kaz there is a wind tunnel much closer to you --ill find out about a price---im building a new bike and i would like some tunnel time probibly around april of 09 if you can wait until then maybe we could go together let me know willie buchta
Willie,
You need "Race Car Aerodynamics: Designing for Speed" by Joseph Katz, ISBN 0-8376-0142-8 He has a whole chapter on wind tunnels and how to correct for ground effects.
The following is HIGHLY simplified explanation of wind tunnels. Sizing your tunnel should be based on about 2X your vehicle width and height. The bigger the better, but fans get expensive really quickly. Fans are available to move a given number of CFM at a very low airspeed, so it is common to use a 3 to 10X cross section increase and literally fill it with fans. For your application you may be able to get away with just one large HVAC fan. This would be great for you since they are belt driven, and you can change speeds by changing belts. More velocity than the motor will pull? Get a second motor and add another belt. It is best if the inlet of the tunnel is a bell mouth (like a velocity stack inlet) that is at least 4X of the tunnel test section area and about 2X as long as it is high or wide, whichever is greater. This gives the incoming air plenty of time to straighten out.
The big issue is the instrumentation. Objects in wind tunnels are normally mounted on a "sting" mounted to a "balance". Plenty of books on this, even Wikepedia may have a design. This takes up a lot of room and constitutes a large portion of the cost of a tunnel.
If you just want to look at smoke and tufts, it's a lot easier. One thing you might look into is mounting a large sheet of acrylic as your ground effect diverter so that you can crawl under and look up at the belly (put tufts there too). Lots of drag underneath these cars that no one ever looks at.