Bayfield Blisters?

[RossD]

First some background. A a few days ago I began scraping and sanding multiple coats of ablative paint from my 1985 Bayfield 29. This particular boat has been sailed exclusively on lake Erie, but now, it's heading for Lake Ontario (for starters).

Up until today, I had not noticed any abnormalities in the paint except that it was in dire need of removal. The scraping is not yet entirely completed, however, I wanted to do some sanding in order to assess the condition of the gelcoat below. I'm not terribly happy with what I believe I may have uncovered. I could see small circles inside the bottom most coat of paint (it's a light green color). No liquid or depressions as one would associate with blisters, but... are these blisters and if so, how should I address them?

Please see pictures below:
First picture is after sanding with 80 grit, Second and fourth pictures are as seen with light green paint and third picture is a perspective view. https://postimg.cc/gallery/1tgyyncvc/

[a64pilot]

You may or may not have small blisters.
As far as what to do with them, I’d ignore them.
When I first got my boat, it had many, small as in 1/4” blisters on it. I was at the boat yard for her first bottom job and asked what the best course was for a repair, the boat yard owner told me that it took 25 years for them to get to 1/4”, maybe in another 10 or 20 years they may be big enough to need fixing.
Now five years later I just had another bottom job, my third since buying the boat, and from the looks of things next bottom job which I hope will be in three years, I’ll probably have them fixed as they have gotten larger.
Probably because my boat is now in warm tropical water all of the time.

From your boats age, they may never get big enough to need fixing

[RossD]

Originally Posted by a64pilot

You may or may not have small blisters.
As far as what to do with them, I’d ignore them.
When I first got my boat, it had many, small as in 1/4” blisters on it. I was at the boat yard for her first bottom job and asked what the best course was for a repair, the boat yard owner told me that it took 25 years for them to get to 1/4”, maybe in another 10 or 20 years they may be big enough to need fixing.
Now five years later I just had another bottom job, my third since buying the boat, and from the looks of things next bottom job which I hope will be in three years, I’ll probably have them fixed as they have gotten larger.
Probably because my boat is now in warm tropical water all of the time.

From your boats age, they may never get big enough to need fixing

So a barrier coat would not provide any benefit at this point? I was thinking of applying VC17, I had such great luck with it in the past, but the bottom must be completely sanded and clean to use that product. After finding the spots, I was tossing the idea around of just smoothing the remaining paint with the sander after it's completely scraped (scraping has done an excellent job of removing most of the old stuff) and going over her with a quality ablative. Wait a few seasons and then pay for it to be blasted clean.

Thank you for your reply, I do feel better about whatever those are!

[a64pilot]

Now all of this is just my opinion, but I believe it’s tempered by the fact that neither of us have new Million dollar boats too.
Barrier coat never hurt anything, but back to the fact that it’s never had it and in almost 40 years it hasn’t caused a problem, maybe your OK without it?
My assumption that your Northerly location with cold waters and likely being on the hard for a large portion of the year likely has something to do with it too, if you were moving to Fl, then I’d say by all means let it dry out as long as you can and then put a thick coat of barrier coat before you leave on it.
But if nothing is changing, maybe don’t work yourself to death and or spend a lot of money that may not be needed.

It seems that often that blister repairs seem to grow immensely both in time and money.

My plan is therefore to have a bunch of money banked up for it, and time put aside, then tackle the job.
I think you have time to decide to deal with this when you want to, don’t fall for the sunk costs paradox.

[rbk]

As it looks like you're stripping the bottom down to the gel coat, I would personally sand out the blisters (not grind as from the pics they appear to be really small and not weeping) let it dry (washing/wiping with methyl hydrate will speed it up), roll on a coat of full flow epoxy then a barrier coat additive, prime and paint. Chances are after that, they will not get any bigger and will be a non issue in the future. If you don't, you will be stripping the hull again next time.

