Grinded tons of blisters. Now what?

[Clivevon]

Ps. If you are going to apply heat to the hull, best to read up about temperature limits of GRP hulls before they start to deform.

[Lodesman]

Originally Posted by Don C L

You know, I was reading about the yellow goo coming out of the blisters being acidic and a catalyst for the reaction that generated the blister. We used baking soda wash on the blisters and they bubbled up quite a bit and then we washed them out. I THINK they dried out much better that way since the acidic liquid did not seem to dry out too well. I've never heard of anyone else applying a neutralizing bath, so we might be crazy.

I was under the impression the liquid in blisters is a styrene solution, and styrene is neutral. I'm prepared to be corrected.

[SimonV]

You have done a lot of the hard work, why not finish it and take off all the underwater gell coat. Do it properly do it once.

[ferrailleur]

Originally Posted by Clivevon

Ideas offered for consideration from my own experience. I didnt do what you are doing, i just threw a shedload of money at the problem because I could - it worked but still hurt though.
Looks like you are doing it all yourself? You dont mention anything about moisture readings? If I were you I would buy a good moisture meter (I bought a Tramex Skipper Plus, available on Amazon for $446.) Given the amount of work gone into the boat it would be nice to be able to keep track of your own moisture readings whenever you like, & compared to the effort you will be putting in, the cost is very cheap. Nothing else will give you that information.
Whatever you do to fill & fair the hull, it will be a temporary patch. The problem wont have gone away & the blisters will come back.
If you seal all the moisture in the hull so it can no longer get out, then it will just go deeper in.... Blisters dont sink boats, but internal fibreglass delamination will certainly weaken the hull below original designed strength. Nice to know next time you pound the hull in bad weather.
Nothing wrong with the approach you are taking, just so long as you know it is temporary & you will have to keep on doing it. Meanwhile you can go sailing, haul the boat for 3 months to dry out over every winter, & use your moisture meter to keep an eye on what is going on. Good luck.

By the way, high pressure water is forcing more water into the hull. Try steam cleaning instead. & if you want to apply consistent heat on the hull, infra red heaters are the way to go - cheap to buy & they only heat what they are directed onto, not the air in between, so no heat loss.

all this is not a permanent solution. The only "permanent" solution starts with drying out the hull thoroughly. But it can keep you going for years.

Great post. Thanks. I realize that I haven't grinded out EVERY blisters. Some small one will still be "alive" even after my filling/fairing/epoxy coatings/paintings.
I will be getting those at the next year hauling out!
And hopefully less of those at the year after next year haul out!
Makes sense?
Thanks again.


If you seal all the moisture in the hull so it can no longer get out, then it will just go deeper in.... Blisters dont sink boats, but internal fibreglass delamination will certainly weaken the hull below original designed strength. Nice to know next time you pound the hull in bad weather.




Thanks: Sure, some blisters could be trapped in because of my multi coats of epoxy barrier..... if they ever popped in inside the hull I will attack them from inside....
Outside epoxy will meet inside epoxy! The war is won. Never heard of such an occurence! Have you?
Thanks again.

[ferrailleur]

Originally Posted by SimonV

You have done a lot of the hard work, why not finish it and take off all the underwater gell coat. Do it properly do it once.

Thanks for the comment. I have not finished grinding. I doubt that I will grind ALL the gell coat! I will probably miss a few "alive" blisters when I have finished my sanding/pairing/filling/epoxy coatings/paintings..
But I will take care of them at the next haul out!
Thanks again.

[ferrailleur]

Originally Posted by ferrailleur

Great post. Thanks. I realize that I haven't grinded out EVERY blisters. Some small one will still be "alive" even after my filling/fairing/epoxy coatings/paintings.
I will be getting those at the next year hauling out!
And hopefully less of those at the year after next year haul out!
Makes sense?
Thanks again.


If you seal all the moisture in the hull so it can no longer get out, then it will just go deeper in.... Blisters dont sink boats, but internal fibreglass delamination will certainly weaken the hull below original designed strength. Nice to know next time you pound the hull in bad weather.




