The completed GPO-2 Secondary Coil.  The coil form is a custom-made one-piece fiberglass shell which is 48 inches tall, 36 inches in diameter at the base, and 18 inches tall at the top.  The custom-made wooden feed-thru insulator is made from birch hardwood.  Note the nylon cap screws that affix the top plate, to eliminate the possibility of corona discharge leakage.