ground effect by smooth undertray on track ??
 

Hello

someone has an idea how much time advantage approx. can bring a

smooth undertray like pic on a grand prix circuit of 3mls lenght.

thanks
alex

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Attachment 67811

Interesting. I have no idea, but want to find out..

You won't get "Ground effects". To do that, you need seriously low ride height, like F1 Ride height or less! I.e. Track car only, and stiffly sprung, low slung track car at that.
You also need Venturi tunnels to feed the rear diffuser, and this takes some serious design to do, like Computational Fluid Dynamics and/or wind tunnel time.

What you may succeed in doing is smoothing out airflow and so reducing lift/ ochieving better air flow under the car, but it would be very much luck of the draw unless some serious effort was put into the air flow under the car, into the wheel wells, through the engine bay etc etc,

i would have thought it would have to go all the way back aswell and as said lower.side skirts that are very low would help, simple in theory, very hard in practise
one of the old williams f1 cars used to have rubber strips that slid up and down in the sideskirts that contacted the ground to stop the airflow leaking out and slower air coming in creating almost a vacuum effect aswell as the wing effect. it was quickly banned.

no idea about techncal sides of thing but ive seen the underneath of a few 'very' quick cars.....

mclaren f1 (roadcar)
mclaren slr
mclaren mp4-12c

..... they are completley flat!

from front to back, newer ones sweep into the rear diffuser.

maybe the difference is keeping the engine cool when it not front mounted etc for different underfloors.

Ask some of the time attack guys as they run flat bottoms.

http://www.surreyscoobies.co.uk/foru...t=38176&page=2

For the ultimate in 'ground effect' - Chaparral Cars 2J

http://ashcom.homestead.com/RMH3257W.jpg

As most of you know the underneath of the car is where you gain the most from aerodynamic efficiency. A flat floor will help because it's all gains because it will smooth the airflow under the car.

As said it's only as good as the diffuser that it feeds if you want downforce. Basically the diffuser is an expansion that draws air out the rear of the car creating a negative pressure. This pressure "sucks" the car down, hence the downforce.

To know how much you would gain would require some sort of simulation be it CFD or wind tunnel testing to determine the difference to before and after. Following this you will then have to perform lap time simulation.

I know as I've done it before and it's a lot more complex than just saying over 3 miles you'll gain X seconds.

As for the Chapparal, that car had skirts that followed the contours of the road and those fans on the back of the car sucked the air out to create a vacuum under the car. Imagine it like trying to pull a jug out of the bath upside down.

I have been talking to friend who is building a track car and he has a friend who had 5 hours in a wind tunnel courtesy of red bull racing, they worked that the back of the impreza bumper and boot floor be removed and a panel fitted, with an angle 30 degrees this gave the most suction to hold the rear of the impreza down on a track day, still not seen car in action so can't give full report on effects

:thumb:

My aero has moved on since then a little ;)

Time difference per lap ... difficult to say but worth it

This can help guys for testing yours flat floors,if they work,its primitive but results are OK

http://autospeed.com/cms/A_111111/article.html

http://www.autospeed.com.au/A_109937/cms/article.html


Jura