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  #1  
Old 01-19-2022, 06:54 PM
wirejock's Avatar
wirejock wirejock is online now
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 5,108
Default Cowl with zits

Ever seen a cowl go through puberty and get some serious acne zits? Click on the photo and zoom.
Go ahead and laugh. I did.
Long day of work gone. Oh bother. At least it's easy to find all the pinholes. Apparently the air in the pin holes off gassed. Curing room must have been too warm.
Click image for larger version

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Larry Larson
Estes Park, CO
wirejock at yahoo dot com
Donated 12/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (3,000+ hours)
Empennage, wings, fuse, finishing kit done. Working FWF
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #2  
Old 01-19-2022, 07:00 PM
Kyle Boatright Kyle Boatright is online now
 
Join Date: Aug 2005
Location: Atlanta, GA
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Default

Ya gotta push hard with your credit card/squeegie or whatever to push the material into the holes and push the air out.
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2001 RV-6 N46KB
2019(?) RV-10
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  #3  
Old 01-19-2022, 07:07 PM
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wirejock wirejock is online now
 
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Default Squeegee

Quote:
Originally Posted by Kyle Boatright View Post
Ya gotta push hard with your credit card/squeegie or whatever to push the material into the holes and push the air out.
I thought I did. Clearly I need an industrial size squeegee! Round two after this mess gets sanded off!
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Larry Larson
Estes Park, CO
wirejock at yahoo dot com
Donated 12/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (3,000+ hours)
Empennage, wings, fuse, finishing kit done. Working FWF
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #4  
Old 01-19-2022, 07:10 PM
Kyle Boatright Kyle Boatright is online now
 
Join Date: Aug 2005
Location: Atlanta, GA
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Default

Quote:
Originally Posted by wirejock View Post
I thought I did. Clearly I need an industrial size squeegee! Round two after this mess gets sanded off!
What are you using? Some folks recommended sheetrock mud, but that didn't work very well for me <I still had a bunch of pinholes>. I went back to an epoxy wipe.
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Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
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  #5  
Old 01-19-2022, 07:16 PM
David Paule David Paule is online now
 
Join Date: Dec 2009
Location: Boulder, CO
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Default

One thing that might help is heating the shop, letting the cowl soak in the heat, shutting the heat off and doing the epoxy. As the shop cools it tends to draw the epoxy in to the pinholes.

Haven't tried this with my cowl, but it definitely works with wood parts (on a previous project).

Dave
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  #6  
Old 01-19-2022, 07:40 PM
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emsvitil emsvitil is offline
 
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Location: SoCal
Posts: 661
Default

They work like the dimples on golf balls and cut down the air resistance.....


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  #7  
Old 01-19-2022, 07:43 PM
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wirejock wirejock is online now
 
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Location: Estes Park, CO
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Default Epoxy

Quote:
Originally Posted by Kyle Boatright View Post
What are you using? Some folks recommended sheetrock mud, but that didn't work very well for me <I still had a bunch of pinholes>. I went back to an epoxy wipe.
Same as every other part I've done.
Skim with neat epoxy.
Cure 30
Skim with neat epoxy
Cure 30
Skim with micro.
I probably wasn't forcing the epoxy into the holes. Should be easy to find them after sanding.
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Larry Larson
Estes Park, CO
wirejock at yahoo dot com
Donated 12/01/2021, plus a little extra.
RV-7A #73391, N511RV reserved (3,000+ hours)
Empennage, wings, fuse, finishing kit done. Working FWF
Disclaimer
I cannot be, nor will I be, held responsible if you try to do the same things I do and it does not work and/or causes you loss, injury, or even death in the process.
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  #8  
Old 01-19-2022, 07:48 PM
BillL BillL is offline
 
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Location: Central IL
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Default

Are you using a steel squeegee? It can apply more pressure on the edge, and leave a thinner layer to sand.

But thinking, I don't think it is the root cause. I recall seeing some acrylic tables (or maybe it was a cooking show) being poured and they took a torch and waved over the top to bring out the air bubbles. I wonder if a heat gun could do that on an intermediate pass (well before the epoxy has begun curing) to identify any voids remaining. Just a wild thought.

Also, my painters just sanded all my glass down to the weave anyway.
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Last edited by BillL : 01-19-2022 at 08:59 PM.
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  #9  
Old 01-19-2022, 08:21 PM
AdamB AdamB is offline
 
Join Date: Dec 2008
Location: Fremont, NH
Posts: 299
Default

You're not the first to be working on the project for so long it's reached puberty..
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  #10  
Old 01-19-2022, 11:19 PM
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BJohnson BJohnson is offline
 
Join Date: Jun 2005
Location: Federal Way, Wa
Posts: 280
Default What do you mean by “cure 30”?

Are you using an elevated temperature cure? Fiberglass skins over core are notoriously porous, not just on the surface, but though the thickness too. It looks like you used a heated cure and air is being forced out of the core cells, bubbling up the epoxy and micro.
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