Various small tasks3h
July 11, 2022
Today I did a few small tasks.
First, I got my new torque wrench. The torque specification for the AN3 bolt is 20-25 lbfin, plus correction for the nylon nut. I estimated the friction drag of the nylon nut to be about 4 lbfin (my torque screwdriver would start to click around that setting). Therefore, I aimed for about 27 lbf*in, somewhere in the middle of the range.
The bolts torqued! I get some weird satisfaction applying the torque seal on the fastener. I guess, it generates a sense of "achievement", which generates some dopamine in the brain.
The next thing was to rivet the nut plates and the root rib to the left elevator spar.
When I was riveting the root rib, I accidentally picked shorter rivets (AN426AD3-3 instead ofAN426AD3-3.5). I only realized that after I already set two rivets. The shop heads were on the small side of the spectrum, but they were acceptable as per the MIL Spec. After debating with myself for a couple of minutes, I decided to drill them out and replace them with properly sized ones.
Not that I had concerns about the strength of the joint (the elevator horn and its twelve AD4 rivets reinforce that joint really well), but more for the aesthetics. Even though these shop heads will be completely hidden.
This time, the horn fit much better than the last time. I still had to run reamer through a couple of holes, but they were off by mostly a few thousand.
Finally, I started working on the elevator trim tab.
The first step was to bend the trailing edge. Then I tried attaching it to the trim tab spar and found that the skin was not symmetrical between the top and the bottom. One side was flat and one side had a depression. After 45 minutes of fighting it and getting all kinds of intermediate results, I managed to massage the trim tab such that both sides are relatively flat. I will revisit it once I finish bending the side tabs.
After bending the trailing edge, I put the tab into my bending setup and started bending the bottom outboard side tab. I am getting a smaller mushroom rivet set tomorrow, which I will use to finish the bend.