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Old 02-08-2015, 01:00 AM   #28 (permalink)
Master EcoModder
Join Date: Oct 2012
Location: Carson City, Nevada
Posts: 612

Jimmy - '00 GMC Jimmy SLT
90 day: 21.18 mpg (US)

The White Gnat - '99 Suzuki Swift
Team Suzuki
90 day: 51.87 mpg (US)
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When I was campaigning my salt flats race car, I wanted to know it's frontal area, so I used the shadow method. At the time, I didn't have a way to drive it (not street legal and/or engine not in it at the time), so I had it on my flatbed car trailer.

Then I took a sheet of particleboard and built a simple brace so I could stand it up at the back of the car trailer behind the car. The board and brace was held up and held together by c-clamps and "quick grip" clamps. Then I went to a place I could park it facing the setting sun and jacked up the hitch until flatbed of the trailer was aiming at the right angle up (the sun was still a few degrees up).

I used the symmetry of shadow on the board to help get the aiming right. Once it was right, I quickly traced the outline of the shadow on the board with a fine tip marker.

Then I drew a grid on the board, spacing the horizontal lines one inch apart. Then I just carefully measured the lengths of each of those lines, wrote them on one side of the shadow outline, and added up the numbers. The result is what I used as the frontal area of the car in square inches.

....To get square feet, just divide by 144.

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