Airfoils and Wind tunnels.

[chrismcb]

I am looking into designing an airfoil to reduce the drag behind a small vechile (about 7 feet long, 1.5 feet wide, and a 1 foot high)
I was thinking about building a small wind tunnel to do this.
Am I crazy? Can I build a small wind tunnel to do this work? Do I need to, is there another way to work on an airfoil? Am I just out of my leaque?

Thanks
Chris

 

[GregLocock]

What makes you think that adding more surface area to a system will help reduce drag?

If your system is not producing any lift or downforce then the best thing to do is often to get as much laminar flow as you can over the main body, and then decide whether a cut off tail will work better than a complete taper.

I think buying a book on aero would probably be a better investment of time/money.

We evaluated the aerodynamic form of our solar car by building a 1/5 model and measuring the pressure distribution using a car and a roof rack and a big sheet of plywood and manometers.

The trim of the final vehicle was set by looking at the power/speed curve, but we could probably have used coastdown data instead.


Cheers

Greg Locock

 

[chrismcb]

Actually the primary goal is to clean up the air behind the vehicle, to make it harder for someone to draft me during a race.

As for doing research, can you recommend a good book on aero?

Thanks
Chris

 

[GregLocock]

"Actually the primary goal is to clean up the air behind the vehicle, to make it harder for someone to draft me during a race."

Ah, devious. The best way to minimise the drafting potential is to punch as small a hole in the air as possible in the first place - that is by improving your pressure recovery - so you want no separation and ideally minimal friction drag. So by a circuitous route we still end up with the same requirement - an additional wing will make things worse not better.

As to books - there's plenty of recommendations further down - Katz is a classic.


Cheers

Greg Locock

 

[matt00000]

As Greg says you would need to make the car into a symetrical wing with zero angle of attack to make the hole smaller! Is that allowed in the rules?
Dont think that a wind tunnel is the way to go.

If someone is drafting you move over!