Here’s a thing. Quite an amazing thing.
Apparently, the efficiency of aerofoils can be significantly increased by adding ‘tubercles’ to the leading edge. This improves both wings and propellers.The tubercles increase efficiency, allow a higher angle of attack and soften out the effects of a stall. And they make the wing/prop quieter. Inspired by the hump back whale.
Here’s a paper describing the effects of various parameters and how more than 20% efficiency can be gained in a prop.https://arc.aiaa.org/doi/full/10.2514/1.C034845
Some more stuff.
Apparently GIN paragliders are working on a wing with a Tubercle leading edge:
And you can download a CAD model from GRABCAD
20% more flying time and a quieter prop. So, who’s first to get to work with a file on the leading edge of their prop then?!