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post #1 of 15 Old 09-23-2012 Thread Starter
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Blister repair prep

To all the specialists out there

I will shortly pull my boat in order to redo the bottom.

While diving on the boat, I have not seen any serious blistering, but I would like to be prepared just in case.

Now, on Lake Lanier the only self service repair yard requires not just an arm and a leg in payment for using their facility - Fees will very quickly mount up.

So, if I do end up with extra repair work in the form of blisters, I would like to minimize the time spent in the yard, thinking about ways to quickly dry out the hull if needed.

What do you guys think about an alcohol filled pouch over an opened blister.

Denatured alcohol is very hygroscopic - will this benefit and reduce drying time?

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post #2 of 15 Old 09-23-2012
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Re: Blister repair prep

Um, I'm having a little trouble envisioning how you would keep the alcohol open to the hull while simultaneously keeping it from being open to the air to prevent the rapid evaporation that would certainly occur.

Another serious consideration is the risk of fire -- denatured alcohol will ignite quite easily, and the flame it produces is pretty much invisible.
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Re: Blister repair prep

The idea is a plastic pouch / patch slightly larger than the blister glued with some type of suitable compound (maybe even using Main Sail's butyl tape).
Stick all around but a small opening at top - fill using a syringe.

Fire risk - I don't smoke and don't intent to bring any heat source close by.

Outside of the application difficulties - would the alcohol actually help drying out the blister?

Pete

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post #4 of 15 Old 09-23-2012
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Re: Blister repair prep

If you only have limited time on the hard I would suggest opening the blister, washing with soap and water then spritzing with acetone regularly until moisture no longer oozes out of the laminate. At this point it is reasonably safe to spot repair with thickened epoxy.

I don't know how you would keep a denatured alcohol pouch in place but in some cases I've placed gauze over the ground out area, taped plastic sheet over the gauze then kept the gauze saturated with acetone until the laminate appeared dry (or as long as possible).
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post #5 of 15 Old 09-23-2012
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Re: Blister repair prep

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I don't know how you would keep a denatured alcohol pouch in place
I wonder how hot-melt glue would hold up to acetone or denatured alcohol?
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post #6 of 15 Old 09-23-2012
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Re: Blister repair prep

The blister is a result of water in an isolated pocket. once you have ground back the problem area, you shouldn't have to worry about moisture elsewhere. A wipe with acetone should be fine.

The only way to permanently fix the blisters is to grind them out to expose the void, then fill them. I used a rasp bit on a drill to grind the blister back until I have exposed good fiberglass. (you will find the blister is likely a spot where 2 layers of glass didn't bond together.) Then you use a clear coat of unwaxed resin to cover the exposed surface. After that fill the "divot" with resin thickened with micro balloons. Sand that smooth, and then apply another clear coat of resin to seal up the repair.

I had a boat with quite a few blisters, some quite large, and I used the above technique. It didn't really take that long. Just a few days on the hard, but after that, I never had the problem again!

1979 Santana 30 Tall Rig
Hull#101

Last edited by SchockT; 09-23-2012 at 02:57 PM.
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post #7 of 15 Old 09-23-2012
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Re: Blister repair prep

Keep in mind that the discussion at this point is theoretical, since the OP doesn't know if he even has a blister problem yet.

The path to success will depend on the severity of the blistering, and where in the lay-up they have taken up residence. If they are between the gelcoat and the first layer of glass, then you've got a mere annoyance. If they are between layers of glass, then you've just bought the can of worms and are now searching for a can opener.

Surface blisters are usually fine with getting them popped, scrubbed out, dried, filled, faired and barrier coated.

The deeper & bigger you go on the blister continuum, so goes the difficulty and time necessary to fix them right.
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post #8 of 15 Old 09-23-2012
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Re: Blister repair prep

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Originally Posted by afrinus View Post
The idea is a plastic pouch / patch slightly larger than the blister glued with some type of suitable compound (maybe even using Main Sail's butyl tape).
Stick all around but a small opening at top - fill using a syringe.

I'd try to find a tape with an adhesive that will withstand the alcohol; I think Gorilla Tape might work. Saturate a piece of cloth (like a piece of t-shirt) with the alcohol, place it over the blister, and then tape the plastic over the whole shebang.

Fire risk - I don't smoke and don't intent to bring any heat source close by.

But you never know about the yard crew or other passers-by; I'm betting that you aren't gonna be camping under your hull while she's out, right?

Outside of the application difficulties - would the alcohol actually help drying out the blister?

Could be. I'd probably double check to make sure that cured polyester resin isn't adversely effected by prolonged exposure to denatured alcohol -- I don't know one way or the other -- but as long as it's safe to use then it may help.

Pete
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post #9 of 15 Old 09-23-2012 Thread Starter
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Re: Blister repair prep

Thanks for the ideas - I appreciate it.
The saturated cloth sounds somewhat easier than just liquid. I also will check if there is anything on the net warning about long-term exposure of the resin to alcohol (If I find anything I'll post here)

Yes, currently it's all theoretical as I'm not sure I do have any issues.
I've scrubbed the bottom twice during the summer and tried to inspect as best I could with the boat in the water. I couldn't find anything that looked or felt "blistery"
I presume serious blisters would be quite apparent by sight and feel - or am I wrong?

"Camping under the hull" Actually yes - I was planning to stay on the boat.
The yard (it's actually a totally self service facility with hardly anyone there) is more than 2 hours from me - I'll try to maximize my work time.

Pete

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post #10 of 15 Old 09-23-2012
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Re: Blister repair prep

The best method is to use a hose and plenty of water - FYI you are not trying to 'dry' out the area from water, although drying is the term people use. Google blister causes

SchockT - #101 had blisters ?

Last edited by WDS123; 09-23-2012 at 06:28 PM.
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