Cut a 7-5/16" section of the wooden rod
In one end drill a 3/8" hole about an 1-1/4" deep for the bolt and in the other end drill a small pilot hole for the eye-screw. Paint the eye-screw end of the wood rod black.
Take the steel pipe nipple and place 6 flat washers and 10 hose washer over it, starting with a flat washer then 2 hose washers then another flat washer and so on, ending with a flat washer. When done the two flat washers on the ends should be flush with the ends of the pipe nipple. Getting the hose washers on can be a pain...I recommend bracing the pipe nipple on flat surface and using a flat washer press them down with. Don't worry if the flat washers keep falling off, they will until the assembly is bolted in place.
Thread a hose washer on the bolt followed by the fin assembly followed by another hose washer. The two hose washers added in this step are for stability and do not go over the pipe nipple (there should be no room for them anyway). Now screw the bolt, with the washers and fin assembly into the wooden rod. If you need more grip from the threads of the bolt to the wood, you can wrap them in duct tape.