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  #1  
Old 08-18-2011, 10:12 AM
ddnebert ddnebert is offline
 
Join Date: Oct 2005
Posts: 118
Default 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.
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  #2  
Old 08-18-2011, 10:17 AM
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scard scard is offline
 
Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,156
Default

Quote:
Originally Posted by ddnebert View Post
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.
Start with all pants and fairings. I think you'll be shocked.
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  #3  
Old 08-18-2011, 10:57 AM
Sig600 Sig600 is offline
 
Join Date: Nov 2005
Location: KRTS
Posts: 1,798
Default

Quote:
Originally Posted by scard View Post
Start with all pants and fairings. I think you'll be shocked.

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
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  #4  
Old 08-18-2011, 12:44 PM
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mkjprice mkjprice is offline
 
Join Date: Jun 2011
Location: Nephi, UT
Posts: 79
Default I had no Idea!

That is an awesome video. I had no idea that the difference would be that dramatic.
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  #5  
Old 08-18-2011, 12:48 PM
bcondrey bcondrey is offline
 
Join Date: Jan 2005
Location: Bellevue, NE
Posts: 524
Default

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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  #6  
Old 08-18-2011, 12:56 PM
Sig600 Sig600 is offline
 
Join Date: Nov 2005
Location: KRTS
Posts: 1,798
Default

Quote:
Originally Posted by mkjprice View Post
That is an awesome video. I had no idea that the difference would be that dramatic.
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!
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  #7  
Old 08-18-2011, 05:14 PM
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RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,271
Default

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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  #8  
Old 08-18-2011, 06:04 PM
ddnebert ddnebert is offline
 
Join Date: Oct 2005
Posts: 118
Default Reflex speed

Quote:
Originally Posted by bcondrey View Post
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
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.
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  #9  
Old 08-18-2011, 06:09 PM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,420
Default

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
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  #10  
Old 08-18-2011, 06:23 PM
eric.kallio eric.kallio is offline
 
Join Date: Aug 2006
Location: Prairieville, LA
Posts: 118
Default 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
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