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Old 02-10-2021, 11:38 AM   #31 (permalink)
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similar

A follow on to Port Royal is ( David ) Hume's Maxim:
' (N)o testimony is sufficient to establish a miracle, unless the testimony be of such kind, that its falsehood would be more miraculous then the fact which it endeavors to establish.'

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Old 02-10-2021, 01:48 PM   #32 (permalink)
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"I need a miracle every day" Jerry Garcia
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Old 02-12-2021, 03:02 PM   #33 (permalink)
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1993, Hucho & Sovran on low drag

AERODYNAMICS OF ROAD VEHICLES, in Annual Reviews Fluid Mechanics, 1993, pp. 485-537, