First, Build a Shed

[Cherrybark]

Thanks for the offer of the grommets Eddie. PM on the way.

[Cherrybark]

Before reading the manual, rigging the wings seemed like a major undertaking. After a couple of readings the mystery began to clear. It went something like this.

"Hey, I never noticed the factory pre-drilled a hole in the trailing edge spar. I get it, pin that spar, position the wing, and drill a hole in the other spar to match the... Wait a second, how am I going to see through the front spar to match drill? Ah, that's why the reference measurements were made to the second mounting hole. But there is absolutely no way am I going to get the hole in the spar perfectly positioned. Oh, that's clever, drill a small hole, shape with a file, then ream to a perfect fit. These Kitfox guys are pretty smart cookies."

As when using clecos for the first time, mounting the wings will feel like I'm really building an airplane. A chance to step back from looking at individual trees and see the whole forest as it were.

[Cherrybark]

Are these tiny little nuts really the only thing that prevent the lift strut bolts from falling out, the wing ripping away and me falling to earth in the familiar "death spiral" the media warns us about? Or did I pull the wrong parts from the wing hardware inventory?

And, yes there should be washers, this is just temporary while rigging the wings.

[jiott]

Yes that little nut is really more than meets the eye. It is what is called a "prevailing torque" nut-it has a deformed all steel thread that actually grips much better than a nylock nut, and has more threads than a nylock. In this application it has no load on it other than vibration and its only purpose is to prevent the bolt from "falling" out. Yes you can go ahead and stake your life on it.

[Cherrybark]

Thanks Jim,

I checked the part number more than once. But I did expect a nylock here and it seemed prudent to ask for confirmation. The things one learn while building an airplane

[PapuaPilot]

Yes, the MS21042 series nuts are every bit as good as the nylock MS21044 nuts. They save weight too.

The main thing I wanted to pass on it that these nuts are typically used one time and replaced with new to assure the locking feature is working. There is a table in AC43.13-1B that gives value for the running/prevailing torque (i.e. the torque just to make it turn) that must be present for the reuse of locking hardware. The problem with the table is it starts with 7/16"-20 nuts, so it isn't very helpful for the typical 3/16" and 1/4" hardware.

One thing I did during my construction was to use non-locking nuts when I was doing all of the trail assembly and saved the actual locking hardware for final installation. Doing this saved time too because you can spin them on by hand and snug them if needed. I actually used some non-aviation nuts from the hardware store, but made sure they weren't used during final assembly.

[colospace]

I have been doing the same as Phil using hardware store nuts for non-flight temporary assembly. To help insure that they do not get over looked later, I first "color" the flats with red fingernail polish or a red permanent marker.