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Old 02-04-2010, 06:15 PM   #3 (permalink)
aerohead
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quantify

Quote:
Originally Posted by KamperBob View Post
I've been following several discussions that touch on this area but I thought it should have it's own thread. I'd like to focus this discussion to pickup trucks.

Several members have fabbed some very nice aero caps for their trucks. There may not be 100% agreement on which is truly best, nor what "best" means from one person to the next. There does seem to be consensus opinion backed by MPG numbers showing improvement over an open stock bed. (Contrast that with great confusion about which produces least drag: tailgate up, tailgate down, tonneau cover, cab-matching toppers provide.)

I have read considerable discussion about side view profile as a design tool (starting point) for aero caps, but very little about top view profile by comparison. So I see that as one area of improvement in our knowledge base.

I would like to suggest some ideas to help quantify and compare designs and applications. Every truck creates a wake in the field of air molecules it plows through. That wake is effected by shape and speed of the truck. I think it could help to stick some numbers to that shape. For example, how far behind would a tailgater benefit appreciably? Call it draft zone.

I have other discussion points but I'll stop here for now.

Cheers
KB
KB,historically,drag coefficient has been the 'language' of aerodynamics.All elements of aero drag are represented within this number.
In 1963,researchers at GM published an SAE Paper which quantified the direct relationship between drag coefficient(Cd) and mpg,for City,Highway,Combined.
Since Cd is the most recognized indicator of shape-efficiency,we might be wise to respect it's use rather than attempt to re-invent the wheel by creating a new 'language.'
Tail-gating,in addition to being illegal in all states,would endanger all attempting to quantify it's affects.That would be better left to a test track as Myth-Busters used.
In the Seminar sticky,there is a complete discussion of the role of Cd to mpg.
As to "plan-taper" of the aeroshell.If one follows the template design tool,for a long-bed pickup you could expect a little over 21% drag reduction and 13% mpg improvement at 70-mph.
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