I have one rebuttal to this. If a three bladed prop is so much better than two and that larger engines can't swing a two bladed big enough, than why does R-680 swinging a 103" two blade and make more thrust than an IO-540 of slightly greater horsepower swinging a three blade that's 84"?
Fred Johnson Reno, NV. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Randy Smith Sent: Wednesday, December 20, 2006 3:02 PM To: KRnet Subject: Re: KR> Props I am not sure what book you refer to but everything being equal a 2 bladed prop will perform better than a 3 bladed prop. A prop disturbs the air in front of it as it comes around and a 3 bladed prop disturbs more air. The perfect prop would only have one blade. The three bladed prop is quieter and smother than a 2 bladed Prop. There are a lot of High performance engines like an IO-520 on Vikings,Cessna 210,Piper and a lot of other High performance aircraft That come from the factory with a 2 Bladed prop. Talk to a prop shop and they will explain the differences. Some planes come with a 3 blade prop because of ground clearance, Some folks like them because they look good. --- Colin Rainey <[email protected]> wrote: > Theoretically a 3 bladed prop that is pitched the > same as a 2 bladed (same > manufacturer is best) and is the same disc area of > length, the 3 bladed > should make approximately 17% more thrust than the 2 > bladed, or behave like > the same 2 bladed prop but 17% longer. I cannot > recall the author's name > right off, but if interested I will look up the book > and post it here. The > author's formula in my specific case said that my 3 > bladed prop at 54 inches > would perform just like a 2 bladed of the same pitch > that was 58 inches long > (.93 times the 2 blade length). As has been stated > here many times, there > are several factors that go into prop selection, > number of blades and pitch > only two of them. > > However, I will make some generic observations for > the group that apply to > those that are beginning to push towards higher > horsepower and torque > engines: > 1) Multi-bladed props climb better than 2 bladed > props, as a rule. > 2) Multi-bladed props are known to be easier to > balance, and inherently > more balanced (two sources confirm this). > 3) Multi-bladed props tend to be a little to much > quieter than 2 blades in > operation. > 4) Higher HP aircraft almost always use > multi-bladed props; I am deducing > because they cannot swing a 2 bladed prop long > enough to handle all the > torque they have, and convert it to thrust (this may > be of interest to > 3100cc Corvair guys etc...). > > We happen to be small aircraft that some people are > beginning to experiment > with higher HP engines, but still have the problem > of ground clearance, so > the answer? Multi-blades... > I too will be running a 3 blade Warp Drive once I > settle on which engine I > will install (already have the prop). > > Colin Rainey > [email protected] > > _______________________________________ > Search the KRnet Archives at > http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to > [email protected] > please see other KRnet info at > http://www.krnet.org/info.html > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to [email protected] please see other KRnet info at http://www.krnet.org/info.html
