Place the Z Channel that is 854mm long on the Bottom Skin at the rivet line aft of the access hole. Position the Z Channel so the center line is visible through the predrilled holes. With a #40 drill bit, drill through the Bottom Skin into the Z Channel and Cleco.
Position the 655mm long Z Channels on the Bottom Skin so the center line is visible through the predrilled holes on the sides of the access hole. With a #40 drill bit, back drill through the Bottom Skin into the Z Channels and Cleco the Z Channels to the Bottom Skin.
Cut 2 pieces of L angle (or Z Channel) 190mm long. Draw a center line on one flange of each L angle. Position the L angles on the Bottom Skin overlapping the Z channels and the edge of the skin. With the center line visible through the predrilled holes in the skin, drill with a #40 drill bit and Cleco. Then expand the holes with a #30 drill bit.
Cut L Angles to the proper length for the lateral stiffeners. The L Angles overlap the Longerons; see drawing 75-FA-1 for details. Draw a center line on the flanges of the L angles. Position the L Angles on the Bottom Skin so the center line is visible through the predrilled holes. With a #40 drill bit, back drill through the Bottom Skin into the L angles and Cleco. Repeat this procedure for the diagonal L Angles. The diagonal L Angles do not overlap any other stiffeners.
