Auto Racing: Homeade Wind Tunnel, soap box derby, john quarles

Question
I am doing a science fair project for high school and was wondering if you had
any knowledge on how to make a small scale (soap box derby type cars) wind
tunnel in which I could do test. Very low budget. If you have any other
information about wind tunnels of aerodynamics that you could share, it would
be appreciated.

Answer
That's a great question.
It is possible...but for the size vehicle you are building it would probably be too expensive. I am assuming that when you say soap box derby, you mean a car that a junior sized person would fit into. Maybe four feet wide by 6 feet long. If that is true then your tunnel would be 10-12 feet wide, 6-8 feet tall and 15-18 feet long. You would need a fan(s) that could pull enough cfm (cubic feet per minute) to move air 10mph (assuming that is a good speed)in that tunnel. the fans and motors would kill your budget.

As alternative would be to scale every thing down to maybe 10th scale. Build a replica of your car out of wood and build your tunnel out of plexiglass or plastic. I have done this before. For the fan, I took an old blower from a house air conditioner and used it on the back end of the tunnel so I was sucking air through the tunnel.

If you have any more questions feel free to contact me by email.

John Quarles
jgquarles@yahoo.com