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3 Blade prop - 11/29/2012 6:33 PM   
acerc



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Status: offline 		I don't know if this is the right place to ask but here goes. I have been debating on whether or not to use a 3 blade prop on a plane. Ihave heard they are not as efficient as 2 blades. I know some of you big bird flyers can give me a good idea of whether I should or not. The plane is a 33% Pitts-s1s, it will be powered by a 55cc twin. Shooting for a 20lb finished weight.
What say you?


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RE: 3 Blade prop - 11/29/2012 6:46 PM   
pe reivers



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Status: offline 		If the total blade area is the same, they are more efficient than 2-blade props, according to NACA studies, and can have a higher disk loading. (more powerfor the same diameter) Exactly that is the caveat, and you need to go to smaller diameters, which lowers the power to thrust conversion efficiency somewhat. To be, or not to be, is the question. On a 55cc a two blade would be the best choice. On a 116 and upwards, the three blade would be.



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RE: 3 Blade prop - 11/29/2012 6:58 PM   
BarracudaHockey



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Status: offline 		3 blades are generally quieter too

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RE: 3 Blade prop - 11/29/2012 7:05 PM   
ROGER RUSSELL



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Status: offline 		Since the thread is labeled 3 Blade Prop I figure this is OK to ask this question and not hi jack the thread!

What would be a good 3 blade on a MOKI 150 on a 100" Ziroli Helcat?

Thanks

Roger


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RE: 3 Blade prop - 11/29/2012 7:19 PM   
acerc



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Status: offline 		reivers, or anyone else, let's say the given two blade would be a 23x8 what would be the appropriate 3 blade and how much efficiency would be lost? Approximate of course.

< Message edited by acerc -- 11/29/2012 7:42 PM >


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RE: 3 Blade prop - 11/30/2012 3:03 AM   
speedracerntrixie


 

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quote:

ORIGINAL: pe reivers

If the total blade area is the same, they are more efficient than 2-blade props, according to NACA studies, and can have a higher disk loading. (more powerfor the same diameter) Exactly that is the caveat, and you need to go to smaller diameters, which lowers the power to thrust conversion efficiency somewhat. To be, or not to be, is the question. On a 55cc a two blade would be the best choice. On a 116 and upwards, the three blade would be.





I used to fly a 150cc powered Extra in IMAC. I ended up using a 3 blade prop to help me keep the flying speed consistant. What I found was the airplane was quieter and had better downline breaking. I did loose about 15% vertical pull but the airplane had plenty to spare. For the 55 I would look into these. Size 20X10



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RE: 3 Blade prop - 11/30/2012 3:06 AM   
acerc



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Status: offline 		Thank's speedracer,  that is exactly what I was looking for. Experienced knowledge. The 20x10 is what I have ordered. I figure I'll start with the 2 blade and then when comfortable with the aircraft go to the 3 blade. I'm useing Beila prop's, how you like them? Or the better question, do you like them?


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RE: 3 Blade prop - 11/30/2012 10:16 AM   
pe reivers



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quote:

ORIGINAL: acerc

reivers, or anyone else, let's say the given two blade would be a 23x8 what would be the appropriate 3 blade and how much efficiency would be lost? Approximate of course.


Use my prop power calculator http://mvvs.nl/prop-power-calculator.xls



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