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Old 10-02-2017, 11:06 PM   #21 (permalink)
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There was some discussion of the ground plane issue at one point, but I don't care enough to recall.

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I wouldn't over-think it. Have you looked at the fore-aft profile of The Template?
I'm not entirely sure I'm so new to aero moding that even that makes me confused lol.
The Template is a theoretical ideal, based on a half-body of revolution. The theory is that air striking in the vicinity of the stagnation point (at the front) will follow the simplest path over or around the shape. The half-body part means that the Zeppelin shape is truncated to present a flat face to the ground plane. Adding wheels is necessary with present-day technology. Adding even rear-view mirrors degrades the perfection.

That area sticking above the Template line is nothing compared to the fore-aft view.

I'd focus on producing the contour rearward with minimal gaps. The recent results from Darko wind tunnel suggest about 3% difference on a pickup. Here's how I did it with my Baja Bug:



The redwood strips define where the contour leaves the body, it's not straight across the top, more of a V- or C- shape. I was able to put a full boat tail with a 45 angle (twice the 22 maximum) plus a reflex curve with four additional feet of length (12—>16ft). This is possible because the body taper starts at the B-pillar, not the rear axle line.

Here is a well designed box cavity. An other possibility is a retractable perforated base plate.



Notice how it reaches forward on the roof to find the point of separation.

Edit: The sides are technically a stepped box cavity. The rear edge of the box is where a smooth curve would fall, but allows retaining the stock taillights.

The flat side of the box allow a place to flow to re-attach.


Last edited by freebeard; 10-02-2017 at 11:18 PM..
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Old 10-07-2017, 01:06 PM   #22 (permalink)
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ground plane and template

Your original fitting of the template is the correct one.The overall height of the RAV4 must be the same as that of the template for the roofline to be trouble-free.
The underside of the RAV4 will determine what kind of belly and diffuser you can use,and once this is determined,you can do what you can to project the new underside rearwards at either 4-degrees,or 2.8-degrees,depending.
The body sides of the RAV4 will also determine how you can handle the plan-taper of the elongation.
For the rear mods to function,you must provide the highest quality of flow from upstream.(flush rocker panels,rear skirts,rocker panel extensions rear of the rear wheels,complete belly pan,with diffuser).
Any elongation will cut drag.You decide what your target is.Also,if you do the simple,vertical Kamm chop,the tail can be modular,adding more length later if your hunger for additional drag reduction increases.

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