[ChazInMT]

ennored, you're right about attached flow ≠ ideal. People seem to think as long as you have attached airflow, you've optimized the Cd. Not the case. You need to have an even balanced pressure return in the back of a car, this is the most critical aspect of trying to optimize a cars shape. If the shape follows the template while maintaining balanced pressure all around, it will have the lowest Cd possible. If the shape is faster/steeper/shorter than the template curve, it will suffer from creating too much of a low pressure area, and the Cd will rise. If it is slower/shallower/longer than the curve, it will start to suffer from more skin drag and on a more esoteric level, the air will not help to push the car along with the same force as it returns the prior state it was in before the shape rammed through it, again the Cd will rise.

So yer right, if one part of the car follows the template shape, and the other parts do not, it isn't ideal.

But it is a fantastic starting place. It is a tool that if used properly will get people closer to an optimized shape for a given form. It is a well thought out basic tool, not the be all-end all for aerodynamics.

If you have a better tool for us we'd love to see it and discuss it. Do you have something that is a more aerodynamically ideal shape for a bluff body moving in ground effect?

I been looking into this for 5 years now and think about it quite a bit, and to me, the templates are as good as it gets for a starting point based on all the research that's been presented by Aerohead over the years.