Wing Root fairings

RV6AussieNick · #1 06-14-2010, 01:47 AM

Hi, I've noticed some very nice looking RV's out there, mainly on barnstormers.com, Does any one know if there is a company out there making wing root fairings or are there some very clever craftsmen doing them for there own aircraft.

Cheers,

Nick

noelf · #2 06-14-2010, 03:35 AM

... in the advertiser's section on this web site.

pierre smith · #3 06-14-2010, 04:38 AM

...and the airplane had a set of the radiused fairings on and was noticeably slower than it should have been.

The owner removed them and re-installed the original 'flat' Van's fairings and picked up 7 MPH!

Best,

carguy614 · #4 06-14-2010, 05:17 AM

slows "em down.
Seems like almost everything that looks fast and slick slows down a 2 place RV. The wing root fairings tried so far are an example.
Van has done a terrific job with our airplanes, and it is a real challenge to get those extra knots with the traditional "speed mods" that we have all seen go on certificated aircraft.
That being said, I suggest you read some of Bob Axom's posts as well as others who have pushed the envelope in the quest for that racers edge.
I have followed all of the speed posts with a great interest. There is a lot of information right here on VAF to help you decide which (if any) mods you may want to work into your build to help with top speed numbers.

Regards,
Chris

RV6AussieNick · #5 06-14-2010, 06:34 AM

I didn't think that the root fairing would make such a difference to speed, I thought it would help drag and airflow over the wing.. Humm..

trib · #6 06-14-2010, 09:35 AM

Apparently research has indicated that the drag is lower for the wing root when the intersection is at 90 degrees vs a large radiused fairing. That's why the fiberglass transitions which look aerodynamically smooth actually have increased drag and reduced speed. I actually like the metal fairing provided with the kit, along with the rubber weather strip. Clean, fast and easy!

Mel · #7 06-14-2010, 10:01 AM

Quote:

Originally Posted by trib

Apparently research has indicated that the drag is lower for the wing root when the intersection is at 90 degrees vs a large radiused fairing. That's why the fiberglass transitions which look aerodynamically smooth actually have increased drag and reduced speed. I actually like the metal fairing provided with the kit, along with the rubber weather strip. Clean, fast and easy!

This is true when the sides of the fuselage are mostly parallel to the airflow as on the RVs. Aircraft that have tapered fuselages in the area of the wing root sometimes benefit from the radiused fairings.

Bavafa · #8 06-14-2010, 11:08 AM

Wow, very interesting and timely reading here. I had heard that the wing root fairing in a RV does not yielled any speed gains but did not know that it actual works against you. I have/had been planning on building a set as my winter project, mainly for the looks and possibly putting a set of landing light in them. Now, I may just stick with what I got and don't fix it if it ain't not broken.

pierre smith · #9 06-14-2010, 02:38 PM

...Van makes good use of known, good aerodynamic practices such as keeping the fuselage wider near the trailing edge of the wing, than at the leading edge.

Furthermore, even our cabin tops have the pressure recovery concave surface behind them in the side-by-sides and the -10, for low drag/speed reasons.

Best,

David Shelton · #10 06-15-2010, 03:01 AM

A 90 degree intersection is indeed the best angle for the wing and fuselage to intersect. This is one of the main reasons that a mid-wing configuration dominates the sailplane world. It also helps that the fuselage isn't highly tapered in the wingroot vicinity. For these reasons, the RV wingroots aren't as terrible as some other airplanes, but there is still room for improvement.

A properly shaped wingroot fairing will reduce interference drag at the wingroot. However, as others have found... it's a lot easier to get it wrong! Like many aero mods, it's a lot of work and it can take a few tries to get even a small benefit. If you want to give it a try, avoid these common mistakes:

1) The fairing radius should be small at the front and begin growing near the airfoils maximum thickness. If you think about it... the front of the airfoil has a favorable pressure gradient and it doesn't need much assistance there. Aft of the maximum thickness, the airflow faces an uphill battle against a less favorable pressure gradient. I've seen a lot of fairings that are aerodynamically backwards (radius large at the front and small at the rear).

2) The fairing doesn't need to be GIANT. When a fairing is too big, the increased wetted area will cancel the benefits.

This one seems to be ok:

Another good fairing: