belly pan vs air dam

[Phantom]

Varn have you thought about bringing the air dam forward so it would start just behind the fog lights?

[Varn]

Hi Phantom
Yes I thought about it but I looked at the material at hand and did what I did. The lower fairing being behind the front makes a rough rounded shape. I plan on making a carbon rounded front end with the center being about bumper level. Incorporating the headlights is a challenge I look at a lot of other vehicles with a similar shape to what I am wanting. I am beginning to think that sharp radiused edges at the front of a vehicle are no good for my vw. Downforce is not economy. Try making one on your vehicle with photos and post your results after 1500 miles.

Originally Posted by Phantom

Varn have you thought about bringing the air dam forward so it would start just behind the fog lights?

[White118]

Thinking about putting some 6" garden edging as an air dam for the front and was thinking of building side skirts but concerned about the air needing a place to exit from under the vehicle. I have a belly pan if that helps. Any thoughts?


-Matt

[pnambic]

Someone correct me if I'm wrong, but I believe the school of thought is as follows:

- the underside of a vehicle without a tray is a big source of drag.
- a simpler step than building a full undertray is to build an airdam and side skirts, essentially limiting the air going under the vehicle in the hopes of minimizing the drag. But creating a front airdam increases your frontal area increasing air resistance. It can also create downforce, which hurts fuel efficiency as well. Its a tradeoff and better than nothing.
- Building a full undertray is the better, though more difficult option as it minimizes underbody drag while making the smallest increase to frontal area possible.

If you already have a full undertray, adding a significant airdam and side skirts would probably be more detrimental than helpful.

hth

[White118]

Anyone else want to chime in on that. I was thinking that an airdam would help and be a plus with a belly pan.

[aerohead]

Originally Posted by pnambic

Someone correct me if I'm wrong, but I believe the school of thought is as follows:

- the underside of a vehicle without a tray is a big source of drag.
- a simpler step than building a full undertray is to build an airdam and side skirts, essentially limiting the air going under the vehicle in the hopes of minimizing the drag. But creating a front airdam increases your frontal area increasing air resistance. It can also create downforce, which hurts fuel efficiency as well. Its a tradeoff and better than nothing.
- Building a full undertray is the better, though more difficult option as it minimizes underbody drag while making the smallest increase to frontal area possible.

If you already have a full undertray, adding a significant airdam and side skirts would probably be more detrimental than helpful.

hth

*The underside of a car can contribute 12% of overall drag.
*A 1960s Citroen DS19 won't benefit from a pan like a Jeep,as the Citroen already has a full pan.The benefit will be on a case specific basis.
*Short of 'doing' a bellypan,the airdam can serve as a palliative,helping to prevent air from getting into the torture-chamber under the car.
*The airdam typically cuts lift,rather than create downforce,although they can certainly be configured for downforce.
*The airdam can be constructed such that it not increase frontal area.
*Even if the airdam increases frontal area,it can still cut drag up to a point,then there is going to be a point where the gain begins to fall off.You'd have to test for that.
* Oddly enough,some of the lowest drag concept cars with full bellypans,also have active airdams which lower at speed to block air from the 'ideal' underside.
* With respect to side skirts,I don't have any data on that.

[t vago]

I remember reading that a full air dam was not quite as effective as a partial air dam that helped direct air around the front tires. Of course, an air dam that covers exposed underbody components would also help.

[lunarhighway]

here's a few of my thoughts on the matter (wich could possibly complicate things more than clarify)

when looking at an airdam design i think it's important to considder is serves two functions.

on most cars it will be fairly straight in the middel where it shields the underside of the car and curved at the sides where the dam shields the tires, wheel wells and perhaps suspention components. these are roughly two different processes that may require differnt shapes and lenths of the airdam.

this graph i came accross sugest the sides of the airdam (in front of the tires) are best as low as possible. (B)


there's a point where the reduction in drag becomes to small to be relevant (and before this point is reached practical ground clearance is compromised. as such the height is dictated by practical considderations rather than aerodynamics)


the center section of the airdam is a different matter. On some cars this is more raised than the sides, especially on cars with aerodynamic undersides. on some cars there's even no dam but a smooth transition to the underbody. info on the opel calibra sugests the center of the dam was raised on this car as this gave less drag where the sides where made as low as practical ground clearance would allow. the car had some underbody aero treathment, but was still fairly rough.

it hink it's therefore important when considdering an airdam to approach these two areas sepparate.

and than there's the chevy volt with it's odly large airdam that seems to contradict all above, yet cleary isn't the most practical solution

Chevy Volt Air Dam Wear After 7 Months | MyChevroletVolt.com