Sat Mar 13 2010

Miscellaneous tailcone work

Well after running errands with Kerin and reading the manual to figure out what to do next, I decided to move the plane over towards the middle of the garage in preparation for fitting the horizontal stabilizer. Once that was done, I embarked on finishing up a bunch of miscellaneous tasks (mostly in the tailcone area). First item was to add another ziptie to the static line to prevent it from chafing. The bend radius is somewhat smaller than the minimum recommended, but having lots of experience with pneumatic tubing I can say with confidence that the minimum bend radius is of the most importance in dynamic (flexing) applications. Since this is a static application, the most important thing to consider is making sure the tubing isn't kinked. Since it's not, we're good to go!

Since I was back there, I bolted on the attach brackets for the shoulder harness cables. I torqued them to 27 in-lb and marked 'em with torque seal. Why would I torque them to 27 in-lb when the correct range is 20 to 25 in-lb for an AN3 bolt? It's because the locknuts create about 5 in-lb of resistance by themselves and that's not supposed to be counted in the torqueing. So if you subtract 5 from 27, you get 22 in-lb which is right in the middle of the range. Clear as mud?

I realized I had forgotten to open the two pilot holes up to 5/8 inch in the F-710 bulkhead per Note 1 on the plans, so I broke out the unibit and drilled them to size.

Since I had been installing some bolts, I decided to install the bolts that attach the lower firewall weldments to the lower longerons. The plans call for an AN3-5A bolt with a single washer, but if you look at this picture you can see that a single washer will not be enough to keep the nut from bottoming out on the grip (unthreaded) portion of the bolt. I decided to add a second washer under the head of the bolt.

Got 'em all torqued and marked with torque seal. Note that when torqueing the bolts, I had to turn the bolt with the torque wrench rather than the nut since there was no access for getting the torque wrench on the nut. It's not the preferred method, but acceptable.

While up near the front of the fuselage, I noticed this rivet which had never been installed. It's going to require a custom bucking bar to buck this fella.

I've got a chunk of steel to make it out of. Essentially I need to cut the end of this bar at an angle as well as remove a triangular chunk from the side. If I was still working at ATS I'd do this on their power bandsaw. Oh well. My buddy Jim offered to help me out on occasions like this, so I think I'll take him up on it.

I started looking into how to use an adel clamp to attach the rudder cable guide tubes to the aft fuselage side skins and decided that I needed a countersunk washer so that the adel clamps don't just getting cranked down against the pointy side of the skin dimples. Here's a piece of scrap .063 thick material which has been drilled and countersunk for a #8 screw.

Once I cut out the areas with the holes, I clamped everything together on a #8 screw and chucked the shebang up in my cordless drill. It was just a quick matter of spinning the assembly in the drill and holding it up to the spinning disc of my disc sander. A little touchup on the scotchbrite wheel and...

...presto! Two spacer washers!

Here's how the spacer washer will get sandwiched between the skin and the adel clamp.

With the washers fabricated, it was time to break out the rudder cables. I thought this was going to be super quick to just run the cables up through the snap bushings, but the fittings which are swaged on to the cables are just barely too big to fit through the snap bushings. So I ended up removing each snap bushing one by one, route the cable through the bulkhead, squeeze the bushing enough that it would slip over the swaged fitting, then reinstall the bushing. Not difficult, but more time consuming than it needed to be.

Err...I see I forgot to open these holes up to 5/8 inch for snap bushings as well. I'll do that tomorrow. It's getting late now.