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2-blade props

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kheindl(at)msn.com
Guest

Posted: Thu Apr 15, 2010 4:43 pm Post subject: 2-blade props

Graham,

  

 I am shure you are correct, but in my experience I have not noticed more vibration, once the carbs ar well balanced.

 Advantages are  -  less weight, less money, less maintenance, easier to balance, easier to ship in one piece, better visibility when feathered on MG, less drag, and bottom cowling comes off easily, without having to remove tailpipe etc.

 Why do most GA aircraft have 2-blade props  ?

  

 Karl

  

 



 

 



  

  Date: Thu, 15 Apr 2010 22:54:04 +0000

From: grahamsingleton(at)btinternet.com

Subject: Re: Weight reduction - Brake Discs

To: europa-list(at)matronics.com



  .ExternalClass DIV {;}    Frans

in theory only is a 2 blade more efficient, you get more vibration that can't be balanced out. More vibration gives more disruption to laminar flow so more drag.

This is also why 2 blade windmills are more likely to throw blades. 2 blades don't cope with non axial air flow, multi blades do

Graham



 

   From: Frans Veldman <frans(at)privatepilots.nl>

To: europa-list(at)matronics.com

Sent: Thursday, 15 April, 2010 23:14:32

Subject: Re: Weight reduction - Brake Discs



Get a two blade prop. One blade of a CS prop is 4Kg's worth. Apart from

that, it cruises more efficiently, cutting down on fuel (read: weight).



Frans



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[b]

grahamsingleton(at)btinte
Guest

Posted: Thu Apr 15, 2010 11:50 pm Post subject: 2-blade props

Karl

Cost I suspect. Most things are a compromise



Graham,

  

 Why do most GA aircraft have 2-blade props  ?

  

 Karl

  

 



 

 



  

  Date: Thu, 15 Apr 2010 22:54:04 +0000

From: grahamsingleton(at)btinternet.com

Subject: Re: Weight reduction - Brake Discs

To: europa-list(at)matronics.com



  .ExternalClass DIV {}    Frans

in theory only is a 2 blade more efficient, you get more vibration that can't be balanced out. More vibration gives more disruption to laminar flow so more drag.

This is also why 2 blade windmills are more likely to throw blades. 2 blades don't cope with non axial air flow, multi blades do

Graham



 

   From: Frans Veldman <frans(at)privatepilots.nl>

To: europa-list(at)matronics.com

Sent: Thursday, 15 April, 2010 23:14:32

Subject: Re: Weight reduction - Brake Discs



Get a two blade prop. One blade of a CS prop is 4Kg's worth. Apart from

that, it cruises more efficiently, cutting down on fuel (read: weight).



Frans



[quote]


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rampil

Joined: 04 May 2007
Posts: 870

Posted: Fri Apr 16, 2010 3:26 am Post subject: Re: 2-blade props

....most commercial GA aircraft have two blade props...

Actually as can be seen convincingly in a stroll about Sun and Fun

today, any new, high performance aircraft , i.e., Cirrus, Cessna,

Mooney, Lancair, etc., etc., has 3 blades.



Just because most aircraft designed 30 years ago or earlier had

two blades doesn't mean that it was best for aerodynamics, just

best for the marketplace at the time.



In the end I think Graham is correct, it was just about money.



Reporting from under the old Oak tree with the Europa Team!

Regards,



Ira

_________________
Ira N224XS

Gilles.Thesee(at)ac-greno
Guest

Posted: Fri Apr 16, 2010 3:42 am Post subject: 2-blade props

Ira and all,

 	  Quote: 	
		   Actually as can be seen convincingly in a stroll about Sun and Fun

 today, any new, high performance aircraft , i.e., Cirrus, Cessna,

 Mooney, Lancair, etc., etc., has 3 blades.

   

Apart from what Karl said, the number of blades has something to do with 
	


the prop *solidity* necessary to transfer power. The aircraft you cite 

have powerful engines, hence the tendancy to increase the number of blades.

 	  Quote: 	
		   Just because most aircraft designed 30 years ago or earlier had

 two blades doesn't mean that it was best for aerodynamics,

   

Our airplane and two-blade prop were designed just a few years ago, and 
	


they are quite efficient aerdynamically.

