Prop Duct for future VTOL hoverbike project.

Can be scaled to suit.
It was reported by NASA that a prop duct like this could increase lift in ducted fan type VTOL aircraft. I'm guessing that the air curves over that lip and creates lift like a wing. Not sure, but it looks cool anyway. See Hiller VZ-1. But the project I was planning uses 2 ducts like a hover bike.
Prob needs supports as my test print without them was a little stringy.I incresed the number of rib supports to make sure it stays rigid enough for a 2mm clearance from the p