I have remixed @Chya excellent vertical axis windmill design to incorporate a plug on one end so that the windmill can spin on the top of a metal spike.
This model should be printed in PETG with organic supports on all the bottom sides of the turbine and support arms.
The small spike cap is optional, but will enable the turbine to spin more easily. The cap is designed to fit over the metal spikes from one of those corrugated plastic “election” signs. Throw the sign away after the election and use the metal part for two wind turbines. Bend the spikes so that as much as possible they are straight vertically.
The author remixed this model.
This remix has a stopper to allow it to sit on top of a spike.