Gull wings?

[raptor22]

Who knows the advantages of a gullwing from a purely aerodynamic standpoint? I have noticed that our feathered brethren in flight often use them, why?

I would have to guess that they decrease spanwise flow, but I can't be sure of that?

Anyone ahve windtunnel tests or anything?


--Alex

[BMatthews]

Like you suggest I also wonder if the true gull shape actually holds the air under the wing better than other shapes. Seems to make sense to me.

However a true gull wing with the outer panels drooped down will result in a neutral or negative dihedral angle. Some fine tuning would be needed I suspect. Certainly ailerons will be required as the usual rolling couple won't work very well if at all.

Sure would make for some pretty models ......

[Sparky Paul]

Gull wings were popular on full-scale gliders, to give the pilot a better view over the top of the wing.
Other than the different appearance on a model, there's no advantage.

[raptor22]

Gull wings were popular on full-scale gliders, to give the pilot a better view over the top of the wing.
Other than the different appearance on a model, there's no advantage.

How would a true gull shape improve over-wing visibility? It should decrease it.

Just for reference, I am not speaking of an inverted gull. A true gull the wings go up then curve downwards.

--Alex

[raptor22]

If there is no advantage, why does almost every very effecient long distance-gliding bird (such as the albatross) have it to at least some extent. a million years in the making, yada, yadda.

--Alex

[Sparky Paul]

If there is no advantage, why does almost every very effecient long distance-gliding bird (such as the albatross) have it to at least some extent. a million years in the making, yada, yadda.

--Alex
Ask God.

[Sparky Paul]

How would a true gull shape improve over-wing visibility? It should decrease it.

Just for reference, I am not speaking of an inverted gull. A true gull the wings go up then curve downwards.

--Alex
.
Sit in a cockpit of the typical gull-winged plane. The wing is mounted above and behind your head. When you're turning, the wing if dihedralled is in your field of view.
The "gulling" lowers the tip in the field of view.. the direction in which you are turning, which is more than "nice" to have, but almost mandatory.
The oldtimey Sperber Junior, early '30s...
With gull and without...

[raptor22]

Oh, alright. I was thinking of a less radically dihedralled plane.

--Alex

[raptor22]

Ask God.

I most certainly will, if I ever get the chance ;)

--Alex

[Sparky Paul]

Everything walking, flying, slithering around today has a great-great............
grandfather whose limbs looked like this... 7 or 8 digits.. not the 5 we have, the 3 of the dinosaur, the single digit of the horse...
Nature takes what is available and adapts it to a specific use.
There's no reason to expect that any configuration that has evolved is THE best configuration for the purpose.

[Majortomski]

On the PZL series of Polish fighters it was primarily to improve forward visibility for the pilot who was seated behind the wing.

On the Corsair (F-4U, inverted gull), having the wing perpendicular to the fuse minimizes the interference drag.

HTH
Tom

[BMatthews]

Actually for the Corsair I've seen a couple of sources that put it as being done to reduce the length of the landing gear while dealing with the humungous prop. The shorter gear offered a much stronger option at less weight. The right angle meeting of the wings to the fuselage was just gravy I would imagine.

In the book Vintage Sailplanes there's a bitof a writeup about the use of the gull wing in the Moazagotl section and how it influenced the use of the same wing in the Minimoa and many other sailplanes. I don't have the book at my fingertips at the moment but I seem to recall that the use given in the Moazagotl writeup was more empiracal than pratical but it made for a distinctive and good performing glider for the time and I suspect the use of the gull shape in subsequent designs was due as much to looks as to looks and good performance due to the choice of pilots as to any possible advantage of the gull wing.

Paul, other than the gull wing gliders very few gliders of that period had much dihedral at all so I'm afraid I'm going to have to call you on the visibility aspect since the gull wing models obviously had a disadvantage in that way over any of the flat winged types.

