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  #1  
Old 03-21-2021, 12:14 AM
jrock836's Avatar
jrock836 jrock836 is offline
 
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Location: Burleson, Texas
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Default Upper Cowling Damage

My upper cowling has cracks and paint damage, mostly around the Phillips head screws. While I work on my Annual next month, I’m thinking about sending my upper cowling to the paint shop for repair and repaint. Has anyone found a better washer/screw combo to use that will protect the paint and distribute the load better than the little plastic washers under the phillips screw head? Is there maybe some type of washer that has a collar that would fit into a counter sunk hole? There has to be something better than the existing setup. Although the existing screws do a good job of holding the cowling in place, it doesn’t really seem to be a well thought out solution.
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Last edited by jrock836 : 03-21-2021 at 12:20 AM.
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  #2  
Old 03-21-2021, 06:28 AM
Kyle Boatright Kyle Boatright is online now
 
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Look for Tinnerman washers. They are designed for countersunk applications and distribute the load over a much larger area than just the screw head. Here's what Spruce offers (note they come in different sizes):

https://www.aircraftspruce.com/catal...49washers2.php
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  #3  
Old 03-23-2021, 05:21 PM
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jrock836 jrock836 is offline
 
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Quote:
Originally Posted by Kyle Boatright View Post
Look for Tinnerman washers. They are designed for countersunk applications and distribute the load over a much larger area than just the screw head. Here's what Spruce offers (note they come in different sizes):

https://www.aircraftspruce.com/catal...49washers2.php
Thanks.. Those might work and will most likely hide much of the flaking paint around the screw heads, if I decide to wait on painting..

Has anyone else done anything differently on an already completed RV12 cowling?
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  #4  
Old 03-23-2021, 05:57 PM
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Piper J3 Piper J3 is offline
 
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I use countersunk washers everywhere...
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 735

LSRM-A Certificate 2016 for RV-12 N633CM
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  #5  
Old 03-23-2021, 07:25 PM
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Quote:
Originally Posted by Piper J3 View Post
I use countersunk washers everywhere...
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Hi Jim.. Did you use them on the front of your fiberglass cowling near the intakes?
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  #6  
Old 03-24-2021, 12:25 PM
Bob Y Bob Y is online now
 
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Quote:
Originally Posted by jrock836 View Post
Hi Jim.. Did you use them on the front of your fiberglass cowling near the intakes?
I just performed an oil change so had to reinstall the cowl. Like others, I use conical washers on every flat-head screw on the exterior, including the landing light lenses. Just for the fun of it, I took one and turned it upside down on the forward cowl screws to which youíre referring. They actually didnít look too bad. Something you might want to evaluate for yourself.
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  #7  
Old 03-23-2021, 11:54 PM
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Piper J3 Piper J3 is offline
 
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That is one location where I have not used the C'sink washers. My upper cowl is scheduled for cosmetic upgrade.
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 735

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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  #8  
Old 03-25-2021, 04:36 AM
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DanH DanH is offline
 
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Quote:
Originally Posted by jrock836 View Post
My upper cowling has cracks and paint damage, mostly around the Phillips head screws....Has anyone found a better washer/screw combo to use that will protect the paint and distribute the load better than the little plastic washers under the phillips screw head?
Curiouser and curiouser.

I think the question here is why you're getting cracks and paint damage under nylon washers and AN526 screws. It's not the washer and screw choice, which are structurally superior to tinnermans. It more likely goes back to prep and paint choices.

Look at the back side of the panel. Do the cracks extend through the fiberglass? Now look close at the painted side. Are the cracks in the paint only?
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