Aerodynamics and the mysteries of "why"..

As already written a few months back, the wing of Concorde came out of the work of this man:

https://en.wikipedia.org/wiki/Dietrich_K%C3%BCchemann

Mainy delta-winged aircraft have "conical camber" at the leading edge of the wing, even the Dassault "Mirage III", albeit relatively subtle. It's very interesting on the two different designs for the Avro Vulcan wing also, the first one having a true straight line, the second one having a large kink and conical camber of this.

Rgds

 

I always thought that this was the Clark WHY airfoil.

 

On delta's, I don't think so Bob (?); if we accept that the SR-71 is indeed a Delta, but I guess it qualifies....
From the german research on Delta's (well, also from these of Payen in France during the thirties) most countries that did develop the delta wing in the forties and fifties adopted "conical camber" on these wings.
Out of my memory, I think that in the US, the F-102 wing also had some "conical camber", but I maybe wrong on that.

Rgds

 

Simply put the conical camber is there to prevent flow separation on the leading edge of the wing.

If you want to get complicated i suggest reading the following :
WARNING this is not for those who decided that Algebra 1 was to complicated in school.

http://naca.central.cranfield.ac.uk/reports/arc/rm/3289.pdf

http://naca.central.cranfield.ac.uk/reports/arc/cp/0428.pdf

 

Haha; yep, I had those links, but decided these were a trifle "overkill"...

Rgds

 

Having participated in the building of several homebuilts, the "CLARK..WHY? airfoil was always the one that was designed by a designer/ builder who lacked any aerodynamic training. The F-102 did have conical camber and I gave up trying to ask aerodynamicists questions about wings because they always quickly dive into unintelligible mathematical lingo that only they can understand. I think that conical camber has something to do with spanwise flow.

 

Was this true on the original F-102 or just on the famous redesign for the F-102A with the longer 'coke bottle' fuselege (even pictured in LIFE magazine)?

Done due to area rule.

I could not find anything on wing redesign, just waist, length, air intakes, narrower canopy, etc. And bigger engine.



There was a thread (somewhere, not here) years ago on the Concord wing design, and the Russians attempts to figure it out for their SST... cannot find it now.

 

I think they ended up calling it the F-106 which is one of my favorite airplanes of all time! Also it still holds the single engine speed record and the record was set with a standard non modified plane.

 

The XF-92 could not go supersonic with the J79 and required a complete redesign to become the F-102. The benefits of both conical camber and area ruling, besides separation on the wing for conical camber, is that the airflow saw a much smaller surface area and drag was proportionately reduced.

 

Area ruling (or the coke bottle) was used to minimize wave drag - especially the sharp increase seen as you tried to pass through Mach 1 - 1.1

Multiple benefits of conical camber, but when it came down to it, a supersonic design had to sacrifice some flight or handling qualities at subsonic speeds. Supersonic aerodynamics is essentially gas dynamics. The variable sweep wing (F-14, F-111, B-1...) was an attempt to mitigate some of these issues between two different flight regimes. Unfortunately, weight and subsystem complexity always reared its ugly head.

 

The swing wing pivot problems are what killed the Boeing original variable sweep design.

 

Wow. Great thread pros. Excellent read. Makes my old laminar wing seem slightly mundane. When we had the Collings B-25 in the museum for two years, I noticed a wash out or strange curve to the rear of the wing tips. Almost like a cupping. Have not seen or noticed this before on any other aircraft. Wonder what that does?

 

With the B-25, I remember reading somewhere that the original plane had perfectly straight wings and had handling issues.

North American solved that by putting dihedral from the fuselege to the engine and anhedral from the engine to the tips. Yes the tips are sort of 'cupped'.

Dihedral/Anhedral from a famous pic:
https://en.wikipedia.org/wiki/File:Army_B-25_(Doolittle_Raid).jpg

"Cupping"
https://en.wikipedia.org/wiki/File:B25-1_300.jpg

 

I'm glad that you asked that because I have an answer to it. In order to control the obstrumentortion of the flodistort there has to be a recurve of the closure angle on the redicranz between the aerodontic guzamont and the unortsamontiliamance flow dauntor. It's quite simple if you multiply the odd fractional goutiont figure from the stall recess monitormotor. You can read the result in the turbulence straightener tort mount. THAT is how the B-25's were able to launch from the aircraft carrier. It's not a popularly known algearhythm because it is very difficult to understand...as you can see.

 

Oblivious, even to the causal observer...

 

Why, soitenly!

 

If I remember, the North American Navion has an NACA 4415 at the wing root and an NACA4409 at the tip. The reduction of thickness in the 4409 causes a prominent under camber with an apparent upper curving of the aft portion. I wonder if the B-25 has the same thing. I'll go look at Historic Flight's B-25 and report later.

 

Someone told me that the NAvion had a wing similar to the P-51 wing. And tail and landing gear.

Edit: Main gear as the P-51 was a taildragger and the NAvion had a nose gear.

 

It could only be similar to the P-51 in planform, The airfoils were much different. Maybe the retraction mechanism of the main gear was similar but configuration was very different. The Nation was / is a nice flying airplane.

 

NACA 4415 and 4409 would have the same camber (4%) with max camber at 40% chord. The 15 versus 9 is just thickness in terms of percent chord. Thinner wing outboard to save a little zero-lift drag and weight. Dihedral was used for static stability, not to tailor lift distribution or efficiency. I would assume they washed out the tips (reduced their incidence angle to the free stream) which could give the appearance of a reflex or cupping back there at the very tip. This was to optimize planform efficiency, reduce lift induced drag, and prevent a nasty wing drop on stall.

Some aircraft are rigged to reflex trailing edge surfaces upward to reduce drag or alter the loads in turbulence (U-2). It is a favorite trick of the glider pilots...

 

HUH.......Great answer Robert. Wish I could remember some of those technical terms off hand. Be fun to jump into someones conversation using those words. Hows things going in the Great Northwest? The new book is progressing along I trust.
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new sparky
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That's the same thing Bob said... you just used smaller words.

 

All this reminds me of the fix that Joe Sutter orchestrated on the 747 when they experienced flutter in the wing on higher speed testing. He twisted the outer wing I think by three degrees and cured the problem. The front spar at the outboard strut is bent down by three degrees and the trailing edge is bent up at the inboard end of the outboard aileron at about three degrees thus imparting a downward angle at the wing tip, washout. When the 747-400 came out , they installed wing tip devices at the tip and I had to do a drawing to show the geometric disparity between the wing chord plane and the tip so that everybody would understand that the -400 tip was really level and the -200,-300 tip had three degrees of twist. If one looks at the trailing edge of a 747-400 they will see a curve downward from the outward end of the low speed aileron (outboard aileron) to the -400 tip. I see it all the time just like the flat spot in the crown loft on the 777 aft of the cab that eliminated the high speed shock that would have occurred if our nice conic curve had been retained.