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Old 08-24-2014, 12:41 PM   #1 (permalink)
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does front/middle matter if rear is to be whaletailed?

Hi people, for any remembering my past chain of posts and projects i've been offline and projects set back almost a year due to... unexpected personal crises. :P



At the moment am wanting to plan out a pickup/SUV option... what i'm curious is that if i'm planning to stick a whaletail on the back anyways of similar shape, does it matter what the middle of the vehicle is? Ie - should I get the same MPG from a single cab pickup, crew cab pickup, and Suburban/Excursion provided they got the same tail treatment? (i'm thinking yes, just curious if anything I missed)

And as far as the front end, since i've seen both blunt and swoopy fronts i'm wondering how much it matters there as well. For instance I might want to use a 1980's chevy pickup because it's easier to modify powertrain/underhood stuff, and although it's got a fairly vertical windshield I read somewhere it was the first pickup designed with computer aided aerodynamic design. (though I cannot find a coefficient of drag anywhere)

Yet the 1990 chevy pickups have the windshield back a bit more I think as well as a smaller frontal area. (i'm guessing the frontal area may have had more to do with the 1-2mpg better highway ratings vs the 1987 pickups but without CoD numbers for either truck I can't be sure) Yet maybe with a full whaletail there wouldn't be much difference?

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Old 08-24-2014, 04:03 PM   #2 (permalink)
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Yes, It matters quite a bit. If you notice the evolution of vehicles, it isn't just the angle of the windshield, it is also about the radius from the windscreen to the roof. This radius has gotten much larger on modern vehicles. The air is going to be moving and have a certain amount of "Momentum" when it hits your "Whale Tail", the way it is moving will have a fairly large effect on how it performs. If the air has been ramped up quickly, it will have a harder time coming back down to your rear enhancement.
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Old 08-24-2014, 05:17 PM   #3 (permalink)
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Quote:
At the moment am wanting to plan out a pickup/SUV option... what i'm curious is that if i'm planning to stick a whaletail on the back anyways of similar shape, does it matter what the middle of the vehicle is? Ie - should I get the same MPG from a single cab pickup, crew cab pickup, and Suburban/Excursion provided they got the same tail treatment?
If they get the same tail treatment, the Subscursion will be longe by the length of the single-cab's bed. Then again, if the double-cab's C-pillar is somewhat narrower than it's B-pillar and if the Subscursion's D-pillar was substantially narrower than both; then you could see an equivalency in Cd that would translate into similar MPG.

Of course it matters: Chop the top.
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Old 08-25-2014, 07:55 PM   #4 (permalink)
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drag coefficient

The 'all-new' '86-87 GMC/Chevrolet 1/2-ton was Cd 0.45.

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