April 1, 2012
Having completed the rear spar bends we could now use the big brake for the aileron and flap skins. Using a CAD program at work I was able to generate the flat pattern for both of the skins so we have the outside dimensions. We marked the sheets being mindfull of how to best use the material given the parts we have left.
Dan used the electric hand shear to cut them out pretty close to the marks.
Even though we used two factory edges of the original aluminum sheets Dan wanted to make sure they were perpendicular to each other. If they are not then dimension errors will creep in and with skins one can get twist at final assembly.
Dan pulled out his trusty framing square that is pretty true. We used the long “bottom” factory edge as the primary datum. We marked the other factory edge with the sqaure and you can see on one side there is barely any pen:
But the other side has a thicker ine of pen as the perpendicular line. To me this shows that you cannot rely on the sheet edges being perfectly square.
Dan saved us a lot of headaches by this check. We trimmed and filed off the pen mark.
Now we have two perpendicular datum edges. In theory the “top” long edge should be parallel with the “bottom” long edge since it was measured from it. Here are the finished skins:
