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

I have to agree with Kur this time.

The elliptical form in itself had aerodynamically only most minimal to vanishing advantages above a trapezoid wing with rounded wingtips but had some advantageous side effects such as increased wing aera and reduced relative chord thickness due to the long chord lengths. That is why supermarine chose elliptical wings above trapezoid wings because these side effects provided advantages with respect to the specifications issued by the ministry.

It came at the cost of a wing very difficult to produce and it was commonly abandoned by all air forces.

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.

[ACE-OF-ACES]

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.

I think you answered your own question when you noted

Originally Posted by 41Sqn_Stormcrow

It came at the cost of a wing very difficult to produce and it was commonly abandoned by all air forces.

War espically WWII was more about logistics and economics.. Along those same lines is one of the reason they went with the P51 over the P38.. economics

[Rumcajs]

Just found this article, really nice to read.
http://thoughtality.com/the-spitfire-wing
It looks like the decision was really influenced by the need to accommodate 8 guns.

A trapezoid wing with rounded wingtips comes close to the "ideal" elliptical wing.

And as Kurfurst mentioned, the advantages of truly elliptical wing are more theoretical than practical. Just in 1934 when the wing was designed it all looked a bit different than during WWII. Average performance of fighter planes was much lower and they probably saw the need for good low speed handling and efficiency. As performance and speed increased these aspects were less important. Also the 8 guns in wings design became obsolete with introduction of more powerful canons.

Back to the original question. I believe the 109 performs worse than the spit at very low speeds, because when it has to deploy slats, the wing is already working far behind its optimum. The spit can achieve similar lift without slats and with lower angle of attack. So yes, the induced drag would be lower. (I don't want to dig into boundary layer separation and stall questions)

At the same time Kurfurst is right, that this aspect became obsolete during WWII.

[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.

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)

[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.

[NZtyphoon]

Originally Posted by 41Sqn_Stormcrow

I have to agree with Kur this time.

The elliptical form in itself had aerodynamically only most minimal to vanishing advantages above a trapezoid wing with rounded wingtips but had some advantageous side effects such as increased wing aera and reduced relative chord thickness due to the long chord lengths. That is why supermarine chose elliptical wings above trapezoid wings because these side effects provided advantages with respect to the specifications issued by the ministry.

It came at the cost of a wing very difficult to produce and it was commonly abandoned by all air forces.

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.

Partly it was a Mitchell design signature, because Mitchell believed the ellipse presented the best aerodynamic compromise available. He also designed a heavy bomber (the B.12/36) and a flying boat with thin, elliptical wings; on some later projects, such as a two-seat, carrier borne version of the Spitfire, he compromised and used wings with straight leading and trailing edges.
A really interesting book to get a hold of is British Secret Projects 3 Fighters and Bombers 1935-1950

Quite similar to Heinkel whose chief designers the brothers Günther had some strange fancy for elliptical wings.

But as I said the elliptical planform in itself brought minor to none primary aerodynamical advantages over trapezoid wings with rounded wing tipps. Only secondary advantages because of higher wing surface allowing to reduce AoA for same lift and a small relative chord thickness. He may as well have achieved the same advantage with a large trapezoid wing with rounded wing tipps like in his seaplanes that he used for winning the snyder trophy.

[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!.