Blister Diagnosis Please

[jpendoley]

Seeking advice for a blister job on my Pearson 365. After blasting twenty years of paint, there were a lot of dime sized blisters. The boat had been barrier coated prior to my ownership with an epoxy coat, but the blisters either were not dry or new ones developed, leaving dozens of old dry, shallow and new shallow blisters. Wanting to get back to a dry smooth hull, I peeled the hull with a marine shaver pro taking off the gel coat and the mat. BTW, the marine shaver pro is a great tool-it allows peeling a very precise amount of material and leaves a relatively smooth surface. Fairing is still required, but it is much less arduous than it would be if a novice (which I am) stripped the gel coat with a grinder. Also, there is zero wast and shavings left behind.
The hull has been drying all winter outdoors in New England since October with multiple pressure washing sessions to help the drying process.
Some areas have some mat remaining and beneath are what I consider to be old, dry shallow blisters. All dime sized, not raised, white and dry when pierced. No where on the hull did a blister go deeper than the mat. I've attached a couple of images-should I do an additional peel before bsrrier coating or can I assume the hull is as dry as it will get?

[Benz]

If there's water deep in the laminate, peeling won't make it drier--it'll just peel more material off.
I can't guess how pressure washing makes it dry out. Wouldn't keeping water away from it promote dryness better than getting it wet?
If you haven't pressure washed it in the last couple of weeks, it's probably dry enough.

[jpendoley]

Pretty sure the moisture was trapped between the mat and the gel coat or the mat and the first layer of roving. Theory I have heard-and there are many theories-is the moisture does not usually migrate into the denser roving. Gel coat is realtively porous, water is absorbed and trapped beneath the mat but usally does not penetrate into the roving beneath the mat. In my case this was true, no blisters went further than the gel coat and mat. The pressure washing theory claims that the acids in the blisters are hydrophylic and a weekly washing during a season or two of drying helps wash away those acids so they don't reabsorb more moisture and start the cycle of blisters again. Make sense to me.
Now what about those remaining dry blisters?

[jpendoley]

Pretty sure the moisture was trapped between the mat and the gel coat or the mat and the first layer of roving. Theory I have heard-and there are many theories-is the moisture does not usually migrate into the denser roving. Gel coat is realtively porous, water is absorbed and trapped beneath the mat but usally does not penetrate into the roving beneath the mat. In my case this was true, no blisters went further than the gel coat and mat. The pressure washing theory claims that the acids in the blisters are hydrophylic and a weekly washing during a season or two of drying helps wash away those acids so they don't reabsorb more moisture and start the cycle of blisters again. Make sense to me.
Now what about those remaining dry blisters?

[Allied39]

Looks like it's about move fwd time.
The last hull job I did , when I sealed the hull I tested my materials.
I am a system three guy. Used hundreds of gallons.
So I had the choice of regular resin, silver tip or clear coat. The price raises from regular to silver tip to clear coat.
The silver tip and clear coat are non blush but I treat them all as blushing resins either way.
So it was either silver tip or clear coat. I did some test patches. The clear coat CLEARLY absorbed deeper. It was obvious. The clear coat was much more money but even thought he boat was being sold I used the clear coat as the "bite/sealer" in the original glass. Just how I do things.
Then the usual barrier coats on top that.
There is loads of info on system three resin, you can call them and talk with them. It is my experience that every product they have does what they say it does and behave like they say it does....except their paint. I used their LPU waterbased paint(admittedly a long time back) and will never touch it again. Awlgrip or nothing for me, but thats another issue

This post is for the OP. I have no interest in arguing various points or dealing with the trolls.

[flyingfin]

Dime size,,,,no problem,,,,,Golf ball size,,,,keep an eye on them for next haulout, Baseball size,,,,time to plan repair,,,,Softball size,FIX NOW

[Phantom Jim]

I agree with flyingfin. These boats (Pearson 365 ketches) are 40+ years old and that is all the blistering? If it were mine I would finish the job and go sailing.

[jpendoley]

Originally Posted by Allied39

Looks like it's about move fwd time.
The last hull job I did , when I sealed the hull I tested my materials.
I am a system three guy. Used hundreds of gallons.
So I had the choice of regular resin, silver tip or clear coat. The price raises from regular to silver tip to clear coat.
The silver tip and clear coat are non blush but I treat them all as blushing resins either way.
So it was either silver tip or clear coat. I did some test patches. The clear coat CLEARLY absorbed deeper. It was obvious. The clear coat was much more money but even thought he boat was being sold I used the clear coat as the "bite/sealer" in the original glass. Just how I do things.
Then the usual barrier coats on top that.
There is loads of info on system three resin, you can call them and talk with them. It is my experience that every product they have does what they say it does and behave like they say it does....except their paint. I used their LPU waterbased paint(admittedly a long time back) and will never touch it again. Awlgrip or nothing for me, but thats another issue

This post is for the OP. I have no interest in arguing various points or dealing with the trolls.

