---------------------------------------------------------- Zenith-List Digest Archive --- Total Messages Posted Wed 12/23/09: 11 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:03 AM - Re: Prop choice (LarryMcFarland) 2. 07:52 AM - Re: Prop choice (Jim Belcher) 3. 09:04 AM - Re: Prop choice (jaybannist@cs.com) 4. 10:51 AM - Re: Prop choice (Craig Payne) 5. 10:52 AM - Re: Prop choice (Jon Bateman) 6. 10:52 AM - Re: Prop choice (Bryan Martin) 7. 10:53 AM - Re: Prop choice (Bryan Martin) 8. 10:53 AM - Re: Prop choice (Jim Belcher) 9. 12:26 PM - Re: Prop choice (n801bh@netzero.com) 10. 01:25 PM - Re: Prop choice (Carlos Sa) 11. 03:02 PM - Re: Prop choice (Klaus Truemper) ________________________________ Message 1 _____________________________________ Time: 07:03:31 AM PST US From: LarryMcFarland Subject: Re: Zenith-List: Prop choice Hi Bill, 70-inch, 3-blade, Warp Drive, 17-degree pitch, 130-mph. Best advantage of the Warp Drive prop is being able to adjust from 15-degrees for learning to fly the plane, then progressively adjust the pitch thru 16, and 17 degrees for a best cruise of 120 or so. I think 3 blades are smoother and quieter. 2-blades are reported to be more efficient, but if you pick the wrong pitch, it can be an expensive mistake. Larry McFarland 601HDS at www.macsmachine.com Bill Naumuk wrote: > All- > I'm interested in hearing about your prop choices for HDSs > (Corvair or 100hp), size, type, pitch and performance. Thanks, and > Merry Christmas! > Bill Naumuk > Townville, Pa. > HDS N601MG/Corvair 95% > * > > * ________________________________ Message 2 _____________________________________ Time: 07:52:47 AM PST US From: Jim Belcher Subject: Re: Zenith-List: Prop choice Larry, I'm not an aerodynamicist, but I was once told by one that the most efficient number of blades was an infinite number. In other words, all other things being equal, the more blades the better. I would suspect weight eventually catches up with the advantage gained. I'm out of my area of expertise, but intuitively, it sounds right. On Wednesday 23 December 2009 09:01, LarryMcFarland wrote: > > Hi Bill, > 70-inch, 3-blade, Warp Drive, 17-degree pitch, 130-mph. > Best advantage of the Warp Drive prop is being able to adjust from > 15-degrees for learning to fly the plane, then progressively > adjust the pitch thru 16, and 17 degrees for a best cruise of 120 or > so. I think 3 blades are smoother and quieter. 2-blades are reported > to be more efficient, but if you pick the wrong pitch, it can be an > expensive mistake. > > Larry McFarland 601HDS at www.macsmachine.com > > Bill Naumuk wrote: > > All- > > I'm interested in hearing about your prop choices for HDSs > > (Corvair or 100hp), size, type, pitch and performance. Thanks, and > > Merry Christmas! > > Bill Naumuk > > Townville, Pa. > > HDS N601MG/Corvair 95% > > * > > > > * > -- ============================================ Do not archive. ============================================ Jim B Belcher BS, MS Physics, Math, Computer Science A&P/IA Retired aerospace technical manager Mathematics and alcohol do not mix. Do not drink and derive. ============================================ ________________________________ Message 3 _____________________________________ Time: 09:04:16 AM PST US Subject: Re: Zenith-List: Prop choice From: jaybannist@cs.com Jim, I'm not an aerodynamicist either, but I've been told the exact opposite -- that is that the most efficient propeller has only one blade (counterbal anced, of course), and that two blades are more efficient than three. Tho se big ole' warbirds nearly always had four, but I think that was to take advantage of the available power while respecting maximum blade length. >From what I see, I think a lot of it has to do with whether the propeller is ducted or not. Obviously, ducted fans and turbojet engines have many, many blades. I have to believe that must be for a very good reason. Jay Bannister -----Original Message----- From: Jim Belcher Sent: Wed, Dec 23, 2009 10:01 am Subject: Re: Zenith-List: Prop choice Larry, I'm not an aerodynamicist, but I was once told by one that the most efficient number of blades was an infinite number. In other words, all oth er things being equal, the more blades the better. I would suspect weight eventually catches up with the advantage gained. ________________________________ Message 4 _____________________________________ Time: 10:51:48 AM PST US From: "Craig Payne" Subject: RE: Zenith-List: Prop choice Actually there was a one bladed prop patented, built and sold in the 30's and 40's. I believe the idea is to minimize the turbulence that the blade see from the upstream blade. Here are some pictures and original articles on the Everel single bladed prop: http://www.notplanejane.com/aeromatic.htm http://www.notplanejane.com/everel.htm -- Craig _____ From: owner-zenith-list-server@matronics.com [mailto:owner-zenith-list-server@matronics.com] On Behalf Of jaybannist@cs.com Sent: Wednesday, December 23, 2009 8:25 AM Subject: Re: Zenith-List: Prop choice Jim, I'm not an aerodynamicist either, but I've been told the exact opposite -- that is that the most efficient propeller has only one blade (counterbalanced, of course), and that two blades are more efficient than three. Those big ole' warbirds nearly always had four, but I think that was to take advantage of the available power while respecting maximum blade length. >From what I see, I think a lot of it has to do with whether the propeller is ducted