Leonardo da Vinci's aerial screw

Some time ago I received a visit from a servant to the Duke for yet another flying contraption, though this time the model was to portray the idea of a device for a theatre spectacle. Again, within minutes, Salai appeared bearing notebooks under his arm. I had no sooner counted out my Ducats from the Duke than I was reaching into my pockets to pay the rascal for the chance to glean more information from the scribblings of the Florentine master.

As always Leonardo's drawings come with a flair of the artistic. They move off the page, alive and in motion. But I must use my mind to see through the moving parts and capture the static details. I find my confirmation in what small jottings Salai will let me see. From the sketch of the master comes my drawing, thus:

As I see it all moves as one, pivoting on the central column against the stationary slatted base. The base is the platform giving purchase to men who will push the whole in its circular motion by pushing the cross bars, like sailors at a windlass on a ship.

I planned for the model to be 5 feet across. I sketched it out and then set to work with old wood, first making the slatted base, and then the external ring seated beneath it. There are four diagonal support struts and a central column planed down to eight sides. From the column, above the braces, I made square mortices every inch and a half and ran 30 inch rods fanning around for one full circle. At this point I began to reduce their lengths by 2 inches successively until I had completed another half turn.  

The devil in the job was applying the cloth to the framework. The radiating struts support a wire perimeter bound in place by twine. The fabric was applied in sections as large as I could manage to reduce stitching. Even so my fingers became weary plying the thread, and I found myself resorting to a system borrowed from bookbinding using application of glue as often as possible. 

I  also fashioned two little manikins to ride on this merry-go-round as though they were running their little hearts out. I am pleased with them for they have the spirit of da Vinci's drawing. 

As I spin it there's a convincing sense of life, but not even a hint of a downward breath from the swirling sail overhead. I have my doubts that this thing would ever fly in real life. It also strikes me that were it to come off the ground, even for a moment, the slatted base would as willingly spin in the opposite direction to the turn of the upper screw. I think this contraption is better kept for the stage.