[RossD]

Originally Posted by rbk

As it looks like you're stripping the bottom down to the gel coat, I would personally sand out the blisters (not grind as from the pics they appear to be really small and not weeping) let it dry (washing/wiping with methyl hydrate will speed it up), roll on a coat of full flow epoxy then a barrier coat additive, prime and paint. Chances are after that, they will not get any bigger and will be a non issue in the future. If you don't, you will be stripping the hull again next time.

Oddly enough there isn't really anything to sand out, once all the paint is removed the small circles vanish. My plan was to scrape, fair and paint this year and have the hull blasted clean when the paint fails again. Would the assumed blisters pop through the new paint? If so I'll have not choice but to barrier now.

[rbk]

Originally Posted by RossD

Oddly enough there isn't really anything to sand out, once all the paint is removed the small circles vanish. My plan was to scrape, fair and paint this year and have the hull blasted clean when the paint fails again. Would the assumed blisters pop through the new paint? If so I'll have not choice but to barrier now.

Real blisters will ooze. If no oozing or weeping it may just be a poor paint application and bottom paint popping off. If everything is dry and no real blisters I would skip the epoxy layer and go straight to a barrier coat (this will cost less than a gallon of bottom paint but is epoxy with additive) and if you have the gel coat exposed it is THE time to do it. A gallon of west systems epoxy, 207 hardener, barrier coat additive and the pumps for a total of $180, roll it on.

[svspirited]

It is disheartening to see that but it may not be anything too serious. How does the hull sound? Take a small hammer and tap the hull. If they are real acid filled blisters you will get a dead sound like a muffled thump. If the sound is a solid bang then odds are there is no moisture in there and what you are looking at is poor paint/gel coat application so nothing to really worry about.

If you hear that dead thump take a sharp implement and poke a few. If a foul pinkish/reddish liquid oozes out then you do have a blister problem, barrier coat will do nothing to fix that or really prevent it from getting worse. Have you tried using a moisture meter, again if they are filled with acid they will register as wet on a meter. If you haven't used a meter before ask someone who has as they are more an art than a science and a lot of things will cause them to read wet when they really are not, metal tanks, high metal bottom paints, grounding strips for SSB, carbon fiber, etc. But a good meter in conjunction with good sounding technique will tell you pretty quickly if you have a real blister problem.

From there I would spot grind a few to get a sense of how deep they go. Is it a wood cored hull, if yes you may have to do some more digging to ensure the core isn't wet or worse rotten. If the blisters are not too deep then you have a mainly cosmetic issue and they are fairly easy to repair, though time consuming and manually intensive.

If the blistering is extensive it may be worth doing a peel, Makita makes a tool that does this quickly and efficiently though it costs about $3,500 US it will still be cheaper than paying someone to do it for you. If it is not spread throughout the entire hull and most of the hull feels solid and reads dryish just grind out the bad laminate with some 36 grit on an angle grinder being careful not to dig deeper than need be and let sit to see if anything new oozes out. Do this until the hull reads dryish. Once you think you have them all ground out then wash down the hull with soap and water followed by an acetone wipe down. Patch up with fresh glass where it is deeper than say 5mm and use thickened epoxy to fill in the rest always sanding and wiping down with acetone if the epoxy cures and you need to add another coat. Sand and fair to whatever level of fairness you care, it's not a racing boat so you don't have to go too crazy fairing and sanding.

That should give you a nice clean bottom to apply a good barrier coat to, personally I used West system 105 resin, 406 for the thickener, and some 6.5 oz glass to repair the deeper areas, followed by 407 fairing. I'm still working on it but once fair I will coat with one coat of 105 followed by 4 or 5 coats of 105 with 422 as a barrier coat.

Osmotic blisters do not dry out, excess moisture in the glass may, but blisters don't simply dry out and like magic the problem is solved, what is in there is an acidic mix of water, styrene, and malic acid and while it may not show on a moisture meter after some air time it is it still there and over time will get wet and continue the delamitation process.

Also, as mentioned above, if you are not bringing the boat to the tropics you could probably leave it as is slap some new bottom paint on and never have a real problem. Good luck!

