Top wing tank cover fit - Strategies for covering later

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Darin Bishop

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Jun 1, 2015, 12:55:27 PM6/1/15
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Hi guys,
 
I suspect if I had any covering experience (other than cotton in A&P school and watching polyfiber videos) I might be able to answer this question myself. As I start to get down the home stretch on my top wing, I am curious about fitting the top wing fuel tank cover, and how it will interact later when I cover the wing.
 
Right now I have the tank cover fitting pretty well all around, and flush with the surrounding ribs, leading edge and aft skin.
 
           
 
And..when covering the top wing I know that some sort of mechanical fasteners, screws most likely, are used to attach the bottom fabric at the first compression rib at the fuel tank bay, since it can't be rib stitched.
 
 
           
 
 
 
 
On the top side of the wing I think I remember Kevin mentioning that they somehow tuck the first layer of fabric in under the tank cover and thus are able to omit the mechanical fasteners used on the bottom side since the screwed in tank cover holds the fabric down.
 
I would like to do this also, and I'm wondering what allowances I need to make to the fit of the fuel tank cover to accomodate this:
1) I assume I should create a little edge gap all around the cover to allow for the fabric to flow into the tank bay, but how much? I'm guessing 1/8".
 
2) What and how many layers of fabric will the tank cover get? Does the first heavy layer of fabric (if any) get wrapped around the edges or cut off flush with the edge?
 
3) Thinking vertically now and how layers of fabric add up on the wing and tank cover, if the fabric is fit inside the tank bay all around, and if the tank cover gets same as the rest of the airplane, one layer heavy cloth with one layer light cloth on top, do I need to remove wood in the tank cover screw line perimeter, essentially lowering the tank cover in the bay to allow for layers of fabric to build it back up to the level of the fabric with the surrounding wing?
 
4) Or do I just get er' done and nobody notices the difference in levels up there?
 
I know I could do #4 but, it would be nice to build a plane that looks somewhat as nice as the ones the Kimballs do!
 
Thanks,
 
Darin
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Kevin Kimball

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Jun 1, 2015, 1:26:36 PM6/1/15
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Darin,

See my responses below.


Sincerely,

Kevin Kimball, President
Jim Kimball Enterprises, Inc.
PO Box 849
5354 Cemetery Road
Zellwood, FL 32798-0849






On Jun 1, 2015, at 12:56 PM, Darin Bishop <db2...@2wings.com> wrote:

Hi guys,
 
I suspect if I had any covering experience (other than cotton in A&P school and watching polyfiber videos) I might be able to answer this question myself. As I start to get down the home stretch on my top wing, I am curious about fitting the top wing fuel tank cover, and how it will interact later when I cover the wing. 
 
Right now I have the tank cover fitting pretty well all around, and flush with the surrounding ribs, leading edge and aft skin.
 
            <Clipboard-3.jpg>
 
And..when covering the top wing I know that some sort of mechanical fasteners, screws most likely, are used to attach the bottom fabric at the first compression rib at the fuel tank bay, since it can't be rib stitched. 
 
 
            <Clipboard-2.jpg>
 
 
 
 
On the top side of the wing I think I remember Kevin mentioning that they somehow tuck the first layer of fabric in under the tank cover and thus are able to omit the mechanical fasteners used on the bottom side since the screwed in tank cover holds the fabric down.
Yes, heavy duty fabric is installed with the tank cover off and tank out.  Carefully heat form the fabric to make the vertical down 1/8” step, then across the cooer mount rail and then down the inner side of the rail.  Same for the front and rear spars.  Bleu down about 1/2-1” of fabric on the spars, the height of the rails on the rails.

 
I would like to do this also, and I'm wondering what allowances I need to make to the fit of the fuel tank cover to accomodate this:
1) I assume I should create a little edge gap all around the cover to allow for the fabric to flow into the tank bay, but how much? I’m guessing 1/8".
Yes a gap but .050” is all the gap you need.  Just enough for varnish on the over and wing plus 1 layer of HD fabric.

 
2) What and how many layers of fabric will the tank cover get?
1 layer of light only on the cover that is the same pice of light that runs from tip to tip.

Does the first heavy layer of fabric (if any) get wrapped around the edges or cut off flush with the edge?
No heavy farce on cover, no fabric wrap on cover.

Cover wing with cover and tank off as noted above.  Shrink, stitch, per manual steps.  Install wing tank, install cover.  Cover with light fabric tip to tip.

 
3) Thinking vertically now and how layers of fabric add up on the wing and tank cover, if the fabric is fit inside the tank bay all around, and if the tank cover gets same as the rest of the airplane, one layer heavy cloth with one layer light cloth on top, do I need to remove wood in the tank cover screw line perimeter, essentially lowering the tank cover in the bay to allow for layers of fabric to build it back up to the level of the fabric with the surrounding wing?
No.  Wing surface has 1 layer of HD and 1 layer of light.  Tank rails have 1 layer of HD.  Tank cover 1 layer of light.  So, all works out same elevation.  

 
4) Or do I just get er’ done and nobody notices the difference in levels up there?
It works out on its own.

 
I know I could do #4 but, it would be nice to build a plane that looks somewhat as nice as the ones the Kimballs do!

 
Thanks,
 
Darin

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Darin Bishop

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Jun 1, 2015, 11:17:03 PM6/1/15
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Thanks Kevin!

That makes it easy, since I have the cover fitting already, it's just a matter of making sure I have that .050" all around it.

Phil Raine

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Feb 2, 2016, 8:33:26 AM2/2/16
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Hi Darin/Kevin,

I suppose your questions and Kevins replies refer to the Kimball double cover method. How would the standard double cover differ from this (Two layers of HD fabric in prop wash)?

Phil Raine

Kevin Kimball

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Feb 2, 2016, 9:51:00 AM2/2/16
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Phil,

Do the same way. Make first layer fold in and form to wing. Second layer after tank is in and cover on. 
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Phil Raine

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Feb 2, 2016, 6:43:48 PM2/2/16
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Cheers Kevin,

Funny how things seem obvious, once you know the answer !
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