Wing Root Fairings

Hi All,
I have a question about people installing wing root fairings....
I saw Greg Hale's plane at KOSH this year and was really impressed by his fairings. See Pics below, They really make the transition look amazing. I went back to his site and figured out he got them from Jesse at Saint Aviation. I also found out they are very expensive.... well made, pretty, but pricey.
The questions I have are regarding options/performance. I'm interested in the cosmetic appeal, but also know that if they are not designed right they can actually INCREASE drag. I really doubt Greg had a chance to fly his plane without and then WITH them to see if there were any differences.
I did some research into other options as well and found:
http://www.fairings-etc.com/WingRoot_6.html

He has some great smaller fairings for 6's and 7's that are priced right, but it doesn't sound like he's interested in making ones for the 10.

So, I'm thinking of fabing up my own. I'm a decent composite guy, so I should be able to pull it off. But then again, I don't want to do that work to just ruin the slip stream. In the end, I could just use one of those nice big gaskets and have it painted to match.....

Thoughts?

Thanks

With the flat fuselage side (vertically) that all the RV's have, paired with the moderate dihedral angle, the intersection is nearly optimal already.

Years ago, fairings were tested on an already flying RV-4 (base line data to compare from the standard fairings) and the new fairings made the airplane slower. I don't know who the manufacturer was. I also don't mean to say that it would be the case with any of the options being produced now, but I will reemphasize that the standard configuration is already pretty well optimized...

Good Info

rvbuilder2002 said:

With the flat fuselage side (vertically) that all the RV's have, paired with the moderate dihedral angle, the intersection is nearly optimal already.

Years ago, fairings were tested on an already flying RV-4 (base line data to compare from the standard fairings) and the new fairings made the airplane slower. I don't know who the manufacturer was. I also don't mean to say that it would be the case with any of the options being produced now, but I will reemphasize that the standard configuration is already pretty well optimized...

Click to expand...

Thanks for the follow up. Like I said, the last thing I want to do is slow anything down.
A lot of race planes have a smooth transition there, or fairing, but, maybe there's something else going on the those designs I'm un-aware of.

Bluelabel said:

A lot of race planes have a smooth transition there, or fairing, but, maybe there's something else going on the those designs I'm un-aware of.

Click to expand...

Google Mike Arnold AR5

Steve Barnard tried this kind of wing/fuse fairing on his 6a-------took them off, and went back to stock.

Mike S said:

Google Mike Arnold AR5

Steve Barnard tried this kind of wing/fuse fairing on his 6a-------took them off, and went back to stock.

Click to expand...

Mike, Checked out the AR-5... so what you're saying is: works on other designs but is an impediment to the design of an RV? If I understand you correctly.

Pretty much. The fairing is a piece of a larger puzzle------or maybe I should say a system.

Did you read up on the AR5, or only look at the photos??

There is a good set of videos that he put out------------very interesting to watch.

http://www.ar-5.com/tapes to dvd.html

John, you don' need "gaskets" if you take the time to fit the fairings carefully to the fuselage.

Best,

Mike S said:

Pretty much. The fairing is a piece of a larger puzzle------or maybe I should say a system.

Did you read up on the AR5, or only look at the photos??

There is a good set of videos that he put out------------very interesting to watch.

http://www.ar-5.com/tapes to dvd.html

Click to expand...

Didn't get a chance to go super in depth. did a quick read. Will dive deeper this evening when I have more time.
Thanks

pierre smith said:

John, you don' need "gaskets" if you take the time to fit the fairings carefully to the fuselage.

Best,

Click to expand...

Thanks Pierre,
I get what you're saying. I'm just trying to see if there's a way to increase the cosmetic appeal of that area without damaging performance. I'm not looking for a speed mod. just don't want to take away from it.

More reading for you.

http://www.ar-5.com/ar6/brit.pdf

A really good book is Hoerner's "Fluid Dynamic Drag." Still available, I think. It's the book Mike Arnold studied.

If I understand the concept (and I might not) when you add the fairing, you increase the wetted area, and thus the parasitic drag. If the decrease in intersection drag isn't at least that much, you haven't helped.

I think that the idea is to gradually increase the radius starting small near the front and getting bigger near the rear. How much or how little, I don't know. And how to orient the aft end of the fairing as it transitions to the fuselage, another mystery.

Dave

In at least 2 planes that were flying without them then added them, one gained 3-4 kts in cruise and the stall speed dropped 3 kts. In the other his testing showed 4-5 kts in cruise increase. He didn't compare his stall speeds. They were designed by an aeronautical engineer and they do work.

I had fairings like these on my first plane. On advice from two of the best builders I removed them and gained 8 knots ground speed. As I was told, if you want to go fast, look at fast airplanes. Fighter jets have no fairings because there is no or little dihedral.

I know this is an old thread and I should probably just start a new one, but I want people to know the contrary views when looking at this, even though testin has shown a speed improvement. As I mentioned in my previous post, these were designed by an aeronautical engineer and they have shown a speed improvement on all installations.

We installed a set of fairings today and should have some independent speed results in the next week or so.

