Will this mehtod of blister repair last?

[Hermit Scott]

I buy a variable speed sander/polisher, some rollers and acetone and head to the coast to do my first bottom job. Armed with a respirator, goggles and 80 grit sanding pads I tear into the blue bottom paint on my catalina 30. I find a total of 9 blisters that range from 2" to 5" diameter all on the starboard side. All below the water line except one that extended up into the boot stripe. I tried sanding them, that took too long so, I used a 4 1/2" grinder with a braided wire wheel. I cut into the first one to get a viniger substance sprayed all over my face and hair. Lovely. Thankfully I was wearing goggles and a mask. I noticed that the woven structure underneath was intact and solid. IS that the case with most blisters?
I used the wire wheel to go outside the blister and work my way in to be sure to find uninfected areas and to be sure all the failed chopped mat was removed. I met a 'professional' that worked in the yard for 20 years. He told me how he filled the holes. I used a 3" roller and mixed a quart at a time of resin, clean the hole with acetone, tear the mat into sections leaving frayed ends. I slopped the resin in with the roller, laid a piece of mat, slopped more resin, another piece of mat, ect. Rolling from the center out to remove air then periodically removing air bubbles with a ribbed roller. It took all of 2 minutes to fill each hole. I sanded them flat, interlux 2000 e, and then interlux CSC, that I picked up for $59 a gallon. (The store was closing and I caught wind they were authorized to go 75% off.) I wanted blue but at that price...it's now red.
I heard alot about letting the blisters dry for a week or more, rinsing with water etc. Why would anyone do that when it's so easy to replace anything suspect or obviously failed?
The worst part was sanding the sloppy fiberglass that was all over the outside of the holes and getting them flat with the hull. This part was downright nasty and difficult to hold a sander up that long.
Any way when I was done they were flat and when I painted over them. You couldn't tell they had ever been there.
Will I have a problem later with this method of blister repair? It seemed too quick and too easy, other than the sanding of hardened resin.

 

[kloudie1]

Sounds like a roll of the dice, but a good one! If you got the wet stuff out, and the water has not wicked along the mat fibers too far, you probably bought yourself several years with those repairs. Most of us have done quick and dirty repairs and then planned a proper one for next opportunity, a year or maybe three or four. Your repair sounds fine except for the part of (maybe) not completely drying the area. (a very carefully applied heat gun can dry local areas pretty well) A barrier coat over the repairs may have helped too. Before next bottom job, go under with a mask and check those areas and nearby areas for more blisters.. that way you’ll have a better idea of how long to plan for the job to take. There is a lot of great info in the files and on the ‘net about blisters and ways to deal with them. Good luck and ENJOY the sailing !!

 

[yachtsmart]

Only thing I would add, is that it is best to use a vinylester resin when filling blisters.
Cap'n Jim
YachtSmart.net

 

[Hermit Scott]

blisters

Kloudie, I cut the mat back until there was no moisture and no delamination at all and went deep enough that any wetness was gone. They were dry as soon as I was done wire wheeling them out. I washed the holes and surrounding area with acetone and gave them one day to see if anything at all leaked or changed color. Nothing changed.
Since it sat for 7 or 8 years with out being hauled, I suspect there may be more blisters forming but how would I know? I found it interesting that there were no blisters portside. One side must have been laid up better at the factory.
What I don't understand and haven't heard a good explination for is; if fiberglass is water proof why would it matter if it gets wet? I thought the fiberglass chopped mat had somehting to do with it but it's the only thing intact in a blister.

 

[Tim R.]

Re: blisters

Fiberglass is not waterproof. Some resins are better than others. I think Epoxy is better than polyester. Gelcoat is what makes your boat waterproof(for the most part). That is why you need to seal the fiberglass with an epoxy barrier coat after you peel the gelcoat.

 

[Don S/V ILLusion]

It seems the chronology is backwards here.
You did the repair and then are asking for advice here - I wish you had asked before starting as you can't really tell if or how dry the mat is without, at a minimum, sealing it up with plastic for a sufficiently long enough period, to see if moisture is present - simply looking /feeling serves little purpose and using a moisture meter in untrained hands can be similarly misleading.

It is not uncommon for people with wet spots to leave them bare for months to ensure it is thoroughly dry.

Chances are you will eventually find more, hopefully small blisters and fore-armed is fore-warned.