Remember that more blades means more drag (I also owned an unlimited 

aerobatics airplane with a 3 blade, and we performed comparative tests 

with a 2 blade).

In some cases, 3 blades are needed with low power (100 hp) in order to 

reduce prop diameter for clearance reasons.



 	  Quote: 	
		   In the end I think Graham is correct, it was just about money.

   

Weight, parts count and efficiency also play a role.
	




Best regards,

-- 

Gilles

http://contrails.free.fr

kheindl(at)msn.com
Guest

Posted: Fri Apr 16, 2010 5:08 am Post subject: 2-blade props

Graham,

  

 Yes, every choice has its pros and cons. If it hadn't been for my MG project, I would have been quite happy to carry on with the Warp Drive. It performed well, and you can't beat the exterior carbon finish, as opposed to painted or varnished propellers. 

 But I also had to have feathering, and the Airmaster hub had become very expensive. I am not really wild about automatic pitch control; I would prefer just manual, with an accurate display in percent or degrees of pitch. I don't think there is such an animal.

  

 Karl

 



  

  Date: Fri, 16 Apr 2010 07:32:26 +0000

From: grahamsingleton(at)btinternet.com

Subject: Re: 2-blade props

To: europa-list(at)matronics.com



  .ExternalClass DIV {;}    Karl

Cost I suspect. Most things are a compromise



 Graham,

 

Why do most GA aircraft have 2-blade props  ?

 

Karl

 

 

 



  

  Date: Thu, 15 Apr 2010 22:54:04 +0000

From: grahamsingleton(at)btinternet.com

Subject: Re: Weight reduction - Brake Discs

To: europa-list(at)matronics.com



  .ExternalClass DIV {;}    Frans

in theory only is a 2 blade more efficient, you get more vibration that can't be balanced out. More vibration gives more disruption to laminar flow so more drag.

This is also why 2 blade windmills are more likely to throw blades. 2 blades don't cope with non axial air flow, multi blades do

Graham



 

   From: Frans Veldman <frans(at)privatepilots.nl>

To: europa-list(at)matronics.com

Sent: Thursday, 15 April, 2010 23:14:32

Subject: Re: Weight reduction - Brake Discs



Get a two blade prop. One blade of a CS prop is 4Kg's worth. Apart from

that, it cruises more efficiently, cutting down on fuel (read: weight).



Frans



[quote]



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ronics.com
	


ww.matronics.com/contribution



http://www.matronics.com/con================







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ronics.com
	


ww.matronics.com/contribution



[b]

frans(at)privatepilots.nl
Guest

Posted: Fri Apr 16, 2010 7:00 am Post subject: 2-blade props

On 04/16/2010 01:26 PM, rampil wrote:

 	  Quote: 	
		   ....most commercial GA aircraft have two blade props...


	


 	  Quote: 	
		   Actually as can be seen convincingly in a stroll about Sun and Fun

 today, any new, high performance aircraft , i.e., Cirrus, Cessna,

 Mooney, Lancair, etc., etc., has 3 blades.


	


It has a lot to do with sound. A 3-blader produces less sound.

Furthermore it has less vibrations, and to some folks looks sexier.



Performance is another subject.



A 2-blade prop IS more efficient. The tips of the prop slice through the

air with almost the speed of sound, if you have two tips instead of

three, you reduce drag quite a lot.

If is the same question versus a two wing airplane or a bi-plane. A

bi-plane has more drag because it has more frontal wing surface. More

wings is not more efficient, just like more propeller blades is not more

efficient.



My propeller still converts the same amount of engine power to thrust,

but it has less frontal surface slicing through the air. Once I' flying,

I will be happy to share performance data.

And no, no first flight today.  The whole airspace has been shut-down

because of the volcanic ash.



 	  Quote: 	
		   Just because most aircraft designed 30 years ago or earlier had

 two blades doesn't mean that it was best for aerodynamics, just

 best for the marketplace at the time.


	


Well, then this must have been the reason the bi- and three-plane

airplanes vanished from the market as well? Just because two wings was

cheaper?



