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Old 15-04-2019, 07:25   #1
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epoxy blister repair question

Let's say you're repairing a blister that you have grinded out.

- Do you directly apply the hardened epoxy (West System 105/205 with thickener)?
- or do you first apply a coat of 105/205 and then fill up with the hardened epoxy (105/205 with thickener)?
Thanks
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Old 15-04-2019, 08:04   #2
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Re: epoxy blister repair question

Brush on a thin coat of unthickend epoxy first, then apply the epoxy with the fillers added
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Old 15-04-2019, 13:17   #3
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Re: epoxy blister repair question

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Originally Posted by pcmm View Post
Brush on a thin coat of unthickend epoxy first, then apply the epoxy with the fillers added
Thanks... the reason I asked is that I have a ton of blisters that I have grinded, washed, brushed acetone on, etc.
At this point, I would like to skip the first thin coat you mentioned and go right away to the final filling to save a lot of time.
Is the first thin coat you mentioned absolutely indispensable?
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Old 15-04-2019, 13:23   #4
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Re: epoxy blister repair question

Let it dry thoroughly after the acetone.

Than brush the thin catalysed epoxy on. It will soak into any open fibers.

Be diligent to get the exact correct mixing ratio with epoxy. Epoxy is not forgiving on this. Only with polyester you can guesstimate how much hardener you need.

Than add the filled epoxy within the time allowed by the epoxy system you use. Don't wait until you need to sand the thin stuff.

Rather do a couple of holes and then the next ones and don't brush the thin stuff on all holes at once.
You risk of getting out of the "green stage" before adding the thickened stuff.

Btw. If you ground out very deep you might need to add some layers of woven cloth and not just fill with thickened epoxy.
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Old 15-04-2019, 13:58   #5
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Re: epoxy blister repair question

Quote:
Originally Posted by ferrailleur View Post
Thanks... the reason I asked is that I have a ton of blisters that I have grinded, washed, brushed acetone on, etc.
At this point, I would like to skip the first thin coat you mentioned and go right away to the final filling to save a lot of time.
Is the first thin coat you mentioned absolutely indispensable?
Not a time to cut corners unless you feel like repeating the process again in the near future.
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Old 15-04-2019, 14:54   #6
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Re: epoxy blister repair question

Quote:
Originally Posted by ferrailleur View Post
Thanks... the reason I asked is that I have a ton of blisters that I have grinded, washed, brushed acetone on, etc.
At this point, I would like to skip the first thin coat you mentioned and go right away to the final filling to save a lot of time.
Is the first thin coat you mentioned absolutely indispensable?
The reason for the first unthickend coat is for the glass to absorb it (if its going to) not a big deal, just mix a first batch and go around the hull and paint it on the ground blisters, then go around a second time with the thickend epoxy. After that you fair and fill and fair, then add some barrier coat additive to another batch and paint on again, and again and again. Then cover it with barrier coat.
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Old 17-04-2019, 06:23   #7
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Re: epoxy blister repair question

FWIW...our Taswell (now 30 yrs old) had a similar issue . Every time we hauled out we would have lots of small, not deep blisters all over the hull. We ground them out and re-glassed them each year, and then reapplied the antifoul. At about the 23-yr point in her life, a local f/g guy happened to stop by, saw the blisters, and told me that is it common for the gel coat to ...:wear out". and when it does, you get lots of blisters. He recommended we peel the bottom, refeather it, reapply a sealer/barrier coat, and then redo the bottom paint. We did, and have not had a single blister since....we haul every year.
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Old 17-04-2019, 14:54   #8
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Re: epoxy blister repair question

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FWIW...our Taswell (now 30 yrs old) had a similar issue . Every time we hauled out we would have lots of small, not deep blisters all over the hull. We ground them out and re-glassed them each year, and then reapplied the antifoul. At about the 23-yr point in her life, a local f/g guy happened to stop by, saw the blisters, and told me that is it common for the gel coat to ...:wear out". and when it does, you get lots of blisters. He recommended we peel the bottom, refeather it, reapply a sealer/barrier coat, and then redo the bottom paint. We did, and have not had a single blister since....we haul every year.
I have seen on YouTube videos which takes all the gel coat down to the laminate.... relaminating the whole hull after that: HUGE EXPENSE for (in my case) a $8,000 Catalina 27.
Your yard guy could have been right.... I'll see next year what amount of blisters have returned.... Thanks

That pic was done half way in my grinding work!!!
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Old 17-04-2019, 16:10   #9
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Re: epoxy blister repair question

I wouldnt peel a Catalina 27. Not worth the cost IMO. I'd just fill the blisters as you have been when they crop up.

