Drilling the trim tab4h
July 12, 2022
Continued working on the left elevator trim tab.
First, I finished the bend on the outboard side. It came out pretty well, no complaints!
The bends on the trailing corner came out exactly where I wanted them. They look a bit too sharp, but I don't see any cracking. I am going to smooth the bends a bit to release any residual stress and reduce the probability of it cracking later.
The inboard side looked good at first.
However, the edge distance for the rivets was too small.
I re-clamped the part into the fixture and massaged it with the rivet gun a bit more. Hammering it moves the wooden block into the part, moving the bend line this way. The edge distance improved, it looks good now. I am going to replace CS4-4 rivets (as per the plans) with the MK-319-BS rivets, as they require a bit smaller hole size (7/64" vs 1/8"). They are also a bit stronger.
While researching the blind rivets used in the kit, I collected the summary of rivet specs.
Finally, I drilled and dimpled all the holes. One area where I got very short edge distances was the hinge. I followed the plans and in the end, the shortest distance I got was 0.160", which is less than 2D (0.188"), but still more than the minimum allowed by the MIL Spec (0.156"). Given how many rivets are holding the hinge, it should not be an issue either way.
Now I am waiting for the remaining parts for the left elevator to finish assembly.