Kammback or rear spoiler?

[Viturro]

Wich one could reduce more drag? What about the lift? Depends on the car?

[Sporty Modder]

Looks to me like the aileron pictured would produce drag vs redusing drag of the kamm

[2000mc]

I think the ailerons you see on some vehicles are just for blowing dust off the back glass

[Viturro]

The rear wing (down part) and the kammback (upper part) (both in red) have the same curve in this example, so i think the drag should be similar, (would have to add the cd of the aileron)
Now, should it decrease the drag of the car?
How much?
Should it have similar or equal lift?

[gone-ot]

The Kammback has an almost 270-degree effective range (top & both sides), whereas the Aileron affects only the top airflow behind the car.

[Viturro]

yes, in the example i just want to know about the roof (the top) of the car. want to know about the difference about the kammback and the aileron.

[kach22i]

It's a tough question because it is presented in 2D, real life and airflow is 3D.

If the Kamback has generously rounded shoulders then it should out perform the aileron.

However, if the Kamback has no sides or has 90 degree edges returning to the hatch, then my money would be on the aileron.

I like the aileron because it causes less lift and directs the air downward better using air pressure and flow differences. However there are bound to be some frightful vortexes forming if not framed with sizable vertical stabilizers (upright wings) which are not currently shown in either option.

[kach22i]

Originally Posted by Viturro

The rear wing (down part) and the kammback (upper part) (both in red) have the same curve in this example, so i think the drag should be similar, (would have to add the cd of the aileron)
Now, should it decrease the drag of the car?
How much?
Should it have similar or equal lift?

Excellent diagram, and as illustrated the Venturi Effect and Bernoulli's principle will be at work with air flow though the narrow slot both accelerating the air and lowering the pressure under the foil.

The higher pressure above will be drawn down to fill the void below.

This will cause the mass flow of air above the vehicle to be sucked in a downward direction behind the vehicle.

Note: the sucking of air too abruptly behind the vehicle will cause turbulence, rotating swills of air (vortex) and other drag inducing elements.

If it cleans the debris off the rear glass in the process, all the better.

[Viturro]

So in your opinion, the aileron could have less lift and similar drag reduction?

I have problems to understand some text even using the translator.

[Viturro]

Now i made a new ''analisis'' of the aileron, i tough that the aileron should end at the same height, then the kammback and the aileron ''keeps'' the same quantity of low pressure between the back of the car and the aileron/kammback that kind of ''boxed'' air.
Then maybe get a closer comparison.