Thanks: Sure, some blisters could be trapped in because of my multi coats of epoxy barrier..... if they ever popped in inside the hull I will attack them from inside....
Outside epoxy will meet inside epoxy! The war is won. Never heard of such an occurence! Have you?
Thanks again.

Originally Posted by SimonV

You have done a lot of the hard work, why not finish it and take off all the underwater gell coat. Do it properly do it once.

doubt that I will remove all the gel coat... at least I'm confident that I killed 90$ of the blisters...

[Sailor 99]

Originally Posted by ferrailleur

She's my Catalina 27 after soda blasting which revealed tons of blisters. Almost finished grinding!!!!
I was thinking of filling the depressions with West System 105/205 plus colloidal 406.
It's too much work at this point.
Should I instead apply two coats of some Interlux epoxy barrier. The first coat would be thicken so it would fill my grinded depressions?
Your thoughts. Thanks.

Do not do this. You must first repair with vinylester or the repairs will fall out.



So this is a area where I unfortunately have a ton of experience. We got a bad survey on a boat and subsequently found it had very bad osmosis. We ended up peeling the hull, washing it down for 30 days with a hot water pressure washer to dry it out and then putting 6 layers of fiberglass mat on it using vinylester resin. I was explicitly told by a yard in the Chesapeake that does this work not to use epoxy. Instead fix the blisters with vinylester or they will just come back.



In order to know how to fix it you need to understand the problem.

• Polyester resin is made by putting together a bunch of different chemicals and collecting the resulting solids. Glycol and phthalic acid are 2 of those chemicals.
• Polyester resin is not stable in water. If you take a solid block of polyester and put it in water it will over time start to dissolve.
• Water is able to migrate through the gel coat and into the polyester and when it does that it breaks down the polyester into its constituent components, glycol and acid. The process is called hydrolization. I am not sure why it does not dissolve the gel coat which is only thickened polyester.
• This process results in the hull becoming acidic.
• When you open a big blister it stinks , thats the acid, and it has green in it and it is sweet to the taste. This is the glycol.
• Because the boat is sitting in water there is pressure on the hull and these compounds ( glycol and acid) migrate into the threads of the fiber glass and it is in the thread under the pressure of the water that was supporting the boat. On a badly hydrolized hull with cracks in the gel coat or missing gelcoat the glycol and acid oozes out of the hull. Glycol and acid are both water soluble and so can be washed off with warm water.

Now you know what happened.

A Note On High Moisture Readings

• We measure the boat with a moisture meter and if it measures high we say the hull is wet but it is not wet with water. It is wet with glycol.
• If you take a hull that measures high and core that hull and then split the layers you will find no moisture.
• Take a badly hydrolized hull and expose the fiberglass under the gel coat and on warm days the exposed glass will get coca cola like brown stains on it and they correspond to places the glass fiber end is exposed. The hull is in essence depressurizing. This can be washed out and over the course of 30 days washing every day for 1 hour with 210 degree hot water at 4000 psi we brought the moisture readings down from 25 to 5..

How to fix.

• Epoxy has no resistance to phthalic acid so you don't want to us it to fix the holes. Depending of course on how bad it was the hull will continue to ooze glycol and acid at the damaged places. So you don't want to use epoxy to fix those holes. The acid will keep oozing out and damage the epoxy bond to the hull and the patch will fall out.
  • The yard that told me how to fix it said they peeled a hull and then used epoxy to put new fiberglass bottom on. 18 months latter sitting at the dock the entire bottom fell off the boat like it has been unzipped. ( his words)
• If you need to put glass back on, then use fiberglass mat and vinylester resin. This all depends on how much you have taken out of the hull. If you have ground half way through you need to put some mat glass back in.
• If you only need to fill the holes for fairing use 3M Premium Filler which is vinylester based. Cures and is sand
• Once all the damage is repaired you can use Interlux or Petite epoxy barrier coat.

Since I fixed my boat 6 years ago now, we have not had a single break through and the hull measures dry. A year after we did our hull there was another boat in the yard with the same problem. The blisters were ground and filled with epoxy. 2 years later that boat was hauled and found to be badly blistered. Again it was fixed with epoxy and bottom coated and launched and 2 years later was again found to be badly blistered.



