August 5, 2006

Major progress since last post. I have all the welds finished and most of the bird cage done. The finish welding has taken a lot of time but it is just about finished. The pictures below show the fitting of the top of the cockpit where the wings attach being fitted to the fuselage. The upper section of the bird cage is critical to get right as it establishes the angle of attack of the wings. The length of the front tubes would be adjusted if a builder wanted to change the angle of attack. The 2+2 has a lower wing angle of attack than the Super Cub; 0 degrees vs 4 or so degrees (guessing here) The lower angle of attack gives the 2+2 a higher cruse speed but a longer take off run. The higher angle of attack on the Super Cub gives it better short field capabilities but slower cruse speed. A builder can change this angle to create the type of plane to meet their desired flight needs. Lots of info at Supercub.org on this subject.

First step here was to locate where the upper structure would be located. I used strings to locate the datum line (center of fuselage) and the front and back location of the upper structure.

Next I placed the upper structure on top of the fuselage to see where it would all need to fit.

Next I built the jig to elivate the upper structure to correct height and angle. The plum bobs are located at the center of the upper structure and hang down to the string that represents the datum line of the fuselage. The main fuselage must be supported level on the floor for all this to work. The jig height can be adjusted via the corner clamps. This was not that hard once I figured out how to build the jig and turned out to be very accurate.

Another shot of jig set up