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08-18-2011, 10:12 AM
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Join Date: Oct 2005
Posts: 118
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Getting more Knots
I have had my RV-10 flying for a year now (150 hours!) and will soon do my condition inspection. I don't have the wheelpants finished/on, but I am reliably seeing only 138-145 Kts TAS at cruise (8500 feet, full throttle, 2400RPM). My plane is a little different than most - I have a carbureted O-540 with a traditional prop (same hub with two F8487A-3R 81" blades). Hartzell engineers assured me that there is only a 6% efficiency decrease on this prop as compared to the vans prop, but I am thinking that the bite on the blade was simply designed for 135Kts cruise, which is what its original installations (Cherokee 235, Maule M7) liked to do. Changing the pitch stops probably won't help, though a prop shop said they'd do that.
The engine burns 11-12gph reliably averaging all phases of flight.
I'm looking for ideas on how to get more speed (fuel efficiency) from the existing system. I've been told that the wheelpants can help up to 9-10Kts by reducing drag, but what other suggestions to you builders have for checking, debugging, and enhancing the plane's performance? I'd sure like to find the extra 30Kts that even the Continental 210HP factory plane has...
Doug.
__________________
Doug Nebert - RV-10, #40546 (SB), started 2/2006, low compression O540 with older CS prop, 375+ hours on Hobbs. Flying since August 2010. Based KONP, Newport, OR
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08-18-2011, 10:17 AM
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Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,156
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Quote:
Originally Posted by ddnebert
I have had my RV-10 flying for a year now (150 hours!) and will soon do my condition inspection. I don't have the wheelpants finished/on, but I am reliably seeing only 138-145 Kts TAS at cruise (8500 feet, full throttle, 2400RPM). My plane is a little different than most - I have a carbureted O-540 with a traditional prop (same hub with two F8487A-3R 81" blades). Hartzell engineers assured me that there is only a 6% efficiency decrease on this prop as compared to the vans prop, but I am thinking that the bite on the blade was simply designed for 135Kts cruise, which is what its original installations (Cherokee 235, Maule M7) liked to do. Changing the pitch stops probably won't help, though a prop shop said they'd do that.
The engine burns 11-12gph reliably averaging all phases of flight.
I'm looking for ideas on how to get more speed (fuel efficiency) from the existing system. I've been told that the wheelpants can help up to 9-10Kts by reducing drag, but what other suggestions to you builders have for checking, debugging, and enhancing the plane's performance? I'd sure like to find the extra 30Kts that even the Continental 210HP factory plane has...
Doug.
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Start with all pants and fairings. I think you'll be shocked.
__________________
Scott Card
CQ Headset by Card Machine Works
CMW E-Lift
RV-9A N4822C flying 2200+hrs. / Cedar Park, TX
RV8 Building - fuselage / showplanes canopy (Done!)
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08-18-2011, 10:57 AM
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Join Date: Nov 2005
Location: KRTS
Posts: 1,798
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Quote:
Originally Posted by scard
Start with all pants and fairings. I think you'll be shocked.
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Watch the video at the link below. You're going to be so po'd at yourself for not fairing up the gear sooner.
http://www.vansairforce.com/communit...ght=drag+video
__________________
Next?, TBD
IAR-823, SOLD
RV-8, SOLD
RV-7, SOLD
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08-18-2011, 12:44 PM
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Join Date: Jun 2011
Location: Nephi, UT
Posts: 79
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I had no Idea!
That is an awesome video. I had no idea that the difference would be that dramatic.
__________________
Mike Price
CFII/Multi Commercial
I'm gonna build me an RV one day soon
"The older I get -- the more I realize that sense is not common."
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08-18-2011, 12:48 PM
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Join Date: Jan 2005
Location: Bellevue, NE
Posts: 524
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I think you'll find on a -10 that the gear leg fairings and wheel fairings combined add 15+ knots. Sounds shocking but it's been proven multiple times. As I recall when Van's switched from the straight blade to the blended airfoil prop for the -10 it was good for about 5 knots.
Another thing to confirm is flap and aileron rigging. If not quite right it will cost a few knots as well. The reflex position is good for about 3-4 knots over 0 degree position.
Bob
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08-18-2011, 12:56 PM
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Join Date: Nov 2005
Location: KRTS
Posts: 1,798
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Quote:
Originally Posted by mkjprice
That is an awesome video. I had no idea that the difference would be that dramatic.
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Think about the low pressure area created on the back side of the gear leg... over the total length of the gear, multiplied by two or three gear legs.
That's a significant amount of surface area! 
__________________
Next?, TBD
IAR-823, SOLD
RV-8, SOLD
RV-7, SOLD
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08-18-2011, 05:14 PM
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Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,271
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Fly a GPS box and verify your static is truly the correct static pressure.
I had installed those lovely machined static ports you can get from Spruce, turned out even with the fairings and spats on I had the slowest RV10 in the world, and then I flew a GPS box and I found I was reading IAS -9knots.
I tried gluing a rivet head over the face of the static port, like the one that Vans supplies. Now I had the fastest!  IAS was now reading +6knots.
After some mucking around with different things the picture below was what we ended up with almost by accident.
Get your spats and fairings done and do the GPS TAS test. Good luck!
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08-18-2011, 06:04 PM
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Join Date: Oct 2005
Posts: 118
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Reflex speed
Quote:
Originally Posted by bcondrey
I think you'll find on a -10 that the gear leg fairings and wheel fairings combined add 15+ knots. Sounds shocking but it's been proven multiple times. As I recall when Van's switched from the straight blade to the blended airfoil prop for the -10 it was good for about 5 knots.
Another thing to confirm is flap and aileron rigging. If not quite right it will cost a few knots as well. The reflex position is good for about 3-4 knots over 0 degree position.
Bob
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Are you saying that 'reflex' will gain 3-4 kts? Interesting. Hartzell's assessment (by the engineering calculations) was about 3Kts difference.
OK, so I'll get those wheel pants done!
Doug.
__________________
Doug Nebert - RV-10, #40546 (SB), started 2/2006, low compression O540 with older CS prop, 375+ hours on Hobbs. Flying since August 2010. Based KONP, Newport, OR
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08-18-2011, 06:09 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
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Yes, the proper setting of full up flaps "reflex" and ailerons will help the speed.
Dont know what Hartzell has to do with flap rigging 
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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08-18-2011, 06:23 PM
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Join Date: Aug 2006
Location: Prairieville, LA
Posts: 118
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don't feel bad
You are far from the slowest- 10. With about 40 hours on mine and all fairings installed 23 MP and 2400 RPM at 4,000 PA I am unable to get above 147 kts TAS.
Eric Kallio
__________________
Eric Kallio
RV-10
N518RV... Flying
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