Quote:
Originally Posted by Chance
I personally see the two examples above as very different from a typical RV with its truncated rear. So much so that I don't think the same theory is applicable.
The bike helmet reduces the rider's coefficient of drag by tapering gradually so that air flow doesn't separate as early as when using a standard helmet. This is same principle as the tail cone of an airplane, which tapers very gradually. Most people think it's the front of vehicles that offers the most potential to reduce drag, but in most airplanes the back end tapers very gradually. And most modern cars with low Cd also taper gradually to reduce creating a partial vacuum behind the vehicle at speed.
By comparison a typical RV has the side walls forming a 90 degree sharp angle with the rear cap. Because of this I expect separation at the rear edge of RV with or without tabs. Likewise I expect the partial vacuum at the rear to be essentially the same. If the pressure is similar, then the total force the engine has to work against is also very similar.
I hope I'm wrong because it'd be great for improvement to be that easy.
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What I was trying to get at, was that I think the air tabs simulate the tapered bike helmet by adding energy to the airflow, so that it flows back smoothly similar to the bike helmet, rather than folding back in behind the blunt rear which causes the eddy currents, turbulence, and drag.
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