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  #1  
Old 04-05-2010, 09:44 PM
RV8R999 RV8R999 is offline
 
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Default Epoxy + Acetone sealant for cowling

As per VAN's instructions, I started the pin-hole sealing job this past weekend using a 50/50 mix of West and Acetone. It goes on very easily but as it began to set I noticed hundreds of tiny little bubbles forming. These set with the epoxy and although most of the pin-holes were filled, these bubbles created their own little pin holes. Sand them all down and recoated. Same bubbles but far less.

Are the bubbles forming as a result of the acetone vaporization?

How many coats did you use till you were done with this? It looks to me it will be about 3 full coats and then maybe a few spot corrections.
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  #2  
Old 04-05-2010, 09:54 PM
SHIPCHIEF SHIPCHIEF is offline
 
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You might not have waited long enough after the acetone wipe, before applying the epoxy-acetone. It will continue to evaporate right thru the applied coating until it's gone or the coating gets hard.
Painting on epoxy is a frothy mess. However, the air bubbles in mine quickly worked their way to the top and dissapeared. My workshop was about 52 degrees F, and the epoxy set up very slowly.
I did have some remaining pinholes, but I brush coated with PPG DP-50 primer, that took care of it. My paint supplier said to just use the DP primer, but I over did it as usual. I used uncut epoxy in the bottom cowl, and acetone cut epoxy in the top cowl.
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Last edited by SHIPCHIEF : 04-05-2010 at 10:03 PM. Reason: corrections
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  #3  
Old 04-06-2010, 05:40 AM
RV8R999 RV8R999 is offline
 
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It was about 6 hours from when I wiped it down to when I applied the first coat and my garage was about 75 deg. Maybe the epoxy is setting too fast (205 hardener).

Thanks for the tip on the PPG primer. I'll do that.

Ken
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  #4  
Old 04-06-2010, 06:32 AM
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DanH DanH is offline
 
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Regardless of ancient Vans advice, the epoxy manufacturers say do not thin their products. If you want to paint on a thin epoxy (viscosity like water) try System Three ClearCoat. Ordinary West seals well using a more mechanical method like a squeegee.
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  #5  
Old 04-06-2010, 08:15 AM
John Tierney John Tierney is offline
 
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Default Smooth Prime

At an EAA Sportair workshop the presenter recommended Smooth Prime for filling pinholes. Anyone have experience with this?
http://www.aircraftspruce.com/catalo...moothprime.php
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  #6  
Old 04-06-2010, 08:29 AM
mstephan
 
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Default Smooth Prime is good

I used it. Water based. Dries quickly. Easy to sand. Covered it with epoxy primer before final paint.

Michael Stephan
RV-8 N991MS
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  #7  
Old 04-06-2010, 01:03 PM
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dedgemon dedgemon is offline
 
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Default Smooth Prime

I used it on my '9 and it tended to post cure and shrink once the top cowl got good and hot. I no longer use it. My preference is to spread a good quality filler (like Metal Glaze) onto the cowl to fill the craters (not pinholes, craters!), sand it all smooth (mostly all of the filler off), then spray a couple of good coats of PPG K36. This will give you a nice smooth finish (after light sanding) for the paint.

No evidence of post-curing, no adhesion problems, all materials sand well. YMMV.

Quote:
Originally Posted by John Tierney View Post
At an EAA Sportair workshop the presenter recommended Smooth Prime for filling pinholes. Anyone have experience with this?
http://www.aircraftspruce.com/catalo...moothprime.php
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  #8  
Old 04-06-2010, 11:39 PM
SHIPCHIEF SHIPCHIEF is offline
 
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RV8R999;
Not to short any of the other contributors here, but I always defer to DanH on epoxy and fiberglass. Although I'm not very good at it yet, everything has turned out well if I read his posts first.
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Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
2019
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  #9  
Old 04-07-2010, 04:44 AM
RV8R999 RV8R999 is offline
 
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thanks to all!
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  #10  
Old 04-07-2010, 08:00 AM
gpiney gpiney is offline
 
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Default Denatured alcohol

You can thin epoxy with denatured alcohol. It does not attack either the resin or hardener. Acetone does.
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