Fuselage Q & A
When the tail brace wires are brought up to app. 250# of tension the elevator starts to bind up. How are builders tensioning the tail brace wires and to what tension? I have the 3/16" wires and have used a Pitts factory tensiometer. Hale Wallace with Steen Areo recommends 300# for the 3/16" wires (this falls into the spec called for by the Pitts factory for this size wire). I found that the upper wires were always 100# above the lower wires. I expect this is due to the legth of the wire and geometry. With the upper wires at 300# and the lower at 200#, the wires felt, and sounded good. However, the elevator movement is pretty stiff. I reduced the tension to 200# on the top wires and 100# on the lower wires and the elevator traved "freed" up. I would appreciate any comments builders might have.
From: Fritz Gunther
flyacro@juno.com
Here is some information that may help the elevator binding problem on some of the
1D's. I have spent the last 2 weeks trying to understand what is happening
with the tail. I completely disassembled the tail feathers and checked the
following: Trim tabs were free with no binding. I then checked the elevator
strap hinges for freedom of movement, I found that the LH outer hinge was rough, I soaked
and worked the hinge with Free-All until smooth. The elevator was then attached to
the stab on the bench and checked for freedom of movement, no problems noted. I removed
the standard KP-4 pivot bearings and installed KPS-4 bearings, these are a self aligning
bearing that will accommodate up to 10' of misalignment (if the wires are in fact pulling
the stab and elevator rearward). They have the same radial load capacity with a
lower axial capacity. The stab. and elevators were installed with the push-pull tube
and spacer block removed from between the horn. The brace wires were slowly and evenly
brought up to tension (aft wires first) with the stab checked for level. The
aft wires are at 250# and the front wires at 200# (Pitts gauge) with no binding of
the elevators. The spacer block was then installed and the elevators started to
bind. The spacer was to wide and pushing the elevators outboard hard against the
hinge collars. The block was removed, the elevators centered in the hinge collars
and the spacer milled to fit the spacing between the elevator horn. The control tube
was then connected and the elevators are free, and smooth. When the stick is let go,
it moves to the full forward position on it's own. I feel the self aligning bearings and
checking the whole system for rubs/binding and eliminating them solved the
"sticky" elevator.
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