Aerodynamics Help
 

If there are any aerodynamics specialists in the room, please stand up !

I'm in the process of installing a new rear race aero wing that is fully adjustable and having a custom mounting plate built to attach it where the old OEM wing is.

This wing is capable of producing 600 lbs of down force at 110 MPH depending on how the forward section and rear section are adjusted in relative terms to the airflow over the car.

If there are any aerodynamicists in the room, can you give me a simple equation that will allow me to adjust the wing at intervals (lbs of downforce) based on the speed of the car, size of the wing area and angle of the wing ?

Re: Aerodynamics Help
 

I'll have a dig through my back issues of Racecar Technology etc. but I think it will largely be trial and error due to all the variables. Also you may end up creating downforce which will be great for the high-speed corners but it may come at the expense of more drag on the straights if you end up running too higher angles of attack.

Re: Aerodynamics Help
 

I do have the formulas but it will cost you some greenbacks for that kind of info. :)

Re: Aerodynamics Help
 

Hey, wait a minute...Aren't Maxwell's Equations free? :p

Re: Aerodynamics Help
 

Gottem' off the internet... drag coefficient and downforce based on wing type, size, angle and velocity.

This is a dual wing set-up with the principal airfoil being a NACA S1221 that measures 56"w X 8"d and a Gurney flap that is a NACA S1220 12% airfoil measuring 56"w X 2.5"d. Both are independently adjustable.

Toughest part was determining a velocity for the calculation. To do this, I went back to all my track times from last season which lists average speed per lap as well as time. I averaged the speed (velocity) on each track independently, then made the calculation at incremental angles of the wing at the averaged speed.

Looks like most tracks will require an 11.5 degree angle for optimal performance (downforce vs drag) Producing an averaged downforce of 212 lbs. While the faster tracks (CAL SPEEDWAY, etc) will require somewhere in the 10 degree range.

Looks like I'm going to have to invest in an INCLINOMETER... My standard Craftsman bubble balance aint gunna do the trick !!! :mad:

Re: Aerodynamics Help
 

I am not familiar with Maxwell's numbers, but I would bet that the angle stated has to be relative to the airflow. For example, assuming the air "hugs" the downward slope of the rear of a coupe, then it would probably be 11 degrees off the downward slope. If the airfoil extends further away from the body, it might require less if the angle of the airflow is closer to parallel to the ground, but it might require more if it ends up in a turbulent area of airflow. Other factors to consider include the air fold shape, flat plate vs. cambered (thickness) and surface area.

Start at 11 degrees from the downward slope of the body. Then try it and adjust. It will require some time, unless you have access to a wind tunnel.

Re: Aerodynamics Help
 

If you are using the speed of the car in your calculations, you will probably get more downforce than you are calculating. The downforce should be calculated based on the local velocity of the air in front of the wing. As the air accelerates over the car, the air velocity near the wing should be higher than the speed of the car. However, depending on how far away the wing sits from the body, and the turbulence of the air near the rear of the car, the local air velocity could be much less than the speed of the car. Your calculations should give you a good starting point, but as Top_Down_SRT said, it will also require some practice to fine tune it. Also, the airflow over one wing section will affect the other. Make sure you are using equations for a wing with a flap, and not looking at each wing separately.

Re: Aerodynamics Help
 

Thanks Craig: I used the prelim calcs to find an angle of attack as a starting point. You're right about testing... It's a ballet dance... I also have to find that point where the downforce on the rear starts to create an understeer situation.

11.5 degrees down is a good start point for now.

Re: Aerodynamics Help
 

I think the Chaparral 2J had it right.
Drop in a big honkin snowmobile engine spinning exhaust fans. Be sure to get the plexiglas skirts the right length so they don't break off on bumps and curbs.

http://www.motorsportcollector.com/C...TOS2/2Jp2.jpeg

Re: Aerodynamics Help
 

hehe Feets...ugh...me thinks they did some adjusting to the rules to keep this from happening again!

That was a very crazy car...

Re: Aerodynamics Help
 

Remember the Brabham BT46 fan car that got banned from F1 too?

Re: Aerodynamics Help
 

Woody, that's always the trade off isn't it...just wanted to know if you (or anyone else here) have any thoughts on adding to front end DF for Derek's effort. We've had a discussion some time back about front end splitters (for aesthetics only in that discussion) but might that be a possibility (is it legal in D's class?) to help with off setting drag from rear end spoiler/wings?

