Gentlemen,

I wasn't talking about aerodynamics; I was talking about the material. I did NOT say Master Airscrews are poorly designed, inefficient, useless except as paint stirrers, or any of that. I simply said, do not spin them at high rpm because the MATERIAL they are made of cannot handle stress or vibration as well as the MATERIAL the APCs are made out of -- and especially at the hub, which, if you notice, has hollows in the back. You might assume (as I did) that those hollows are carefully engineered and that the tensile strength of the remaining material still gives plenty of safety margin, but you would be wrong.

Aerodynamically, they're fine. In fact, I chose a Master Airscrew for a cut-down bench prop because the airfoil and blade area at the hub looked better than any of my wood or APC props for what I wanted it for, namely moving air to cool the crankcase. But if I had known then what I know now about the length and composition of the fibers in the material, and the way glass-filled nylon will instantly fail when it reaches that magic combination of load, flex, and vibration, I would've thrown that thing as far away as I could.

You can happily run Master Airscrews for combat, or aerobatics, or as a replacement for the little cooling fan that came with your beach hat and water bottle for all I care. But you should NEVER, EVER use one for bench break-in or any other high-rpm/high-power application. If you do, you are looking at a bomb waiting to go off in your face. They can sue me for saying it, but truth is a defense. I have photos and witness statements to back me up.

Over and out.