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Old 05-05-2019, 06:54   #1
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Blister Filling Question

Boat was glass blasted to remove hundreds of blisters below vessels waterline. All gelcoat removed and now down to bare laminate.

Areas where blisters were left depressions in the glass. All of these depression have been ground out to a depth of about a 1/4 inch using a Rotozip tool and the edges of this work feathered to hulls original profile.

What has been left with areas to be repaired ranging in size between a quarter and fifty cent sized circles.

I am familiar with working with most products and materials used in filling areas to be repaired. I am looking to considerably shorten the next step and the thought of cutting hundreds of glass patches, the multiple steps required for 3M filler and potential issues of epoxy leads me to consider using polyester.

So question is will using polyester resin, mixed with 1/4 inch fiberglass chop strand, then thickening cabosil to make a non sagging putty be a viable option for repair ?
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Old 05-05-2019, 07:00   #2
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Re: Blister Filling Question

No poly! Use "Superbond Epoxy glue its a easy 1-1 mix and peanut butter consistency. Available from FG Coatings in St pete FL.
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Old 05-05-2019, 07:51   #3
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Re: Blister Filling Question

don't want to use epoxy
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Old 05-05-2019, 07:54   #4
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Re: Blister Filling Question

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Originally Posted by cburger View Post
don't want to use epoxy
Epoxy is what Surveyors recommend---otherwise choose your poison---- polyester is what blistered in the first place--so you might get blisters on the blisters. Epoxy is what all Blister barrier coats are made of---- epoxy is about 10X stronger than polyester and sticks far better than polyester...….. lol
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Old 05-05-2019, 08:05   #5
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Re: Blister Filling Question

Poly and chop strand is what largely allowed the blistering to happen in the first place so I wouldn't go down that road. If the cuts really are 1/4" deep you are going to want to build up with some glass which is a pain but I would do it to get them built up a little. Don't worry about making the cuts all that neat, just get glass roughly cut and epoxied in there and leave the hairy ends dry of epoxy, once it cures you can shave them off with your sander, makes the application much faster since you aren't fiddling too much with cutting them to size. Once that is done a fairing compound over the top to smooth things out a bit will do the trick.

I just went through this with mine and it is a royal PITA but I feel like it really is the best way to do it and maintain the integrity of the hull.

Quote:
Originally Posted by cburger View Post
Boat was glass blasted to remove hundreds of blisters below vessels waterline. All gelcoat removed and now down to bare laminate.

Areas where blisters were left depressions in the glass. All of these depression have been ground out to a depth of about a 1/4 inch using a Rotozip tool and the edges of this work feathered to hulls original profile.

What has been left with areas to be repaired ranging in size between a quarter and fifty cent sized circles.

I am familiar with working with most products and materials used in filling areas to be repaired. I am looking to considerably shorten the next step and the thought of cutting hundreds of glass patches, the multiple steps required for 3M filler and potential issues of epoxy leads me to consider using polyester.

So question is will using polyester resin, mixed with 1/4 inch fiberglass chop strand, then thickening cabosil to make a non sagging putty be a viable option for repair ?
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Old 06-05-2019, 14:13   #6
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Re: Blister Filling Question

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Poly and chop strand is what largely allowed the blistering to happen in the first place so I wouldn't go down that road. If the cuts really are 1/4" deep you are going to want to build up with some glass which is a pain but I would do it to get them built up a little. Don't worry about making the cuts all that neat, just get glass roughly cut and epoxied in there and leave the hairy ends dry of epoxy, once it cures you can shave them off with your sander, makes the application much faster since you aren't fiddling too much with cutting them to size. Once that is done a fairing compound over the top to smooth things out a bit will do the trick.

I just went through this with mine and it is a royal PITA but I feel like it really is the best way to do it and maintain the integrity of the hull.
I figured this was going to end up with epoxy. So rather than cutting hundreds of individual fiber-glass patches multiple times to get to profile what would the problem be with using an epoxy, silica, and chop strand to make thickened putty and fill in one pass, would wet out voids prior to filling?
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Old 06-05-2019, 14:27   #7
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Re: Blister Filling Question

Chop strand and epoxy don't really work well together, you really need to use a vinylester or polyester resin to dissolve the glue that holds the chop together and the poly resins are what allow for the bulk of osmosis that caused your blisters in the first place. If you use epoxy, the resin to glass ratio is too high and you end up with voids and an overall weak repair leading to future blisters. There is something called knytex, at least I think that is what it is called, which is sort of like a mix of chop strand woven into a regular glass mat grid that does not use a glue to bind the strands together. That stuff is great for bulking up and works just fine with epoxy but it may be overkill for what you are trying to do.

I would recommend epoxy with a middle weight glass like 7.25oz matt. It is 90x90, meaning the strands are woven at 90 degree angles to one another so it is easy to form, reasonably strong, wets out nicely, and is easy to shave when the expoxy cures.

