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HShack(at)aol.com
Guest

Posted: Tue May 15, 2007 4:36 pm Post subject: FireFly prop & others

In a message dated 5/15/2007 11:54:29 AM Eastern Daylight Time, etzim62(at)earthlink.net writes:

  	  Quote: 	
		  But a two blade prop will out perform a three blade every time when  

everything is optimized, especially prop diameter and prop speed 	


  

 Outperform?  What does that mean?  I have a FS II, 503DCDI, 3.47:1 C Box, & 68" 3 blade Kiev prop; weight of plane is 470 [wet] & I was 275 when the following results were obtained:

  

 Outclimbed & outran 2 other FS II's; one was grossed same as mine & one 70 lbs lighter.  Both had B boxes & with 2 blade props.

  

 The results were the same when I ran a 3 blade Warp, 68" w/ taper tips.

  

 YMMV



  

 Howard Shackleford

FS II

SC



See what's free at AOL.com. 

  [quote][b]

Eugene Zimmerman

Joined: 10 Jan 2006
Posts: 392

Posted: Tue May 15, 2007 7:02 pm Post subject: FireFly prop & others

Hey, I don’t doubt your experience.



I assume you concluded, based on your experience, that a three-blade  

prop will always have the potential to out climb and out run a two  

blade?



A prop blade is simply a rotating wing and the reason a two blade  

will always have the "potential” for better performance is the same  

reason  high performance sailplanes never have bi-wings.



Performance is maximized by minimizing performance robbing drag  

created by the wing tip vortices.  A long high aspect wing has better  

performance than a shorter bi-wing because the bi-wing has twice as  

many drag creating wing tip vortices.



On May 15, 2007, at 8:27 PM, HShack(at)aol.com wrote:



 	  Quote: 	
		   I have a FS II, 503DCDI, 3.47:1 C Box, & 68" 3 blade Kiev prop;  

 weight of plane is 470 [wet] & I was 275 when the following results  

 were obtained:



 Outclimbed & outran 2 other FS II's; one was grossed same as mine &  

 one 70 lbs lighter.  Both had B boxes & with 2 blade props.



 The results were the same when I ran a 3 blade Warp, 68" w/ taper  

 tips.

ElleryWeld(at)aol.com
Guest

Posted: Tue May 15, 2007 7:05 pm Post subject: FireFly prop & others

You should show the other guys how to set there Prop ?

 

                             Ellery

 

 do not archive 

**************************************

 See what's free at http://www.aol.com.  [quote][b]

HShack(at)aol.com
Guest

Posted: Tue May 15, 2007 7:39 pm Post subject: FireFly prop & others

In a message dated 5/15/2007 11:06:03 PM Eastern Daylight Time, ElleryWeld(at)aol.com writes:

  	  Quote: 	
		  You should show the other guys how to set there Prop ?



                            Ellery 	


 No, some of them have concluded they need to duplicate my setup; others are quite happy with less than optimal performance.



  

 Howard Shackleford

FS II

SC



See what's free at AOL.com. 

  [quote][b]

d-m-hague(at)comcast.net
Guest

Posted: Wed May 16, 2007 2:54 am Post subject: FireFly prop & others

At 11:01 PM 5/15/2007, Eugene Zimmerman wrote:

 	  Quote: 	
		  



Performance is maximized by minimizing performance robbing drag

created by the wing tip vortices.  A long high aspect wing has better

performance than a shorter bi-wing because the bi-wing has twice as

many drag creating wing tip vortices.


	


Actually it's not the wing tip vortices.  A biplane is less efficient 

because of interference between the wings; the closer together the more 

interference.  Similarly, the close together the prop blades are (i.e. 3 

blade vs. 2 blade) the more interference.



Wing top vortices are part of induced drag, which depends on aspect 

ratio.  If you could build a biplane with the same aspect ratio for each 

wing as the sailplane, AND get them sufficiently far apart for no 

interference, you'd get the same performance... but you CAN'T get them far 

enough apart, practically speaking, and then there's the drag of supporting 

structure, etc...