[RossD]

Gentlemen this is exactly what I needed to know, thank you all so much!

First step, once it stops raining here, is to sound the hull more thoroughly. I did do that quickly in one area and it was ringing as a good solid substance would. The hull has little to no wood although I believe the engine mount area might use wood inside to beef it up. The deck is cored but from the toe rail down it's all solid laminate. Strength is enhanced with a structural grid molded of fiberglass and bonded to the inside of the hull.

Second step- check some of the visible spots for liquid. Depending upon results, proceed per the suggestions above.

[svspirited]

When you go to sound again, do it in as tight a grid as possible and go around the boat several times on different days. It's pretty amazing how it can ring true in one spot and there could be a blister only a centimeter away that is full of liquid. It also isn't the end of the world if you miss a few. If you pull the boat every year anyway you can always fix any that you missed over time.

[RossD]

Originally Posted by svspirited

When you go to sound again, do it in as tight a grid as possible and go around the boat several times on different days. It's pretty amazing how it can ring true in one spot and there could be a blister only a centimeter away that is full of liquid. It also isn't the end of the world if you miss a few. If you pull the boat every year anyway you can always fix any that you missed over time.

If these indeed are blisters, I'm not certain now how I would handle it. They are all over under the paint and very small, some the size of a pencil lead, others perhaps eraser size. Given they have all vanished with sanding, I may just sand it and paint it for now (one of the suggestions above), applying the epoxy the next time after a walnut shell cleaning . To say the least, at my age this is a daunting task.

Hopefully the wind and rain (now snow) subsides a bit today. I'm anxious to perform the suggested testing.

[a64pilot]

This is what small blisters look like.
They stand proud and if you take a screwdriver and press the edge hard enough on one, it will bust. When it busts a liquid that smells of vinegar will come out and of course there is a hole. These pictured were in the gel coat only, didn’t go into the fiberglass laminate.
You can’t just sand blisters into non existence, if you have little circles that don’t contain liquid, and don’t leave holes when popped, I’m not sure what you have, but pretty sure it isn’t blisters.

[a64pilot]

That was five years ago, my boat came from Maine, and in the five years since being in tropical waters, some of those tiny blisters have grown to quarter sized.
I think they are big enough now that they need to be addressed at the next bottom job.
Just an opinion.

[RossD]

Originally Posted by a64pilot

That was five years ago, my boat came from Maine, and in the five years since being in tropical waters, some of those tiny blisters have grown to quarter sized.
I think they are big enough now that they need to be addressed at the next bottom job.
Just an opinion.

The anomalies do not stand proud, if anything they are flush. I could not see the small blisters in your picture well enough to compare them with mine, however, I do not have anything oozing from them. Pilot, thanks for posting up the picture.

This afternoon the weather broke enough for me to sound the hull and to attempt to pop or otherwise dig into the "circles". My boat has been on the hard for at least 18 months as I just purchased it VIA RCR in Buffalo, so they may have completely dried up, I really don't know. The hull rang true everywhere I tapped. The only change in the sound is where the structural grid is glassed into the hull sides, I expected that. Using a sharp banana knife, I poked and dug into several of the anomalies, they are solid. I cannot pop them or dig into them without gouging the gelcoat.

[svspirited]

Then odds are you are good to go.

Originally Posted by RossD

The anomalies do not stand proud, if anything they are flush. I could not see the small blisters in your picture well enough to compare them with mine, however, I do not have anything oozing from them. Pilot, thanks for posting up the picture.

This afternoon the weather broke enough for me to sound the hull and to attempt to pop or otherwise dig into the "circles". My boat has been on the hard for at least 18 months as I just purchased it VIA RCR in Buffalo, so they may have completely dried up, I really don't know. The hull rang true everywhere I tapped. The only change in the sound is where the structural grid is glassed into the hull sides, I expected that. Using a sharp banana knife, I poked and dug into several of the anomalies, they are solid. I cannot pop them or dig into them without gouging the gelcoat.