Quote:
Originally Posted by cburger View Post
I figured this was going to end up with epoxy. So rather than cutting hundreds of individual fiber-glass patches multiple times to get to profile what would the problem be with using an epoxy, silica, and chop strand to make thickened putty and fill in one pass, would wet out voids prior to filling?
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Old 06-05-2019, 14:32   #8
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Re: Blister Filling Question

Epoxy is only 15% stronger than polyester.
Use either vinylester or polyester and re-gelcoat, epoxy through a lot of surveyors recommend it is not good for big repairs because it cures harder than polyester (search hard spots )
Epoxy makes better profit as well
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Old 06-05-2019, 14:38   #9
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Re: Blister Filling Question

Epoxy is only 15% stronger than polyester.
Use either vinylester or polyester and re-gelcoat, epoxy through a lot of surveyors recommend it is not good for big repairs because it cures harder than polyester (search hard spots )
Epoxy makes better profit as well
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Old 06-05-2019, 15:06   #10
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Re: Blister Filling Question

Using chop strand and cabosil mix upside down is never going to work. Those short fibres are just to hard to handle and when the cabosil sets it is like trying to sand concrete. The other thing is you have to roll the air bubbles out of that mess and the ester resins all have to short a cure time.
You are all ready half way there so why not finish the job properly with epoxy slow hardner/glass in the blisters that are back to laminate and just fill the blisters in the gelcoat?
The idea that epoxy is good profit is just crazy. As a marine surveyor I only recommend what works. Considering how often I see the same boats out of the water I know the epoxy/glass thing works.
The idea that epoxy is not good for big repairs is interesting. But what you are doing I would not consider a “big repair”.
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Old 06-05-2019, 21:11   #11
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Re: Blister Filling Question

Sail Life (youtube channel) did a similar job. As I recall, he filled the blister holes with thickened epoxy, and then laid one sheet of glass over the entire hull to provide additional protection and thickness, followed by fairing and then epoxy barrier coat and paint (he used Coppercoat rather than paint and antifoul). That would be a good way to go from where you are, and you'd have certainty over both the finish and the integrity.
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Old 06-05-2019, 21:16   #12
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Re: Blister Filling Question

Quote:
Originally Posted by cburger View Post
Boat was glass blasted to remove hundreds of blisters below vessels waterline. All gelcoat removed and now down to bare laminate.

Areas where blisters were left depressions in the glass. All of these depression have been ground out to a depth of about a 1/4 inch using a Rotozip tool and the edges of this work feathered to hulls original profile.

What has been left with areas to be repaired ranging in size between a quarter and fifty cent sized circles.

I am familiar with working with most products and materials used in filling areas to be repaired. I am looking to considerably shorten the next step and the thought of cutting hundreds of glass patches, the multiple steps required for 3M filler and potential issues of epoxy leads me to consider using polyester.

So question is will using polyester resin, mixed with 1/4 inch fiberglass chop strand, then thickening cabosil to make a non sagging putty be a viable option for repair ?

No poly, no epoxy. Use vinylester. Works just like polyester. Does not have a blistering problem. Hull maybe a little acidic now so epoxy not good.


We did a huge bottom job 6 yrs ago. Used vinyl ester no issue. Just passed survey last week.


Vinylester and then of course Interlux epoxy barrier or similar.
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Old 06-05-2019, 22:01   #13
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Re: Blister Filling Question

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Originally Posted by Dark Horse View Post
No poly, no epoxy. Use vinylester. Works just like polyester. Does not have a blistering problem. Hull maybe a little acidic now so epoxy not good.


We did a huge bottom job 6 yrs ago. Used vinyl ester no issue. Just passed survey last week.


Vinylester and then of course Interlux epoxy barrier or similar.

I am not sure about how your putting your chopped strand in but if your going to mix it in with your resin I think you will not have fun. I tried this and just ended up with a glob.



Much better to use unthickened vinylester and 1.5 oz mat.



Get a tool something like this.


https://www.amazon.com/Hollow-Leathe...ateway&sr=8-32


and punch out a few hundred holes which will be bound together with the mat binder. This binder dissolves in vinylester or polyester but not in epoxy.


Don't thicken the vinylester. You also want to be sure it is unwaxed.


Once you have your assortment of mat circles, wet out the hole with a brush and press in one of the circles. Wet it out with the brush and repeat till the hole is full.



In an hour it will all be hard and in 2 hours ready to sand any excess.


Then get either polyfair f26 ( cheap ) or 3M premium filler ( vinylester) and just fair the hole. You can do this up to a week later. No sanding of the initial vinylester required ( because it was unwaxed) . Both harden very quickly and are sand-able in an hour. I prefer the polyfair. 1/4 price


Epoxy barrier coat and your done.


Beware... if you decide to go with epoxy and you have to re do this then you need to remove all the epoxy if your going to then try it with one of the esters.... Epoxy will bond to polyester and vinylester but either will bond properly to Epoxy.


PM me if you want more info.
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Old 06-05-2019, 22:06   #14
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Re: Blister Filling Question

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Originally Posted by gmakhs View Post
Epoxy is only 15% stronger than polyester.
Use either vinylester or polyester and re-gelcoat, epoxy through a lot of surveyors recommend it is not good for big repairs because it cures harder than polyester (search hard spots )
Epoxy makes better profit as well

Not sure why you would re gelcoat. The gelcoat was the problem.


Once you are done repairing the hull you epoxy barrier coat it.



I never use epoxy for the actual glass repairs. I put 6 layers of glass mat on 600 sq ft bottom using vinyl ester. Cures fast and even and you can just add layers without sanding. No amine blush, no sanding ( use unwaxed resins)
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Old 07-05-2019, 01:02   #15
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Re: Blister Filling Question

A couple of questions Dark Horse. I see your in Toronto Canada so is your yacht in the water all year? When you say Poly Fair is that the pink filler commonly called car filler or builders bog? Another question, why 6 layers of glass Mat.Why not a structural layer of 450gm double bias and skip a couple of Mat layers?
Just curious, I love the hole punch idea.
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