Flaps Rigging (5)

5 hours

It's time to finally get the control surfaces set up!  I started with the flaps.

The flaps attach to the flap drive tube with a short pushrod on each flap.  The first challenge I ran into was that as soon as I tried to connect the pushrods it was obvious that they were too long.  I think the plans specified a 3" piece of threaded rod, plus the rod end bearings on each end.  After a bunch of trial and error I figured out a good length was actually more like 1-7/8".  Anyway that took a while but once I got that figured out I was able to connect the pushrods and start working on adjusting them.

The process of adjusting the pushrods was pretty much just setting the flaps in the neutral position with the actuator all the way up.  That's pretty much it I guess, and then the downward travel is just whatever you get from the actuator's travel.  Anyhow, while setting the top of the travel I found that the flaps would just barely contact the back of the wing right at the top of their range, which would then cause the fuse to pop before the actuator stopped.  I upped the flaps fuse from 5 amps to 7.5 amps, and then I ended up just setting them as far up as I could without popping it.  With some measuring I found that position to be about 0.3 degrees down from where the plans specified.  I think that's probably close enough and as good as I can get it, plus with the flaps up I can easily lift them a little farther just with the slop in the actuator, so if that isn't aerodynamically neutral the air will probably just push them there anyway.

I also realized that with the pushrods installed you can't access it at all to adjust the length!  The only way to really get at it, and especially to tighten the jam nut, was to let the flap hang straight down and then pivot the pushrod parallel to the flap so it also dangled below the fuselage.  In order to get the pushrod into that position, I had to file a little notch in the bottom of the flap skin to let the pushrod go by.

Then it was reasonably possible to tighten the jam nuts.

Finally, after a many iterations of adjustments, tests, and popped fuses, I got the flaps to match each other, go pretty much all the way up, and they appear to travel about 27 degrees down from neutral.  I've read on the forums that around 27 degrees is pretty common so I think it'll work.