Kammback or rear spoiler?

[kach22i]

Originally Posted by Viturro

Oh, I thought you were giving an opinion.

The only opinion that really counts is the wind's.

[justme1969]

An aileron is attached to the end of a wing or similar fixed wing to spoil the air and create lift in a slighter degree than a flap.
It gives minute changes required at higher speeds as in flaps down at high speed would rip the wing off an aircraft. they are Identical inshape and similar effect an aileron on a cargo jet would be bigger that of I hope that explains this. then there is a flaperon and horizontal stabilizers etc. all do similar things but the wings are fixed in 98% .. blah blah blah

[aerohead]

Originally Posted by Viturro

Thanks aerohead for your opinion! i was waiting for you : D
but i still not conviced about some-things.
I did some Flow ilustrator jobs (i know that the program isnt a guide at all, but its something)



the setup of the program is stock but with 200 on velocity. it was tested with and without floor with similar results on the upper part of the cars.
in the image you can see that the lowest drag of the ''CARS' is the kammback with airfoil one ,and looks like it have just a little drag on the airfoil.

Repeat: i know that the program isnt a guide at all,it have bugs and other unreal things but its ''something'' to see what i mean a little better.

I went back through Hucho's book and then to Hoerner's from which he referred.
*As early as 1933, investigator Frey(Forschung Ingenieurwesen,1933,p.67) was testing airfoil-type vanes,of which in one configuration,was directing air around the back of a blunt-nosed,Carafoli-type,rounded tail airfoil section which showed good effect.
*The section had a drag minimum of Cd 0.83.
*When the vanes were added,the drag dropped to Cd 0.27.
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*The bummer is,that this 2-D flow technology has never had success in 3-D flow in ground proximity.
*Of the add-on 'cheater' technology,only the air-tight box cavity has shown any benefit.
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*The 1969 AMC JAVELIN was tested and its rooftop 'wing' did nothing.
*CAR and DRIVERS 1974 Dodge van showed an mpg loss with the addition of a rooftop wing.
*The Mercedes-Benz 190 EVO's Kamm roof extension showed a benefit.
*Toyota's Celica Supra rooftop wing showed no performance.
*Ford's 1994 ESCORT RS Cosworth with rooftop wing showed a Cd 0.04 penalty.
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Since the airfoil is 'aspirated' it cannot perform the deceleration function of the local airstream,so it cannot increase the static pressure of the surrounding flow,hence no benefit to base pressure,which is at the heart of streamlining.
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Again,since the airfoil generates lift,it is by definition adding induced drag which increases overall drag and hurts fuel economy,not to mention that it is an escrescence,erupting into the airstream with its own CdA.