WING SPAR FLANGE

[Snader, Douglas E.]

While working on my wings I noticed that the flanges on the main wing
spar were over bent , in some places by an 1/8 inch. Does anybody else have
this problem and what can be done or should be done about it? Some concerns
I have are , will this crystaize the spar because of too severe of bend ,
will the wings be straight , will there be undue stress when the wing skins
are pulled down to the spar between the main ribs and the leading edge ribs
, will all this be cosmetic or will there be strucural problems? I need help
or reassurance.


DOUG SNADER {Elite 582}

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[Wayne G. O'Shea]

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Hi Doug,

I have built 11 wings now! 9 Rebel wings and 2 Super Rebel wings. All use
the same main spar for a "base", being .063 x 6061T6 Aluminum and I would
presume that the Elite is no different ( exception is the AULA model Rebel
that uses .050" main spars).

All spars I have received have been slightly "over bent" past 90 degrees.
This allows for the wing to blend nicely from the main skins to the leading
edge skins without a flat spot. If you only bent to 90* or happen to come up
short and left the sharp edge proud, this would be like a knife blade
pushing on the wing skin and could cause structural problems. Over bending
slightly makes sure that the skin sits tight to the radius'd edge of the
spar instead. 1/8" seems a little more than normal, usually about a 1/16th,
but I have had a couple close to this amount.

To reassure yourself, take a real good look along all the radius's and look
for cracks. I don't think you will find any, but if you find anything
questionable, contact the factory and demand express replacement! Note that
6061T6 can be bent at a much tighter radius than 2024T3. I don't mean to
slight any AME's (structural or otherwise) but this is where a lot of the
misconception and fear comes with regards to bend radius's in our kit
planes. AME's that have only worked with 2024 all their lives see the tight
radius's on our parts and knowledge from "cracks gone by" tell them that
these parts will break due to the tight radius. It is not so!! If you bent
.063 x 2024T3 along the grain like the supplied wing spar, it would snap
clean along the grain, but the 6061 will be fine.

If you want some reassurance as to the strength designed into the rebel
wings, see if there is a rebuild shop close to you that does Cessna wings
and go see how light everything is inside them! Once you have a look inside
a Cessna wing, you will no longer doubt the strength of your 3 spar,12
stringer, 13 and 1/2 rib Elite wings!

Happy building,
Wayne G. O'Shea
www.irishfield.on.ca

-----Original Message-----
From: Snader, Douglas E. <snaderde@tvfr.com>
To: Rebel Builders List (E-mail) <murphy-rebel@dcsol.com>
Date: Thursday, March 09, 2000 6:08 PM
Subject: WING SPAR FLANGE

While working on my wings I noticed that the flanges on the main

wing

spar were over bent , in some places by an 1/8 inch. Does anybody else have
this problem and what can be done or should be done about it? Some concerns
I have are , will this crystaize the spar because of too severe of bend ,
will the wings be straight , will there be undue stress when the wing skins
are pulled down to the spar between the main ribs and the leading edge ribs
, will all this be cosmetic or will there be strucural problems? I need

help

or reassurance.


DOUG SNADER {Elite 582}

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*

*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*




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