Proposal to Repair Deep Blisters

[Scout 30]

I hate to get back into the same old epoxy versus polyester resin debate. I'll just say that for a secondary bond polyester resin is inferior and there are epoxy resins that can take gelcoat. Here's some information:
https://www.westsystem.com/wp-conten...Prevention.pdf
https://www.jamestowndistributors.co...2Polyester.pdf
https://www.westsystem.com/wp-conten...anual-2015.pdf

[US1Fountain]

Its odd why they would shrink when the boat is haul out, since they are above the water line in the 1st place.

[skipgundlach]

Originally Posted by Suijin

I'm fairly certain those are the result of uncured resin, not osmosis, given how far above the waterline they are. Are you sure they are shrinking when out of the water and it's not just an optical thing? Looking at them from the water, they are going to look bigger than when you're standing under the boat when it's hauled.

"stern inboard sides"...is that both sides? What do you mean by "inboard"...do you mean where the hull curves down to the waterline?

Polyester resin and gelcoat don't stick very well to epoxy. I would do it all with polyester, particularly if you want to finish with gelcoat.

What he said! above, highlighted. Here's a pretty good thread on the subject: Do I need to strip my bottom? - Page 2 - Cruisers & Sailing Forums

Generally speaking, if you got anything out of the blister (as you did) that was water soluble material (WSM). Blisters nearly always are a product of uncatalyzed resins in polyester layups, and you can leave them in the sahara for years and never resolve the issue.

Being water soluble, the answer is to flush them out - with water. Wet it down after grinding back to where you think you've got it all, off and on all day, and then hit it with a low-power pressure wash the next day. That gets rid of all that has seeped out, and rinses any more which may be left. I'd bet you got more seep - in which case, rinse, repeat, so to speak.

From a log I wrote at the very beginning of what turned out to be a full-year bottom job, in April 2011:

"Much is made of blisters on a fiberglass hull, and, while they're usually
not of any structural concern, they're unsightly when the hull is out of the
water, not "fair" (the bottom isn't smooth) and otherwise something that
most cruisers want to "fix."

To do that, most who remove all the covering material down to the raw
fiberglass try to "dry the boat out" by leaving it open for a time
(sometimes, years). However, it turns out that it's not WATER that comes
out of a blister, or hides, deep in the lamination. Instead, it's water
soluble compounds used in the resin formula when it's made.

Thus, one could wait forever and not get any dry results from testing with a
moisture meter. Counter-intuitively, the cure for a "wet" layup (the
fiberglass laminate) or blisters is to saturate them with water, which will
allow the hydroscopic material to migrate to the surface as the water dries.
One then pressure washes it off the hull, and keeps doing this until the
moisture levels reach a satisfactory level.

Thus, we'll be pressure washing the boat after keeping it wet for a minimum
of 30 minutes and allowing it to surface-dry, as many times as we have time
to do before applying our barrier coat and bottom paint (the latter being
the stuff which discourages marine flora and fauna from attaching itself to
a bottom)."


As well, though not directly related to your situation, here's a conversation I had with a fellow cruiser about bottom jobs in general:

"A bottom job discussion with a fellow cruiser:
Here are the relevant links for both types of bottom paint. Spec is 2-3 years, and easily-brushed slime is typical after 18 months per their info, but we’ve gotten much longer from ours.

Copper Bottom Anti-Fouling Paint #45 - Protective & Marine – what we have, available in 4 colors

Seaguard Ablative Anti-Fouling Coating - Protective & Marine – what my buddy I told you about has, and he’s happy; it’s more likely to be in stock, though you might have to go to FTL to get it. I don’t recall now whether I had to go there or they inter-office shipped it to the local S-W shop.

https://www.paintdocs.com/docs/webPD...&prodno=N51B45 – ours

https://www.paintdocs.com/docs/webPD...prodno=P30BQ12 – buddy’s

They also made our barrier coat; https://protective.sherwin-williams....3Aproduct-6939

This is the fairing compound we used. It comes in one and two gallon pails (mix batches, total 2/4 gallons): http://www.axson-technologies.com/si...0UltraFair.pdf

An example at retail: https://www.merrittsupply.com/produc...ltra-fair-kit/

We used cheap thin plastic cutting sheets (like a cutting board but very thin) to mix on, and then washed them with acetone, ditto application tools. Several hours to green, but a full day made it like concrete, despite the expected full cure being several days.

You can see our bottom job work here: Pictures: Flying Pig Refit 2011-2012/Bottom Job

And the paint (barrier coat and bottom paint) work here: Pictures: Flying Pig Refit 2011-2012/Bottom Job/4 - Barrier and Bottom Coats "

We are currently showing black (the color under the surface red) in several places - well over 5 years from launch. At this rate, I expect that we'll not have to haul for bottom issues for several years. All this (except this summer's US East coast trip) in tropical waters, and most of it in the extremely foul ICW at Vero Beach. So to say that we're happy with our $85/gallon (in 5 gallon pails) bottom paint would be an understatement. I realize that your holes are not under water - but one thing may lead to another.