                                 -Dana

--

--

Okay, who put a "stop payment" on my reality check?

jim

Joined: 03 Nov 2006
Posts: 107
Location: N. Idaho

Posted: Wed May 16, 2007 5:52 am Post subject: FireFly prop & others

Then why is a high-bipass turbofan so efficient?  These are found on

747-767 and are just a whole bunch of ducted short propeller blades.






At 11:01 PM 5/15/2007, Eugene Zimmerman wrote:

 	  Quote: 	
		  



  Similarly, the close together the prop blades are (i.e. 3
	


blade vs. 2 blade) the more interference.

                                 -Dana

_________________
Jim
N. Idaho

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Wed May 16, 2007 8:24 am Post subject: Re: FireFly prop & others

 	  jim wrote: 	
		  



Then why is a high-bipass turbofan so efficient?  These are found on

747-767 and are just a whole bunch of ducted short propeller blades.



                                -Dana 	




A high bybpas turbofan is NOT efficient.  If you look at a jet compared to a prop plane, there is no comparison in in efficiency, the prop wins every time.   Where did you get the idea that a turbofan is so efficient , by comparing it to a turbojet, which is even less efficient     



It is well known that a 2 blade prop is more efficient than a 3 blade.  The problem is that there is not always room for a long 2 blade prop, or noise is more of an issue etc. etc.  But the 2 blade is more efficient.



If someone outclimbed someone else with a 3 blade prop, making the assumption that it was because of having a 3 bladed prop is just dumb.   Ever think it could have been variations in the airplane, pilot technique, or a hundred other possible factors ???



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

d-m-hague(at)comcast.net
Guest

Posted: Wed May 16, 2007 8:33 am Post subject: FireFly prop & others

At 09:52 AM 5/16/2007, Jim Dunn wrote:

 	  Quote: 	
		  



Then why is a high-bipass turbofan so efficient?  These are found on

747-767 and are just a whole bunch of ducted short propeller blades.


	


Well, that's a different situation.  You can't really compare that to a 

prop on a low speed aircraft; you have to compare it to a conventional 

turbofan or a pure jet engine... and it IS larger than those.  Also a 

ducted fan is very different; the duct eliminates the tip vortices so the 

aspect ratio isn't as significant.  Ducted fans (and jets for that matter) 

aren't very efficient at low airspeeds.



                                 -Dana

--

--

Okay, who put a "stop payment" on my reality check?

HShack(at)aol.com
Guest

Posted: Wed May 16, 2007 5:06 pm Post subject: FireFly prop & others

In a message dated 5/16/2007 12:25:46 PM Eastern Daylight Time, orcabonita(at)hotmail.com writes:

  	  Quote: 	
		  If someone outclimbed someone else with a 3 blade prop, making the assumption that it was because of having a 3 bladed prop is just dumb.   Ever think it could have been variations in the airplane, pilot technique, or a hundred other possible factors ???



Mike 	


  

 It must be me you're calling dumb.  I never said it was the 3 bladed prop that allowed me to outclimb them- just that I did, using  certain parameters,ie. brand, # blades, & length of prop, & ratio of PSRU.

  

 By the way, I also usually burn less gas than them on a given trip.

  



  

 Howard Shackleford

FS II

SC



See what's free at AOL.com. 

  [quote][b]

ceengland(at)bellsouth.ne
Guest

Posted: Sun May 20, 2007 9:50 am Post subject: FireFly prop & others

Actually, they aren't that efficient; they are just better than turbines 

without the bypass. They would be a lot more efficient if you could put 

a 2 blade prop on them, but a 2-blade big enough to absorb that much hp 

would probably have a larger diameter than the plane & weigh more than 

the plane, too.

The entire *system* is efficient, but that's because of extremely low 

drag, extreme span-loading of the wings, flying at extreme altitude, etc.

Charlie

Jim Dunn wrote:

 	  Quote: 	

 Then why is a high-bipass turbofan so efficient?  These are found on

 747-767 and are just a whole bunch of ducted short propeller blades.

