I am thinking about building a cyclone DC for my shop with a different shape for the lower cone. I have noticed that tornadoes have a characteristic "tornado-ey" type shape. Not straight sided cones but pinched in on the sides. Almost a perfect cylinder near the ground that widens in a characteristic curve to a much wider cone at higher altitudes.
Okay, I know I can build this with fiberglass using standard boatbuilding methods. But has this already been tried and found to be lacking?