This was brought up in another post and I didn't want to hijack the thread. Kona brought up the subject of the aerodynamics of leaving the tailgate up or down. I've seen the explanation that leaving the tailgate up is more aerodynamic but I've always wondered if that was a myth. After a quick (read, not exhaustive) google search I found a study done by a mechanical engineering student in which he watertunnel tested a scale model of a dodge pickup. Here are the coefficients of drag that he found:
Quote
Baseline condition Cd = 0.432 (without mirrors)
Square Cap Cd = 0.480 11.11% Increase in drag
Replace tailgate with a cargo net Cd = 0.461 6.71 % Increase in drag
Removed Tailgate Cd = 0.447 3.47% Increase in drag
Lowered Tailgate Cd = 0.414 4.17% Decrease in drag
Tonneau Cover Cd = 0.381 11.81% Decrease in drag


With the tailgate down, the coefficient of drag decreased as compared to the tailgate up. Interestingly, the cargonets increased the drag. To add some credibility this guy won the 1997 American Society for Mechanical Engineering Young Design Engineer's Paper Competition International Award, whatever that is.

Here's the website.

Last edited by Robinhood150; 10/21/03 12:06 AM.
Steve
My Website ||Gettin' off 4wheel drive club member
'93 4Runner V6 4x4 auto tranny
If you have to ask about a SAS, you're not ready for it.