(page 09-10) Nutplates and counterweights.....                                


After reading the horror stories on the forum about stripped threads in nutplates, it was with fear and trepidation that I installed the control horns on the box spar. With the box spar all closed up and the stabilator skins attached, it occurred to me that if the threads in one nutplate stripped, I'd be screwed. There's no way to reach the inside of the box spar. 

A fair number of builders on the forum advocate running a tap through the threads prior to running the bolt in.  My gut feeling is that this would negate at least part of the self-locking feature of the nutplates.  Having bolts back out of the elevator control horns could ruin your whole day (picture a smoking hole in the ground).  The torque required to turn the bolts in the flattened part of felmale threads varied from 3 to 10 in-lbf among the eight bolts on the control horns.  I added this to the published torque spec (20 - 25 in-lbf in the case of AN3 bolts) to get the value to which I torqued each bolt.

By contrast, the counterweights attached with no issues.  The tail cone is next.