Just as the ribs required to be fluted to get then straight from back to front, the flanges needed some bending to make them 90 degrees so the skins will lay flat on them. Although this step is not covered in the construction manual, it is just as important for the proper alignment of each flange. This is were researching other builder sites has come in handy once again.
This was done by a small hard wood tool I made as part of the second practice kit that I assembled. Since I had already fluted the ribs I had to stop and make a smaller version so it would fit in between the flutes.
After bending the flange little by little, I would check several places along the rib with the combination square to assure the flange was 90 degrees to the face of the rib.
