Ok, here is the ugly truth about tube and fabric construction. When you are involved in a major rebuild, as I am, you have to put everything together so you can take it apart. I know, this sounds crazy, but think about it. All the critical attach points have to be correct, the structure welded, and then blasted and primed. When everything fits, then you know it will go together again after you cover it with fabric. Trying to weld (high temperature) with fabric in place is not a good idea….
However, with my new wings really in view, some other issues come to the fore. Turns out these wings had electric fuel gauges. Guess what, these are not on my approved list and Gregg has decided to go with the original float system (no paper work). The electric system would have probably been a Field Approval and not an STC, much more difficult. I will not even try to go in the direction of how these gauges got here. Simply put, there is no STC, and there is no record of a field approval in the paperwork (OUCH). The problem is that the old installation of the electric transmitters forced a modification of the fuel bay covers. That modification has resulted in a large hump in the fuel bay cover, and Gregg really dislikes the look. Work on this issue will have to wait until the wings are removed.
Needless to say, while this is going on other things are happening. The installation of the control system means that the control limits for the rudder and elevator must be set. Remember, I am of the older generation, and these adjustments are not made with an adjustable (screwed) system. I have a fixed post for each limit, and the limit is determined with a grinding wheel. If you take too much metal off, you add some weld metal and start over. In any case, the end result is that my limits comply with the Type Certificate Data Sheet. It should be noted the adjustment on the ailerons is screwed.
Most folks do not realize that there are really two structures in the forward part of Cubs. There is the tube structure, which attaches the engine to the airframe. Then there is the u-channel structure which forms the shape of the Boot Cowl. This is an additional structure that Gregg has yet to address. The entire structure is Brazed into place, because it is not considered to be structural. Another reason for Brazing is the thickness of the u-channel. The metal could be welded, but its thinness and location would make welding very difficult. Gregg fabricates a French Curve from quarter inch plywood, and uses it to form the required bends. Once the u-channel is formed, it is Brazed to the tube structure. Another point that is easy to forget, is there are several fabric formers in the belly, sides, and top of the fuselage. In my original configuration Piper used wood for these formers. A continuing effort to modernize is Gregg using extruded aluminum as a replacement material. In many of these locations the stand off’s are Brazed into place. (Pictures in following articles will show these pieces.)
Hopefully, you the reader, remember I am a PA-12. That means I have a single cabin door, which swings on hinges (not like the clam shell door of a J-3 or PA-18). Because of my damage I did not have door hinges, even though I did have a door. With the wings installed, it is important to get the hinges installed. The door has to swing correctly, and not hit the bottom of the wing. I know, this sounds mundane, but to me it is a big deal, and it is impossible to get correct without the wings in place.
OK, so let’s review the progress with the wings on. The aileron cables have been rigged. The flaps are now legal with an STC, and the new cable runs are in place. A flap handle has been built, and rigged to function correctly. The rudder and elevators have gotten the cables run and the control limits set. The continuous cable loop for the trim system, plus its associated pulley’s and fairleads have been installed. The door hinges have been built and installed.
Now that I have gotten the major controls under my belt, I go to pieces again! You know, it is really the s—— to have been in my condition for years to go to pieces AGAIN! Oh Well, Gregg has been the only person to pay major attention to me for a long time, and now I must keep the faith. Do I have a choice!
Anyway, while I am off getting blasted and primed, I am hopeful that many new things will be in the hangar when I get back.
eaa670 