Those are impressive holes. I hope they don't turn out to be harbingers of a job similar to ours!

L8R

Skip

[Scout 30]

Originally Posted by skipgundlach

What he said! above, highlighted. Here's a pretty good thread on the subject: Do I need to strip my bottom? - Page 2 - Cruisers & Sailing Forums

Generally speaking, if you got anything out of the blister (as you did) that was water soluble material (WSM). Blisters nearly always are a product of uncatalyzed resins in polyester layups, and you can leave them in the sahara for years and never resolve the issue.

Being water soluble, the answer is to flush them out - with water. Wet it down after grinding back to where you think you've got it all, off and on all day, and then hit it with a low-power pressure wash the next day. That gets rid of all that has seeped out, and rinses any more which may be left. I'd bet you got more seep - in which case, rinse, repeat, so to speak.

From a log I wrote at the very beginning of what turned out to be a full-year bottom job, in April 2011:

"Much is made of blisters on a fiberglass hull, and, while they're usually
not of any structural concern, they're unsightly when the hull is out of the
water, not "fair" (the bottom isn't smooth) and otherwise something that
most cruisers want to "fix."

To do that, most who remove all the covering material down to the raw
fiberglass try to "dry the boat out" by leaving it open for a time
(sometimes, years). However, it turns out that it's not WATER that comes
out of a blister, or hides, deep in the lamination. Instead, it's water
soluble compounds used in the resin formula when it's made.

Thus, one could wait forever and not get any dry results from testing with a
moisture meter. Counter-intuitively, the cure for a "wet" layup (the
fiberglass laminate) or blisters is to saturate them with water, which will
allow the hydroscopic material to migrate to the surface as the water dries.
One then pressure washes it off the hull, and keeps doing this until the
moisture levels reach a satisfactory level.

Thus, we'll be pressure washing the boat after keeping it wet for a minimum
of 30 minutes and allowing it to surface-dry, as many times as we have time
to do before applying our barrier coat and bottom paint (the latter being
the stuff which discourages marine flora and fauna from attaching itself to
a bottom)."


As well, though not directly related to your situation, here's a conversation I had with a fellow cruiser about bottom jobs in general:

"A bottom job discussion with a fellow cruiser:
Here are the relevant links for both types of bottom paint. Spec is 2-3 years, and easily-brushed slime is typical after 18 months per their info, but we’ve gotten much longer from ours.

Copper Bottom Anti-Fouling Paint #45 - Protective & Marine – what we have, available in 4 colors

Seaguard Ablative Anti-Fouling Coating - Protective & Marine – what my buddy I told you about has, and he’s happy; it’s more likely to be in stock, though you might have to go to FTL to get it. I don’t recall now whether I had to go there or they inter-office shipped it to the local S-W shop.

https://www.paintdocs.com/docs/webPD...&prodno=N51B45 – ours

https://www.paintdocs.com/docs/webPD...prodno=P30BQ12 – buddy’s

They also made our barrier coat; https://protective.sherwin-williams....3Aproduct-6939

This is the fairing compound we used. It comes in one and two gallon pails (mix batches, total 2/4 gallons): http://www.axson-technologies.com/si...0UltraFair.pdf

An example at retail: https://www.merrittsupply.com/produc...ltra-fair-kit/

We used cheap thin plastic cutting sheets (like a cutting board but very thin) to mix on, and then washed them with acetone, ditto application tools. Several hours to green, but a full day made it like concrete, despite the expected full cure being several days.

You can see our bottom job work here: Pictures: Flying Pig Refit 2011-2012/Bottom Job

And the paint (barrier coat and bottom paint) work here: Pictures: Flying Pig Refit 2011-2012/Bottom Job/4 - Barrier and Bottom Coats "

We are currently showing black (the color under the surface red) in several places - well over 5 years from launch. At this rate, I expect that we'll not have to haul for bottom issues for several years. All this (except this summer's US East coast trip) in tropical waters, and most of it in the extremely foul ICW at Vero Beach. So to say that we're happy with our $85/gallon (in 5 gallon pails) bottom paint would be an understatement. I realize that your holes are not under water - but one thing may lead to another.

Those are impressive holes. I hope they don't turn out to be harbingers of a job similar to ours!

L8R

Skip

Great post! I didn't even know Sherwin-Williams sold bottom paint. Considering how crazy expensive Trinidad has gotten I'll seriously consider Sherwin-Williams paint at my next haul out.

[Sonosailor]

Suijin: It is a cat, with two hulls; and the blisters are in two groups, not quite opposite, on the inboard sides at the stern. You do get that I would wish to use polyester to allow a better gelcoat repair.

Thanks to the rest of you for your comments. Some have to be modified as the responder appears to have missed either that these did not appear until the boat was over 20 years old and neither used differently or subjected to other changes, and that these deep blisters are appearing at a foot above the water line.

