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Old 05-21-2011, 04:32 PM   #64 (permalink)
Pendragon
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As you have observed, "the template" frequently suggests impracticably long afterbodies. If using "the template" at all, I would be inclined to use an abbreviated form of it. I would establish a line of the angle of departure of the roof line just in front of the rear window and then find a parallel line which is tangent to "the template" at that point and then move it forward until it was in place over the rear of the roof. This would place the area of clean airflow closer to an achievable afterbody. Even so, "the template" simply does not suggest a realistic option in my view.

The reason that I surmised that a five or ten degree slope on the trunk lid extension would be a more balanced choice than the thirty degree one suggested is that the steeper one becomes more of a wing or spoiler and I think that the down force generated at highway speed would be sufficient to unbalance the car and might generate more net drag (including increased front end drag) than the benefits could overcome. The objective, after all, is to reduce total drag.

Another example of a small "flip" is the Honda Civic Hybrid. On a car which has gone to the trouble of utilizing a (standard equipment) underbelly and wheels that suggest they were designed to both reduce (unsprung) weight and aero drag with the concession of some ventilation for the brakes, I do not think Honda would have installed the trunk lid "flip" purely for styling reasons on a car that is supposed to compete with the Toyota Prius. The idea, I think, is simply to catch enough of the disturbed airflow in the region to establish some degree of order to the airflow. Sure, something larger might have doe slightly better, but this is a car to be used as everyday transportation and Honda are know to be conservative in their styling.

If we take a look at the '99 Honda Civic HX, there is absolutely nothing remarkable about it aerodynamically, but it achieve rather good FE because of other optimization. (Note: Another thread remarked about the continued high price of this car. I saw a national average of around $5,500 for one with less than 150k miles so I guess its FE is being valued in the market place.)





Quote:
Originally Posted by California98Civic View Post
I was just studying these template again, this time with a well drawn image of my coupe from the 1998 Honda service manual. It looks like the highest point on the car is just ahead of the center pillar. Got freeware in the form of Paint.Net and used Aerohead's template from this site and made this workable image of my car. It does seem I would need a much larger spoiler, no? Would it even be legal?
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