You will need to dab in some unthickened epoxy. The reason you want to apply this coat and let it kick before you apply thickened is to give the thickened a wetted out surface to adhere to.

If your looking to save time, it's not skimping on the method, rather skimping on the fairing process. Fill the blister, fair it once to knock any hard points off, barriers coat it and bottom paint.

You'll loose some speed, you'll have a lumpy bottom, but atleast the filler wont fail on you.
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Old 17-04-2019, 16:32   #10
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Re: epoxy blister repair question

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I wouldnt peel a Catalina 27. Not worth the cost IMO. I'd just fill the blisters as you have been when they crop up.

You will need to dab in some unthickened epoxy. The reason you want to apply this coat and let it kick before you apply thickened is to give the thickened a wetted out surface to adhere to.

If your looking to save time, it's not skimping on the method, rather skimping on the fairing process. Fill the blister, fair it once to knock any hard points off, barriers coat it and bottom paint.

You'll loose some speed, you'll have a lumpy bottom, but atleast the filler wont fail on you.
Thanks..... I called West System.... they also encouraged me not to skip the wetting stage before applying the thickened epoxy....
It's going to be a long stage by stage process in my case!
Re fairing.... after all is filled up I plan to grind wit 80 grit all around before 3-4 coats of Interlux epoxy barrier... and paint
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Old 17-04-2019, 18:10   #11
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Re: epoxy blister repair question

You sound impatient and this is a serious mistake with this job. Are you certain the hull is dry ? It can (almost invariably) take months for a hull to dry out after the blisters are opened up.

I suggest you read Moisture Meter Mythology right to the last paragraph and invest in a cheap moisture meter.

Failure to ensure the hull is dry is a guarantee you will be doing this job again.
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Old 18-04-2019, 10:37   #12
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Re: epoxy blister repair question

Quote:
Originally Posted by ferrailleur View Post
Thanks..... I called West System.... they also encouraged me not to skip the wetting stage before applying the thickened epoxy....
It's going to be a long stage by stage process in my case!
Re fairing.... after all is filled up I plan to grind wit 80 grit all around before 3-4 coats of Interlux epoxy barrier... and paint
Yes, it is a long process with a LOT of sanding. You can use West 105 as a barrier coat. Each coat must be washed and lightly sanded before next coat.
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Old 18-04-2019, 18:54   #13
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Re: epoxy blister repair question

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Originally Posted by boatpoker View Post
You sound impatient and this is a serious mistake with this job. Are you certain the hull is dry ? It can (almost invariably) take months for a hull to dry out after the blisters are opened up.

I suggest you read Moisture Meter Mythology right to the last paragraph and invest in a cheap moisture meter.

Failure to ensure the hull is dry is a guarantee you will be doing this job again.
Correct I'm kind of impatient... The boat has been on the hard for six months with soda blasting and me grinding blisters hours and hours.... rinsing and rinsing and "acetoning" the cavities....
Now I'm brushing non hardened 105/205 West System epoxy... and filled the cavities with hardened epoxy.....
I know that some blisters will return next year at haul out.....
But so what? If it's only 5-10% ???
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Old 20-04-2019, 11:11   #14
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Re: epoxy blister repair question

Quote:
Originally Posted by ferrailleur View Post
Correct I'm kind of impatient... The boat has been on the hard for six months with soda blasting and me grinding blisters hours and hours.... rinsing and rinsing and "acetoning" the cavities....
Now I'm brushing non hardened 105/205 West System epoxy... and filled the cavities with hardened epoxy.....
I know that some blisters will return next year at haul out.....
But so what? If it's only 5-10% ???
Being impatient is fine, but atleast focus on doing the job right.

It's no point to do the work and do it wrong when you'll have to go back and do it all over again because the "fix" you did failed.

That's something I've learned over the years working on my boats, working as an engineer. If your going to do something, do it right once, and be done with it or dont do it at all. It will only waste time and in turn money
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Old 20-04-2019, 11:23   #15
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Re: epoxy blister repair question

Go to the source for accurate information:

https://www.westsystem.com/wp-conten...Prevention.pdf

Just did a few myself.....!
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