Quote:
Originally Posted by Cd
Thanks Phil !
Aerodynamics really seems to be a 'black art' as I have seen you describe it in the past.
It's as if the air does whatever it wants to. ( I think i've expressed that same reaction in previous threads ! )
What baffles me is that a low drag car versus a high drag car can be only millimeters apart in their sheetmetal, yet the air will cling to one and not the other.
I was under the assumption that wake size was the main factor in a low Cd.
How can this be, if for example the MX-3 has an overall smaller wake than something like a Scion Xb, yet both have the same Cd of point 32 ? ( I have included a tiny thumbnail image because this thread is getting image heavy )  |
here's something to consider:
*any car built in 1968 or later can achieve Cd 0.25 with detail optimization.
*any car that you can think of!
*thousands of body types can achieve Cd 0.25.
*and getting there can involve any and all the parts of the body and wheels.
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*low drag,by other's definitions,begins at Cd 0.25,going lower.
*and as Hucho reminds us,there is a point where you're stuck,unless you address the aft-body,which means that the wake isn't the primary criteria until you're at about Cd 0.25.(which is essentially where Kamm quit,due to practical length considerations).
*from Cd 0.25,down to Cd 0.13 we can use elongations which comply with something like the 'Template.' Both in elevation and plan-view.
*to go below Cd 0.13 requires integration of the wheels into the body,or copious amounts of wheel fairings.
*with this,Hucho says that we can approach Cd 0.08 for the bare form.
*and for 'practical' considerations,we'd be talking about 'active' aerodynamics.