why the spit turns most effectively at the limit edge and the 109 doesnt

[Kurfürst]

Originally Posted by Rumcajs

The wing is elliptical. Lift distribution is modified to a certain degree that's true, but it still has lift more evenly distributed than the wing of a 109. And the elliptical shape is responsible for that.

I'd love to see some lift distribution graphs to support that.

Your claim is not exactly true, because induced drag simply has something to do with the shape and lift distribution. You are right that the wing of a spit is large and that's why lower angle of attack ... ok. But the shape contributes too.

Certainly shape is a factor, but I do not think it's a major or measurable factor compared to sheer wing size. The Spitfire had a very large wing for a very small airframe, much larger than any other with the possible exception of the Zero.

If wing shape would have been such a factor, planes like the Curtiss Hawk, Zero or Hawker Hurricane wouldn't run circles around the Spitfire, but they did.

BTW if the elliptical shape didn't bring advantages, why would the Brits bother to manufacture them?

Simply because the British Air Ministry specified an 8-gun armament, and Supermarine could not find space in the wings to house them without enlarging the original trapezoid wing of the Spitfire (which was meant for a four gun armament). The design team was simply practical about it.

[palker4]

Spit has a negatively twisted wing that means that angle of attack will be always lower on the wingtip + wingtip probably uses different airfoil than root with different lift characteristic so that it will never stall first. That means spit can have eliptical wing without dangerous stall characteristics.

[Rumcajs]

Originally Posted by Kurfürst

I'd love to see some lift distribution graphs to support that.

There are plenty of resources on the internet. Not sure if one can find exactly the spitfire's lift distribution, but generally there are many sources for elliptical and other shaped wings.

Originally Posted by Kurfürst

If wing shape would have been such a factor, planes like the Curtiss Hawk, Zero or Hawker Hurricane wouldn't run circles around the Spitfire, but they did.

Size, shape, weight, airfoil .... many variables go into the equation. No need to make simplifications like this.

Originally Posted by Kurfürst

Simply because the British Air Ministry specified an 8-gun armament, and Supermarine could not find space in the wings to house them without enlarging the original trapezoid wing of the Spitfire (which was meant for a four gun armament). The design team was simply practical about it.

http://en.wikipedia.org/wiki/Supermarine_Spitfire
In 1934, Mitchell and the design staff decided to use a semi-elliptical wing shape to solve two conflicting requirements; the wing needed to be thin, to avoid creating too much drag, while still able to house a retractable undercarriage, plus armament and ammunition. Beverly Shenstone, the aerodynamicist on Mitchell's team, explained why that form was chosen:
The elliptical wing was decided upon quite early on. Aerodynamically it was the best for our purpose because the induced drag, that caused in producing lift, was lowest when this shape was used: the ellipse was ... theoretically a perfection ... To reduce drag we wanted the lowest possible thickness-to-chord, consistent with the necessary strength. But near the root the wing had to be thick enough to accommodate the retracted undercarriages and the guns ... Mitchell was an intensely practical man... The ellipse was simply the shape that allowed us the thinnest possible wing with room inside to carry the necessary structure and the things we wanted to cram in. And it looked nice.

So again, you are doing a simplification here.

[mazex]

Originally Posted by 41Sqn_Stormcrow

If the elliptical form would have been so advantageous why did so few other air forces not adopt them? Supermarine was neither the inventor nor the patent holder of the elliptical wing.

Agreed, and the He 70 sure had a wing that Mitchell and the guys had peeked at...



/mazex

[engadin]

I read somewhere Spit's turning capabilities were also related to the way the wing root was designed and implemented, hence forcing the stall to start at the wing tip and moving inward to the root, so avoiding the 'stall as a whole' mentioned by kurfurst at first.

[Rumcajs]

Originally Posted by engadin

I read somewhere Spit's turning capabilities were also related to the way the wing root was designed and implemented, hence forcing the stall to start at the wing tip and moving inward to the root, so avoiding the 'stall as a whole' mentioned by kurfurst at first.

Well most designers tend to design wings that stall near the fuselage first. That allows the pilot to realize he is about to stall while the plane is still controllable by ailerons. And that's why the elliptical wing has to be twisted so the angle of attack is lower where ailerons are. Actually all wings are twisted to prevent sudden loss of lift and control. So no, the idea of stalling at wingtips first is a bad one. The wing is designed to stall near fuselage first.

[engadin]

Originally Posted by Rumcajs

Well most designers tend to design wings that stall near the fuselage first. That allows the pilot to realize he is about to stall while the plane is still controllable by ailerons. And that's why the elliptical wing has to be twisted so the angle of attack is lower where ailerons are. Actually all wings are twisted to prevent sudden loss of lift and control. So no, the idea of stalling at wingtips first is a bad one. The wing is designed to stall near fuselage first.

You're right, I knew it one way or the other. Thanks!.

Originally Posted by mazex

Agreed, and the He 70 sure had a wing that Mitchell and the guys had peeked at...



/mazex

Actually some supermarine engineer said that they looked at the He70 rather in terms of smoothing things up. The He70 wing is albeit elliptically also thicker than that of the spit and a gull wing.

But when you look at the wing root fuselage transition at the trailing edge the similarities are there with the long stretched curve and the soft transition on the upper side:





(courtesy: http://www.luftarchiv.de/index.htm?/...inkel/he70.htm)