Since the W-931 rib will be bonded and riveted in place I had to scuff sand the interior surface of the W915 Tips. Used 80 grit sandpaper. Fluted the W-931 Rib and adjusted the flange angles. Got a fairly good fit. After positioning the W-931 Rib in the wingtip and marking it's position inside the wingtip I used a bright light in the W-915 WingTip and marked the location of the rib on the exterior of the wingtip.
