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  #1  
Old 10-28-2020, 08:48 AM
Fenderbean Fenderbean is offline
 
Join Date: Jun 2018
Location: Huntsville AL
Posts: 57
Default Two to Four?

Hi guys on my path to enlightenment this popped in my brain today. I do have some idea bout props like this from an RC stand point and wondering if applies to real world.

Is it true to say less blades equals more efficient?
More blades give a braking effect on spool down?
More blades less the noise?
More blades more thrust with less RPM?

Besides the sexy factor what would be the bonus of a three/four blade over a two in something like the RV-10/IO540 combo

Any thoughts on Carbon vs aluminum playing in here or Cost?
Links to any threads is always help full, thanks up front!
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  #2  
Old 10-28-2020, 09:32 AM
rocketman1988 rocketman1988 is online now
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 2,225
Default prop

Three blade climb will be a bit better but cruise will like be a few knots slower than a two blade.

The -10 is nose heavy already; putting an aluminum three blade up front would make it worse.

Three blade makes removing the cowl more challenging...HOWEVER, if you split the bottom cowl down the middle, cowl removal becomes a non issue. This mod is probably one of the best ones that I did. It is straight forward and did not take very long to complete.

...and yes, the three blade looks really nice when sitting on the ground with the engine off. Once you start it, it makes no difference as you can't see the blades.
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Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
EFII System 32 - Done
297 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful
Wiring...

Dues+ Paid 2019,...Thanks DR+
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  #3  
Old 10-28-2020, 10:47 AM
Fenderbean Fenderbean is offline
 
Join Date: Jun 2018
Location: Huntsville AL
Posts: 57
Default

Quote:
Originally Posted by rocketman1988 View Post
Three blade climb will be a bit better but cruise will like be a few knots slower than a two blade.

The -10 is nose heavy already; putting an aluminum three blade up front would make it worse.

Three blade makes removing the cowl more challenging...HOWEVER, if you split the bottom cowl down the middle, cowl removal becomes a non issue. This mod is probably one of the best ones that I did. It is straight forward and did not take very long to complete.

...and yes, the three blade looks really nice when sitting on the ground with the engine off. Once you start it, it makes no difference as you can't see the blades.
Are carbon fibers lighter or heavier typically? I'm planning on building a plane for speed, I want to travel cross country and get there as fast and with least amount of fuel used I can. You are correct the look doesn't play into it for me personally. I will keep the split cowl idea in mind, im planning on the show planes cowl and intake system.
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  #4  
Old 10-28-2020, 05:03 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,891
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Quote:
Originally Posted by Fenderbean View Post
I want to travel cross country and get there as fast and with least amount of fuel used I can. .
You can get one of these, but not both at the same time. -
Sometimes I can get to a destination sooner by going slower a lower power setting almost always improves the miles/gal if the lower power setting lets me skip a fuel stop.
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  #5  
Old 10-28-2020, 05:08 PM
airguy's Avatar
airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,215
Default

Quote:
Originally Posted by BobTurner View Post
You can get one of these, but not both at the same time. -
Sometimes I can get to a destination sooner by going slower — a lower power setting almost always improves the miles/gal — if the lower power setting lets me skip a fuel stop.
You beat me to it... there is a sliding scale with "fastest" on one end and "least fuel" on the other. I'm a big fan of climbing up high and cruising there without stopping.
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #6  
Old 10-29-2020, 04:40 PM
Fenderbean Fenderbean is offline
 
Join Date: Jun 2018
Location: Huntsville AL
Posts: 57
Default

LOL yeah I understand, I guess I made that sound wrong. Completely understand im not going to be firewalled on throttle thinking im going to be save gas. I really just looking for the best combination in a prop that gives overall speed at the lower power settings like you do when its trimmed out throttled back, leaned and cruising. Something tells me this maybe like a lot of things here, no best solution.
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  #7  
Old 10-29-2020, 06:17 PM
airguy's Avatar
airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,215
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Wide open throttle does not mean low efficiency - just use it to climb up high in thin air and get where you are going. I always cruise wide open throttle, lean of peak with a 2-blade constant speed prop and get great efficiency.
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Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #8  
Old 10-30-2020, 01:40 PM
Fenderbean Fenderbean is offline
 
Join Date: Jun 2018
Location: Huntsville AL
Posts: 57
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**** 6.3 man with that I would be willing to add a couple gph for more speed. I didnt know you could get that kind of fuel burn on a 540
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  #9  
Old 10-30-2020, 01:58 PM
airguy's Avatar
airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,215
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Quote:
Originally Posted by Fenderbean View Post
**** 6.3 man with that I would be willing to add a couple gph for more speed. I didnt know you could get that kind of fuel burn on a 540
Heh... I wish... that's an IO360 in my RV9A, and that pic shows me cruising 20 knots below Vne and getting 25 miles per gallon doing it. The point I was trying to make is to use altitude to limit your manifold pressure, not the throttle plate, and you'll be more efficient everytime while still keeping good speed.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #10  
Old 11-02-2020, 09:49 PM
Fenderbean Fenderbean is offline
 
Join Date: Jun 2018
Location: Huntsville AL
Posts: 57
Default

Quote:
Originally Posted by airguy View Post
Heh... I wish... that's an IO360 in my RV9A, and that pic shows me cruising 20 knots below Vne and getting 25 miles per gallon doing it. The point I was trying to make is to use altitude to limit your manifold pressure, not the throttle plate, and you'll be more efficient everytime while still keeping good speed.
DOH! lol almost made me give up on my search a for diesel alternative there LOL
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