civic splitter

[k.civic.f4i]

would a nascar style splitter(going forward from bumper) hurt or help mpg? i know for sure that it would produce down force but.... not necessarily drag.

what are your thoughts?

[Christ]

Ok, so downforce is drag, first of all. In order to have zero gross drag, you need a neutral shape which produces no downforce, negative or otherwise.

Secondly, it would lower the stagnation point of the front of the car. No real telling (from me, anyway) whether that would help or hurt anything.

[Hermie]

Originally Posted by Christ

Ok, so downforce is drag, first of all.

Not necessarily. The shape of an airplane wing gives large amounts of lift, with a minimal drag coefficient. The same would hold true if you turned it upside-down to provide downforce.


k.civic: What you could do if you want a reduction of both drag and lift is build an air dam that's angled forward, so the forwardmost point of the front end is on the bottom tip of the air dam. Drag reduction would be even more effective if you make the top of the dam flush with the bumper. Don't forget you'll need to cut out at least a small grille in the air dam.

[Christ]

Originally Posted by Hermie

Not necessarily. The shape of an airplane wing gives large amounts of lift, with a minimal drag coefficient. The same would hold true if you turned it upside-down to provide downforce.


k.civic: What you could do if you want a reduction of both drag and lift is build an air dam that's angled forward, so the forwardmost point of the front end is on the bottom tip of the air dam. Drag reduction would be even more effective if you make the top of the dam flush with the bumper. Don't forget you'll need to cut out at least a small grille in the air dam.

They teach you that in school?

Show me an airplane wing that generates down force, positive or negative, and has zero drag, and I'll agree with you.

Regardless of the relationship between them (linear, curved, inter-racial, etc.) ANY disturbance in flow is a manifestation of drag.

[winkosmosis]

Downforce created by an angled foil does create drag, by definition... An airplane wing perfectly aligned with airflow doesn't create much drag, but it also doesn't create much lift. A plane has to tilt its wings to fly (contrary to what they taught is in school about the Bernoulli effect).

The question to ask is first of all, what does the splitter do? Does it create downforce, or does it reduce lift? Then you have to ask how it does that-- by channeling existing airflow, or by acting like a sloped wing? It obviously isn't a sloped wing, because it's attached to the vehicle and blocked off at the back by the grill.

It probably reduces lift by preventing airflow from being directed under the vehicle, so it could be reducing drag also.

[equation112]

Originally Posted by Christ

They teach you that in school?

Show me an airplane wing that generates down force, positive or negative, and has zero drag, and I'll agree with you.

Regardless of the relationship between them (linear, curved, inter-racial, etc.) ANY disturbance in flow is a manifestation of drag.

actually, hermie is absolutely right. any non-symmetrical wing will produce substantially more lift at a zero angle of attack than drag (given that drag can normally never be 0). downforce is lift. where drag increases become significant on wings is under increased angle of attack (you get large increases in lift, but as the angle of attack approaches the stall point, drag increases greatly).

[equation112]

Originally Posted by winkosmosis

Downforce created by an angled foil does create drag, by definition... An airplane wing perfectly aligned with airflow doesn't create much drag, but it also doesn't create much lift. A plane has to tilt its wings to fly (contrary to what they taught is in school about the Bernoulli effect).

lift at any given angle of attack is entirley dependent on the wing shape. there certainly are a great many airfoils that are able to fly with 0 Alpha so long as sufficient power is applied to maintain the needed speed. the only airfoils that generate no lift at 0 alpha are symmetric ones (including flat plates).

but then, in the real world, no airfoil is ever at a true 0 alpha.

[Christ]

Originally Posted by equation112

lift at any given angle of attack is entirley dependent on the wing shape. there certainly are a great many airfoils that are able to fly with 0 Alpha so long as sufficient power is applied to maintain the needed speed. the only airfoils that generate no lift at 0 alpha are symmetric ones (including flat plates).

Sources/References?

[Frank Lee]

Wing efficiency doesn't really enter into this.

The bottom line is, when lift is produced, drag is also produced. More lift > more drag.

Less lift > less drag.

*Whatever* angle of attack or airfoil design doesn't matter; the above holds true... unless you want to get funky and talk about undesireable situations like stalls and whatnot.

Keep in mind that "lift" can be in an up or down vector, depending on. For cars we tend to want "down".

[equation112]

Originally Posted by Christ

Sources/References?

the aforementioned bernoulli's laws are all you need. like I edited above however, in the real world no wing can ever be expected to maintain a zero alpha for more than an instant. there are also engineering considerations to consider - a wing may be forced to be too heavy to fly and keep a 0 alpha at a given speed for instance.