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  #1  
Old 01-04-2013, 04:02 PM
stabilizer tips stabilizer tips is offline
 
Join Date: Nov 2011
Location: bulverde , texas
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Default what is your take on wing root fairings?

i have seen a few planes with wing root fairings they finish the transition between the wing and fuselage nicely and give the plane a more streamlined look. i like the look and think it would cut down on parasitic drag just a little but would you put an affordable set on your plane?
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  #2  
Old 01-04-2013, 04:28 PM
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Mel Mel is offline
 
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Rounded wing root fairings have been tried several times on various RVs and no improvement was found.
Actually as the wing/fuselage intersection approaches 90?, a rounded fairing adds drag.
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USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
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  #3  
Old 01-05-2013, 12:44 AM
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John Clark John Clark is offline
 
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Mel is correct, take a look at any modern airliner or bizjet and you will see the 90 degree intersection. Here is a shot of a 747-400, no radius, no fairing. Cool paint job, though!



John Clark ATP, CFI
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RV8 N18U "Sunshine"
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  #4  
Old 01-05-2013, 01:15 AM
chrish chrish is offline
 
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Location: Australia
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Default

That is 'Wunala Dreaming', VH-OJB - Qantas 747-438. I used to fly it
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  #5  
Old 01-05-2013, 01:51 AM
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MauiLvrs MauiLvrs is offline
 
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Question

Quote:
Originally Posted by Mel View Post
Rounded wing root fairings have been tried several times on various RVs and no improvement was found.
Actually, on an 8 .... didn't they adversely affect the stall characteristic and lead to the need to install a strake?
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  #6  
Old 01-05-2013, 04:59 AM
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pierre smith pierre smith is offline
 
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Location: Louisville, Ga
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Quote:
Originally Posted by chrish View Post
That is 'Wunala Dreaming', VH-OJB - Qantas 747-438. I used to fly it
Beautiful airplane with extreme visibility.

Best,
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  #7  
Old 01-05-2013, 05:54 AM
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plehrke plehrke is offline
 
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Quote:
Originally Posted by pierre smith View Post
Beautiful airplane with extreme visibility.

Best,
But I bet slower than all the other 74s
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  #8  
Old 01-05-2013, 07:07 AM
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Mel Mel is offline
 
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Quote:
Originally Posted by MauiLvrs View Post
Actually, on an 8 .... didn't they adversely affect the stall characteristic and lead to the need to install a strake?
Not quite! The problem with the -8 was the relationship of the landing gear fairing to the wing.
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Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
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RV-6 Flying since 1993 (sold)
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  #9  
Old 01-05-2013, 08:12 AM
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F1Boss F1Boss is offline
 
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Location: Taylor Texas
Posts: 811
Default Again, it depends

The wing root fairing makes up for an 'incorrect' fuselage section at the wing attach area. I'll wager the 747 has a nearly 90 deg angle there, with no fuselage taper. Very efficient, almost like a mid-wing application.
To exhibit the opposite, look at a Spitfire, or a C-47: absolutely the largest fairings in the business!
All 3 ships are known as good flying types, and very good in their intended mission profiles. The fairings fitted to each help with their success.
A wing root fairing is supposed to help with climb, and maneuvering flight - both higher alpha than cruise flight.
To better understand the design intentions, read up on the AR-5. I see similar straight flow lines on the Evo fuselage, if that is the design intention of the application.
Does the typical RV need a larger fairing? Probably not, but simplicity has triumphed over any R&D to determine if such might help.
Personally, I think they 'look' appropriate, so they are fitted to my designs. Do they help? Dunno, but the chick's dig 'em.
Also, on the Evo, part of the flap operating system is hidden under the fairing...so they actually serve a second purpose!
I have sold a few sets of fairings to -8 builders, but have never heard back regarding any performance changes.

Carry on!
Mark
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  #10  
Old 01-05-2013, 10:18 AM
terrye terrye is offline
 
Join Date: Feb 2010
Location: Vancouver, BC, Canada
Posts: 860
Default Sport Aviation Magazine April 1997

David Lednicer a CFD guru with VSAERO did an interesting CFD analysis of an RV-6A in the Sport Aviation Magazine April 1997 issue (when Sport Aviation actually had a technical element to its articles). He explains there are two reasons for wing/fuselage intersection fairings: drag reduction, and moving the wing upper surface pressure isobars so they are straight lines across the span. This means that the wing is producing equal lift across its span. He says:

"To improve the wing pressure distrubution, I first designed a new wingtip. My aim was to straighten out the isobars near the tip of the wing, with constraints that the wing span could not be increased and that all changes to the tip had to occur aft of the faired in navigagation light. After three design iterations, the wingtip isobars were now well-shaped and the calculated induced drag had decreased.

Next, I designed a wing root fairing. I felt that a large convex obstruction was needed at the wing root to force the isobars forward. After several iterations, I found such a shape, and the calculated induced drag again diminished. By contrast, a conventional concave was found to have little effect on the wing pressure distribution and to produce no improvement in induced drag. The traditional concave wing root fairings are not always the way to reduce drag!"

My editorial comment is that the convex wing root fairings do not enhance the aesthetics of the RV-6A. In addition, since this is a CFD program, he does not address the issue of how his new wing tips and wing root fairing affect the stall behavior. If you decide to experiment with wing root shapes, this would be something to check: stall behaviour before and after the wing root fairings are added.
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