Adding Rudder Trim

2-12-18 and 2-13-18 – 4.5 hours spent

So here is the trim tab I decided to add to my rudder.  Note the holes in the corners of the cutout.  I cut the skins with a Harbor Freight “High Speed Panel Saw.” It worked fairly well after I re-tightened all the loose set screws that it came with.

Here is the trim tab spar.  It extends about 1.5 inches past the trim tab on each side.  This was a complicated fold, as the rudder tapers, so the spar lines are not parallel.  I was pretty happy with how the spar folded and went together – nailed it on the first try!

I drilled the stiffeners off the inside of the trim tab, but cutting away the stiffeners on the inside of the rudder was tricky.  I borrowed a dremel with cut-off wheel, and sliced through the bent portion of each stiffener.  I also ground halfway through the flat portion.  After folding the bent portion relatively flat, the stiffeners could be bent the other way.  A couple of back and forth bends, and they snapped neatly off.

Here are the cut stiffeners.  No damage to the inside of the skins.

Here is the hinge going onto the spar and into the opening.

Spar, hinge, cut/broken off stiffeners, and the c-clamps to get them into position to drill.

So I was so proud of myself when folding the rudder trim tab spar.  Folding the spar for the other side did NOT go well.  The Z-fold didn’t work on my brake, and I ended up trying 5 times before I finally got it right.  Here are 4 failures.  The final one that did work is not in this pile.

The trim tab going together.  You can really see the Z bend in the spar.  I’ll fill the rivet holes before prep and paint.

Trying to dimple inside the tiny spar openings was hard.  I eventually had to build my own very low profile female dimple die.  I chucked a unused rivet set in my drill, and profiled it on the grinder while spinning.  Next, I drilled the hole with a #40 drill bit.  Finally, I finished the countersunk portion with a standard #40 100 degree countersink.

Zinc Chomate on all the new parts.

Next up – forming a control horn and riveting the hole thing back together.

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