SailNet Community banner

1 - 15 of 15 Posts

·
I'd rather be sailing....
Joined
·
119 Posts
Discussion Starter #1
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?
 

·
Señor Member
Joined
·
1,457 Posts
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.
 

·
I'd rather be sailing....
Joined
·
119 Posts
Discussion Starter #3
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
 

·
Registered
Joined
·
488 Posts
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).
 

·
Registered
Joined
·
2,335 Posts
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!
 

·
Señor Member
Joined
·
1,457 Posts
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.
 

·
Señor Member
Joined
·
1,457 Posts
Comments in blue:

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
 

·
I'd rather be sailing....
Joined
·
119 Posts
Discussion Starter #9
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
 

·
Banned
Joined
·
649 Posts
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 ?
 

·
Registered
Joined
·
2,335 Posts
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 ?
No, I have never found a single blister on my Santana! It is a very well laid hull!

The boat I had blisters on was my Hotfoot; a trailer boat that I was keeping in a slip.
 

·
Registered
Joined
·
765 Posts
Do nothing at all about blisters. Instead read David Pascoe's articles on the subject. All blister fixes make the non-problem worse allowing more moisture to be drawn along the exposed fibers. At worst, blisters are a cosmetic issue. Attempts to fix them ussually result in more damage than the blister.
Been there, done that, regretted it.
 

·
Registered
Joined
·
2,335 Posts
Do nothing at all about blisters. Instead read David Pascoe's articles on the subject. All blister fixes make the non-problem worse allowing more moisture to be drawn along the exposed fibers. At worst, blisters are a cosmetic issue. Attempts to fix them ussually result in more damage than the blister.
Been there, done that, regretted it.
I don't see it. How could leaving the pocket of water inside the laminate layers be better than eliminating the water and filling the void? Perhaps a poor repair job could make things worse, but repaired correctly it certainly won't!

From a performance perspective blisters are more than cosmetic. If the hull isn't fair it isn't fast! I know many cruisers don't care how lumpy their bottoms are, but some of us have higher standards than that! ;)
 

·
Registered
Joined
·
765 Posts
ALL blister repairs make matters worse (or at least most). It is not possible to "dry" the hull because ti really isn't wet. The blisters are filled with "gunk" that is hydrolyzed resin that does not really dry. Attempting to repair them simply opens more pathways for water to wick into the gelcoat and hydrolyze more.
Blister repair is one of boatings biggest scams.
 

·
Señor Member
Joined
·
1,457 Posts
Frog,

While I respect your opinion, I don't happen to agree with you in everything you've said.

Think about the chemistry and physics for a moment. The hydrolyzed resin is mildly acidic. Left alone, it will continue to hydrolyze increasing amounts of cured resin. This is akin to a very slowly growing cancerous tumor within your body.

When filling opened up blisters, almost everyone recommends using epoxy. Epoxy is not water permeable. The schedule is a wet-out with epoxy, followed by applications of thickened epoxy. The choice of thickener is also important -- a non-absorbent filler like Cab-o-sil is the way to go. Deeper repairs should include use of cloth (bi-axial is a good choice in many cases.) Once the area is faired, another coat or two of epoxy to seal the repair.

Most solutions for blistering also include application of an epoxy barrier coat, either over the top of the repaired area or better yet, the entire hull.

When done properly, a repair is pretty much impregnable to water.

However, if corners are cut and a few steps ignored, or inferior products are used then you are destined for future work.
 
1 - 15 of 15 Posts
Top