 At 11:01 PM 5/15/2007, Eugene Zimmerman wrote:

> 

>

   Similarly, the close together the prop blades are (i.e. 3

 blade vs. 2 blade) the more interference.

                                  -Dana

captainron1(at)cox.net
Guest

Posted: Sun May 20, 2007 12:28 pm Post subject: FireFly prop & others

I think the point he is trying to make and legitimately so is that; if          a two blade prop was so efficient you would have a 2 blade fan          section. Obviously a multi fan is more efficient considering the space          allocated and the parameters in which it operates. Its an important          distinction to make. As someone else pointed out in a perfect world          many things would be different.              

         In an imperfect world you create perfection through adaptation for the          task you need to perform. One of those things is a multi blade prop. I          can see where theoretically a two blade is superior however in real          life it is almost never the case. In real life almost always a 3 blade          prop is superior performance wise to a two blade prop and a 4 blade          prop is most times superior to 3 blade prop. Its hard to win against a          theoretical argument, the only way to "win" is to do a real world          comparison when all the real factors that exist including bugs and          paint chipped off the leading edge come into play.              

         I will install a 4 blade prop on my M3X and then I will try a 2 blade          prop I will be surprised if I get better performance at *any* flight          regime with the 2 blader.              

         Ron              

         ========================

---- JetPilot <orcabonita(at)hotmail.com>          wrote:



=============

--> Kolb-List message posted by:          "JetPilot" <orcabonita(at)hotmail.com>

jim          wrote:

 	  Quote: 	
		  



 Then why is a high-bipass turbofan so          efficient? These are found on

 747-767 and are just a whole bunch          of ducted short propeller blades.



 -Dana


	




A          high bybpas turbofan is NOT efficient. If you look at a jet compared          to a prop plane, there is no comparison in in efficiency, the prop          wins every time. Where did you get the idea that a turbofan is so          efficient , by comparing it to a turbojet, which is even less          efficient [Laughing]



It is well known that a 2 blade prop is          more efficient than a 3 blade. The problem is that there is not always          room for a long 2 blade prop, or noise is more of an issue etc. etc.          But the 2 blade is more efficient.



If someone outclimbed          someone else with a 3 blade prop, making the assumption that it was          because of having a 3 bladed prop is just dumb. Ever think it could          have been variations in the airplane, pilot technique, or a hundred          other possible factors ???



Mike



--------

&quot;NO          FEAR&quot; - If you have no fear you did not go as fast as you could             

      [quote][b]

jindoguy(at)gmail.com
Guest

Posted: Sun May 20, 2007 1:15 pm Post subject: FireFly prop & others

Consider the original Supermarine Spitfire Mk 1, #5054, had a two blade prop. By the Mk IX it was running a four blade prop and by the Mk XIV, with the RR Griffon engine replacing the Merlin, it was running a five blade. The difference in speed between the Mk I and the Mk XIV was almost 100 MPH. The difference in HP was a bit over 800 between the two and the extra three blades were required to soak it up. 



Rick



On 5/20/07, Ron <captainron1(at)cox.net (captainron1(at)cox.net)> wrote:[quote]                                

         I think the point he is trying to make and legitimately so is that; if          a two blade prop was so efficient you would have a 2 blade fan          section. Obviously a multi fan is more efficient considering the space          allocated and the parameters in which it operates. Its an important          distinction to make. As someone else pointed out in a perfect world          many things would be different.              

         In an imperfect world you create perfection through adaptation for the          task you need to perform. One of those things is a multi blade prop. I          can see where theoretically a two blade is superior however in real          life it is almost never the case. In real life almost always a 3 blade          prop is superior performance wise to a two blade prop and a 4 blade          prop is most times superior to 3 blade prop. Its hard to win against a          theoretical argument, the only way to "win" is to do a real world          comparison when all the real factors that exist including bugs and          paint chipped off the leading edge come into play.              

         I will install a 4 blade prop on my M3X and then I will try a 2 blade          prop I will be surprised if I get better performance at *any* flight          regime with the 2 blader.              