 

[Hermit Scott]

advice

Keep in mind I had no idea what I was dealing with. I didn't really understand what it would be like doing fibergalass work, and I didn't really know what a blister would look like on the inside.
I got advice before I ever pulled the boat, even had a phone conversation with TonyB about it, but what I planned to do and what I did changed. I expected to pop the blisters and then let them weep dry occasionally spraying them with a water hose. I thought it was going to be like a zit, instead there was a hard outside layer and it was hard underneath and the fiberglass chopped mat was all there. It appears that the resin degraded into a brown liquid in a localized pocket, but only in the chopped layer not in the woven substrate underneath. I don't even know what's beneath the woven, maybe nothing from the way it sounds when I knock on it.
I planned on repairing the holes with a woven mat. But the people in the yard said that would take forever as the woven mat will be as thin as tissue paper once it is wetted, and would take many many layers to reach the gel coat height. And I would have had to keep mixing batches of resin.
From what I read on laying up fiberglass, getting it all in at one time seems to help prevent any water penetration.
I thought I would be able to have a few layers of woven mat all laid at once and fill in the hole completely. I still don't understand the bonding nature or the long term nature of fiberglass.
Also on deck repair maine sail said it was best to replace the deck core with what ever was taken out. i.e. don't take out end grain balsa and fill it in with solid fiberglass. (I think that was his advice) Anyway I expected to see woven fiberglass, instead it was a chopped layed, like shredded stuff on top of a woven layer, So I wanted to replace it with what came out. I may be wrong on that principle though.

 

[Don S/V ILLusion]

you did "good" Hermit

I apologize - you did exactly as you should soliciting advice first and then following it. That's what I get for assuming...

A lot of manufacturers used chopped strand mat over the gel while in the mold so not surprised that's what you found - although not the best choice, they do it to save $$$. It matters more, as Tim said, what resin you use than what substrate.

 

[Prime Time]

Re: you did "good" Hermit

There are some important issues here that you have brought up:
1. The chemical contamination of the blister contents
2. Residual moisture in the hull at the time of repair
3. How to get the strongest secondary bond to the hull
4. Is fiberglass/gelcoat water proof and why were there blisters.

This is a very interesting thread, and I will be interested in hearing how things work out for you,
I purchased a Mirage 27 that sat in a fresh water lake for many yrs. There were a number of blisters of a similar nature to what you have decribed. There was no issue with the gelcoat, but the outer mat was separated from the inner laminate by the blisters. Gel coat is definately not completely water impermeable. Moisture is able to pass through it and mix with the uncatalyzed resin residue in the hull, being drawn in by osmotic forces. Many boats use chopped strand mat as an outer layer to prevent "print through" of the pattern into the gelcoat.
(It is said that the chemical residue of the blister needs to be removed to prevent a poor secondary bond during the repair.)

It took over 2 years for the hull of my boat to dry out while sitting in my backyard. I used a moisture meter to evaluate the progress. Finally, I "tented" the hull with plastic and placed a dehumidifier within the tent to finish drying it. When it was dry, I chose to use fiberglass cloth and epoxy rather than mat to repair the hull.(Epoxy produces a stronger seconday bond as compared to polyester resin)

I tapered the repair with a 12:1 ratio in terms of distance of feathering the repair relative to the depth of the repair. I used epoxy thickenned with silica microparticles to help fair the repair. I then placed 10 coats of epoxy on the entire hull from the waterline down. Since the gel coat was no the issue, I did not peel it off before doing the epoxxy bottom job.

This was a fair amount of work, and would be interested in seeing how long my repair lasts relative to yours. My boat has now been in the water for 3 north east sailing seasons, stored on land during the winter. I have a link to a web page I've been making about the restoration below.

 

[seatravellerhawaii]

You ask in your last line "will I have a problem with this blister repair". In a nut shell "YES". The reason is you did not let the the fiberglass dry out. I had blisters on my boat and used the West System to repair it. I popped the blisters most of which had fluid, then ground them out per instructions then used water to remove any hard particles , then acetoned and then skirtted the bottom part of the hull and left it drying the hawaiian sun for two months. I checked every week with a moisture meter until it was dry and continued with the rest of the procedures in the west system blister repair guide. From all the people I sought help from they all said the drying of the hull was the most important step.
That said I do hope your repair holds up because as you stated this is a nasty job.
I will note that from all I have read that if the repair is not done properly the blisters will return much quicker the the original ones.
Best of Luck.

 

[Hermit Scott]

blisters

Why did you guys that waited that long to dry your hull wait that long? Did you do it because someone recommended that is what it takes, or did you try a quick method first only to have it fail?
Also is it the repairs themselves that fail, or is it that more blisters appear elsewhere?
I also would like to hear from someone who had a blister repair fail, and what method they used that failed.

 

[Prime Time]

why wait so long

I waited for the hull to dry as long as it needed based on a moisture meter. While I was waiting, I did other major renovations. When I finished those, I tented the boat and accelerated the drying.

 

[sailingdog]

I think you're going to have a problem with blistering again... as it doesn't sound like you really let the laminate dry out sufficiently, and may have trapped more liquid behind the newly added repairs.

You also don't say what kind of resin you used. You also don't say how old your boat is. If your boat is an older one, polyester and vinylester resins won't bond to the material very well, since it is likely that most of the bonding sites have been used, leaving it the patches relying on the much weaker secondary bonding characteristics of polyester/vinylester resin.