Great perspective, thank you. I took the local yards advice and ordered Seahawk barrier coat material. On a previous job I used Interprotect 2000, after peeling the gel coat on my 1966 Vanguard. 20 years later, the bottom looks new. Hoping the Seahawk product works as well.

[jpendoley]

Originally Posted by Phantom Jim

I agree with flyingfin. These boats (Pearson 365 ketches) are 40+ years old and that is all the blistering? If it were mine I would finish the job and go sailing.

I hear you, but before peeling there were hundreds of old blisters. What you see in the pictures are the few that escaped the gel peelers blade. To get them I would need to peel a tad more which would entail more fairing. I just want to do it right so I don’t have to do the bottom again in ten years

[GordMay]

Originally Posted by Benz

... I can't guess how pressure washing makes it dry out. Wouldn't keeping water away from it promote dryness better than getting it wet? ...

Washing promotes the dissolution of crystalized salts, in the laminate, after the blisters are opened up.
Grind all day, and wash last thing, allowing to dry [again] overnight.

[jpendoley]

Originally Posted by GordMay

Washing promotes the dissolution of crystalized salts, in the laminate, after the blisters are opened up.
Grind all day, and wash last thing, allowing to dry [again] overnight.

Gord May's tag line says it best.

"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

I spent $1000 on a gel peeler (bought it used-GREAT tool) and want to never peel it again. As the pictures show, there are a few dried blisters (they show as white in the pictures) dime sized, beneath a few small areas of remaining CSM. Thinking of repeeling that area to remove the remaining mat and dried blisters.The peel job is very fair-this would give me an area that is a large low spot that will need build up and a bit more work to fair. Question is is it worth the extra work as a precaution?

[Heath68]

Originally Posted by flyingfin

Dime size,,,,no problem,,,,,Golf ball size,,,,keep an eye on them for next haulout, Baseball size,,,,time to plan repair,,,,Softball size,FIX NOW

I am looking at an 18yr old catamaran whose owner (when viewing) admitted to 10% of the hull has blisters.. is it a case of haul it out and look to see how big they are? ... and then decide whether to go ahead and buy it?

I am also nervous that a statement to the effect that I know about the blisters has appeared on the sales contract and I am worried that (if the 10% all turns our to be softball size) then I won't have any comeback on the sale price.. Should I ask this to be removed just in case?
Many thanks

[bstreep]

Originally Posted by Heath68

I am looking at an 18yr old catamaran whose owner (when viewing) admitted to 10% of the hull has blisters.. is it a case of haul it out and look to see how big they are? ... and then decide whether to go ahead and buy it?

I am also nervous that a statement to the effect that I know about the blisters has appeared on the sales contract and I am worried that (if the 10% all turns our to be softball size) then I won't have any comeback on the sale price.. Should I ask this to be removed just in case?
Many thanks

If you aren't having the boat surveyed, you certainly should. A surveyor will be able to tell you about the blisters. Our boat is out of the water right now, having the bottom done (every 3 years). When we bought it 13 years ago, our surveyor (who is one of the most highly respected in the US) told us "every time you pull the boat for a bottom, grind and fill as many as you can afford, paint the bottom, and repeat. Soon you will be down to just a few." He looked at our boat yesterday. 6. His advice was perfect. AND it saved the sale. He has an unfounded reputation as a deal-killer.

[Heath68]

Originally Posted by bstreep

If you aren't having the boat surveyed, you certainly should. A surveyor will be able to tell you about the blisters. Our boat is out of the water right now, having the bottom done (every 3 years). When we bought it 13 years ago, our surveyor (who is one of the most highly respected in the US) told us "every time you pull the boat for a bottom, grind and fill as many as you can afford, paint the bottom, and repeat. Soon you will be down to just a few." He looked at our boat yesterday. 6. His advice was perfect. AND it saved the sale. He has an unfounded reputation as a deal-killer.

That's probably some very good advice. I am having it surveyed so fingers crossed the work required is not immediate.

[LittleWing77]

Originally Posted by Allied39

Looks like it's about move-forward time.
The last hull job I did, when I sealed the hull I tested my materials.
I am a system three guy. Used hundreds of gallons. I had the choice of regular resin, silver tip or clear coat.

Allied,

Is "System Three" the brand name? I would just like to file your info away for future reference, so I'm wondering about the specific products and the manufacturer of those you mentioned.

Thanks in advance,
LittleWing77