         Ron              

         ========================

---- JetPilot <orcabonita(at)hotmail.com (orcabonita(at)hotmail.com)>          wrote:



=============

--> Kolb-List message posted by:          "JetPilot" <orcabonita(at)hotmail.com (orcabonita(at)hotmail.com)>

jim          wrote:

 	  Quote: 	
		  



 Then why is a high-bipass turbofan so          efficient? These are found on

 747-767 and are just a whole bunch          of ducted short propeller blades.



 -Dana


	




A          high bybpas turbofan is NOT efficient. If you look at a jet compared          to a prop plane, there is no comparison in in efficiency, the prop          wins every time. Where did you get the idea that a turbofan is so          efficient , by comparing it to a turbojet, which is even less          efficient [Laughing]



It is well known that a 2 blade prop is          more efficient than a 3 blade. The problem is that there is not always          room for a long 2 blade prop, or noise is more of an issue etc. etc.          But the 2 blade is more efficient.



If someone outclimbed          someone else with a 3 blade prop, making the assumption that it was          because of having a 3 bladed prop is just dumb. Ever think it could          have been variations in the airplane, pilot technique, or a hundred          other possible factors ???



Mike



--------

&quot;NO          FEAR&quot; - If you have no fear you did not go as fast as you could             

      [quote][b]  http://www.matronics.com/Navigator?Kolb-List http://forums.matronics.com 

when you live at the airport.  [quote][b]

possums(at)bellsouth.net
Guest

Posted: Sun May 20, 2007 2:39 pm Post subject: FireFly prop & others

At 04:27 PM 5/20/2007, you wrote:



 	  Quote: 	
		  I think the point he is trying to make and legitimately so is that; 

if a two blade prop was so efficient you would have a 2 blade fan 

section. Obviously a multi fan is more efficient considering the 

space allocated and the parameters in which it operates. Its an 

important distinction to make. As someone else pointed out in a 

perfect world many things would be different.



In an imperfect world you create perfection through adaptation for 

the task you need to perform. One of those things is a multi blade 

prop. I can see where theoretically a two blade is superior however 

in real life it is almost never the case. In real life almost always 

a 3 blade prop is superior performance wise to a two blade prop and 

a 4 blade prop is most times superior to 3 blade prop. Its hard to 

win against a theoretical argument, the only way to "win" is to do a 

real world comparison when all the real factors that exist including 

bugs and paint chipped off the leading edge come into play.



I will install a 4 blade prop on my M3X and then I will try a 2 

blade prop I will be surprised if I get better performance at *any* 

flight regime with the 2 blader.



Ron


	




We tried a 6 blade - double 3 blade - prop on one of ours that had enough

house power to turn it and it didn't do worth a crap.

flykolb(at)pa.net
Guest

Posted: Sun May 20, 2007 2:44 pm Post subject: FireFly prop & others

Hi Ron and Kolbers,  

Over the many years at TOK I experimented with many different 2 and 3 blade propellers on the FF, FS, TS, M2, M3, SS and Laser.  It is my recollection that a 2-blade would be faster than a 3-blade every time.  The only reason we would run a 3-blade was for their typically smoother operation.  I used the same aircraft for speed runs using a stopwatch to measure the speed over our 3,000 ft runway.  This was done in zero-to- minimal wind conditions – usually late evenings -  and I would average the run in both directions.  This gave very repeatable results.  This was my experience -  I’ll let others debate the theory.  

Dennis  

From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of Ron

 Sent: Sunday, May 20, 2007 4:28 PM

 To: kolb-list(at)matronics.com

 Subject: Re: Re: FireFly prop & others  

I think the point he is trying to make and legitimately so is that; if a two blade prop was so efficient you would have a 2 blade fan section. Obviously a multi fan is more efficient considering the space allocated and the parameters in which it operates. Its an important distinction to make. As someone else pointed out in a perfect world many things would be different.   

In an imperfect world you create perfection through adaptation for the task you need to perform. One of those things is a multi blade prop. I can see where theoretically a two blade is superior however in real life it is almost never the case. In real life almost always a 3 blade prop is superior performance wise to a two blade prop and a 4 blade prop is most times superior to 3 blade prop. Its hard to win against a theoretical argument, the only way to "win" is to do a real world comparison when all the real factors that exist including bugs and paint chipped off the leading edge come into play.   

