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Old 09-13-2020, 11:04 PM   #28 (permalink)
JulianEdgar
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Quote:
Originally Posted by hat_man View Post
So what you are saying is that if the advice is deemed as flawed it shouldn't be followed? And if it is followed, then it has no advantage? This is what I mean by something is better than nothing. A "flawed" template is better than no template at all, no?

Should this guy be shot down because his shape didn't meet your idea or Aerohead's idea of the template? I'm sure it could be improved on and needs much refining. People here at EM would share their opinions and knowledge. I have a feeling your only advice would be to buy your book.

I think the "template" we have recognized at EM was designed to be a "smidgeon more conservative" rather than a shape that is "right on the ragged edge of flow seperation."

I wish I could find the drawing of AST-II. It might be more to your liking as I believe it was a bit steeper than AST-I. I also believe someone here stated that "The AST-II is the second-most aggressive profile and fits standard rooflines with rapid descending contours. The AST-I fits more conservative contours."

According to a guy name Hucho, the most aggressive profile was by some other guy named Buchheim. I think that Hucho guy wrote a book also. Too bad he isn't around anymore. I'd bet he'd share his knowledge here in the Wiki section.
Dr Hucho is alive and well - he wrote me an email just last week.

This idea of 'battle of the templates' is just so bizarre. I would suggest never starting with any template at all! Why on earth would you start with a pre-determined shape and not actually develop the best shape for your own car?

Would you take a Nissan Micra's spring, damper and sway bar rates and apply them to your Mercedes 300SEL? Would you take the engine management map from a naturally aspirated V8 and plug them into your four cylinder turbo's engine management? Or, and this is an even closer parallel, would you state that the air/fuel ratio in your car's engine should always be 14.7:1, because that's 'stoichiometric' - the chemically correct proportions for complete combustion?

The canopy shape looks alright - sure. But why on earth wouldn't you first develop the best shape for that vehicle by doing some testing? For example, first just lay a flat sheet from the roof to the tailgate and see if the airflow stays attached. Even better, do that and measure some pressures. The depicted shape might be best, but it's highly likely it isn't.

I think blindly following a template - any template - is an utterly stupid way of modifying car aero. It seems completely predicated on the idea that testing isn't allowed. Just imagine doing engine management or suspension like that - what are the chances you'd luck-out and get the best results by copying what someone says is best for every car?
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