Saturday, August 18, 2012

Stabilator Hinge Bracket Installed

Other than skin the stabilator skeleton, installing the anti-servo tab hinges and placing weights on the counterbalance arm there is not much left to do on the stabilator except install the hinges. Installing the hinges was just a matter of bolting them onto the spar box and torque the bolts to the proper setting which is 20 – 25 inch pounds for AN3 hardware. However, those numbers do not reflect the tension the nut plates and fiber nuts place on the bolts ... so the additional drag of the nutplates should be added to the torque requirement for the bolts to ensure the proper tension. In my case, the nutplates and fiber nuts were all around 6- 8 inch pounds of drag. So I added that to the requirement and selected 31 inch pounds on my torque wrench.
                           Measuring the drag the platenuts add to the bolt with a torque wrench that goes that low.
                                                      Setting the proper bolt tightness with a torque wrench.

After all the bolts were tightened to the proper torque, I used a torque seal product on the heads of the bolts and the fiber nuts. This will give a good visual reference during inspections to determine if the bolts are tight or are coming loose.
                                                                Torque seal placed on the bolts and nuts.

The stabilator skins require prepping and primer and I was just not up for that today because when I prime, I like doing more than one part to make the spraying prep work and cleanup worth while.  That said, there is always something to do so I decided to jump ahead in the plans an work on some of the tail cone parts. There were a few pieces that needed separating on the band saw, filed smooth followed by deburring on the Scotch-brite wheel.

The next item that got tackled was some fabrication for the tail skid bracket/tie down which is made from some AEX tie down extrusion. This piece requires some cutting and shaping. There is a template plate that is match drilled to the metal. The template is used as a pattern for a radius on one corner, then a small notch is made on one side, followed  by drilling two ¼”holes that are used to form a radius curve where some metal is removed near the top of the piece. The most challenging aspect was cutting a taper from the end of the metal to a point 1 inch back from the edge.

                                                   The drill press was used to make two ¼” holes which will
                                                   become the radius for cuts that will be made later.
                                     All the cutting and shaping is done … next the hole gets tapped for threads.