This is the source of great controversy, discussion, and advice as to how to go about marking and drilling the holes for the rivets that end up attaching this main rib to the front spar and subsequently to the nose rib - sort of a 3 layer sandwich of thin alumimum that must be solidly attached by riveting them all together. The controversy revolves around measuring and marking the holes to be drilled, while maintaining proper edge distance from the material. Setting a rivet too close to the edge can cause cracks or failures in the part, so this does have to be done correctly.
After spending lots of time reading and studying the plans, I had an epiphony of sorts. Realizing that the front spar is just the middle layer of the sandwich, the real challenge was to get the rivet holes of the ribs in the right spot, while making sure that the two rib pieces line up correctly. I also realized that the mounting holes in each rib that are used when forming each part appear to be in alignment with each other. As shown here, I simply clamped the two pieces together, lining up the two forming holes as closely as possible, while checking the outer edges to ensure they also were aligned.
I also used two pieces of aluminum from the trim bundle and placed them on both sides of the ribs where the flanges join to further ensure that the ribs are in proper alignment. Then youn really need to pay attention to the lovely drawing in the plans, which, much to my disappointment, is a bit too small to properly show all of the detail regarding how the edge distance and marks for each hole are determined. Be careful, and spend quality time here to fully understand how each set of refernce lines for each rivet hole are determined. Posts on VAF also very clearly discuss this problem.
