Number 1. Is mainly encountered in a certain series and make of production boat. The manufacturer corrected the problem several years ago.
Number 2. Is rare and not typical of production type boats. I have encountered it sporadically. In each instance the boats were manufactured by companies who normally produce a very good product.
Number 3. This is the one occurring frequently and which is the one most of us have seen evidence of and which is the topic of this article.
Let's examine the procedure. Water migrates through the gelcoat. This takes time. The speed depends on the thickness and or the porosity of the gelcoat. In fresh water, the effect can be quicker because fresh water is thinner and lighter than salt water.
Lessons to be learned from this are: Do not sand or scrape the gelcoat prior to painting with anti-fouling paint because it makes the gelcoat porous and thinner. (I have been preaching against sanding and scraping for years. Now, some manufacturers, such as Hunter Marine, do not allow sanding of the gelcoat. It will void the warranty against blistering of the gelcoat. Perhaps my cries of agony have been heard!)
Older boats are less likely to get blisters because their gelcoat is thicker, as a matter of fact, so is their entire lay-up, thicker that is. Some older boats will never get blisters because they were built differently.
The laminates of most glass boats consist of mat and woven roving impregnated with resin. Roving are strands of glass fibers which are woven together as in a piece of textile. Mat, on the other hand is made up of chopped up strands of glass fibers which are held together by a starch like substance. In each case, the whole thing becomes a solid piece when saturated with resin.
Woven roving has tear strength. It is difficult to pull apart. Mat has no tear strength and can easily be pulled apart. It acts as a filler, making the hull thicker and stiffer. It has some impact strength, but that is all.
 
