Rudder hanging

Time to get back at it. Tonight I decided to see about getting the rudder hung, preparatory to setting up the proper travel.

First oder of business, dating back to when I fitted the rudder stop a while ago, was relieving the center of the stop to allow for the rod-end hinge point to move freely, since I’m mounting the stop in between the hinge brackets. To get started, I removed the lower rod end from the rudder (and wrapped tape around the shaft to make sure the stop nut didn’t move and I could put it right back in the position I removed it).

At first I was thinking of making a cardboard template, tracing the rod end’s outline, and then using that against the stop, but then I realized there was a much simpler solution. I used a couple long bolts to put the stop in place on top of the upper bracket, and another long bolt to align the rod end with its pivot point. Then I just used a Sharpie to trace the outline of the rod end:

Then I just went to town on the stop with a sanding drum on the dremel. I was surprised how little material I had to remove. I saw someone else’s build log who’d done the same thing, and they’d marked off a pretty large area to remove. It only took a couple trial-and-error iterations to get the clearance I needed. Kind of hard to tell, but in this photo the rod end is sitting inside the stop’s pocket where it was above in the previous one:

Then I installed the stop in place between the brackets, including the necessary spacer washers (because the stop is thinner than the gap between the brackets). Then it was time to get the rudder hung!

This ended up being a bit more of an operation than I expected. Way back when I first did the empennage, I adjusted the rod ends for proper alignment when mounted to the vertical stab, so I expected to have the rudder just fit nicely, but…wrong. When I installed it the first time, I lined up the upper hinge, then the center one, and…the lower one was nowhere near being aligned with the brackets. Best I can figure is that as built, the stab spar had a bit of a bend in it, which was remedied when I fitted it to the fuse and ensured alignment.

Since I used a taut string to align the brackets, I figured I’d use the same approach to getting the rod ends aligned. But there was also the question…which of the three rod ends should I adjust? Upon inspection, the center one was clearly far further out than the others, so I decided to move it in. I also used the measurement from the spar to the rod end centers as a baseline for alignment.

This ended up requiring a couple of iterations as well to get right. The first attempt after checking with the string, the center rod end was actually too far in, so I got to remove the rudder again, thread it out a bit, and try again. Fortunately, that time everything lined up, and I got the bolts dropped in. So now I’ve got a rudder in place:

Next up will be setting the travel. At the moment, the stops clearly need a fair bit of material removed, there’s way too little travel. Before I can set this properly, though, I’ll have to work out a method for measuring the rudder angle. This was easy to do with the elevators, since a digital level could show angular displacement, but that won’t work for this. I suspect I’ll end up making a sort of manual protractor drawn on the floor, using a plumb bob on the rudder to track the travel. That’s for another night, though…

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