S

stabilizer tips

Member
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?
 
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.
 
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!

0064579_zpsae29edc7.jpg


John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
 
Mel said:
Rounded wing root fairings have been tried several times on various RVs and no improvement was found.
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Actually, on an 8 .... didn't they adversely affect the stall characteristic and lead to the need to install a strake?
 
MauiLvrs said:
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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Not quite! The problem with the -8 was the relationship of the landing gear fairing to the wing.
 
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.:D
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
 
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.
 
Terry, I believe this was done to Steve Barnards plane, n157st.

Steve only flew a short time with the root fairings, and then removed them.

At the time, he had the fastest 6a, Tracy Salor had the fastest 6, and of course Dave Anders with his 4 was the fastest RV. This was in the "golden" years of CAFE competition.
 
I have been reading Kelly Johnson's autobiography "More Than My Share of It All." He was trying to correct a directional instability problem on the Lockheed model 10 Electra. One of the fixes was "we removed the wing fillets, or fairings onto the fuselage--put on apparently because they were coming into style and being used successfully on such airplanes as the Douglas DC-1."
 
Me too.

I would also be interested in something other than the standard rubber fairings. Not trying to go faster (tho that would be OK) but trying to find something that won't break away at the most inopportune times. You wouldn't believe the racket that a flailing rubber fairing makes when it separates at 200+ knots!

I suppose I could lay up some composite fairings but there must be someone who has already done the work. Anybody?
 
ronschreck said:
You wouldn't believe the racket that a flailing rubber fairing makes when it separates at 200+ knots!
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Haha, same thing happened to me. (170kts though). Coming out of a loop one of the rubbers popped out and made a horrible noise. It's amazing how calmly you get the airplane straight, level and slowed down before trouble shooting those noises.

Back to the thread topic....

The Speed with Economy book talks in length about how any angle less than 90 needs to have a radiused fairing. Our wings meet the fuse with less than 90 because of dihedral. I haven't tested but I have heard 20 people say 20 different things.
 
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Get rid of them

On my first RV6 I had molded wing root fairings. They looked really nice. My friend(guru) who has won more awards for RV construction and speeds than most, took one look and told me to get rid of them and put it back to Van's design. I did speed test and GAINED 8 KNOTS by going back to the original design.(Read my article on speed mods) I just might mention that gaining speed in the air by reducing drag means a difference in amount of fuel used at a given RPM. I happen to think that is an important benefit to having a slicker airplane. Also I might mention that if the distance between the fairing and the fuselage is the required 1/8 inch, the rubber will not come out at 17 knots. I'll prove that to anybody who wants to go for a ride with me.
 
Not too many of us going purposefully over 200kts (Smokey). I would find out what extrusion supplier Van's is using for that part. My guess is that it is a standard product. With the thousands of extrusions out there, if you where able to find one with a deeper cut or overlap and perhaps slightly thicker and/or stiffer, it might just work. That would be a relatively easy "fix".
Another idea, and one I am not a big fan of, would be to glue the extrusion on. This has been tried with mostly bad results. However, if you where to just glue a few inches of each end, perhaps it would keep the thing from un-zipping?
 
John Clark said:
Here is a shot of a 747-400, no radius, no fairing. Cool paint job, though!
Click to expand...
That's what happens when you park your airplane too close to the perimeter fence in Sydney, overnight!
 
KRviator said:
That's what happens when you park your airplane too close to the perimeter fence in Sydney, overnight!
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The problem we are having is too many of them are being 'parked' permanently with no replacements. In fact the boss has no qualms about parking all of the aircraft for pilots wearing a red tie :mad:
 
Evo style fairings on RV-8

F1Boss said:
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.:D
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
Click to expand...


I'd be interested in hearing from anyone actually flying with the Evo style fairings on their RV-8. Very much like the look, just wondering about flight characteristic impact (aside from a possible speed penalty.)

Thanks -

Another Mark...
 
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