A friend of mine just bought a P-tip.. Paid extra for the leading edge protection?? I can only ASSUME it is under the finish?? I don't understand leading edge protection "under" the finish? What's the point? Personally I wouldn't buy one of his props.. Had a very bad experience with him a few years ago.. Total jerk.. Just my .02. Ron
________________________________ From: "laser...@juno.com" <laser...@juno.com> To: kr...@mylist.net Sent: Monday, August 6, 2012 5:54 AM Subject: KR> Propellers > "The 'p' tip on the Prince prop does improve performance and is quieter." I used to believe this when I bought a beautiful 52 X 54 from Lonnie a few years ago. I did get good performance from it but had to take it off the first time I ran into rain. The leading edges dissolved. I had paid for the "leading edge protection" he had at the time - whatever it was. I could find no evidence of any protection but, in any case, it didn't work. I understand he has gone to Sterba's technique of embedding urethane in the leading edges. Ironically, it was Lonnie who many years ago gave Ed the urethane he currently uses for leading edge protection, so Lonnie has gone full circle on this issue. Re the p-tips, as time went by I got to know Paul Lipps - I'd read his work in Contact Magazine and other magazines and went up to Santa Maria two years ago to balance his prop and talk to him about props and aerodynamic issues with my KR. He happened to mention that he had cut the P-tips off a Prince prop and goten not only more RPM but also, when run at the same RPM as when the p-tips were on, more thrust. He has been (he died a few months ago unfortunately) taking first place for the last several years in a couple of the categories at Reno with his prop designs. The P-tip idea is dead in the water and I think even Lonnie would admit that in light of Lipp's documented testing and if he knows he's talking to someone who has done a bit of research. I plan to have Lonnie take my tips off and put urethane on the leading edges . . . I just haven't gotten around to getting the prop to him yet. He refinished it (for a price) after my leading edge problem so it's still sitting in the shipping box - a brand new black 52 x 54 P-tip. I'd sell it for $800 if anyone's interested. Meantime I'm using a 52 x 56 Sterba and a 52 x 53 Sterba re-worked and re-finished by Ed. The Prince has some sophisticated blade shaping that gives it a slight edge in efficency over the Sterba but the P-tips only add drag. I guess they make the prop quieter too . . . that's why Hartzell used them in limited fashion, but that could have been a gimmick for Hartzell just as it has been for Prince.. You don't see them in widespread use. Paul would say that prop noise is evidence of thrashing the air, wasting energy. His props, even at Reno turning almost 4000 RPM are amazingly quiet. Lonnie plays with lots of prop designs and has incorporated Paul Lipp's concepts into some of them - such as a very small tip to reduce drag and progressive compound angles with more attention to the root area. Most props actually produce negative lift at the root area. Paul's don't. Here's a quote from Paul Lipps and a link to the article it came from: "And any prop that further complicates a wide tip with a wide, turned-under or turned-up tip really throws away engine power. Those may look very techie, but they aren?t very efficient!" http://www.eaa.org/experimenter/articles/2009-02_elippse.asp ************* That's interesting about how the tip Mach speed relates to efficiency. I've known for years that my engine and 52 inch props have their sweet spot at between 3000 and 3100 RPM. It varies a bit with altitude. I've been thinking it was just my engine/prop/altitude and the way they fit together, but I'm now reminded that mach tip speed is also an important factor. Mike KSEE ____________________________________________________________ 53 Year Old Mom Looks 33 The Stunning Results of Her Wrinkle Trick Has Botox Doctors Worried http://thirdpartyoffers.juno.com/TGL3141/501fa2ba1d09522b93963st01vuc _______________________________________ Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. To UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
