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Old 12-05-2020, 14:02   #1
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Epoxy or Vinylester Barrier Coat

So my hand laid fiberglass Westsail hull that has a reputation for not blistering when hauled after being in the Northern colder waters for six years had a large number of blisters. I paid a company to glass blast and remove all the gelcoat down to the first layer of cloth mat. Blast process was great removed all the blisters. The divets where then enlarged and the edges beveled and thousands of fiberglass patches where laminated with vinylester to fill and fair.

The vessel was built in 1976, era of oil embargo and questionable resins. When you look at the glass now removed of the gel you can see very clearly evidence that many fibers where starved of polyester.

So to say that I don't ever wish to do this process over again is an understatement. Would appreciate some opinions on choice of epoxy barrier coat or vinylester barrier coat for the next step?
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Old 12-05-2020, 14:17   #2
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Re: Epoxy or Vinylester Barrier Coat

Although expensive Epoxy is the norm. There have been questions as to the effectiveness of vinylesters against osmosis. You have done the hard yards, donít back off now, the labor component is the greater expense on the next step and itís the same for vinyls or epoxy.
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Old 12-05-2020, 14:42   #3
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Re: Epoxy or Vinylester Barrier Coat

We had blister repair done about a year ago. After grinding down the blisters, vinyl ester resin was applied. Then, on top of that, an epoxy film was applied. Then, paint primer. Then, two coats of paint (first black, then blue). This repair was done about a decade after the previous one and only epoxy was applied. It is expected we should not experience blisters for about a decade.
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Old 12-05-2020, 14:52   #4
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Re: Epoxy or Vinylester Barrier Coat

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Although expensive Epoxy is the norm. There have been questions as to the effectiveness of vinylesters against osmosis. You have done the hard yards, donít back off now, the labor component is the greater expense on the next step and itís the same for vinyls or epoxy.


I forgot to mention the epoxy is applied on dynal cloth.
So a coat of epoxy straight on the DRY bare hull then followed by the dynal cloth and at least two coats of epoxy on top of the cloth
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Old 13-05-2020, 08:06   #5
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Re: Epoxy or Vinylester Barrier Coat

Thank you all who have replied. One of the so called local experts indicates Interprotect is only good for 10 years, that a bit unsettling?
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Old 13-05-2020, 08:19   #6
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Re: Epoxy or Vinylester Barrier Coat

Apologies in advance for the long comment


I went through a similar process about 9 years ago. The work was done in a very reputable yard in Florida. There were no true blisters at the time, merely tiny pimples under the epoxy barrier coat--not in the gelcoat. Upon removing the barrier coat, it was discovered that the boat had been previously treated for blisters. Since we could not be certain of the quality, the hull was peeled again. Vinylester was applied in accordance with the manufacturers specs. It was hot-coated with an epoxy barrier coat, again according to the manufacturers specs. Almost immediately, bubbles appeared. The affected area was repaired and a second coat of epoxy applied. More bubbles, which brought the manufacturer to the site with their experts the very next day. It was sampled for materials, lab tested etc, and they decided to redo the affected areas. Problem appeared fixed, boat was launched, and sailed to its new home port.



Upon arrival, I had a diver examine the hull. A large area was devoid of epoxy barrier coat and antifouling. The boat was hauled. Manufacturer came within a day or two. Samples were taken. Area was repaired/repainted at their cost.


Then, when taking the jack stands away to relaunch, the paint/epoxy was stuck to the stands. There was complete failure of the epoxy to bond to the vinylester. The vinylester was peeled off and the entire bottom was treated with West system, with sheathing etc.and then epoxy painted. The manufacturer paid all of this. Nine years later, no problems.


