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Old 25-09-2020, 12:56   #1
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Ground out the osmosis

Hi all.
I finally decided to grind out the blisters on my hull. I'm up to around 70 now. Some are deeper than others. In all cases I ground in until I popped the weeping bubble and then kept going until I was left with clean dry laminate beneath it and out to the sides
Now I face filling which is pretty straightforward and well within my skillset.

My question relates to washing and drying. I figure on washing with acetone then leaving for a few days and filling with epoxy and layered mat.
I've read that some leave their boats for months to dry out but that's not practical. If I've ground out below the blisters what am I drying? The laminate beneath is sealed and dry...
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Old 26-09-2020, 05:13   #2
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Re: Ground out the osmosis

Leaving for months would appear to me to be predicated on the source of the water being interior, not exterior, and yours appears to be from the outside, as expected. I'm not sure that you can get exterior blisters from interior water.

Your blisters are small, if numerous. You've left the spots rough, so your repairs can grip. Good.

Acetone will replace water and evaporate in the immediate. A difference in temperature from the inside to the outside (the inside of the boat stays cool while the outside air warms in the sun) will cause condensation in a humid atmosphere. That potentially will happen every morning. Ergo, I recommend that you do not wait before getting to the repair work. As an added, if you are in a humid atmosphere (near an ocean?) you might warm the inside of the boat above the ambient temperature to prevent condensation while you work.

Your diligence in chasing blisters is admirable. Good luck with it.
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Old 26-09-2020, 06:34   #3
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Re: Ground out the osmosis

You did great... I had 700 small ones in my old polyester based coppercoat.

I strongly recommend the next steps:

1- pressure wash it and let dry overnight

2- clean every spot with a rag soaked in denatured alcohol. Turn the rag to clean side as it gets dirty

3- get some West System epoxy and hardener (or other equal brand) and some 1708 or fiberglass bidirectional or woven cloth. Have someone cut circles as you brush epoxy on a spot, add the circle and wet out with brush. This only takes 30 seconds per spot. For bigger or deeper ones, add more layers with smaller and smaller circles. Filling up with fiberglass is better than with filler and itís easy.

4- as the spots start curing, do the fingerprint test: no epoxy on finger but print on epoxy means itís ready for filler. I like a ready to use product like Awlfair or Totalfair. Make sure itís epoxybased.

5- cure overnight, next day pressure wash and sand smooth. If needed, repeat fairing. When okay, brush the spots with barrier coat to seal the fairing compound. If no barrier coat at hand, use unthickened epoxy/hardener. Wait for finger print test to trigger, then coat with anti fouling.

6- next day, light sand and anti foul the whole hull.
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Old 26-09-2020, 11:32   #4
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Re: Ground out the osmosis

Thanks everyone.
Jedi that's pretty much my plan except for the pressure wash. I'm edgy about forcing water at the glass. I think I'll just wipe with acerone instead.
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Old 26-09-2020, 11:41   #5
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Re: Ground out the osmosis

I would say just clean with acetone and fill. Do not leave too long, it’s could just become contaminated again. 1 hour then fill.
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Old 26-09-2020, 12:50   #6
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Re: Ground out the osmosis

Pressure wash is the proven method to get moisture out of the laminate after osmosis treatment. It also ensures that all osmosis liquid has been washed off.
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