Create shims to fit between rudder skin and bottom gusset

The rudder bottom gusset side flanges fit between those of rib1, yet the skin is pulled against both of these. To avoid the consequential depression in the skin, shims of 0.64mm 6061-T6 were created to sit between the skin and the gusset side flanges. This thickness is chosen to match that of rib1. These shims do nit interfere with rib1 and create a level surface for the skin to sit against. They are etch-scrubbed and primed in the usual way.