Frans

frans(at)privatepilots.nl
Guest

Posted: Fri Apr 16, 2010 7:00 am Post subject: 2-blade props

On 04/16/2010 01:41 PM, Gilles Thesee wrote:



 	  Quote: 	
		   Apart from what Karl said, the number of blades has something to do with

 the prop *solidity* necessary to transfer power. The aircraft you cite

 have powerful engines, hence the tendancy to increase the number of blades.


	


Right. If you increase the amount of power, at some point you have to

increase the diameter of the prop. If you can't do this (for clearance

reasons), you will have to revert to adding some more blades. More

blades is a compromise.



 	  Quote: 	
		   Our airplane and two-blade prop were designed just a few years ago, and

 they are quite efficient aerdynamically.


	


I can't think of ANY reason why more blades would be more efficient. I

can however think of reasons why less blades is more efficient.



Frans

rampil

Joined: 04 May 2007
Posts: 870

Posted: Fri Apr 16, 2010 11:36 am Post subject: Re: 2-blade props

Actually 2 blades being longer radii get less efficient as the length

blade in the transonic or faster regime grows. More blades keeps the tips

out of the transonic regime by keeping the radius down.

Of course we will discuss this in detail at the "Engineering" meeting

this evening for the Europa group at SnF



Cheers,



Ira

_________________
Ira N224XS

kheindl(at)msn.com
Guest

Posted: Fri Apr 16, 2010 4:26 pm Post subject: 2-blade props

 	  Quote: 	
		   

Frans wrote :
	


 	  Quote: 	
		   

 It has a lot to do with sound. A 3-blader produces less sound.

 Furthermore it has less vibrations, and to some folks looks sexier.


	




 



I am not sure about the sound difference. My 2-blader makes a very attractive low-frequency sound. To me it appears quieter than the Warp Drive. You have the same prop, so maybe you can sometime compare it to another Europa

raimo.toivio(at)rwm.fi
Guest

Posted: Sat Apr 17, 2010 10:45 am Post subject: 2-blade props

Frans,



you are absolutely right: 



More

 	  Quote: 	
		   blades is a compromise.


	


Just one is best = most efficient. 



They (Germans) have done that, with a counterbalance of course.

More blades compromise an efficiensy because of ground clearance, noise, tip speed, how it look and so,.



Raimo OH-XRT



---

rparigoris

Joined: 24 Nov 2009
Posts: 805

Posted: Sat Apr 17, 2010 11:54 am Post subject: 2-blade props

Hi Raimo"More blades is a compromise. Just one is best = most efficient.  They (Germans) have done that, with a counterbalance of course."I made a 1 bladed prop for a hot Cox 020 model motor. Worked for hours and hours trying to get it to be reasonably balanced with a die grinder spinning it up.  Not too much joy when approaching the 20K plus RPMs the engine is capaible of. Less RPMs not too bad, but I think the differential thrust caused harmonics that I was unableto get rid of.Ron Parigoris   [quote][b]

grahamsingleton(at)btinte
Guest

Posted: Sun Apr 18, 2010 3:40 am Post subject: 2-blade props

From: Raimo Toivio <raimo.toivio(at)rwm.fi>

To: europa-list(at)matronics.com

Sent: Saturday, 17 April, 2010 19:28:44

Subject: Re: Re: 2-blade props

--> Europa-List message posted by: "Raimo Toivio" <raimo.toivio(at)rwm.fi (raimo.toivio(at)rwm.fi)>

Frans,

you are absolutely right: 

More blades is  a compromise.

Just one is best = most efficient. 

Raimo OH-XRT

Not true Raimo, it is impossible to balance out the assymetric thrust. Vibration will be awful, so no laminar flow.

Graham

  [quote][b]

Fergus Kyle

Joined: 03 Jun 2007
Posts: 291
Location: Burlington ON Canada

Posted: Sun Apr 18, 2010 9:10 am Post subject: 2-blade props

I think the number of blades in our types of machines is mainly ethereal because the power range is so small.  

The Spit began with 700horse had two wood blades, the -5 had 3, the -6 had 4 and eventually a copy came out with 10 (two contra-rotating 5’s) – al to accommodate larger more powerful engines. I think later models had 3 times the prototype’s poop.  

        That’s why I opted for 3 – I liked the look.  

