Thursday, August 23, 2012

Drilling Stabilator Hinges

The stabilator hinges are drilled using the opposite end of the template used for drilling the anti-servo tab hinges. The plans call out not drilling two holes on each hinge so that location is covered with blue tape. If the marking was done right, when rotating the hinges around the two blue tape marks should line up.
Hinges are a mirror image of each other so the tape marks should line up if one of the hinges is flipped around.
                                                       Drilling stabilator hinges using the drilling template.
                                                      Drilled and deburred stabilator hinges.

After the hinges are drilled, they both get mounted on upper and lower flanges of the right stabilator skin. The two holes that were omitted on each hinge using the blue tape will now get match drilled using a hole in the skin as a guide. In addition, one additional hole is also match drilled using the stabilator skin’s inboard third hole in as a guide.
                             Left and right hinges Clecoed to stabilator skin ready for match drilling three holes on each
                             hinge. The two holes omitted while drilling with the template and one additional hole.
                                      Match drilling stabilator hinges using the stabilator’s skin holes as guides.

Not having anything left to do on the stabilator before priming, decided to work on some of the tail cone parts. There is a J stiffener which comes with three stiffeners that need do be separated. The part was to long for the band saw so used a metal snip to cut one of the attaching tabs but had to use a cut off wheel to cut the tabs where the “J” curve is.
                                                  Using a metal cutoff wheel to separate the three J stiffeners.

One of the first items in the tail cone plans calls for breaking the edge of the tail cone’s top, bottom, and side skins. I have a new tool for doing this sold by Cleaveland Aircraft Tool … but have never used this type of edge breaking tool before. So thought it would be a good idea to bone up a little and play a bit on a spare piece of aluminum before turning myself lose on the tail cone skins.

The Cleaveland edge breaking tool has two rollers … one of which (the roller on the right) has a small taper on the lower portion of the wheel which can be seen in the following photo. The small taper on the wheel when rolled down the outer edge of the metal places a small few degree downward taper on the skin’s outer edge.  The purpose for this is to help make tight joints where skins overlap each other. Without the small “break” on an overlapping joint, the riveting process has a tendency to pull the skin upward slightly along the rivet line. Breaking the edge prior to riveting helps keep the skin snug to the surface being overlapped.

The tendency is to over adjust the tool. The tool is easy to adjust …  basically slide the very outer edge of the rollers over the material to be broken and adjust the tool so the rollers just touch the material. Once adjusted, start at the edge to be broken and make sure the edge of the metal to be broken is riding along the raised ridge or guide on the far inside of the wheel and pull the tool smoothly and evenly along the edge to be broken. Do not tilt the tool up or down … just drag it straight back and let the tool do the work.  It pulls fairly easily but I read on one builder’s site that putting a little WD-40 on a rag and lubing the metal with a thin coat helps. Will give that a try tomorrow.
                                         The Cleaveland edge breaking tool … the tapered roller which creates
                                         “the break” can be seen on the lower portion of the right roller.

                           The break can be seen clearly as light under the straight edge at the outer edge of the skin.