Saturday, June 16, 2012

Stabilizer Brace Wire Bushings

 The brace wires for the stabilizer attach to fittings which are bolted to the stabilizer with 1/4" bolts.  The bolts go through bushings, short pieces of 3/8" tubing, which are welded to the front and rear spars next to the last full rib at the tip.  I needed some way to hold these in position while I welded them.  It probably isn't critical but I wanted them nicely square to the spars and lined up with each other.  I found a piece of steel channel I salvaged from an old fold up table a few years ago.  You know, one of those things you save because some day you'll have a use for it.  Glory be, I have a use for it!  How cool is that?
I cut 2 lengths long enough to hold the bushings next to the front of each spar.  Next I punched 1/4" holes in one piece and duplicate punched them in the second piece.  That way the bushings would be parallel.
 By grinding nice square ends on the bushings with the belt sander it all clamps together tight and square.  I used Stainless Steel bolts and nuts to hold the bushings tight to the channels.  Stainless doesn't get welded into the bushing so easy if I get it a little to hot.  The little piece of welding rod was used as a spring to center the bottom end.  The whole assembly just hangs from the top bushing.  I tacked each bushing to the spar and the ribs before removing the jig.
Originally it appears the bushings were either a couple inches inboard or not welded to the rib.  The rib on the stabilizer, but not the elevator, was moved outboard about 2 inches.  I think the bushing was originally just welded to the spar and the spar probably cracked so they moved the rib out to help support the bushing better.

I still have two tabs to add for mounting the Fin front spar but I don't want to weld them until I fit everything to the fuselage, so I'm sure the holes all line up.

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