Ferg  

     [quote][b]

raimo.toivio(at)rwm.fi
Guest

Posted: Mon Apr 19, 2010 6:24 am Post subject: 2-blade props

Not true Raimo, it is impossible to balance out the assymetric thrust.  Vibration will be awful, so no laminar flow.

Graham

  

 Well Graham - Germans have done many "impossible" things  during centuries...

 I have seen a film about this construction (but maybe it  was shit who knows!).

 Please remember, they built also the first ever diesel  aircraft (Junkers Jumo?) during -30s.

 That should have been also "impossible"...

  

 Raimo

  

  

  

 

 

 [quote] 	  Quote: 	
		  



href="http://www.matronics.com/Navigator?Europa-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com

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[b]

grahamsingleton(at)btinte
Guest

Posted: Mon Apr 19, 2010 2:27 pm Post subject: 2-blade props

Think about the one blade for a moment. It produces thrust one side of the airplane only, left, top, right then bottom. And that doesn't include the asymmetric effect of angle of attack.The airframe will oscillate in a corkscrew fashion, what a horrible prospect  I can almost feel my teeth rattling at the thought of it!

2 stroke diesel? Now that is a good idea, most efficient form of piston engine.

Graham

From: Raimo Toivio <raimo.toivio(at)rwm.fi>

To: europa-list(at)matronics.com

Sent: Monday, 19 April, 2010 15:23:55

Subject: Re: Re: 2-blade props

ï»¿    DIV { MARGIN:0px;}    

Not true Raimo, it is impossible to balance out the assymetric thrust.  Vibration will be awful, so no laminar flow.

Graham

 Well Graham - Germans have done many "impossible" things  during centuries...

 I have seen a film about this construction (but maybe it  was shit who knows!).

 Please remember, they built also the first ever diesel  aircraft (Junkers Jumo?) during -30s.

 That should have been also "impossible"...

 Raimo

  	  Quote: 	
		   	  Quote: 	

href="http://www.matronics.com/Navigator?Europa-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/c

href="http://www.matronics.com/Navigator?Europa-List">http://www.matroniclow" target="_blank" href="http://forums.matronics.com">http://forums.m=   --> 	

  [quote][b]

peterz(at)zutrasoft.com
Guest

Posted: Mon Apr 19, 2010 3:35 pm Post subject: 2-blade props

"2 stroke diesel? Now that is a good idea, most efficient form of piston engine." 



reborn as the Gemini - Oh how I hope it makes a comeback from the 'new engine development' graveyard.

 



Cheers,

 Pete

A239

geminiEngine.JPG

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kheindl(at)msn.com
Guest

Posted: Mon Apr 19, 2010 4:21 pm Post subject: 2-blade props

  

Just to throw another spanner in the works: what about steam engines ? The Besseler brothers were flying around in one in California in the 30's. It performed very well, engine is almost silent, and performance does not degrade with altitude. The steam kettle would be part of the fuselage.  

  

 Karl

 



  

  Date: Mon, 19 Apr 2010 22:23:34 +0000

From: grahamsingleton(at)btinternet.com

Subject: Re: Europa-List: Re: 2-blade props

To: europa-list(at)matronics.com



  .ExternalClass DIV {;}   Think about the one blade for a moment. It produces thrust one side of the airplane only, left, top, right then bottom. And that doesn't include the asymmetric effect of angle of attack.The airframe will oscillate in a corkscrew fashion, what a horrible prospect  I can almost feel my teeth rattling at the thought of it!

 2 stroke diesel? Now that is a good idea, most efficient form of piston engine.

Graham



 

   From: Raimo Toivio <raimo.toivio(at)rwm.fi>

To: europa-list(at)matronics.com

Sent: Monday, 19 April, 2010 15:23:55

Subject: Re: Europa-List: Re: 2-blade props



ï»¿   .ExternalClass DIV {;}   

Not true Raimo, it is impossible to balance out the assymetric thrust. Vibration will be awful, so no laminar flow.

Graham

  

 Well Graham - Germans have done many "impossible" things during centuries...

 I have seen a film about this construction (but maybe it was shit who knows!).

 Please remember, they built also the first ever diesel aircraft (Junkers Jumo?) during -30s.

 That should have been also "impossible"...