or not. Obviously, ducted fans and turbojet engines have many, many blades. I have to believe that must be for a very good reason. Jay Bannister -----Original Message----- From: Jim Belcher Sent: Wed, Dec 23, 2009 10:01 am Subject: Re: Zenith-List: Prop choice Larry, I'm not an aerodynamicist, but I was once told by one that the most efficient number of blades was an infinite number. In other words, all other things being equal, the more blades the better. I would suspect weight eventually catches up with the advantage gained. ________________________________ Message 5 _____________________________________ Time: 10:52:30 AM PST US From: Jon Bateman Subject: RE: Zenith-List: Prop choice On my first plane I had a 3 blade in-flight adjust IVO prop. It did two th ings for me. It was quieter and had better prop to ground clearence. After 100 hours I changed it to two blades for better performance. Also running b ehind a Rotax 503 it didn't sound as much as a flying lawnmower. My 601XL i s going to be powered by a Lyc. O-290D. I know it is a little heavy but I c an change out a few heavy items Prop=2C starter=2C alt. and mags and loose a lot of weight. I am tossing around either a three blade warp or 2 blade E d Strerba wood prop. I have a freind that has owned two Sterba props on bot h a Soneri and Thorpe. He can't say enough good about them and plans it for his next project Jon Bateman Subject: Re: Zenith-List: Prop choice From: jaybannist@cs.com Jim=2C I'm not an aerodynamicist either=2C but I've been told the exact opposite - - that is that the most efficient propeller has only one blade (counterbal anced=2C of course)=2C and that two blades are more efficient than three. Those big ole' warbirds nearly always had four=2C but I think that was to t ake advantage of the available power while respecting maximum blade length. >From what I see=2C I think a lot of it has to do with whether the propelle r is ducted or not. Obviously=2C ducted fans and turbojet engines have man y=2C many blades. I have to believe that must be for a very good reason. Jay Bannister -----Original Message----- From: Jim Belcher Sent: Wed=2C Dec 23=2C 2009 10:01 am Subject: Re: Zenith-List: Prop choice Larry=2C I'm not an aerodynamicist=2C but I was once told by one that the m ost efficient number of blades was an infinite number. In other words=2C all ot her things being equal=2C the more blades the better. I would suspect weight eventually catches up with the advantage gained. _________________________________________________________________ Hotmail: Trusted email with Microsoft=92s powerful SPAM protection. ________________________________ Message 6 _____________________________________ Time: 10:52:57 AM PST US From: Bryan Martin Subject: Re: Zenith-List: Prop choice Most turbofan engines, which are basically a gas turbine running a ducted fan, are producing thousands of horsepower. They need all those blades to make use of all that power. On a turbo jet engine, on the other hand, the blades you see in the intake have little to do directly with producing thrust, they just compress the air for the combustion process. The jet exhaust produces all the thrust. Pure turbojets aren't used much anymore, most "jet" aircraft use turbofans. On Dec 23, 2009, at 11:24 AM, jaybannist@cs.com wrote: > Jim, > > I'm not an aerodynamicist either, but I've been told the exact opposite -- that is that the most efficient propeller has only one blade (counterbalanced, of course), and that two blades are more efficient than three. Those big ole' warbirds nearly always had four, but I think that was to take advantage of the available power while respecting maximum blade length. > > >From what I see, I think a lot of it has to do with whether the propeller is ducted or not. Obviously, ducted fans and turbojet engines have many, many blades. I have to believe that must be for a very good reason. > > Jay Bannister -- Bryan Martin, BSAE N61BM, CH 601 XL, RAM Subaru, Stratus redrive. do not archive. ________________________________ Message 7 _____________________________________ Time: 10:53:12 AM PST US From: Bryan Martin Subject: Re: Zenith-List: Prop choice Actually, the most efficient number of blades on a propellor is one. The more blades you have, the lower the overall efficiency. A single blade prop with a counterweight has actually been used on some aircraft. There is a recent self launching glider that uses one, the prop is designed to be folded back inside the fuselage while soaring. Of course, this is a very low power application. Two bladed props are the norm for small aircraft because it's the easier to implement. Instead of engineering a counterweight to counteract the forces of one blade, you just use two identical blades. It's also minimum number of blades that eliminates the off-center thrust of a single blade, so it runs smoother. The main reason multi-bladed props are used is that, with more powerful engines it gets tough to get the prop to absorb the extra power and still have adequate ground clearance unless you add blades. A three blade prop can absorb the same power as a much longer two blade prop. Another reason for using a three blade prop where a two blade prop will do is that the three blade prop will run smoother and can greatly reduce propellor noise. Some aircraft make a gawd-awful racket on takeoff with a two blade prop due to sonic effects at the tips. Using a shorter three blade prop can greatly reduce the noise and keep the