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wing fillets

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evmeg(at)snowcrest.net
Guest

Posted: Sun Aug 13, 2006 9:37 am Post subject: wing fillets

UH OH! Be careful here guys...Talk to the guys at Vans before you put any

wing fillets on your airplane. There have in the past been discussions about

this causing some odd flight characteristics...I believe Van himself wrote

an article on the subject a few years back in an RV ator..... Despite

popular opinion, those engineers DO know more about these planes than any

other group of experts. If you know what you are doing and understand the

consequences then by all means knock yourself out with the mods...the rest

of us should build it the way it was designed.

Cheers..

Evan Johnson

www.evansaviationproducts.com

(530)247-0375

(530)351-1776 cell



do not archive



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cjensen(at)dts9000.com
Guest

Posted: Sun Aug 13, 2006 10:55 am Post subject: wing fillets

I assumed Nic's reference to the wing/fuselage design deficiency was due to the 90 degree intersection, which is well understood to be 'draggy' and not as efficient as a faired/filleted one.  But the fillet negatively impacts flight characteristics?  Any further info on that or was it just a recollection to that effect?



Chuck

Do Not Archive



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evmeg(at)snowcrest.net
Guest

Posted: Sun Aug 13, 2006 1:40 pm Post subject: wing fillets

Just a recollection.....so take it at face value. As I recall it had

something to do with flutter problems on RV8 in particular. Maybe I dreamed

the whole thing but I don't think so....worth a call to the home base to

find out before you do such a thing.

Evan



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martin(at)gbonline.com
Guest

Posted: Mon Aug 14, 2006 6:25 am Post subject: wing fillets

All listers,

When I was near the completion of my RV8  SN2 in 1999,  I considered the 

large fillets for my RV8.  Fortunately at that time EAA was running a series 

of articles in Sport Aviation  featuring the series of tests that were being 

run by the CAFE group in California ( I think) on the efficiency of wing 

fillets vs the square cut juncture as used by Vans on the RV8.  It was the 

conclusion in this article that the square cut junction was better than the 

large fillet.  I am sorry that I cannot recall the exact issue of SA for all 

of you to research,  however perhaps some of you who are computer experts 

can find that article in the archives of Sport Aviation.

Dick Martin

RV8 N233M

the fast one

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gyoung

Joined: 09 Jan 2006
Posts: 211
Location: Republic of Texas

Posted: Mon Aug 14, 2006 11:04 am Post subject: wing fillets

Actually Chuck, you've got the drag part backwards. It goes against

intuition but in theory, a non-filleted 90 deg intersection is the

lowest drag. The RV is close enough to 90 deg that the fillet will

increase drag. The F4U Corsair used it - bent wing and round fuselage

gave them a perfect 90 deg intersection - no fillets needed. Van and

Chance Vought knew what they were doing. Flight characteristic changes

with fillets are a different thing and could be good or bad.



Greg Young



 	  Quote: 	
		   

 

 I assumed Nic's reference to the wing/fuselage design 

 deficiency was due to the 90 degree intersection, which is 

 well understood to be 'draggy' and not as efficient as a 

 faired/filleted one.  But the fillet negatively impacts 

 flight characteristics?  Any further info on that or was it 

 just a recollection to that effect?

 

 Chuck

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cjensen(at)dts9000.com
Guest

Posted: Mon Aug 14, 2006 1:15 pm Post subject: wing fillets

I'll be....not the first, and certainly not the last thing that I've had

backwards.  I have no idea where I came up with the belief that a fillet

would reduce drag over a 90 degree intersection--probably the same place

that a lot of people come up with their 'aeronautical' ideas.



Thanks for setting me straight...I wondered why the cart was out head of

the horse!!!



Chuck Jensen

Do Not Archive 



 	  Quote: 	
		   

 

 Actually Chuck, you've got the drag part backwards. It goes 

 against intuition but in theory, a non-filleted 90 deg 

 intersection is the lowest drag. The RV is close enough to 90 

 deg that the fillet will increase drag. The F4U Corsair used 

 it - bent wing and round fuselage gave them a perfect 90 deg 

 intersection - no fillets needed. Van and Chance Vought knew 

 what they were doing. Flight characteristic changes with 

 fillets are a different thing and could be good or bad.

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gcomfo(at)tc3net.com
Guest

Posted: Mon Aug 14, 2006 3:34 pm Post subject: wing fillets

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dbris200(at)sbcglobal.net
Guest

Posted: Mon Aug 14, 2006 4:49 pm Post subject: wing fillets

I believe the problem  associated with the fairings on the 8 was that when they were left off completely, the turbulence had a very negative effect on the tail. I don't recall anything about the shape affecting the handling on the 8.

 

 Dave

 

 Evan and Megan Johnson wrote: [quote]   [quote]--> RV-List message posted by: "Evan and Megan Johnson" <evmeg(at)snowcrest.net> (evmeg(at)snowcrest.net)  Just a recollection.....so take it at face value. As I recall it had something to do with flutter problems on RV8 in particular. Maybe I dreamed the whole thing but I don't think so....worth a call to the home base to find out before you do such a thing. Evan  ---

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gmcjetpilot(at)yahoo.com
Guest

Posted: Tue Aug 15, 2006 12:09 pm Post subject: wing fillets

I don't think anyone did formal analysis of the wing fillet or wrote and 

article. I know cafe foundation did not do a report. If any SA article 

was printed I don't recall any detail analysis or comparison. However 

I do know a RV'er who tried it and went back to stock wing-body 

faring because he found no measurable change in performance.

 

One thing no one mentioned is when you install one of these big 

wing junction fairings you introduce a bunch of small detail. You end 

up with another edge along the fuselage and extra fasteners. Usually 

made of fiberglass, the aftermarket fairings have more thickness at 

the edge where the fairing laps over the wing and fuselage. The 

stock aluminum fairing is very thin and has no edge lapped up onto 

the fuselage. 

 

Just from the above EDGE FACTOR" what ever gain you get will 

likely be negated buy extra drag from the installation. If you have a 

custom wing to  side of body fairing you may be able to feather all 

edges making this less of an issue, at the expense of extra work and 

possible body fillers.

 

I hear the theories about the wing is near 90 degrees and the Corsair 

F4U and other comments, which may be true, but until you do wind 

tunnel work or better flight test, you don't know. 

 

A well designed and installed (no draggy details) wing root fillet 

fairing could improve "intersection drag". I say COULD, but like all 

things in aerospace design there are trade-offs, compromises and 

the famous no free lunch rule. 

 

Gain verses extra weight and more details? Even if perfectly 

executed, it's likely this modification will produce only small benefit. 



  The off the shelf fairings are too small (radius wise) and have poor 

installation details. The fairing should blend right into the mating 

surfaces of the wing and fuselage  with no edge or protruding 

fasteners.

 

The plan flat stock Van's set up provides a light weight, simple, least 

attach hardware and holes. As far as drag it is pretty good and if you 

could improve it in any way with a swoopy fillet, wing root to body 

junction faring, it would be hard to measure. 

 

Often fiberglass fairings start to warp and gap after time, especially 

a big wing body fairing with long straight edges. I had the ORIGINAL 

fillet wing/body faring on my RV-4, which had a wrap-around fiberglass 

wing leading edge cuff. The remainder of the fairing was made with 

aluminum sheet fillet on top, flat aluminum on bottom. As with Van's 

designs, it was pretty darn good. Again you still need fasteners in the 

fuselage. It was OK, but I replace it with the newer style flat faring; it 

was just cleaner looking. I did not do a before after because I made 

several changes at the same time. 

   

 

George RV-4/RV-7

   

   



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