Finally... you can put epoxy on vinylester or polyester but you can not put the esters on epoxy. It will not bond and will fall off.

[skipgundlach]

Someone way up from here mentioned pressure washing.

That's the ticket for really allowing the hull to dry out. I covered our massive bottom job several years ago; I'll spare the others the story, which is pretty long, but here's the link if you'd care to have a look:
Do I need to strip my bottom? - Page 2 - Cruisers & Sailing Forums

[Sailor 99]

Originally Posted by Clivevon

By the way, high pressure water is forcing more water into the hull.

This is false. It is impossible to force water into the hull with a pressure washer.


I pressure washed a large hull with hot water every day for 30 days. The hull became dryer, from a high of 25 to 5/6 on a moisture meter, as we washed out the phthalic acid and glycol.



We were not washing inside the hull. We were blowing away the previous days weepings of phthalic acid and glycol which is moist while in the hull but hardens when it is exposed to air. Heating with the hot water allows the glycol and acid to flow better. The hot water helped a lot.

[Greg Mason]

I have to side with Clivevon. You have gone this far, why not finish the work? My 3/4 ton was done twice after they added micro balloons to make sanding easier. I never understood why epoxy if you want want easy sanding. The surveyor is answering the wrong question IMO, maybe no boat ever sank because of blisters, but how many deals sank because of them? After the second permanent fix, after 6 months of drying, my waterline came up 1". No story to tell with did it cheap and fast.

[Sailor 99]

Originally Posted by SimonV

You have done a lot of the hard work, why not finish it and take off all the underwater gell coat. Do it properly do it once.

I would not do that.

[Sailor 99]

Originally Posted by skipgundlach

Someone way up from here mentioned pressure washing.

That's the ticket for really allowing the hull to dry out. I covered our massive bottom job several years ago; I'll spare the others the story, which is pretty long, but here's the link if you'd care to have a look:
Do I need to strip my bottom? - Page 2 - Cruisers & Sailing Forums

100%. When you pressure wash you wash off the dryed glycol and phthalic acid that has weeped out and it allows more to weep out to be washed off tomorrow.


Hot water helps.

[icemate]

Originally Posted by ferrailleur

She's my Catalina 27 after soda blasting which revealed tons of blisters. Almost finished grinding!!!!
I was thinking of filling the depressions with West System 105/205 plus colloidal 406.
It's too much work at this point.
Should I instead apply two coats of some Interlux epoxy barrier. The first coat would be thicken so it would fill my grinded depressions?
Your thoughts. Thanks.

When I did mine, I contacted West Systems and they gave me the best advice. They used to be boat builders before going solely to epoxies. I repairs hull and applied 3 coats of West Barrier Coat. Easy and fast. 10 years later and not one blister. Good Luck

[Cheechako]

I had a boat like that. Using the epoxy colloidal mix is difficult because it's very hard sanding and fills paper fast. So keep that in mind.
If you really want to take short cuts then just put in Marine (bondo) filler to fill those divots. It's not the very best solution, but those look real shallow and it has been done by hundreds or thousands of people before. Light coat glass laminating resin in the divots first, then bondo. (Do not use the "final coat" resin with the wax in it.)
Here's the most important part: when fair and ready, roll coat the hull with two layers of actual epoxy resin.... not paint. On mine that's what I did and it lasted 4-5 years before I sold without blister return.
Let those dry out though, how long has it been out? I let mine dry 3 months.

[SteveSadler]

It's only time consuming if you're not skilled at it. Get a $100 moister meter. If there is any moisture in it, blisters will form again. A plastic squeegee is the right tool to fill the holes and the epoxy needs a thickener like thicksill so it won't run before it sets. After mixing, pour it onto a piece of plywood so heat doesn't build up and set it off prematurely. Get a 9" sander/buffer variable speed with a firm foam sanding disc 80 grit, and it should take 2 or 3 hours to fair the entire bottom. Less if you've done it before. Roll 3 thick coats of epoxy on it without sanding one after the other, as soon as it's tacky. It takes 30 minutes per coat. Sand carefully not to go thru the epoxy, another 2-3 hrs, patch with thicksill if you do, lightly sand again and paint it. It's only 26' not a big job.