View Single Post
Old Oct 11, 2012, 03:09 PM
C₄H₁₀ is online now
Find More Posts by C₄H₁₀
Wake up, feel pulse, be happy!
C₄H₁₀'s Avatar
United States, MN, Minneapolis
Joined Aug 2009
12,997 Posts
Looks like Eli/Chuck finally took the 40. Good riddance....

Now, RR, I don't believe I ever covered the topic of the efficiency of high-performance molded props. I'm hungry and food is a long walk away so I'll keep it brief, but it comes down to stiffness as much as anything. If any prop can hit the efficiency levels of APCs or Graupners, it's doing pretty well. Those props are commonly replaced in the high-performance world with small (4.7"-5" diameter) folders made by Georgi Mirov or some such supplier for two main reasons: 1) The stiffness of the carbon blade allows for less depitching at high RPMs, allowing more performance, and 2) The folding design protects the prop on landing. It's not so much a matter of absolute aerodynamic efficiency as simply how well the prop can cope with the extremely high power levels. If someone flew a parkflyer with a GM carbon folder, it most likely wouldn't be any different than an APC or Graupner in terms of performance... But on a 220mph F5D plane, you could have the most efficient nylon prop ever made and it could still be outperformed by a crappy composite screw.

The other aspect would be the really big (17"+) folders used in hotliner applications. We can assume that they have relatively good aerodynamic performance just because of the people who make them, but I honestly don't know where they fall on the absolute scale. Those props are also commonly run with twisted yokes to affect the average pitch of the blade, which generally isn't good for efficiency but is still done for a variety of reasons. Since a majority of these props are developed for and used in high-level competition, I suspect that there's not much room for improvement.

I think there was a thread in High Performance that actually addressed the topic of relative prop efficiencies in that arena, and those guys are miles ahead of most of us when it comes to air-screwing technology.
C₄H₁₀ is online now Find More Posts by C₄H₁₀
Reply With Quote