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maggie-k

Member II
Part 2

Early fiberglass boats were built over male molds, up side down. The inner layer of the glass was the first layer, the outer layer the last. As a rule, the last layer was woven roving, not mat. Gelcoat was applied last, as a finish. (The very early boats had no gelcoat at all. The hull was faired, sanded, and then painted) In some cases, especially with hard chine hulls, the hull was gelcoated and tightly wrapped with plastic. When the gelcoat was cured, the plastic was removed, and bingo, a smooth finish!
As building techniques progressed, hulls were built in female molds. It was discovered that the gelcoat could be applied first to the inside of the mold and then the layers of roving and mat were laid over that. It was soon discovered that, upon close examination, the pattern of the woven roving, which was adjacent to the gelcoat, would show, especially if the gelcoat was thin. This is called "print through".
This caused the manufacturers to reverse the procedure and put the mat next to the gelcoat instead of woven roving. (Mat has no pattern and a much finer texture) There is only one problem - the fibers in mat are held together with a starch like substance. I believe this to be the culprit of the blisters to some extent and the reason of the damage caused by the blisters to a great extent.
The general consensus amongst chemists is that when water migrates through the gelcoat and remains there for some time without circulation, (REMEMBER THIS) that a chemical reaction takes place which produces acid. It appears that the acid dissolves the starch like substance which in turn dislodges the resin and possibly evacuates this through the process of osmosis. In other words, it slowly disperses back out through the gelcoat to set up a balance with the surrounding water.
When the blister becomes the approximate size of a quarter, as a rule, when opened up, a small cavity can be seen in the outer laminate, which is the layer of mat. What one sees are the loose glass fibers, the resin is absent. Providing the boat was built properly in the first place, meaning same is not kept afloat on this layer of mat, in which case it would have broken up well before the blisters appear, these cavities do not weaken the structure.
I have never seen the woven roving affected by this process, which again proves the fact that it is the acid combined with the binding agent in the mat, and not the resin, which is the culprit.
Remember that in order for the chemical reaction to take place, the water has to have been trapped under the gelcoat for some time without circulation. It therefore follows that if the blisters are punctured at an early stage, before they have been able to cause any damage, there will be circulation, thus, the acid will not form or get to a stage where it can be harmful.
In any event, as I said, the damage, if any, is restricted to the outer layer of mat, which is not a structural component of the hull laminates anyhow and is there strictly for cosmetic purposes. In fact, many fiberglass boats have been built and repair jobs have been done, without a coating of gelcoat. Obviously, there is no need to spend a fortune by peeling layers of glass from the hull.
At most, to achieve a cosmetically pleasing appearance, the blister can be removed by sand blasting or grinding to remove the gelcoat, or by peeling of the gelcoat only, faired with filler and then sealed with any of the products readily available and suitable for that purpose. Or, otherwise, just grind the blisters off and paint!
Whatever you do, do not strip layers of laminates from the hull. This will structurally harm the vessel. There is no guarantee that the new layers applied will stick properly. In many cases where I have seen this done, the new layers are blistering, then you do have a problem because the hull laminates are now weakened!
A fiberglass hull does not absorb water. Core material, yes, but solid glass, no! Glass and resins are inert. There is no space for water. That plastic bucket that has contained water for many years, is as dry as a bone when the surface is wiped and dried. I put a humidity meter on a water bucket which my wife had used for many years in the paddock of her horse. I emptied it, gave it a good wipe and left in the sunshine for twenty minutes. The humidity reading was 5 percent, exactly the same as a brand new one.
It is often claimed that a hull has absorbed water and has therefore become heavier. These findings are based on readings with a humidity meter. Both statements are inaccurate. The humidity meter in the wrong hands is a dangerous instrument. The thing works by means of conductivity. The electrical current takes the shortest route through material with the least amount of resistance.
A humidity meter cannot be used over anti fouling paint because it is more conductive than fiberglass. Fire retardant resins cannot be metered for the same reason. Damp cloth, interior liners, paint, steel fuel tanks, water tanks, wooden frames and floors, if installed against or near the fiberglass measured, will throw the meter off scale. I started using a humidity meter in 1981, and I am still learning. Further more, what is often misunderstood is that the meter gives a reading of RELATIVE humidity. Not solid water content. Listen to the weather report, the announcer may state that the relative humidity is 65 percent. That does not mean that we are standing up to our necks in water. In fact, I was told by an employee of Sovereign Moisture Meters that when the meter's needle is at 100 percent, the actual water content is equivalent to one drop of water per cubic foot of fiberglass.
The question of weight is another mystery. The statement goes, "the glass has absorbed water and therefore has become heavier." In the first place, glass cannot absorb water, it could only absorb water if there was vacant space in the laminates. (poorly built and delaminated) or, if water has displaced those areas previously occupied by fiberglass. In other words due to some mysterious process, water has removed the fiberglass from the hull and taken its place.
Let's assume for argument's sake that this is possible. Water is now occupying space that was previously occupied by fiberglass. Well, it now becomes a question of specific gravity. All I know is that if I dump a piece of fiberglass in the ocean, it sinks like a stone. Yet, the water which I pour from a bucket seems to just sort of float around. To me that indicates that water is lighter than fiberglass. In other words, if I substituted portions of fiberglass from my boat with water, the boat should become lighter, never heavier!
Coatings of paint, epoxy and gelcoat will blister. Paint will blister on wooden boats and houses, epoxy coatings blister on steel and ferro cement boats, gelcoat will blister on fiberglass boats. What does all this mean?
When a boat has blisters, I find I have to depreciate its value, not because of her being unsound or unsafe, but due to misinformation. The general public will either not buy that boat, or expect a price reduction. The result? There are a lot of good boats out there which are going cheaply because they have blisters, but will provide the same enjoyment and are as safe as those with the smooth bottoms. For racing sailors, there is actually an advantage to having a boat with blisters. If they loose the race they can blame it on the blisters rather their sailing skill!
How long does fiberglass last? Nobody knows, it hasn't been around long enough. Perhaps my Grandfather can give us some idea. Not long ago I was in Grenada, West Indies. I was looking for an ex crew member of mine who had opened up a bar on Hog Island. I went there to look him up, but he had gone away on some errand.
As I stood waiting I scanned the boats in the anchorage. One sail boat looked awfully familiar. I borrowed a dinghy and went in for a closer look. I rowed around the boat and eventually could not stop myself from being rude and climbed on board. I checked her over pretty carefully and concluded she was in pretty good shape and obviously ready and trimmed to take her owners on the next leg of their voyage.
As I rowed away, I stopped to give her one last look. The yacht had swung away, showing her transom. On it was her name, it read, Josephine. "Not bad", I thought, "she is now almost fifty years old and she keeps going, and going, and going..."
About the Author
 

Annapolis E-27

Member III
Can we put this to bed now?

Hooray..."gelcoat blisters don't matter!" Finally someone with the guts to officially admit this. As far as I know there has not been a catastophic failure of a hull from blisters however, a racer may loose .1kt but will still be safe.
 

Shadowfax

Member III
I too heard the stories that hcpookie refers to about the blistering in Ericson's began when the hulls where being made in Mexico. At the time of these stories the reason was that the hulls where laid up in humid, i.e. not air conditioned, conditions and thus moisture entered the mix.

Your guess is as good as mine as to how true this might be
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Liquid in our "Matrix"

Fully noting that "exceptions prove the rule" I actually remember reading about an Islander sailboat that was cut up and tossed, in Hawaii in the 80's. FWIW the Islanders had/have a blister problem. I have observed several with a lot of "shrinkage cracks" all over their cabin and decks, appearantly from the gel coat being applied too thickly. Not a structual issue, per se, on the ones I have seen, but the result shore aint purdy. :p

This is not related to the Valiant problem in the late 70's when they and some others builders tried the fire-retardent resin and found that it caused raised blisters all over -- cabin sides, etc.
I do know personally of one of these V-40's that was peeled and rebuilt to a pristine condition and then cruised blue water for many years.

Having seen bottom blisters in the gel coat layer on a lot of boat brands from all over the quality spectrum, I would agree that beyond resin chemistry, there is a further world of causality involved in manufacturing environment and QC, and perhaps even a little bit of Voodoo as well...
:confused:

Loren
 

CaptnNero

Accelerant
Jan de Groot, blistering reason #2

I read Jan de Groot's article with great interest. He covers a lot of technical ground and even points out the sales liability issue due to buyer perception, regardless of structural integrity. He makes some good points about the structural irrelevane of the cosmetic gelcoat and chopped strand mat layers.

With all due respect to Mr. de Groot, I am troubled by a single contradiction in his article. He starts out with the strong assertion "Gelcoat blisters don't matter". Then in his explanation of the three reasons that gelcoat blisters occur he contradicts himself. Under reason number two, "Poor building procedures", he concludes with "This is a structural problem and is difficult if not impossible to repair. " .

This cause appears to account for a small percentage of bisters and he says that it doesn't necessarily produce any blisters. The problem is that to determine the cause of blisters, it seems that some invasive hull surveying must be done and then repaired.
 
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Guy Stevens

Moderator
Moderator
Mix your chemicals well...

The Islanders in question did not have GELL COAT blisters, they had Interlaminate blisters.

Some blistering may occur also because the mixing of the MEKP did not go well. The MEKP is hydroscopic and may draw the water into the sections of the glass where it is not correclty mixed with the resin. This can cause either gell coat or interlaminate blisters. Bad QC. So mix those chemicals well if you ever lay up a hull :)

I was doing some consulting for a client in a yard yesterday and saw a really sad sight. A Catalina 38, The really pretty early ones designed by Sparkman and Stephens. A beautiful boat. The owner had gone at her really poorly with a hand grinder, taken out deep pockets not only of gell coat, but in most cases way into the laminate. He had then filled these craters with suposedly west system and cabisil. He had removed a significant portion of strength from the hull. Where there had been glass there was now only brittle epoxy and filler. He was going to have to fill all of them again even after he had ground down the high spots due to the epoxy shrinkage and saging. Looking at the boat, it was ruined her hull destroyed by his "fix" of the situation. There were a sufficient number of these craters that you could not easily grind them back out fair them, and repair the damage, it would take weeks of work if not a month or more to repair the fix.

Looking at the hull, I saw no signs that any of these blisters had been anything other than gell coat blisters. I may have been that they were interlaminate blisters, but I doubt it. I watched the owner with the grinder on its side, trying to remove the sags out of one of the filled craters, and believe that his inability to correctly use the grinder was the main cause of ruination of a beautiful boat...... He would have been much better to have put another coat of paint on her and put

Guy
:-(
 
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