Poor Man's Wind Tunnel

I ordered a wind tunnel from ACME Wind Tunnels, but due to Katrina it has not yet arrived. In the mean time I thought I would read a bit about wind resistance. One of the major factors a cyclist must overcome is wind resistance. Other factors include rolling resistance, and of course gravity. One of the major factors affecting wind resistance is frontal area. Yes, I know the shape and slickness of the frontal area has a lot to do with it as well, but reducing the frontal area is key to reducing wind resistance. Anyway without my ACME wind tunnel I decided to take another tact. I thought I would photograph my subject (daughter Liz in this case) from the front, then magically (through some home made software) remove everything from the picture except the bike and person. Voila, the number of pixels left would be a rough gauge of frontal area. For sure I could compare one position on the bike versus another and then determine which position had the smallest number of pixels and therefore frontal area. Given the resolution of modern digital cameras, I was able to "see" the difference when she had exhaled vs. inhaled. That was proof enough for me that I am on to something. I have not run through all the math as of yet, and only consider this to be in the beginning stages but so far I know that Liz takes up 52 % of the frontal area when she rides on top of the bars, 46 % when she is on the hoods, and an amazing 40 % when she is in a somewhat sloppy Time Trial position. Here are all the pictures, including a screen shot of the software that calculated the non background data.

Thanks to the good folks at Electric Pi (www.electricpi.com) for providing me with Electric Pixer, an image annotation piece of software which I was able to add a background removal function.