Used fine Sharpie to mark up the left aileron skin for trimming and drilling. Noted that a couple of dimensional derivations are necessary: 1) The vertical rivet center lines on the front web. The actual distances to these lines is NOT the same as the dimensions shown on the drawing to the center lines of the top of the ribs. Because of the 87 degree angle of the ribs it is necessary to measure the distances from the edge of the skin to the points where the rib top center lines intersect the line defining the face of the front web. Transfer these dimension to the web to ensure one consistent centerline all the way around each rib. 2) The bottom cutout is shown as 94mm from the plane where angled cut on the top skin intersects with the top of the front web. Measured this distance to be 10mm from the edge of the un-cut skin so the actual pre-cut distance to the bottom cuttout (at the bottom of the front web) is 104mm from the untrimmed skin edge.
Once all of the rivet centerlines were drawn I used the adjustable rivet spacer to mark the rivet holes.