Hopefully, you used epoxy, but it doesn't sound like it. Generally, you're better off using cloth rather than CSM with epoxy as well. Epoxy is a much better resin to use for blister repairs for several reasons. First, it is far more resistant to osmosis than polyester or vinylester resin. Second, it has far better secondary, or adhesive, bonding properties. Third, it is physically stronger than either polyester or vinylester resins.

The one downside to epoxy over vinylester or polyester resins is that it is more susceptible to heat deformation and is also subject to UV degradation. Neither of these are a big issue when you're working below the waterline.

BTW, when working on blisters, you really should be wearing a full-face respirator, since the contents of osmotic blisters are generally under very high pressure and fairly caustic. I use one like this one, which is available at Jamestown Distributors:

I also find that they're more comfortable than goggles and a half-mask, provide much better protection—especially for your eyes from dust, and tend to fog far less.

 

[Hermit Scott]

blisters

I am fairly confident that the repairs I made will not fail. However, the chance of blisters on the starboard side of the the boat seems pretty high. I would bet $1000 that the portside will not blister though.
I am not sure what you mean by 'may have trapped more moisture'? The repair sites were as dry as they could be. The bonding area couldn't be drier, however in other areas of the hull, there may be blistering.
I think the only way to solve this problem permanently is to dry the boat out and seal the hull like prime time.

 

[Maine Sail]

Hermit..

I am fairly confident that the repairs I made will not fail. However, the chance of blisters on the starboard side of the the boat seems pretty high. I would bet $1000 that the portside will not blister though.
I am not sure what you mean by 'may have trapped more moisture'? The repair sites were as dry as they could be. The bonding area couldn't be drier, however in other areas of the hull, there may be blistering.
I think the only way to solve this problem permanently is to dry the boat out and seal the hull like prime time.

Hermit,

Moisture can't be seen or felt. The only way to know for sure that it is dry is to use a moisture meter. Most reputable boat yards, though the vast majority are not, won't even barrier coat a hull until it tests dry. My yard strips in the fall and barrier coats in the spring letting it dry all winter. Evacuating moisture from fiberglass is a time consuming task that can take months and months if you don;t do a full peel. A full peel speed up drying times but is grossly expensive. The hull should be dried to a reading of less than 10, 7 is better, on an Electro Physics or J.R. Overseas moisture meter. Many blister repairs fail because yards are too eager to make the almighty buck and don't let the hull dry out to levels below 10%.

The best evidence of this can be found on forums. I've seen questions and statements from people who feel the barrier coat they paid 4k for has failed and "let water in" when if fact they yard never let the water out and the blisters are and were still "blistering" underneath the fresh barrier coat. In cases like this the barrier coat did not fail. The boat yard failed to follow the directions that say to apply to a dry substrate.

Again, you have no way of knowing how dry or wet your hull is without a moisture meter.

Also, as Dog said, it is best to use epoxy resins for this job as polyester resins have lousy secondary bonding characteristics that are only exacerbated when the hull is still wet..

I quote Don Casey here:

Do not use polyester resin for blister repairs; you need the stronger adhesion and better water impermeability epoxy provides.

 

[sailingdog]

I am fairly confident that the repairs I made will not fail. However, the chance of blisters on the starboard side of the the boat seems pretty high. I would bet $1000 that the portside will not blister though.
I am not sure what you mean by 'may have trapped more moisture'? The repair sites were as dry as they could be. The bonding area couldn't be drier, however in other areas of the hull, there may be blistering.
I think the only way to solve this problem permanently is to dry the boat out and seal the hull like prime time.

Unfortunately, I think this is just wishful thinking... any laminate that has blisters the size of the ones you were describing will generally take MONTHS to dry out, unless you're using heat lamps and vacuum bagging. From your OP...

I find a total of 9 blisters that range from 2" to 5" diameter all on the starboard side.

How much osmotic fluid do you think it takes to create a blister 5" in diameter??? and how saturated do you think the laminate must be for that to happen????

 

[Hermit Scott]

