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  #1  
Old 09-02-2018, 09:54 AM
sblack sblack is offline
 
Join Date: Dec 2009
Location: Montreal
Posts: 1,456
Default Tricks for perfect cowl to fuse gap

I am fitting the cowl on my -4. I know I need a non zero gap between the fibreglass and the aluminum. I am using skybolt fasteners on the top and sides and piano hinges where the bottom attaches to the firewall. I suspect on the bare glass I need 1/32" or so to provide room for primer and paint. I was going to find some sheet styrene or similar to put in that gap and the spread some flox up to the edge. Are there any other tricks out there that people use to get the fit just right? It is one of those real noticeable things that sets a nice
Y built airplane apart so I would like to get it right.
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Old school simple VFR RV 4, O-320, wood prop, MGL iEfis Lite
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  #2  
Old 09-02-2018, 10:13 AM
Mike S's Avatar
Mike S Mike S is offline
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
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Default

Zero gap??

No room for paint?
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Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

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  #3  
Old 09-02-2018, 10:16 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,296
Default

I used hinges on the cowl to firewall interface (on the sides). It's been a while, but I recall just block sanding the cowl and marking with sharpies until I had the abutment fit that I wanted. Then held the cowl tight and strethed out the hinge as I drilled the holes. I then block sanded a bit more after it was fully fitted to the the gap I wanted.

I am surprised you are using hinges on the bottom. It was my understanding that this gap gets the greatest loads and most with hinges down there get damage to the eyelets.

Larry
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  #4  
Old 09-02-2018, 11:36 AM
sf3543 sf3543 is offline
 
Join Date: Jan 2005
Location: San Antonio, TX
Posts: 1,024
Default

I fit the cowl to the plane and then just create a thin gap between the skin and cowl as good as i can.
Then I take an old credit card or something and stick on sand paper on one side
Use the sandpaper side against the cowl and you can create a perfect gap. Use something thicker if you want a wider gap.
You can also sand on the aluminum if it isn?t perfectly straight and needs to be trued up. Just wrap the sand paper on both sides.
I also use this method wherever I need a nice gap, such as the wheel pant halves, but I usually used a piece of hacksaw blade to get the gap started and then wrap sandpaper around the blade to final sand.
The gap is just right to accept the paint.
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  #5  
Old 09-02-2018, 01:26 PM
xblueh2o xblueh2o is offline
 
Join Date: Apr 2011
Location: SF East Bay
Posts: 852
Default

This is what you are looking for. Spruce has them.
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RV-8 with the Showplanes Fastback conversion
Emp completed except for glass work
Wings completed except for bottom skin and glass work
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  #6  
Old 09-02-2018, 02:28 PM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,189
Default Gap

Realize that there will be paint on both sides of that gap. Also realize that there WILL be vibration and relative movement between the cowl and fuselage. Too small a gap will guarantee paint removal...
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Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
297 HP Barrett Hung
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  #7  
Old 09-04-2018, 09:36 AM
sblack sblack is offline
 
Join Date: Dec 2009
Location: Montreal
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Default

Quote:
Originally Posted by Mike S View Post
Zero gap??

No room for paint?
I wrote "non zero gap"
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Scott Black
Old school simple VFR RV 4, O-320, wood prop, MGL iEfis Lite
VAF dues 2020
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  #8  
Old 09-04-2018, 09:37 AM
sblack sblack is offline
 
Join Date: Dec 2009
Location: Montreal
Posts: 1,456
Default

Quote:
Originally Posted by sf3543 View Post
I fit the cowl to the plane and then just create a thin gap between the skin and cowl as good as i can.
Then I take an old credit card or something and stick on sand paper on one side
Use the sandpaper side against the cowl and you can create a perfect gap. Use something thicker if you want a wider gap.
You can also sand on the aluminum if it isn?t perfectly straight and needs to be trued up. Just wrap the sand paper on both sides.
I also use this method wherever I need a nice gap, such as the wheel pant halves, but I usually used a piece of hacksaw blade to get the gap started and then wrap sandpaper around the blade to final sand.
The gap is just right to accept the paint.
Thanks Steve
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Old school simple VFR RV 4, O-320, wood prop, MGL iEfis Lite
VAF dues 2020
Instagram @sblack2154
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