Landracing Forum
Tech Information => Aerodynamics => Topic started by: Paolo Castellano on January 21, 2017, 11:15:41 PM
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Just wondering if anybody would have any idea how to calculate how much down force a rear pro mod wing would generate with different total surface areas for length and width and then say if you increased height of the back end of the wing by say 5-7 degrees max.
From what I understand the wing allows the air going over the top of the car off the back end to have a less turbulent boundary layer that creates rearward suction and drag.
Also how about a calculation for what downforce a splitter on the front end would generate surface area-wise as well assuming zero degrees in relation to the rake of the car.....
I know this is not a simple question with a simple answer, but I just want to know if anybody has some general way to approximate what additions like this might generate.... I have seen some really smart posts from some of the guys on here so I figured I would ask...
I remember Mike LeFevers telling me about some lakester car that went 0-312 MPH at El Mirage on 6" wide tires on Nitro with an adjustable rear wing that was trimmed out the faster he went. Anybody remember the name of that guy and car? It's been so long I do not remember.
I saw a rear wheel drive car at the 1/2 mile today go 228 MPH but he could not put a lot of power to it until he was near the end. Just trying to figure out how to ball park adjustable aero for front and rear. I have laser ride height sensors so I will be able to monitor ride height and plan to blow the exhaust out the back of the car to improve the recombination of the air coming over the top, bottom and sides of the car to minimize drag and improve downforce.
Can anybody point me in the right direction? Thanks!
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Bueller? Bueller??
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Paging Ferris, where are you, Ferris Bueller?
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Ummm, He's sick. My best friend's sister's boyfriend's brother's girlfriend heard from this guy who knows this kid who's going with the girl who saw Ferris pass out at 31 flavors last night...... I guess it's pretty serious........
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How come no replies on this post by Paolo????.
Woody??????. :cheers:
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For the wing - Give me the NACA number, camber details and square footage and I'll post the results and formula - I'll do it old school with pen and paper too!
If you want to see how the calculations work, pick up "The theory of wing sections" and give it a read. Really good stuff - HORRIBLE READING though. Not many pictures, lots of math and a whole bunch of charts.
The formula you are looking for to calculate lift/drag on the wing is pretty straight forward though.
Not sure if this is the whole book or not but it has enough to get the lift/drag numbers for a wing:https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090976.pdf (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090976.pdf)
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How come no replies on this post by Paolo????.
Woody??????. :cheers:
Mike, I got stuck on his original question: "Is anybody smart here?"
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Mike, I got stuck on his original question: "Is anybody smart here?"
What did you come up with? :roll:
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bbarn - for full credit be sure to "show your work". :mrgreen: :mrgreen: :evil: :-D
vic
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How come no replies on this post by Paolo????.
Woody??????. :cheers:
Mike, I got stuck on his original question: "Is anybody smart here?"
:-D :-D :-D :wink:
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Well at least he didn't ask about a Roadster.
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Well at least he didn't ask about a Roadster.
Or, heaven forbid, a /RMR :dhorse:
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The roof, tail, rear undercarriage shape & size all affect how the wing works, as does height, placement, and angle.
When you're done with the math you still have to try it out.
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Not sure if this is the whole book or not but it has enough to get the lift/drag numbers for a wing:https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090976.pdf (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090976.pdf)
I cant open the link :? :?
[/quote]
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Not sure if this is the whole book or not but it has enough to get the lift/drag numbers for a wing:https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090976.pdf (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930090976.pdf)
I cant open the link :? :?
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It is just a pdf. See if it downloaded it for you automatically...chrome will do that
Sent from my SM-T280 using Tapatalk
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Just wondering if anybody would have any idea how to calculate how much down force a rear pro mod wing would generate with different total surface areas for length and width and then say if you increased height of the back end of the wing by say 5-7 degrees max.
From what I understand the wing allows the air going over the top of the car off the back end to have a less turbulent boundary layer that creates rearward suction and drag.
Can anybody point me in the right direction? Thanks!
Short answer is: Depends on the NACA profile.
There are L/D plots for angles of attack published for most NACA's. However, a Promod wing will likely not be in the published tables. The NACA tables are not published by calculation but by physical testing. Any test data on race car wings is usually propitiatory.
Since stall positions are affected by more than just airflow (particularly in cars on the ground) Lift and Drag profiles are not necessarily going to reflect the NACA tables either. And even CFD struggles to predict this (which is why you need to take most CFD data with a pinch of salt unless there is serious tested verification to prove the model).
Can it be calculated? Yes. Do you want to? No. Best solution = A day in a Wind Tunnel.
Now which wind tunnel.... that is a whole new can of worms! Tunnels can be wrong too.
Look for: Reynolds Sensitivity, Boundary Layer Displacement (Rolling road vs Static ground), Blockage Ratio and Static Pressure Gradient. If they can't answer any of those questions, look elsewhere. (And even if they can answer them, make sure they are the right answers).