Aligning Tail Pieces

On a recent trip to Harbor freight I picked up another pair of adjustable height support stands to help figure out why the tail doesn’t seem to be lining up right.

I used these stands in an effort to more reliably position the tail pieces for measurement.

I leveled the fuselage left-right with a water level at the wing attach points. From there I levelled each stab half with a bubble level.
Left-Right Level

I used a bubble level to level the stab halves, carefully positioning it between rib stitches.

I also raised the tail to level the stab halves front-back and then rechecked the other measurements. I spent lots of time scratching my head, but here’s a summary on what I have so far. The stab halves seem to be built with a little bit of error in the vertical positioning of the parts. I wonder if the left and right halves were built in the same jig, such that a slight error due to gravity would be down on one half and up on the other half, thus providing the 1/8″ or so error that I see between the left and right halves. My solution is to adjust the hinge supports a little so that the elevator halves will be parallel, and just accept the error in the trim system.

Straght Trailing Edge

From this angle you can see that the trailing edges of the two stab halves are parallel.

The trim horns don’t quite line up right, so there will be a little bit of binding and friction. Since the trim system needs a little friction anyway, this will work out well. Also, the trim horn only moves slightly, so I don’t know if the binding will even be noticeable in the range of motion that it will see in service.
Trim Horn Alignment

Note the trim hole alignment as I rotate the horn.

Trim Horn Alignment

Notice that with the horns turned 90 degrees, the misalignment is still only vertical.

Trim Horn Alignment

Finally, here is a shot with 180 degrees of rotation. These pictures convince me that the trim shafts are straight but not coaxial.

In the end there might be a slight difference in height between the left and right stab halves (1/8″ or so) but both will be level with reference to the wing attach points, so I’m not really concerned.
Right Tube Verification

I verified that the removable pieces were installed correctly on the right...

Left Side Verification

... and on the left.

I spent some time getting the aluminum part of the flap handle finished. I drilled holes where the notches would go, and plan to take the piece home to cut out on my wood cutting bandsaw. I started making up the fuel lines that connect the tanks to the inboard rib. Tonight at the EAA meeting Wade brought his punch and cut out the lightening holes in the battery box.
Wade Punches

The picture is a little bit blurry, but here Wade is punching the holes at the EAA meeting.

The conduit punch had no trouble with the thin steel.

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Hours Logged This Session: 2.1
Total Hours: 1883.75

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