Dear mark:
my name is Alejandro, I am an Aeronautical Engineer from Argentina. With a friend we are restorating an old Gnome 80 HP engine, so I tooked the propeller cosntruction for this engine. Almost I finished the design, but there are some dark points that are a mistery for me:
1) I have seen that the propeller constructors cut the leading edge of the airfoils near the hub. some cuts until 20% of radius, others prefers 30 - 35%. I have asked everybody, but nobody did give me the reason. always said to me "take what you want, near the hub, the thrust have no relevance over the total thrust" (?) is this "cutting" empirical? I know this cutting is interrelated with the THICKNESS of the propeller (that determines the HUB thisckness), but HOW??? readed and readed every book / paper / web site, but no author explain clearly this point!
My question is, once are determinated the pitch and the airfoil angles, how to determinate the hub thickness? this thickness is who determines leading edge cutting path?
I will appreciate what help you can give me. Thank you!