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Barrier coats

Posted: Sun Sep 15, 2019 11:16 pm
by fallguy1000
Okay, so sort of a poll type question...

The West Systems manual suggests microballoons are porous..and they suggest as many as 6 coats of epoxy after final fairing. They also recommend a final light layer of glass after final fairing (???). Anyhow, obviously I am using epoxy primer and plan to use two coats, but does anyone have an opinion about putting up to 6 neat coats on the boat? Let's assume 50 yards of surface on the Skoota. 2 ounces per yard is about a gallon of epoxy per coat or 9 pounds additional weight....


The West Systems book suggests 10 mil or 0.010 per coat. It might suck to sand it.

Is anyone even considering such a move?

Re: Barrier coats

Posted: Mon Sep 16, 2019 12:19 am
by joe2700
I would not consider putting epoxy over fairing compound. Epoxy doesn't level well, and would undo a lot of the fairing work in addition to being heavy and expensive. I would only use 2 part epoxy primer over fairing compound.

Note I am using system 3 silvertip expoxy, quickfair, and yacht primer. I'm confident it's ok to paint right over the quickfair because the literature for the yacht primer says the following which makes that clear:
Epoxy resin‐coated surfaces
Sand the epoxy surface with 100‐120 grit
paper.
2. Fill surface imperfections with SilverTip
Quikfair. Sand repair areas until smooth
using 100‐120 grit paper.
3. After sanding, vacuum or with clean, dry
shop air remove sanding dust.
4. Wipe the surface with denatured alcohol
and clean rags.
5. Apply SilverTip Yacht Primer with roller and
brush...

Re: Barrier coats

Posted: Mon Sep 16, 2019 7:06 am
by piperdown
fallguy1000 wrote:
Sun Sep 15, 2019 11:16 pm
Okay, so sort of a poll type question...

The West Systems manual suggests microballoons are porous..and they suggest as many as 6 coats of epoxy after final fairing. They also recommend a final light layer of glass after final fairing (???). Anyhow, obviously I am using epoxy primer and plan to use two coats, but does anyone have an opinion about putting up to 6 neat coats on the boat? Let's assume 50 yards of surface on the Skoota. 2 ounces per yard is about a gallon of epoxy per coat or 9 pounds additional weight....


The West Systems book suggests 10 mil or 0.010 per coat. It might suck to sand it.

Is anyone even considering such a move?

Is that for the whole boat or just from the water line down onto the hull bottom?

That's not that much difference from us rolling on 4 coats of epoxy/graphite on the hull bottom up to the water line.

Re: Barrier coats

Posted: Mon Sep 16, 2019 8:17 am
by terrulian
What Joe2700 and piperdown said.

But I'd like to know if "piperdown" references bagpipers leading a suicidal battle charge, or maybe a steamfitter after a boiler blows up?

Re: Barrier coats

Posted: Mon Sep 16, 2019 9:05 am
by Capt UB
terrulian wrote:
Mon Sep 16, 2019 8:17 am
What Joe2700 and piperdown said.

But I'd like to know if "piperdown" references bagpipers leading a suicidal battle charge, or maybe a steamfitter after a boiler blows up?


Did you ever use Cold Tar Epoxy on your keels/boats? Was reading a thread in a Boat builders FB page, asked if I was any good. The last time I used it was in the 80's, did not know it was still around!

Re: Barrier coats

Posted: Mon Sep 16, 2019 9:17 am
by fallguy1000

Re: Barrier coats

Posted: Mon Sep 16, 2019 9:46 am
by terrulian
Yep, I see it. The only reason I myself would use a couple of final layers of neat epoxy as last coats before a topcoat would be when leaving the wood clear with no filler at all. If you are going to use anything opaque as a filler, I see zero reason to follow West's advice. It is not that easy to sand epoxy for a really smooth finish compared to a two-part epoxy primer like System Three, which is itself opaque.

Re: Barrier coats

Posted: Mon Sep 16, 2019 10:18 am
by fallguy1000
terrulian wrote:
Mon Sep 16, 2019 9:46 am
Yep, I see it. The only reason I myself would use a couple of final layers of neat epoxy as last coats before a topcoat would be when leaving the wood clear with no filler at all. If you are going to use anything opaque as a filler, I see zero reason to follow West's advice. It is not that easy to sand epoxy for a really smooth finish compared to a two-part epoxy primer like System Three, which is itself opaque.
Right. Sandpaper city.

So are they just trying to sell epoxy or is it because microlite is porous as they say?

A bit confused.

However, I see an upside to the approach. For all the times you have a minute depression in the work surface; you would be filling it. And 10-20 mils will hide a lot of crap. Then you paint and the primer coat would be nicer... you are not getting 10 mils from primer...

Re: Barrier coats

Posted: Mon Sep 16, 2019 10:23 am
by piperdown
terrulian wrote:
Mon Sep 16, 2019 8:17 am
What Joe2700 and piperdown said.

But I'd like to know if "piperdown" references bagpipers leading a suicidal battle charge, or maybe a steamfitter after a boiler blows up?
Mike Myers "So I Married and Axe Murderer"
1:05 in

Long story....I used to play the bagpipes (about 10 years)....

https://www.youtube.com/watch?v=L1DGPENoKhY

Re: Barrier coats

Posted: Mon Sep 16, 2019 10:29 am
by piperdown
fallguy1000 wrote:
Mon Sep 16, 2019 10:18 am
terrulian wrote:
Mon Sep 16, 2019 9:46 am
Yep, I see it. The only reason I myself would use a couple of final layers of neat epoxy as last coats before a topcoat would be when leaving the wood clear with no filler at all. If you are going to use anything opaque as a filler, I see zero reason to follow West's advice. It is not that easy to sand epoxy for a really smooth finish compared to a two-part epoxy primer like System Three, which is itself opaque.
Right. Sandpaper city.

So are they just trying to sell epoxy or is it because microlite is porous as they say?

A bit confused.

However, I see an upside to the approach. For all the times you have a minute depression in the work surface; you would be filling it. And 10-20 mils will hide a lot of crap. Then you paint and the primer coat would be nicer... you are not getting 10 mils from primer...

From their other manual on page 13 under Epoxy barrier coating: https://www.westsystem.com/wp-content/u ... ishing.pdf


The object of epoxy barrier coating is to build up an epoxy layer that protects the substrate from moisture. In doing so it stabilizes the substrate and provides a smooth stable base for the finish coating needed for UV protection.
For an effective moisture barrier on most exterior surfaces, apply a minimum of three
coats (about 10 mils) of WEST SYSTEM epoxy. Moisture protection will increase with
additional coats, up to six coats or about a 20 mil thickness. A minimum of six coats is
recommended on fiberglass hulls below the waterline.


I'm guessing they just want to make sure you have complete control of moisture infiltration below the water line.