(Geoff Miller) wrote in news:TvydnR2K2
net:

http://blizzard.zmm.com/thunderbird/starboard.jpg

The note says the aluminum prop is the slower prop. It is normal for a
steel prop to have faster top speed than aluminum, all other numbers being
equal, because steel allows for thinner blades and thus less drag. The
steel prop may have slight efficiencies due to shape as well, such as rake
and cupping, which are easier to do with steel and seldom seen with
aluminum.