[Sparky Paul]

Ben, I've been wring before... :)
Designs from that period of time should show a vast difference in configurations, as the whole idea of endurance gliding was fairly young, and every designer would have his own ideas, based on experience or wishful thinking as to what would be optimum.
Many times the designers weren't pilots, and came up with wierd and wonderful and sometimes deadly ideas as to how to construct a flying machine.
Another design, the Harbinger used a forward sweep on the inner panels, to get the wing ahead of the second cockpit, letting the c.g. be properly placed.
A side benefit was additional sideways visibility from the front and rear cockpits.
Imagine the wing not having the forward kink, and going straight in from the outboard leading edge...
.
On these things I'd be expecting to see a lot of attention paid to side clearance visibility.
The Manuel Crested Wren had a pylon mounted wing, with the pilot sitting underneath, which must have been awful to fly.

[Pete P]

There was a neat article a while back in PopSci about wing design, and it had a quip/pic about a super-duper effecient Gull, might be worth looking into....

[tim hooper]

I have noticed that our feathered brethren in flight often use them, why?

--Alex

Alex,

Just a guess, but would it give the birds wing muscles some kind of mechanical advantage, especially in a high-aspect ratio configuration?

tim

[vintage1]

A gul wing can give you pitch stabiliy without affecting lateral stbility too much - that is its equivealent to a pylon mounted wing if you like - CG well below lift center.

The reverse kink - stuka etc - allows for, as is said, shorter landing gear with large props.
Kinks in plan view help with visibility, or generate sweepback.

Its just another vairable in the overall aerodynamic/structural compromises.

[Ollie]

http://fsc.fernbank.edu/Birding/skeleton.htm
The function of bird's gull shape is for flapping, sweep in flight, folding on landing, changing dihedral in flight,etc., etc. The sailplane gull wing is not meant to flap, fold, etc, ect.

[Flying Scotsman]

The reverse kink - stuka etc - allows for, as is said, shorter landing gear with large props. Dont forget F4U Corsairs

[BMatthews]

.....The sailplane gull wing is not meant to flap, fold, etc, ect.

At least not intentionally. Sad would be the look on the face of the builder to see his work more accuratley mimicing it's natural inspirational source.... :eek: LOL :D

Speaking of pretty how about this Airhopper but with the dihedral angle at the root reduced so the outer panels assume a slight droop angle. Further I would add a double break at the transition so the effect was a more gradual and segmented break to further add to the smooth curved look.

It's important to note that gull dihedral puts the roll couple in the worst possible place for flying with rudder and elevator. As such aileron control would be essential.

[Andy W]

My opinion on this is - if there was any aerodynamic advantage to this design, it would exist in modern aircraft.

Personally, I love the Minimoa, but I'm biased.. (http://www.mindspring.com/~libelle3k/Hallofame/Shelly%20Page.htm)
..a

[Scaledown]

If you had to hang by your arms all day every day, I reckon your shoulders would be permanently pushed back.

[raptor22]

http://fsc.fernbank.edu/Birding/skeleton.htm
The function of bird's gull shape is for flapping, sweep in flight, folding on landing, changing dihedral in flight,etc., etc. The sailplane gull wing is not meant to flap, fold, etc, ect.

Ahh, that makes sense,a nd answers my questions.

It is in herent in their body structure, which is optimized for fmuscle driven flapping power.

Thanks,
Alex

[Joel K. Scholz]

Here is a photo of one of several kite designs I have made using a gull wing. This is the first kite I tried it on. I thought perhaps this wing configuration would be too unstable in flight. I figured that once the kite dropped a wingtip and lost lift on the down side , it would probably not recover. I was pleasantly surprised to find the opposite was true. Not only did it correct itself , but was capable of flying stabily in winds in excess of 30 mph. Something not many kites are capable of. Another interesting thing, by adjusting the pitch on the wing I could make a 10 foot+ span kite (8 sq. feet) pull so lightly that I could fly it in 20mph on 10 lb. test line if I was inclined to do so.

[Pook]

On larger sea birds like say the Albatros the center section of the wings would stay almost still while the outer wing flaps - so the center of the wings still produces lift even on the upswing. Not that that really helps an Rc application.

Piers

[Ollie]

Why the Albatross don't have to flap:
http://www.wfu.edu/albatross/atwork/dynamic_soaring.htm
Why an R/C sailplane can go faster:
http://www.sloperacing.com/results/ds-speeds.htm

The gull wings have nothing to do about DS aerodynamic results.