How to start designing a multi-element wing?

[weis]

Hi all,
I am working on front and rear wing design for a Formula car. i wonder how should i start?do i have to start with 2D profile analysis to get the distance between the elements?how can i get a good aerofoil profile?anyone could guide me with some references?
thanks in advance

[Monstrobolaxa]

"competition car downforce" - Simon Mcbeath

Like Simon points ou in his book on a first simplistic approach though you have 2 alternatives!

First - figure out the amount of downforce you want (don't look at drag now)...grab the wing width you want....through a simplistic calc you can figure out the CL of the wing.....then grab a airfoil profile catalogue and take a look at the profiles there....and choose the one that best suits you.

Second - if you have the the Hp of the engine...you can determine the amount of Hp you're willing to sacrifise for drag (hp at the wheels not at the flywheel...so consider the losses)...with this info you can calculate the Cd of the wing.....and going to the catalogue once again.....

You can also include the weight distribuition in order to know what the diference of downforce is between the front and back to maintain an aproximatly the same amount of diference between downforce at the front and rear, and weight dist front-rear.

After this I'd say.....go to a 3D design software....and after that start CFD testing....untill you find reasonable/expected values! Then tweek with the wing shape...position....kinds of profiles.


The first approach actually is my own approach (didn't read it)....the second one came from the book! I prefer to start with the downforce even if it compromises drag and then try to eliminate drag....

[West]

That book is really helpful for the novice; it will show u how flap lengths/gaps are calculated and examples of a few NACA profiles.

[Monstrobolaxa]

Another book....though a little more technical also very helpfull:

"Racecar Aerodynamics" - J. Katz

IMO "R.A." is better in terms of overall aerodynamic interaction and analysing it mathematicly...."C.C.D" is a more simplistic book that is very good for "novices" and it basicly only really talks about wings! It does talk about other aspects put it focuses more on wings (design, analysis), while "R.A." almost everything. (do you agree West?)

[West]

I haven't read RA... in fact CCD is the only technical book I have... aside from the F1 Technical Analysis books... I spend too much money on model cars instead. Maybe this year will be different, as there aren't any cars that really interest me right now (except Alonso's and the TF105).

What I really want to get are the vehicle dynamics books by the Milliken brothers. I heard they are excellent.

BTW I heard Simon McBeath will make you a wing if u need one; he made one for the project car in Race Tech Magazine

[Monstrobolaxa]

Miliken is fantastic.....I have it....a scanned version of it! In any case it's fantastic, it's more or less the bible of vehicle dynamics.

[West]

How is that book? At around 80 - 100 bucks it isn't cheap. Also, my engineering background is very basic, even tho I'm about to graduate, so i was wondering how "easy" it is to understand, or how easy it is to apply to a road car. My friend autocrosses, so I was wondering if it would help me setup his car.

[Monstrobolaxa]

Hummm...I haven't read Miliken....but I've heard in quite a few magazines that it's the way to go! I have gone through it and I think it's a little on the tech side!

I have one called "Chassis Engineering" - Adams which is used by a few FSAE/Student teams to design the suspension geometry....or at least to get the info in a acessible way! I can't really mention a book on proper car setup.....I don't have any! But IMO opinion a book like that is only a very generic one....setups aren't that linear they might vary a lot from car to car due to the diferent suspension geometries....

[West]

I have that book too... I only really appreciated how weight transfer works on tires. But it still felt a little too simplistic. I also didn't like the idea that they actually cut springs, whearas nowadays suspension suppliers would not recommend doing so.

[Monstrobolaxa]

Yes that one of cutting the springs caught my eyes too.....probably in the next version they'll have the briliant idea of torching the springs..... (it would be a good idea if they added that they should go back into the "oven" to distribui the metalic properties equally through all the spring)

[West]

Another good book would be something from Caroll Smith... I forgot what it's called, something like Engineering to Win. It will set u back around 80 bucks tho, but usually it's the standard to build a race car.

I am spending more time playing BF2 than keeping up w/ engineering. Once school starts I'll probably start buying some technical books.

[Scuderia_Russ]

I own Engineer to Win and can confirm it is an excellent book. Covered are-
*metallurgy
*bplastic and elastic deformation of metals
*Iron and steel making
*Alloying and heat treatment of steels
*Historic overview of mans production of iron and steel
*Metal Fatigue
*Threaded fasteners
*Joining materials -riveting,bonding,welding.
*Plumbing
*brRacing wheel and tyre
*Springs and shocks
*The wheel and tyre
*Load transfer +susp. geometry
*'box and final drive
*Tools and tips

.....plus many more chapters. It's full of useful information and a must to have on the bookshelf! It only cost me £17.99 which i guess is about $35- $40. Try Amazon, they are usually pretty cheap and have most publications in stock.

[Monstrobolaxa]

Carol Smith has a big collection of books......you can buy the whole collection at the SAE website...if you buy the whole collection you get a discount.

[weis]

Greetings!
Thanx very much for the reply. I will try to look for the books. I guess i ll take the first approach bcos drag should can be reduced at further design stage, down force is much important in my case. Btw, i have been searching around in internet, is there any links to airfoil profile catalogue?
(the points, Cd, CL, Naca series etc...)

Thanks again. This forum is very knowledgable.

"competition car downforce" - Simon Mcbeath

Like Simon points ou in his book on a first simplistic approach though you have 2 alternatives!

First - figure out the amount of downforce you want (don't look at drag now)...grab the wing width you want....through a simplistic calc you can figure out the CL of the wing.....then grab a airfoil profile catalogue and take a look at the profiles there....and choose the one that best suits you.

Second - if you have the the Hp of the engine...you can determine the amount of Hp you're willing to sacrifise for drag (hp at the wheels not at the flywheel...so consider the losses)...with this info you can calculate the Cd of the wing.....and going to the catalogue once again.....

You can also include the weight distribuition in order to know what the diference of downforce is between the front and back to maintain an aproximatly the same amount of diference between downforce at the front and rear, and weight dist front-rear.

After this I'd say.....go to a 3D design software....and after that start CFD testing....untill you find reasonable/expected values! Then tweek with the wing shape...position....kinds of profiles.


The first approach actually is my own approach (didn't read it)....the second one came from the book! I prefer to start with the downforce even if it compromises drag and then try to eliminate drag....

[Guest]

Here is an excellent little java applet that will calculate a NACA airfoil profile for you according to the pareameter you choose (max camber etc.)

http://www.pagendarm.de/trapp/programmi ... NACA4.html