I have some friends in F1 land who are connected to teams...I don't what I can find out but i'll see if they have some resources they can point D to.

Derek...having looked at the point system in your class...now I can see how your mods/weight reduction and such have put you in this fix...will the wings/splitters just add to the problem or are you well within (low enough points) where aero upgrades won't move you up to "B"?

Re: Aerodynamics Help
 

I'm firmly planted in TTC this year. No getting around it. So now that I'm in that class, I have some more modification points to play with, thus the reason for the installation of the rear aero wing which added +3 points... The splitter has been discussed with my mechanic, as well as a full belly pan and a few other things. We still are looking at ways to lighten the car even more. I'm down to about 2,570 lbs. which has turned this thing into a rocketship in acceleration. If I can shave another 100 lbs and then goose another 20hp out of the car, I'll be happy.

PS: This car is not pretty now... It's chopped-up and cut-up and needs a good clean-up paint job with cool graphics. But I promise you, it will be the fastest damned Limited in the US when I get done with it....

Re: Aerodynamics Help
 

Yep, I've been thinking of this and keep sketching out ideas. I started to think about more whilst photoshoping some race graphics at the weekend. I'll post something up when I get chance to put something together.

I think I have alluded to this before, but the designers have payed a lot of attention to the aerodynamics on this car; just look how smooth the unedrside is, the undertray and the fairings on the rear wishbones to preventing disturbance to the airflow before it leaves via the rear diffuser.
I think shaving those big mirrors may be worthwhile too on a race car. Oh well, out with the sketch book again.....

Re: Aerodynamics Help
 

I finally got the new aero wing temporarily installed. I had to have some new brackets built and a plate that attaches it to the hatch. I have not finished the install and need to do some minor tweaks before it is completed and painted. I'm going to cut slots into the OEM wing so it fits back over the "indentation" and around the brackets of the new wing so it doesn't look so bad and fills in the "indentation" much like when the OEM wing is in the down position. The width of the wing was cut down to allow sideview mirror and follow the airflow from the cabin... And the angle has not been adjusted yet...

I told you the car was a mess right now, you should see the inside !!! LOL

Re: Aerodynamics Help
 

Derek,

That thing is MASSIVE! Geez... I bet you get more downforce than the SRT wing.

What are the recommendations from the manufacturer for spacing on the mounts? They look a little close together to me, but I suspect you are using the stock mounting areas as they are more beefy.

Lookin good bro! Keep us up to date!

Re: Aerodynamics Help
 

Nice work Derek! Like Timelord say - its MASSIVE, animals and small children beware:D .
I actually took mould off the oem rear spoiler if you just want thin piece of GRP to cover the recess rather than steel. I'll get a pic at the weekend.

Re: Aerodynamics Help
 

OK Guys: I wouldn't have done this if it was a street car... It's way too studip looking to not use it for the specified purpose... 212lbs of downforce on the rear... Period, end of story...

It would look like a retarded BLING BLING street car if I was driving it around Hollywood... but then again it's not a street car any longer and please try to keep that in mind... There is a method to my madness... And my madness has not come without some research and a few laps around the track. ;)

Don't hate me for making this car a bit faster without spending too many $$$ on modifications... I'll get to the other high dollar mods when I have the money and time...

Lighter weight + more downforce = faster times and less apologies !!! I got screwed with the new rules for NASA and it put me into a faster class. I didn't have the time, money, or resources to do the engine mods before the start of the season in February and the fact that I'm having to uproot myself and move to South Carolina in less than a month.

PS: the wing is not as HUGE as it appears in the photos. Perhaps it was the angle... It is barely perceptual from the front of the car, but it still should give me the added speed through the corners that I will need.

We'll see...

Re: Aerodynamics Help
 

No problems here Derek, its a race wing, on race car! Very similar to the wings they run on the British Touring Cars.

Re: Aerodynamics Help
 

Yeah, it's BUTT ugly if it was installed on a street car, heck, it's butt ugly on this car and ruins the pretty lines... I hate the looks... But I know how my car reacts on corners now that the traction control has been disabled and I end-up with alot of turns the produce unmounted weight and a big slide till the car settles again.

Unfortunately I will not have a chance to test the car until Feb 10th & 11th when I run the first event for the season in the Southeast Division. On a track that I have never even seen in person... And I'm going balls-to-the-wall this season and want a podium.

What the hell, it's all about the fun...