I will install a 4 blade prop on my M3X and then I will try a 2 blade prop I will be surprised if I get better performance at *any* flight regime with the 2 blader.   

Ron   

========================

 ---- JetPilot <orcabonita(at)hotmail.com> wrote:

 =============

 --> Kolb-List message posted by: "JetPilot" <orcabonita(at)hotmail.com>

 jim wrote:

 >

 >

 > Then why is a high-bipass turbofan so efficient? These are found on

 > 747-767 and are just a whole bunch of ducted short propeller blades.

 >

 > -Dana

 A high bybpas turbofan is NOT efficient. If you look at a jet compared to a prop plane, there is no comparison in in efficiency, the prop wins every time. Where did you get the idea that a turbofan is so efficient , by comparing it to a turbojet, which is even less efficient [Laughing]

 It is well known that a 2 blade prop is more efficient than a 3 blade. The problem is that there is not always room for a long 2 blade prop, or noise is more of an issue etc. etc. But the 2 blade is more efficient.

 If someone outclimbed someone else with a 3 blade prop, making the assumption that it was because of having a 3 bladed prop is just dumb. Ever think it could have been variations in the airplane, pilot technique, or a hundred other possible factors ???

 Mike

 --------

 &quot;NO FEAR&quot; - If you have no fear you did not go as fast as you could   

   	  Quote: 	
		    http://www.matronics.com/Navigator?Kolb-List 	
0 	  Quote: 	

1 	  Quote: 	

2 	  Quote: 	

3 	  Quote: 	

4

        [quote][b]

jbhart(at)onlyinternet.ne
Guest

Posted: Sun May 20, 2007 4:56 pm Post subject: FireFly prop & others

From: "Dennis Souder" <flykolb(at)pa.net>

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Over the many years at TOK I experimented with many different 2 and 3 blade propellers on the FF, FS, TS, M2, M3, SS and Laser.  It is my recollection that a 2-blade would be faster than a 3-blade every time.  The only reason we would run a 3-blade was for their typically smoother operation.  I used the same aircraft for speed runs using a stopwatch to measure the speed over our 3,000 ft runway.  This was done in zero-to- minimal wind conditions  usually late evenings -  and I would average the run in both directions.  This gave very repeatable results.  This was my experience -  Ill let others debate the theory.
	


 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


	


Kolbers,

 

If you keep the same propeller diameter and switch from a two to three blades and set the engine to top out at the same rpm, the two blade will cruise faster due to greater pitch.  The three blade will climb better.



Jack B. Hart FF004

Winchester, IN

captainron1(at)cox.net
Guest

Posted: Sun May 20, 2007 5:18 pm Post subject: FireFly prop & others

Yes we will get to a point of diminishing returns, however with more          blades you will need to optimize the diameter of the blades (smaller)          etc.. The only drag increase that I can off hand think of is parasitic          drag etc... However its of minor significance and the multi blade          better radial efficiency during flight should more than compensate for          it.              

         Ron (Arizona)              

         ============================

---- possums <possums(at)bellsouth.net>          wrote:



=============

--> Kolb-List message posted by:          possums <possums(at)bellsouth.net>



At 04:27 PM 5/20/2007,          you wrote:



 	  Quote: 	
		  I think the point he is trying to make and          legitimately so is that;

if a two blade prop was so efficient you          would have a 2 blade fan

section. Obviously a multi fan is more          efficient considering the

space allocated and the parameters in          which it operates. Its an

important distinction to make. As          someone else pointed out in a

perfect world many things would be          different.



In an imperfect world you create perfection          through adaptation for

the task you need to perform. One of those          things is a multi blade

prop. I can see where theoretically a two          blade is superior however

in real life it is almost never the          case. In real life almost always

a 3 blade prop is superior          performance wise to a two blade prop and

a 4 blade prop is most          times superior to 3 blade prop. Its hard to

win against a          theoretical argument, the only way to "win" is to do a

real          world comparison when all the real factors that exist including

bugs          and paint chipped off the leading edge come into play.



