Mark Langford said, > "See http://www.krnet.org/kr-info.html for more info on which props work > with which KRs and engines. Sterba props tend to be numbered maybe 2" > more than most other props, has been my experience, although Ed Sterba > would disagree."
I've read that one can't, using strictly diameter and pitch numbers, depend upon the various prop makers conforming to one strict standard. Especially regarding pitch, the number given by the manufacturer is going to be a ballpark reference only. I've had the opportunity to compare Sterba's numbers to Lonnie Prince's numbers and found that my Prince 52 x 54 is almost identical in max RPM to my Sterba 52 x 56. This statement isn't designed to prove anything one way or another . . . it's just a point of reference. In other words, rounding off the numbers, GP 2180 w/Ellison TB Prince 52 x 54 = 3100-3200 WOT at altitude. Sterba 52 x 56 = 3100-3200 WOT at altitude. Sterba 52 x 52 = 3500-3600 WOT at 2500 MSL Each prop maker is going to be a little different with a given pitch number because of their differing techniques in carving and measuring their blade angles. Our choice in choosing a prop depends on engine size and what the owner wants to optimize for within the limitations of ground clearance and engine operating temperatures. In my case, I spend very little time taking off and climbing compared to the time spent going somewhere - thus optimizing for efficiency in cruise makes my choice easy. You can't beat Ed Sterba's props for value and customer service but if I were buying another prop and if I wanted the very best design . . . and if I was willing to get on his long waiting list . . . I would talk to Bruce Catto. His props are based on the race-proven designs of Paul Lipps and are truly works of art - but then, has there ever been such a thing as an ugly propeller? I've never seen one. Catto's have excellent leading edge protection too - although I certainly have no complaints with Sterba's superb urethane edge protection. Catto is truly the ultimate choice in props these days thanks to all the aerodynamic research that's gone into them. They cost more than Sterbas, but then, so does Prince and Sensenich. Another thought to keep in mind. It's possible to re-work a prop to take pitch out - to flatten an existing blade pitch. Putting pitch into an already existing prop however is only slightly possible. I sent my 52 x 52 back to Sterba for sprucing up after it had over a thousand hours on it and asked him to "put some pitch in it" if possible as he was re-finishing it (which he did at no cost!). When I got it back it rendered exactly the same performance as when I sent it in, so my thought is it's better to guess on the side of extra pitch rather than less. If the prop you choose turns out to be too coarse, it's possible to flatten it out some. If the prop you order is too flat however, there's very little modification possible. Some miscellaneous prop pictures: http://tinyurl.com/y5ekw2cs Mike Stirewalt KSEE ____________________________________________________________ Man Makes Shocking Discovery At Ark's Final Resting Place tracking.nmhfiles.com http://thirdpartyoffers.juno.com/TGL3141/5caa5cd8a9d2b5cd80647st02vuc _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to [email protected]
