Aero/wing question...with a twist...and my name is not Hyper
#1
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Aero/wing question...with a twist...and my name is not Hyper
So, next year I plan on running a wing for autoX. I've been reading the rules for mounting such a rice device, and they are as follows...
-May be no more than 8 sq/ft
-May not hang further back thatn the rear most part of the rear bumper
-May not be wider than the body of the car
-May be NO higher than 6" above the highest point of the car (windshield frame)
-Must mount no further than the center point of the rear axle.
-No part of the wing can exceed 6" forward of the rear axle line.
So with that layed out, I got to wondering, I know everyone tends to mount wings to the most rearward position. Also, we know the Miatas profile isn't very friendly to aerodynamics...and in my case, I don't have a hard top. So I'm wondering about mounting a wing to the forward most possible position (within the rules allowed). My reasoning to seek insight is based partly on the old Chaparral race cars that had the wings mounted in middle of the car and on the idea of catching air right as is expands/sinks off the rear roof line to restrict airflow under the wing but not sit it right up against the top.
Attached is my quick rendering of the restrictions.
What do you guys think would be the effects of mounting a wing like this?
-May be no more than 8 sq/ft
-May not hang further back thatn the rear most part of the rear bumper
-May not be wider than the body of the car
-May be NO higher than 6" above the highest point of the car (windshield frame)
-Must mount no further than the center point of the rear axle.
-No part of the wing can exceed 6" forward of the rear axle line.
So with that layed out, I got to wondering, I know everyone tends to mount wings to the most rearward position. Also, we know the Miatas profile isn't very friendly to aerodynamics...and in my case, I don't have a hard top. So I'm wondering about mounting a wing to the forward most possible position (within the rules allowed). My reasoning to seek insight is based partly on the old Chaparral race cars that had the wings mounted in middle of the car and on the idea of catching air right as is expands/sinks off the rear roof line to restrict airflow under the wing but not sit it right up against the top.
Attached is my quick rendering of the restrictions.
What do you guys think would be the effects of mounting a wing like this?
#4
Placing it forward will also apply the downforce right on the rear axle, as opposed to creating a moment about the rear axle which (slightly) unloads the front tires.
It would be a very small difference, and is surely offset balance-wise by the weight of the turbo kit, and placing it further back applies the force behind the rear wheels without adding pendulum-like weight back there.
It would be a very small difference, and is surely offset balance-wise by the weight of the turbo kit, and placing it further back applies the force behind the rear wheels without adding pendulum-like weight back there.
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Funny thing about CSP...
They are allowed to add an element to the rear of the car, but it cannot act as a wing....so they're running those spoilers. I've often wondered how much difference in benefit there is between a large spoiler and a large wing like Chris Swearingen's car...
They are allowed to add an element to the rear of the car, but it cannot act as a wing....so they're running those spoilers. I've often wondered how much difference in benefit there is between a large spoiler and a large wing like Chris Swearingen's car...
#8
You might notice in that picture there is a spoiler and a wing. I believe that to be a legal configuration, but have never run it at a "big" event, so I don't know how it would hold up to protest.
I did a quick cut and past to show the comparison of mounting locations for you. I don't know that the forward location will get as clean an airflow as the rear section will. If you add a diffuser as part of the rear valance, the further back will help improve the performance of the diffuser.
Edit: I added my proposed splitter/air dam and canard changes as well
I did a quick cut and past to show the comparison of mounting locations for you. I don't know that the forward location will get as clean an airflow as the rear section will. If you add a diffuser as part of the rear valance, the further back will help improve the performance of the diffuser.
Edit: I added my proposed splitter/air dam and canard changes as well
Last edited by Chris Swearingen; 12-09-2009 at 03:26 PM.
#12
When you talk to them (APR) you want the 55" GT-II wing, but you want both elements to be the 7.5" high camber wings. You will wind up building your own end plates (14x14 inches to take full advantage of the allowance) and adding a Gurney flap to the upper element. Talk to them about custom mount spacing as well if you want to mount at the edges of the trunk lid.
#13
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center of pressure * distance from pivot (wheels and/or CG) = rearward downforce moment. further back = more rear downforce.
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I think you are going down the wrong direction. For big aerodynamics it would best to take the body off your car and weld a boxfish shaped sheetmetal to your frame.
Boxfish.
See what I'm getting at?
Boxfish.
See what I'm getting at?
#17
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Oh shut up. I am being a little silly with the boxfish thing but it's true:
See:
The bionic car - MSN Autos
See:
The bionic car - MSN Autos
#19
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faeflora-Don't worry, I have a spare trunk lid that i'll be using to affix any aerodynamic aids to...and will be keepinf the one that is currently on the car nice and cherry
I wish I knew someone who could help me get the car into a mag. SCC was going to do it, but they folded right in the middle of our discussions.
Chris- Don't worry, I have no forgotten a single thing you have discussed with me about aerodynamics I was just contemplating and take all information in. I wish we could run diffusers in SSM :(
thagr- I knows, about wing placement and how the rear axel acts as a fulcrum point. I am curious as to what might be the effects of putting the weight straight down on the wheels.
I wish I knew someone who could help me get the car into a mag. SCC was going to do it, but they folded right in the middle of our discussions.
Chris- Don't worry, I have no forgotten a single thing you have discussed with me about aerodynamics I was just contemplating and take all information in. I wish we could run diffusers in SSM :(
thagr- I knows, about wing placement and how the rear axel acts as a fulcrum point. I am curious as to what might be the effects of putting the weight straight down on the wheels.