I          will install a 4 blade prop on my M3X and then I will try a 2

blade          prop I will be surprised if I get better performance at *any*

flight          regime with the 2 blader.



Ron


	




We tried a 6          blade - double 3 blade - prop on one of ours that had enough

house             

      [quote][b]

d-m-hague(at)comcast.net
Guest

Posted: Sun May 20, 2007 7:14 pm Post subject: FireFly prop & others

At 05:15 PM 5/20/2007, Richard Girard wrote:

  	  Quote: 	
		  Consider the original Supermarine Spitfire Mk 1, #5054, had a two blade prop. By the Mk IX it was running a four blade prop and by the Mk XIV, with the RR Griffon engine replacing the Merlin, it was running a five blade. The difference in speed between the Mk I and the Mk XIV was almost 100 MPH. The difference in HP was a bit over 800 between the two and the extra three blades were required to soak it up. 	


 True, but consider the reason... it wasn't practical to make the landing gear long enough to put on a sufficiently large prop of less blades to absorb all the available power.  Even the early Spitfires had very limited prop ground clearance, so that pilots had to be very careful not to let the tail get too high while on the ground.



                                 -Dana

 

 --

 --

 Okay, who put a "stop payment" on my reality check?    [quote][b]

tnt1(at)rangebroadband.co
Guest

Posted: Tue May 22, 2007 6:56 pm Post subject: FireFly prop & others

Howard, What made you go with the 3.47 box? I went with I think 2.62 on an  e-box wwith a two blade taper -tip on a 503 DCDI. What is your rpm WOT straight  and level? What would I gain with 3.47 gears on my Firestar  II? Your  advice always appreciated.    Thanks Tim D.

 [quote]   ---

HShack(at)aol.com
Guest

Posted: Tue May 22, 2007 7:42 pm Post subject: FireFly prop & others

In a message dated 5/22/2007 10:57:13 PM Eastern Daylight Time, tnt1(at)rangebroadband.com writes:

  	  Quote: 	
		   Howard, What made you go with the 3.47 box? I went with I think 2.62 on an e-box wwith a two blade taper -tip on a 503 DCDI. What is your rpm WOT straight and level? What would I gain with 3.47 gears on my Firestar  II? Your advice always appreciated.    Thanks Tim D.

	


  

 When I bought my kit, I asked Dennis Souder what set-up he would recommend for best climb considering my weight [270 at the time].  The 3.47 box w/ Warp 3 blade, 68" taper tip is what he recommended.

  

 My WOT is 6500.  I don't know that you would gain anything by changing your setup;  my setup works for me, may not work for you.  Is your plane heavy?  What is your personal weight?  Are you seeking more climb?  Probably not worth the expense to change.

  

 I think most FSII's fly great no matter what the set-up.

  



 Howard Shackleford

FS II

SC



See what's free at AOL.com. 

  [quote][b]

DAquaNut(at)aol.com
Guest

Posted: Tue May 22, 2007 8:02 pm Post subject: FireFly prop & others

In a message dated 5/22/2007 10:43:13 PM Central Standard Time, HShack(at)aol.com writes: 

 

 

 	  Quote: 	
		  My WOT is 6500.  I don't know that you would gain anything by changing your setup;  my setup works for me, may not work for you.  Is your plane heavy?  What is your personal weight?  Are you seeking more climb?  Probably not worth the expense to change. 

  

I think most FSII's fly great no matter what the set-up. 

  

 

Howard Shackleford 

FS II 

SC 

 

 

           Ive not seen anything mentioned about economy during this lengthy prop discussion. Has anyone done a comparison on which prop gets the best distance or mileage. Seems  it is accepted that the 3 blade is smoother than the 2 blade, but which would be best if you were going for a distance record on a set amount of fuel? 	
 

                  

               Ed Diebel   FF # 62 

   

**************************************

 See what's free at http://www.aol.com.  [quote][b]

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