Now, what happened. If you use vinyester, it must completely 'gas' before applying to it. It will take up to a week or more. The ultimate test is to soak an area with acetone. If it softens (becomes even slightly tacky) wait another week. Knowing what I know now, I would peel, clean thoroughly immediately before applying epoxy with cloth (personally, I suspect micro-dust particles are what starts the blistering). Then do the barrier coat in epoxy.
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Old 13-05-2020, 08:46   #7
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Re: Epoxy or Vinylester Barrier Coat

Resin chemistry is very complex so there could be a number of issues that lead to osmosis in the first place. I would suggest getting a resin expert to look at it and determine any issues with the hull at this point then plan on corrective measures rather than going for a 'standard' epoxy treatment.
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Old 13-05-2020, 12:47   #8
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Re: Epoxy or Vinylester Barrier Coat

1) strip all paint down to gelcoat with soda blasting
2) grind all blisters
3) dry, dry, dry....
4) apply acetone and dry again
5) fill up blisters with West System 405/105 (I think it's the #)
6) apply 5 coats of Interprotect 2000
7) apply two coats of whatever antifouling you like....
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Old 13-05-2020, 13:04   #9
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Re: Epoxy or Vinylester Barrier Coat

Sherwan Williams makes a 2 part epoxy-polyamide. It was previously restricted to the military and professionals. It's now available in 1 gallon cans.
It's called Formula 150, Type III( Part A & B). Interprotect looses it's effectiveness over time and then starts to trap water between it and the hull. I hade to peel and resurface my hull afer 9 years, and it was applied at the factory! Redid thre hull 11 uears ago and its still dry. JMHO
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Old 13-05-2020, 13:46   #10
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Re: Epoxy or Vinylester Barrier Coat

Interprotect 2000 does not loose itís effectiveness nor does it falloff the hull. Those problems are all caused by improper work... yes even when it was the best and most expensive yard.

Be wise, use epoxy only. If you have not touched constructional laminate with the blister treatment (or you have so much of that so that it doesnít matter) then you donít need to add fiberglass, but if you do, do it with epoxy and hot coat it (finger print test: you see your fingerprint in the epoxy but it does not leave epoxy on your finger = go time) with Interprotect 2000. This eliminates amine blush problems and epoxy is compatible with epoxy. Stay within overcoat times and with the final coat, do the fingerprint test again for timing the first coat of antifouling. I recommend Micron 66 for that first coat.
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Old 22-05-2020, 11:44   #11
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Re: Epoxy or Vinylester Barrier Coat

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Originally Posted by Scrimshaw4 View Post
Sherwan Williams makes a 2 part epoxy-polyamide. It was previously restricted to the military and professionals. It's now available in 1 gallon cans.
It's called Formula 150, Type III( Part A & B). Interprotect looses it's effectiveness over time and then starts to trap water between it and the hull. I hade to peel and resurface my hull afer 9 years, and it was applied at the factory! Redid thre hull 11 uears ago and its still dry. JMHO

I have been considering using the Sherwin Williams product. Water was indeed trapped behind the Interlux. Did you use the Formula 150 when redoing your boat?
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Old 23-05-2020, 06:00   #12
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Re: Epoxy or Vinylester Barrier Coat

The Sherwin Williams was applied to my hull 11 years ago and the hull is still dry.
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Old 15-07-2020, 12:34   #13
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Re: Epoxy or Vinylester Barrier Coat

Quote:
Originally Posted by Scrimshaw4 View Post
Sherwan Williams makes a 2 part epoxy-polyamide. It was previously restricted to the military and professionals. It's now available in 1 gallon cans.
It's called Formula 150, Type III( Part A & B). Interprotect looses it's effectiveness over time and then starts to trap water between it and the hull. I hade to peel and resurface my hull afer 9 years, and it was applied at the factory! Redid thre hull 11 uears ago and its still dry. JMHO
This is exactly what happened with the old interprotect. I am planning on using the Sherwin Williams product. Do you know if its available in different colors?
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Old 15-07-2020, 12:52   #14
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Re: Epoxy or Vinylester Barrier Coat

It is always best to follow the manufacturer's instructions.

The product I used was the Interlux Interprotect 2000E I applied five coats per the instructions onto the bare gel coat, as-shown in this reply.

When I am shuffling stands and blocks I always use a thick plastic sheet layer to avoid damaging the finish.


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Old 15-07-2020, 15:06   #15
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Re: Epoxy or Vinylester Barrier Coat

Vinylester is junk. Barrier coats are epoxy for a good reason.
Must be done correctly like Wingless says.
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