[aerohead]

Originally Posted by Cd

Hello all, I didn't want to ask this question in a new thread, since the subject has been discussed to absolute death.
This appears to be the latest version on the Template, so I thought this might be the most up to date conversation.

Question : what is the maximum angle of curvature that you can still have attached flow on a roofline ?
What's that you say ? This has been answered a million times over ?
Well yes, I know this, but I plan to begin skinning my Kammback / boattail tomorrow afternoon, and have limited time to read the hundreds of replies for an answer.
Why I ask : We have discussed anomalies, such as the EV-1 and Pillbug design that fall out of the curve of the template, but here recently, I have begun to see more super slippery designs that ignore the template as well, such as the Mercedes EQ-S, the Lucid Air, the Model 3 and model X.
I must admit I favor the LOOK of a "faster" roofline that is closer to the template, but I am also looking to make my wake as small as possible.
( The smaller the wake, the lower the drag - correct ? )
I could just make a design and continue to lower it farther and farther off of the template curve till I get turbulent flow, but I have a very limited amount of Coroplast that I am using and would like to get it right the first time.
One thing I notice for certain, is that in each of these low drag designs that fall out of the template, there is a very gradual curve to the roofline, and then a quick wick downwards out of the curve.
It's just a guess, but I'm thinking the airflow follows the curve of the front portion of the roofline that IS in the template curve, and just continues onwards down the curve that is out of template, as if it had fallen off of a Kammback ( the roofline that IS in the curve )
On a hatchback car that has a roofline that has a very minor curve, I'm thinking that too steep a curve would result in detached flow, since the airflow is following the angle of the roofline more that the steep Kammback you might add to the rear.
What's your ideas on this ?
If I create a tail that is as steep as a Model X's curve, I can have a super small wake area.
( The height of my license plate ! ) rather than one that is 4-5 times that size if it follows the template curve.
- Thanks.

1) The EV1, @ Cd 0,197, achieved Cd 0.137 by elongating the tail out to the AST.
2) The Schlorwagen is a bit better than the Renault Vesta-II, and VW XL1 of similar drag.
3) The M-B EQS is less efficient than the Tesla Model S Plaid, Lucid Air, CNR-PF, and modified Audi A2, by Coventry University.
4) The Lucid Air is less efficient than the CNR-PF, EV1, VW L1, and Coventry Audi A2.
5) The Tesla Model 3 is less efficient than the Alfa Romeo Giulia Advanced Efficiency, and Tesla Model Y.
6) The Tesla Model X, with 3-position rear deck spoiler, is a AST form, and has no peer for it's fineness ratio.