Rebel - Elevator Reinforcement

[Rich Dodson]

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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