of the outboard ribs so that you now have two rivets into the spar to stop
the rib from rotating as it does using the manuals single rivet.....which
leads to the cracking of the rib flange and then skins.
Wayne
----- Original Message -----
From: "Rich Dodson" <r_dodson@yahoo.com>
To: "Rebel Listserve" <rebel-builders@dcsol.com>
Sent: Wednesday, August 30, 2006 4:32 PM
Subject: [rebel-builders] Rebel - Elevator Reinforcement
Gents,
Thanks for the tips on the rudder trim. I have decided to wait and see
how she (eventually) flys before pursuing it further.
On to the instructions for the elevator. I noticed in the archives some
discussion and a couple of photos of a reinforcement modification. Please
read the below to see if I have this correct...
The outboard edges of the elevator are subject to a stress concentration
due to the counterweighted elevator tip cap meeting the elevator skin at
the location where the skin is joined to the spar and the tip cap. I take
it that in the past this stress has eventually resulted in the skin
tearing.
There are two recommended modifications to the assembly of the elevators
at the outboard ends.
The first is to take some 0.025 aluminum and make a doubler for (I am
guessing from the picture) about the first third of the outboard end rib,
where it meets the spar. That doubler is placed inside the end rib and
riveted to it on the ribs' spans prior to the (now doubled) flanges being
riveted to the skin and the spar.
The second involves making four (two per elevator, one for the top and one
for the bottom of each) 1/4 circle doubling plates of about 3" radius out
of 0.025 aluminum. These plates double the skin in the high stress area
where the skin is riveted to the end rib on the outboard end of the
elevator and where it is riveted to the spar. These plates are first
riveted flat to the skin on the inside (non-visible) faces and then they
are drilled out along the two straight edges (using the pilot holes on the
skin as a guide) so that the doubled skin correctly meets the end rib's
flange and also meets the spar for joining nice and tight. Of course, on
the end rib flanges this now means we have one heck of a metal sandwich
(from the top down): skin, skin doubler, end rib flange, end rib doubler
flange.
Please chime in if I have this wrong. I am trying to use this project to
understand things like stress (on the plane, I have enough already in me!)
and strain.
Thanks for your help!
Rich
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