Attached are pictures of the new installation. We have these in stock and are offering them now for $2,000 installed (installation options vary, but his would be the lower cost option included in this price). We can install them in an afternoon. Of course, paint is not included, but the fairings are filled and primed, so a tiny bit of prep will get them ready for paint. No pinholes. The added weight should be about 6 lbs, again, depending on the installation format.

Do you have to install them?

Jesse, do you have to install them or are they available as a "kit"?

Bob

They are available as a kit. Pricing would depend on your desired attach method, but they install quickly, so there would not be a big discount of shipped. If you pick them up we can offer a little better price.

What are the attach methods?

What are the different attach methods?

Bob

Along the inboard end of the wing it's pretty much just the same screws as would hold the standard fairing. Along the fuse side skins the options are rivets (fastest), rivnuts (relatively fast, but the possibility of the rivnut spinning) or nutplates (the best method if easy removal is desired, but much more work to get all of the nutplates installed). Then you can choose the size of the rivets or screws. You also need to decide the spacing of the fasteners.

The rivet method works really well and inspection of the wing root can be done from the bottom, so it would not be necessary to remove them unless perhaps in the case of n ding to remove a fuel tank or the whole wing. The rivets would then need to be drilled out. In our installation today we used CS4-4 rivets and the normal #8 screws on the wing.

RV9

Jesse,
Did you ever consider to install these fairings on a RV9 ?
How much weight do they add to the plane?

Thanks Pit

I think these are a great product! Glad to see more folks are putting them on after flying without first. Hopefully get some more data from them. They give it a great look as well.

Wing root fairings

Hey Jesse

Any report back on the couple of wing root fairings installed? I'm interested and would like to know from others whether there was any speed penalty

fairings and drag

Depending on what your mission is, fairings may or may not help. It is hard for them to hurt. I'm often puzzled by the anecdotes about putting fairings on RV's and hurting their top speed. Most any fairing reduces the wetted area slightly. (A quarter circle has 78% of the circumference of 1/4 of a circumscribed square). A well designed fairing should help top speed a little bit.

But the more important issue for fairings is at higher lift coefficient, such as very high altitude cruise, or cornering around pylons. In those cases, there is a definite advantage to a properly designed fairing compared to just butting the wing onto the flat side of the fuselage. There is an induced drag benefit by supressing the shedding of a side-of-body vortex that causes the lift distribution to dip across the body.

Look at the P-51 and the Spitfire. I promise you those wing root fairings were not done for aesthetics. Bleeding less energy in turns is what wins dogfights.

If you study those fairings, you will notice some common traits.
1. Start with a very small radius at the leading edge. For an RV, maybe a 1" radius at the leading edge. It doesn't help anything to add a lot of wetted area there. There is a small benefit to preventing separation of the attachment line flow on the fuselage, which forms a necklace vortex. But this is a minor benefit compared to the major benefit that happens at the trailing edge.
2. gradually increase the radius of the fillet as you go aft. Ending up with maybe a 4" radius or a little more than that at the wing trailing edge should be good.
3. Most important - loft the contour of the fillet to follow the airfoil shape right off the trailing edge and keep going. Form the trailing edge of the fillet by intersecting that straight loft with the straight loft off of the lower surface, and the bottom of the fuselage. This should make a nice curved trailing edge. Depending on the proximity of the fuselage bottom, this may truncate the fairing pretty quickly behind the wing. DO NOT reflex the contour of the fairing upward just to extend it farther aft. Any upward reflex of the fillet will defeat the main function of this part of the fillet, which is to support lift carry-over onto the fuselage without shedding a side-of-body vortex. If it reflexes upward, it will dump the lift. Even with straight contours, the shape of the trailing edge of the fillet will still tend to curve upward, just because of the shape of the fuselage. Thats OK.

When I put my new wings on my -8, thats the type of fairing I will make.

scsmith said:

I'm often puzzled by the anecdotes about putting fairings on RV's and hurting their top speed. Most any fairing reduces the wetted area slightly. (A quarter circle has 78% of the circumference of 1/4 of a circumscribed square).

A well designed fairing should help top speed a little bit.

Click to expand...

Maybe in theory, but not always.


I am personally familiar with the installation of wing root fairings onto an RV-4 many years ago. They were the popular rage at the time (until word spread that they would make the airplane slower).

In the instance I am familiar with the fairings were temporarily installed with speed tape. Flight testing done, and then removed after the discovered results.

I am aware of other tests where fairings have been added with no speed change.... makes the extra cost, work and weight just not worth it.

That is not to say that these fairings for the RV-10 wont provide any performance benefit. Maybe they do. But without someone having specific data to show from detailed/controlled comparison testing, I am not a believer.

I followed Steve's theory exactly on my Emeraude fairings almost twenty years ago. Last year I tore them out, slapped fabric over the joint and gained three knots. Go figure.

There is no speed penalty. The recent plane that had me off hen added them did significant testi. He had one speed run of 179ktas and the rest 181-182kts with the fairings on. He had one speed run of 181 and the rest 178-179 with the fairings off. because of this data he would not publish a speed increase, but there is definitely no penalty.