neighbors happier. And some people think a three blade prop just looks cooler. > > Larry, I'm not an aerodynamicist, but I was once told by one that the most > efficient number of blades was an infinite number. In other words, all other > things being equal, the more blades the better. I would suspect weight > eventually catches up with the advantage gained. > > I'm out of my area of expertise, but intuitively, it sounds right. > -- Bryan Martin N61BM, CH 601 XL, RAM Subaru, Stratus redrive. do not archive. ________________________________ Message 8 _____________________________________ Time: 10:53:17 AM PST US From: Jim Belcher Subject: Re: Zenith-List: Prop choice On Wednesday 23 December 2009 10:24, jaybannist@cs.com wrote: > Jim, > > I'm not an aerodynamicist either, but I've been told the exact opposite -- > that is that the most efficient propeller has only one blade > (counterbalanced, of course), and that two blades are more efficient than > three. Those big ole' warbirds nearly always had four, but I think that > was to take advantage of the available power while respecting maximum blade > length. It has little to do with Zeniths, but Piper once tried a single blade prop on the J3 with a couterweight. Their reasoning was yours: a single blade would be better. For whatever reasons, things didn't work out. I doubt any of those J3s survive today. -- ============================================ Do not archive. ============================================ Jim B Belcher BS, MS Physics, Math, Computer Science A&P/IA Retired aerospace technical manager Mathematics and alcohol do not mix. Do not drink and derive. ============================================ ________________________________ Message 9 _____________________________________ Time: 12:26:01 PM PST US From: "n801bh@netzero.com" Subject: Re: Zenith-List: Prop choice One blade is optimum,, two is faster, three is ALOT smoother,,,, Pick yo ur poison. do not archive Ben Haas N801BH www.haaspowerair.com ---------- Original Message ---------- From: Jim Belcher Subject: Re: Zenith-List: Prop choice > Larry, I'm not an aerodynamicist, but I was once told by one that the mo st efficient number of blades was an infinite number. In other words, all o ther things being equal, the more blades the better. I would suspect weight eventually catches up with the advantage gained. I'm out of my area of expertise, but intuitively, it sounds right. On Wednesday 23 December 2009 09:01, LarryMcFarland wrote: om> > > Hi Bill, > 70-inch, 3-blade, Warp Drive, 17-degree pitch, 130-mph. > Best advantage of the Warp Drive prop is being able to adjust from > 15-degrees for learning to fly the plane, then progressively > adjust the pitch thru 16, and 17 degrees for a best cruise of 120 or > so. I think 3 blades are smoother and quieter. 2-blades are reported > to be more efficient, but if you pick the wrong pitch, it can be an > expensive mistake. > > Larry McFarland 601HDS at www.macsmachine.com > > Bill Naumuk wrote: > > All- > > I'm interested in hearing about your prop choices for HDSs > > (Corvair or 100hp), size, type, pitch and performance. Thanks, and > > Merry Christmas! > > Bill Naumuk > > Townville, Pa. > > HDS N601MG/Corvair 95% > > * > > > > * > -- ======================== ==================== Do not archive. ======================== ==================== Jim B Belcher BS, MS Physics, Math, Computer Science A&P/IA Retired aerospace technical manager Mathematics and alcohol do not mix. Do not drink and derive. ======================== ==================== ======================== =========== ======================== =========== ======================== =========== ======================== =========== ____________________________________________________________ Criminal Lawyer Criminal Lawyers - Click here. http://thirdpartyoffers.netzero.net/TGL2241/c?cp=Mer2R6S9DOqqHMGkScZTi QAAJ1HwQ8b1VOas4hI8eG3vvLZKAAYAAAAAAAAAAAAAAAAAAADNAAAAAAAAAAAAAAAAAAAiF gAAAAA ________________________________ Message 10 ____________________________________ Time: 01:25:04 PM PST US Subject: Re: Zenith-List: Prop choice From: Carlos Sa There's an interesting overview of this subject here: http://www.gnrtr.com/Generator.html?pi=211&cp=3 Carlos ________________________________ Message 11 ____________________________________ Time: 03:02:20 PM PST US From: Klaus Truemper Subject: Zenith-List: Re: Prop choice Hi, Recently I replaced the original 3-blade GSC propeller with a 2-blade composite Sensenich propeller. Both propellers are ground adjustable, but the Sensenich propeller is substantially more efficient. Pictures and preliminary flight data are on the website http://www.utdallas.edu/~klaus/Airplane/airplane.html At 5400 rpm of the 80 hp Rotax, having done 1220+ hrs, the 601HDS achieves 115kts = 132 mph. This with a climb setting, where max rpm in level flight is somewhere between 5500 and 5600 rpm. Adjustment of the Sensenich propeller is very easy since a center delrin piece assures symmetric adjustment of the two blades, just the way a constant speed prop does though not with delrin material. Finally, the blades are extremely light, which is a big advantage for geared engines. Happy flying, Klaus ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message zenith-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Zenith-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/zenith-list Browse Digests http://www.matronics.com/digest/zenith-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.