  

 Raimo

  

  

  

 

 

 [quote] 	  Quote: 	
		  



href="[url=>http://www.matronhref=]http://forums.matronics.com'>http://www.matronics.com/Navigator?Europa-List">http://www.matronhref="http://forums.matronics.com">http://forums.matronics.com[/url]

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[b]

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fklein(at)orcasonline.com
Guest

Posted: Mon Apr 19, 2010 4:34 pm Post subject: 2-blade props

Paul Lipps had this to say about single blade props:

 	  Quote: 	
		  

Single-Blade Myth

One of the myths that has been propagated in the aviation community, to the point that it’s almost become gospel, is that the most efficient prop is a single-blade and that all props with higher numbers of blades fall further and further short of this paragon. Did you ever consider that a single-blade prop, developing thrust on only one side of the plane as it revolves, would cause the engine to cone violently in its mounts as it is twisted by the prop?

Airbus Military’s latest turboprop transport, the A400M, has eight-blade props! The Boeing MD-900 helicopter has a five-blade rotor. A popular regional turboprop airliner has a five-blade prop. Hasn’t anybody filled these aircraft manufacturers in on the errors of their ways? In a past issue of a popular aviation magazine, the author of an article on props uttered the same fallacy. He maintained that multiple blades interfere with each other.

When I pointed out to him that at 200 mph and 2800 rpm the blades on my three-blade prop follow three distinct helical paths through the air, and each blade is 25 inches ahead of the previous blade at the same point of rotation, he rather lamely explained that in static conditions interference occurs. Static? Who uses static thrust? Airplanes are meant to fly, not pull tree stumps! 	


	http://www.eaa.org/experimenter/articles/2009-02_elippse.asp

Fred



On Apr 19, 2010, at 3:23 PM, GRAHAM SINGLETON wrote:

 	  Quote: 	
		  Think about the one blade for a moment. It produces thrust one side of the airplane only, left, top, right then bottom. And that doesn't include the asymmetric effect of angle of attack.The airframe will oscillate in a corkscrew fashion, what a horrible prospect  I can almost feel my teeth rattling at the thought of it!



From: Raimo Toivio <raimo.toivio(at)rwm.fi (raimo.toivio(at)rwm.fi)>



Well Graham - Germans have done many "impossible" things during centuries...





	






 [quote][b]

jrgowing(at)bigpond.net.a
Guest

Posted: Mon Apr 19, 2010 5:09 pm Post subject: 2-blade props

Good one Graham!

 JR 327

 do not archive

 [quote]   ---

raimo.toivio(at)rwm.fi
Guest

Posted: Tue Apr 20, 2010 7:07 am Post subject: 2-blade props

OK Graham,

  

 I got it and lift my hands. I feel I am a poor victim of  "One Blade Awesome Myth Aspect (OBAMA)".

  

 Raimo 

  



  From: GRAHAM SINGLETON (grahamsingleton(at)btinternet.com) 

 Sent: Tuesday, April 20, 2010 1:23 AM

 To: europa-list(at)matronics.com (europa-list(at)matronics.com) 

 Subject: Re: Re: 2-blade props

 



 Think  about the one blade for a moment. It produces thrust one side of the airplane  only, left, top, right then bottom. And that doesn't include the asymmetric  effect of angle of attack.The airframe will oscillate in a corkscrew fashion,  what a horrible prospect  I can almost feel my teeth  rattling at the thought of it!

 2 stroke diesel? Now that is a good idea, most efficient form of piston  engine.

Graham



 

   From: Raimo Toivio  <raimo.toivio(at)rwm.fi>

To:  europa-list(at)matronics.com

Sent:  Monday, 19 April, 2010 15:23:55

Subject: Re: Re: 2-blade  props



ï»¿  DIV { MARGIN:0px;}   

Not true Raimo, it is impossible to balance out the assymetric thrust.  Vibration will be awful, so no laminar flow.

Graham

  

 Well Graham - Germans have done many "impossible" things  during centuries...

 I have seen a film about this construction (but maybe it  was shit who knows!).

 Please remember, they built also the first ever diesel  aircraft (Junkers Jumo?) during -30s.

 That should have been also "impossible"...

  

 Raimo

  

  

  

 

 

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