Definitely, it would be good to find the route the water and the solution are taking, and I will think on it. At present, I believe this is an impossible job.

Happy to have you all aboard! What a happy hour we could have...

[Cadence]

Originally Posted by Sonosailor

Suijin: It is a cat, with two hulls; and the blisters are in two groups, not quite opposite, on the inboard sides at the stern. You do get that I would wish to use polyester to allow a better gelcoat repair.

Thanks to the rest of you for your comments. Some have to be modified as the responder appears to have missed either that these did not appear until the boat was over 20 years old and neither used differently or subjected to other changes, and that these deep blisters are appearing at a foot above the water line.

Definitely, it would be good to find the route the water and the solution are taking, and I will think on it. At present, I believe this is an impossible job.

Happy to have you all aboard! What a happy hour we could have...

Just maybe a dumb question. Are there deck fittings on both hulls that may have been causing water intrusion after bedding compounds failed? For some reason the lay up may not have had great saturation in those areas during MFG.

[Sonosailor]

Cadence: Not dumb at all. It is an old boat. I am constantly on the search for leaks. I rebedded the port toerail and stansions last year, and even though I found no smoking gun, the mysterious water that collects in the port bilge decreased significantly. There is always something to rebed, and I am at it a lot.

I do feel that the bumps were decreasing rapidly after the boat was removed from the water last April, and circled them with a marker before they disappeared. They do not vary with rain storms, so I intend to focus on below-water areas when I get back and carry out the repair. It is the age of the boat that has me scratching my head. why 20 years without this?

Thanks for your interest.

[gmakhs]

This can be by uncured resin or really hitting hard the dock and creating cracks on the gelcoat and fiber glass I would grid around them let them dry and apply fiberglass and gelcoat.
Epoxy is nice but not really needed and a waste of money .

[Cadence]

Originally Posted by gmakhs

This can be by uncured resin or really hitting hard the dock and creating cracks on the gelcoat and fiber glass I would grid around them let them dry and apply fiberglass and gelcoat.
Epoxy is nice but not really needed and a waste of money .

I believe he said it was on the inside of the hulls.

[reed1v]

If you got these above the waterline only, then the layup was at fault. Blame sun induced blistering. Eventually you will need to peel off the entire upper hull and redo with vinyl esters or other suitable materials by a competent yard. It appears from your photo you got one heck of a structural problem with the hull. Good luck selling it .

[Cadence]

Originally Posted by reed1v

If you got these above the waterline only, then the layup was at fault. Blame sun induced blistering. Eventually you will need to peel off the entire upper hull and redo with vinyl esters or other suitable materials by a competent yard. It appears from your photo you got one heck of a structural problem with the hull. Good luck selling it .

As I understand it, they are on the inside of the hulls close to the stern. Probably not a place of high sun exposure. Because of the symmetry I'd guess something in MFGing or water intrusion from some mirror deck fittings.
Peeling the top sides would not strike me as a future necessity. I'm glad I'm not the OP reading that suggestion of inevitability. I'd have to go change my shorts.

[reed1v]

Originally Posted by Cadence

As I understand it, they are on the inside of the hulls close to the stern. Probably not a place of high sun exposure. Because of the symmetry I'd guess something in MFGing or water intrusion from some mirror deck fittings.
Peeling the top sides would not strike me as a future necessity. I'm glad I'm not the OP reading that suggestion of inevitability. I'd have to go change my shorts.

Guess you have limited experience with constant sun exposure reflecting off water. We had a lot of rubber seals disintegrate from indirect solar radiation. But admittedly that was from a decade of sailing.

[Cadence]

Originally Posted by reed1v

Guess you have limited experience with constant sun exposure reflecting off water. We had a lot of rubber seals disintegrate from indirect solar radiation. But admittedly that was from a decade of sailing.

Rubber seals and fiberglass, I feel to see the correlation. I know you can get a hell of a sun burn from reflection off the water.

[Sonosailor]

Originally Posted by reed1v

If you got these above the waterline only, then the layup was at fault. Blame sun induced blistering. Eventually you will need to peel off the entire upper hull and redo with vinyl esters or other suitable materials by a competent yard. It appears from your photo you got one heck of a structural problem with the hull. Good luck selling it .

Well, since the pressurized fluid only was released after the hull was ground at least 1/4" deep and sometimes more, peeling off the entire upper hull is just not the answer. The blisters are within one square foot on each hull, appeared only 2-3 years ago, are increasing very slowly, and appearing no-where else. Thanks for giving it some thought, though.

[Sonosailor]

Okay, thanks guys. I will return to the boat in the fall, repair the grindings likely with polyester and glass and a lot of care, continue to work on the fittings, and then next spring, after being hauled, I'll clean down the bottoms to below all the ablative, and give it a good inspection. I suspect a possible crack near the area where the molds were glassed together. I can also overdrill some fittings and rebed in epoxy in the area. I will report on this next year.