One has to wonder if DaVinci had his own model. https://instructional-resources.physics.uiowa.edu/demos/10c1020-propeller-stick-hand-helicopter https://instruc

One has to wonder if DaVinci had his own model. https://instructional-resources.physics.uiowa.edu/demos/10c1020-propeller-stick-hand-helicopter https://instructional-resources.physics.uiowa.edu/demos/10c1...