Quote:
Originally Posted by solarguy
A semi has less surface area than a car, per pound.
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I think you mean cross-sectional area? It's something people tend to forget when they talk aerodynamics. Cd is a function of shape, so a low Cd is better, but drag is Cd * cross-section. So even though the semi may have a high Cd, the cross-section relative to total weight is much smaller, so drag per pound is less.