blisters

I wasn't worried about barrier coating for that very reason. I am sure the hull has high moisture. I don't think it would ever dry out until at least the gel coat was stripped off and a tent was set up with a much lower ambient humidity. If I thought a high moisture content would sink my boat then I would take care of it now. In a couple of years when it's time to paint the bottom again, I will strip the hull down to the fiberglass and set up a tent with a dehumidifier.
It sat unattended for 5 to 8 years not being used. Just sitting there building a coral reef under it and soaking up moisture through a neglected bottom.
I would think most any boat that wasn't barrier coated from the factory, or dried out and sealed would have a high moisture content in the hull, and IF they develop blisters I think it is becasue something was not done right during the layup (ie chemically deficient resin). A boat can have high moisture and not develop blisters, just look at the portside of my boat. There was bare fiberglass in some spots but still no blisters. That's why I think the portside won't develop blisters, NOT becasue I think it's dry. I know it has a high moisture content.
I think blisters are likely on the starboard side though because they have already developed there.
"How saturated does it have to be?' I don't think a hull would have to saturated very much before blisters developed if all conditions were met to break down the poor quality resin.
Water alone is not causing this. Other wise it would happen everytime water came into contact with hardened fiberglass resin.
In the blisters on my boat. If you carefully cut around a blister and slowly peal back the outter skin, you will see that the resin that was supporting and surrounding the matt has turned to a fluid. The matt is there in place, floating in liquified resin. Fully hardeden resin is waterproof, and does not react to water. Water does seem to be one of the ingredients to liquify this resin. I expect blisters to develop in the poor quality resin, until it is completely dried out, or all stripped away and replaced as I did with the blister spots. I don't think blisters will develop in the repair sections becasue I removed ALL the matt and replaced it with new resin and matt. I do wish that I used epoxy though, I used resin through ignorance, hopefully the bond will hold even though I didn't use the epoxy.

I could be wrong, after all this is my first rodeo in the boat yard.
I value your knowledge and experience, and appriciate your posts, even when, especially when it's bad news for me. I will keep an eye out for new blisters as I do believe you that new ones will appear.

 

[BobM]

Hermit,

Live and learn. For what you paid for the boat just go and enjoy it. If the blisters come back next year you are certainly capable of dealing with them now. From the sounds of things this is not a structural issue and resale isn't a big issue for you at the moment, unless I miss my guess.

 

[Maine Sail]

Hermit

In your specific situation I don't think it really matters or warrants huge amount of attention unless a blister repair pops off, which even with the use of polyester, is unlikely. A 5" blister is a huge blister but so what. Fix it well enough to keep the water on the outside and move on to the next project until she's sea worthy so you can go sailing.

Just keep her floating and learn as much as you can. Eventually you'll upgrade and it is quite likely you be able to recoup what you paid for the boat. Think of this boat as a foundation for your foray into sailing and go sail...

Based on your description your boat would likely not fully dry in even a year and you're not barrier coating so just go have fun..

 

[Prime Time]

Hulls can dry with gel coat on

My hull did dry despite not stripping the gel coat. It did take a long time. The hull can dry out from the interior as well.

These types of blisters that form between the outer mat and the inner laminates are worrisome to me interms of structural integrity. Given the layup schedule of your boat, this may or may not be an issue.

My dad has a 1972 Bristol 40. Never been barrier coated, never had a blister but has a "wet" hull by the meter. However, better quality of resin and layup has not resulted in blisters.

I wasn't worried about barrier coating for that very reason. I am sure the hull has high moisture. I don't think it would ever dry out until at least the gel coat was stripped off and a tent was set up with a much lower ambient humidity. If I thought a high moisture content would sink my boat then I would take care of it now. In a couple of years when it's time to paint the bottom again, I will strip the hull down to the fiberglass and set up a tent with a dehumidifier.
It sat unattended for 5 to 8 years not being used. Just sitting there building a coral reef under it and soaking up moisture through a neglected bottom.
I would think most any boat that wasn't barrier coated from the factory, or dried out and sealed would have a high moisture content in the hull, and IF they develop blisters I think it is becasue something was not done right during the layup (ie chemically deficient resin). A boat can have high moisture and not develop blisters, just look at the portside of my boat. There was bare fiberglass in some spots but still no blisters. That's why I think the portside won't develop blisters, NOT becasue I think it's dry. I know it has a high moisture content.
I think blisters are likely on the starboard side though because they have already developed there.
"How saturated does it have to be?' I don't think a hull would have to saturated very much before blisters developed if all conditions were met to break down the poor quality resin.
Water alone is not causing this. Other wise it would happen everytime water came into contact with hardened fiberglass resin.
In the blisters on my boat. If you carefully cut around a blister and slowly peal back the outter skin, you will see that the resin that was supporting and surrounding the matt has turned to a fluid. The matt is there in place, floating in liquified resin. Fully hardeden resin is waterproof, and does not react to water. Water does seem to be one of the ingredients to liquify this resin. I expect blisters to develop in the poor quality resin, until it is completely dried out, or all stripped away and replaced as I did with the blister spots. I don't think blisters will develop in the repair sections becasue I removed ALL the matt and replaced it with new resin and matt. I do wish that I used epoxy though, I used resin through ignorance, hopefully the bond will hold even though I didn't use the epoxy.

I could be wrong, after all this is my first rodeo in the boat yard.
I value your knowledge and experience, and appriciate your posts, even when, especially when it's bad news for me. I will keep an eye out for new blisters as I do believe you that new ones will appear.