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aerodynamic drag and body style

Shocks, Springs, Brakes, Frame, Body Work, etc

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Dragsinger
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aerodynamic drag and body style

Post by Dragsinger »

Specifically 3rd gen Camaro [which is what I am building] [Ed once said we are all most interested in what applies to our cars and in general he is correct] especially the drag caused by the rear of body shape. What shape or spoiler can help?

Or, since it is 1/8 mile bracket racing, is it a non-issue?

To me, it seems it is important because the last 1/2 of the track is over 80 MPH. Also, if you are racing into a headwind the drag will be increased.

Any feedback?
Larry Woodfin - Team Woodfin Racing - Owner, Woodfin Automotive
miniv8
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Re: aerodynamic drag and body style

Post by miniv8 »

Don't forget the subtle changes on the underside of the chassis that can make difference too. If you look under a lot of the newer cars, there are little winglets that direct airflow to and from components to not only aid cooling, but also reduce drag.
Just from the top of my head, I had a cheap Skoda from the Volkswagen-Audi Group that was really well thought out aero wise under the chassis. When the beancounters allow this for production of their cheapest, there must be something to it.

I would consider trying out a flat belly pan, covering most of the undergcarriage before adding a rear cone or such drastic aero mods. Closing up the front end and lowering the car as you can within the weight transfer needed, helps.
The bellypan can be made from a sheet of plastic and held up by a beams of thin channel bent aluminum. Just be sure to have it overlap from the front so it doesn't balloon on you.

Automakers are now looking at ways to rid the cars of side mirrors, using cameras and computers instead, because it makes sense for mileage.

Here's a good thread: viewtopic.php?f=1&t=40750

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Re: aerodynamic drag and body style

Post by j-c-c »

First, in this context I define a rear spoiler as an aero device that actually "spoils' air flow, and that disruption causes a local air pressure increase upstream, acting normally on a flat/slightly sloping horizontal surface, with the main intended result, greater DF. The biggest downside is increased drag. Again IMO a true spoiler has air movement only on one side vs a "wing", with air movement on upper and lower surfaces. A "draggy" wing can also give some "spoiler" type results.

A poorly utilized "spoiler" can reduce drag, by allowing turbulent air downstream of the spoiler to reattach/recombine easier with air stream. An example would be a very laid over spoiler that can almost be flat ( that spoils little and has little DF) that extends past the cars (bluff) body, I call that a "Lip" and one side of a "box Cavity", another feature known to reduce aero drag.
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MadBill
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Re: aerodynamic drag and body style

Post by MadBill »

I don't think you'll find any measurable benefit, especially considering that you're running brackets. A few decades ago streamlining was explored by a number of Top Fuel teams. They found that the few extra pounds of bodywork more than cancelled out any potential gain.
https://www.hotrod.com/articles/drag-ra ... dragsters/
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Re: aerodynamic drag and body style

Post by David Redszus »

Dragsinger wrote: Fri Aug 07, 2020 10:07 am Specifically 3rd gen Camaro [which is what I am building] [Ed once said we are all most interested in what applies to our cars and in general he is correct] especially the drag caused by the rear of body shape. What shape or spoiler can help?

Or, since it is 1/8 mile bracket racing, is it a non-issue?

To me, it seems it is important because the last 1/2 of the track is over 80 MPH. Also, if you are racing into a headwind the drag will be increased.

Any feedback?
A data logger that can capture coast down data, (speed vs time), will permit the calculation of drag forces, and CdA,
as well as rolling resistance.

Knowing the frontal area (A) will permit the determination of Cd. But if there is no change in frontal
area, the CdA number can be used. Remember, it is the total drag force that is important to know.
Also, air density (temp & pressure) will have a measurable effect.

Given: Frontal area = 26 sqft, Cd = 0.45;
at 75 mph, drag power loss = 33 hp
at 100 mph, drag power loss = 78 hp
at 125 mph, drag power loss = 152 hp
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Re: aerodynamic drag and body style

Post by David Redszus »

MadBill wrote: Thu Aug 27, 2020 10:26 pm I don't think you'll find any measurable benefit, especially considering that you're running brackets. A few decades ago streamlining was explored by a number of Top Fuel teams. They found that the few extra pounds of bodywork more than cancelled out any potential gain.
https://www.hotrod.com/articles/drag-ra ... dragsters/
The Hot Rod magazine article is a very interesting read. The drag racing pioneers certainly had imagination and
creative designs; some even worked. Seems like everyone was in hot pursuit of slick bodies...automotive mostly.

You raise some very interesting issues. A streamline shape that reduces drag is beneficial if power is limited.
But if sufficient power is available, such that we become grip limited, then downforce (even with a drag penalty) becomes more important. Often we find tradeoffs between lift and drag (L/D ratios) forces. And those L/D ratios
can vary considerably.

A Formula One race car can have a drag coefficient (Cd) over 1.2, which is a lot of drag, but has the downforce necessary
to avoid wheel slip. And enough power so that the drag penalty is obviated.

So we are left with several interacting variables: power, weight, tire grip, aero drag, and downforce.

For a given vehicle and purpose, which combination of variables would be appropriate?
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Re: aerodynamic drag and body style

Post by MadBill »

It's not uncommon for a car's optimum qualifying setup to be high downforce, but needing to be 'trimmed out' for the race, since the former's high drag leaves the car a sitting duck in traffic on a long straight.
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Re: aerodynamic drag and body style

Post by David Redszus »

MadBill wrote: Wed Nov 25, 2020 12:23 am It's not uncommon for a car's optimum qualifying setup to be high downforce, but needing to be 'trimmed out' for the race, since the former's high drag leaves the car a sitting duck in traffic on a long straight.
Quite right. But then we try hard to increase downforce while also reducing drag. They are not always mutual opposites
as indicated by wide L/D ratios often seen. Well, not seen but measured.
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