Wednesday, April 24, 2013

Fin Forward Brace Wire Fitting

 The brace wires on the stabilizer cross.  The wires at the front of the fin and fuselage go to the rear spar on the stabilizer.  The wires at the rear of the fin and fuselage go to the front spar on the stabilizer.  The fittings for the wires on the lower fuselage longeron are welded to the longeron. The fittings for the stabilizer and rear of the fin are bent tabs bolted to the structure.  We'll get to them in another posting. The fitting at the top front of the fin sets on the top tube and is held in place by the clevis pin welded into the front spar.  The brace wire angles back 15 degrees and down 23 degrees.  I used the string to double check my math for the angles.

 The fitting is made from .095" steel.  It can't just be bent in place because bending it would damage the tubes.  Instead I bent it around a 3/8" pipe nipple.  I used the nipple because I'm going to use a piece of it for a spacer under the fitting.  The spacer is needed because of the weld bead where the pin stick through the top tube.

The fitting was bent cold with a hammer until it matched the paper gauge I made to check the angles.

 The ends of the nipple were cut of and the cuts cleaned up on the belt sander.  The tube was split by slipping it over a piece of dowel to make it easier to hold.  Again the cut surfaces were cleaned up on the belt sander.
A 5/16" hole was drilled to fit the pin and the underside was ground out to provide clearance for the weld.

 The spacer fits nicely over the tube providing a nice mount for the without grinding out the fitting to fit over the weld.

The pin was left long so it could be cut to fit all of this.  A new cotter pin hole was drilled and the end of the pin cut off to a nice length.

I need to make up all the brace wires.

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