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By C. Jake Williams. March 31, 2008
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I draft while driving. I don't do it to save time, I do it to save money.
There are 100 miles of gas-saving opportunity between West Jordan and Logan, and I take full advantage of that pavement.
Drafting is the idea that if two cars work together, their combined aerodynamic resistence can be decreased. Alone, Your car runs face first into stationary air molecules and has to move them out of its way. Moving matter, even air, takes energy. Energy means fuel. But if You tuck Your car behind another, then the air molecules will already be in motion and much of that motion will be in the same direction as You. Less energy to move the air means less fuel.
Now don't get me wrong, You know drafting has a racing connotation. We've all seen NASCAR and Indy drivers tuck within two feet of the racer in their way. That's not what I'm doing. That's not what I'm saying You should do.
What I'm saying is that You still have an effect on the air that lies three seconds behind Your moving car, and that's where You'll find me. If You slam on Your breaks, I still have time to hit mine without hitting You. I'm not close enough to cause an accident, just close enough to spend less at Chevron.
Are You mad at me? You should be mad at me, because I'm stealing from You in the process. Not only am I reducing the air resistance on my car, but I'm increasing the drag on Yours. Let me explain.
The speed of sound is roughly 700 mph, but what does that really mean? The concept we've dubbed 'the speed of sound' is a measure of how fast air molecules can communicate with one another. As long as an object is moving under 700 mph, the air it impacts will warn the air up ahead that something is coming.
Have You ever heard a sonic boom, which occurs when an object exceeds the speed of sound? Well that boom is the equivalent of the scream You make when I successfully sneek up on and scare You. "Holy fuck!" the air says. "Why wasn't I warned an F-16 was coming?" Lets get back to our cars.
While I'm cruising in the lowered air pressure bubble created behind You, I'm slowing You down. This is because the air around my car, travelling well below 700 mph, has plenty of time to communicate with the air up ahead. Up ahead, like where You are.
Your car will pull mine along the road while Your car will pull Yours back. The air acts like a rope between us, and I'm the one wakeboarding.
I save about ten percent on fuel efficiency using this method. Instead of 30 mpg at 75 mph, I get 35 mpg behind a semi if I can find one willing to drive that fast. Most of the time I can't though, so drafting ends up saving me ten percent at the pump but costing me in time spent on the road.
That's a fair trade.
You were there.