I'm always a little uncertain about work that is more complicated. Simple is usually better, more universally accessible. For this piece I had some nicely figured cherry that I used for the fins. I like the base - a crotch piece of walnut shaped like a river stone. There was a lot more engineering for this piece than most I do and that part was fun - reason enough to do it. It spins nicely though a little off center despite considerable effort to get it right on.
For the technically inclined here is some detail. I ripped the central core as accurately as I could to give me a piece 4 x 4 x 12, marked the centers, then ripped off the corners to give me a long octagon. On the lathe turned the piece but left 1/2' of the octagon at each end. Using the 1/2" as bearing surfaces I ripped the eight slots for the fins on the table saw and then drilled the holes at either end on a horizontal boring setup. The top hole is counterbored and the top turned with a tenon to fit.
The fins are a thin sandwich - 1/8' matched veneers with a 1/16" strip of lead embedded at the edge between pieces. I just had a feeling that I needed weight to overcome the wind resistance of the fins for the piece to spin for any length of time. I thought the weight should be placed at the edge but I don't know why. My physics question is: could I have placed this weight at the core for the same effect?
See the diagram for the method of mounting the piece to spin. Thanks to my friend Jerry for advice. It is basically the way he mounted a weather vane. The main problem I had is that it is difficult to drill a large hole into end grain and the bit drifted off center. So in the end the piece rotates a little off center instead of the dead on Swiss watch perfect I would have liked. I said it was fun I didn't say I did it that well. I'm letting go of this.