Wed Sep 02 2020

Elevator trim tab cable restraints and setting trim tab travel

Did a bit more trimming, notched the support plate, and drilled the spout to the support plate. Also added a couple holes for a zip tie to tie the cable down.

Because of the small amount of clearance between the support plate and the fuel lines, I'm putting the flush head of these rivets down.

At the aft end, I fabricated this little bracket in order to help prevent chafing of the cable against the edge of the lightening holes in the aft deck (shown here), and in the root rib of the horizontal stabilizer (through which it passes).

The manual specified that the cable needs to be adjusted so that the trim tab has 25 degrees up movement, and 35 degrees down movement. Here's the neutral position.

Initially getting something like 36 or 37 degrees up movement.

When adjusting the trim tab down, I felt some binding at about 25 degrees of down movement.

Turns out that the leading edge of the bottom surface of the of the trim tab was rubbing the aft edge of the bottom skin of the elevator.

Kind of hard to see here, but the rubbing is just near the inboard end of the trim tab.

The whole edge needed adjusted (just bent it by hand over the trim tab spar), but the inboard end needed adjusted quite a lot.

After correcting the trim tab skin, I still wasn't getting enough down travel. I needed to adjust both the position of the cable as it screws into the weldment on the mounting plate as well as the clevis end. Pics further down.

Better. This is about 36 degrees of down travel.

Still have around 29 degrees of up travel.

Here is the position of the anchor nut weldment relative to the threaded portion of the cable.

The clevis end isn't shown in this pic, but the edge of the tape marks how far it threads on. This is a little over 2/3 of the threaded length.

After removing the trim tab, elevator, and horizontal stabilizer, and putting the shop back in order, I got to work on another restraint bracket where the trim cable passes over the aft edge of the fuel pump mounting plate. The larger holes are for a zip tie to hold the cable in place.

Here's how it'll work. I think I have enough parts ready for priming. I'll probably do that tomorrow.