Considering the fact that this test was made over 25 years ago and it
stated that "Lockheed has learned a lot about car and truck aerodynamics"
in the past 15-20 years, the test results may be correct for the older body
styles. Also, this test was, more than likely, done on a STOCK
Truck...let's put some bed-rails on it or a large toolbox. Now, run the
test one more time...Totally different results will appear since the
"seperated bubble" effect is now altered...guaranteed.
Put a Tonneau cover on it and run the test again...different results...
What about these "Super Intelligent" people who put the silly wings on the
back of their trucks...run the test again....different results.
This could go on and on but to make it simple, different things work in
different scenarios. The only proof what really works is your own results.
Nothing against the Military or Locklheed, but their test(s) data is one-sided.
At 04:04 PM 04/07/1999 -0400, you wrote:
>I'm an aerodynamics engineer. When I was in the U.S. Air Force a few years
>back, I worked with folks from the Lockheed low-speed wind tunnel. In the
>1970s, aircraft production went into a slump, and Lockheed started looking
>for other customers for its wind-tunnel services. Prime candidates were the
>auto makers, and Lockheed was successful in convincing Ford, among others,
>that the wind tunnel would help them reduce drag and wind noise on their
>vehicles. Needless to say, in the past 15-20 years, Lockheed has learned a
>lot about car and truck aerodynamics. Anyway, they actually performed drag
>tests on pickups with the tailgate both up and down, and found that drag was
>actually LOWER with the tailgate CLOSED! This ran counter to their intuition
>(and yours). The reason is that a closed tailgate sets up a large "bubble"
>of stagnant air that slowly circulates around the bed of the truck (we aero
>types call this a "separated bubble"). When air approaches the truck, it
>"sees" the bubble as part of the truck. So to the air, the truck looks like
>it has a nice, flat covering over the bed, and the air doesn't "slam" into
>the vertical tailgate. If the tailgate is open, or replaced by one of those
>"air gate" nets, however, that nice, separate bubble in the truck bed does
>not form (it "bursts"). Then the air approaching the truck "sees" a truck
>with a flat bed on the back of a tall cab. This is a very nonaerodynamic
>shape with a very LARGE drag. So, believe it or not, it's best for gas
>mileage to keep the tailgate CLOSED. Hope this information is helpful. Ed
>Fitzgerald, Research Assistant, Dept. of Aero/Mechanical Engineering, U. of
>Notre Dame
>
>
>
Bernd D. Ratsch
Pflugerville, TX
http://lonestar.texas.net/~bernd/Dakota.htm
1997 Dodge Dakota SLT/CC (V6)
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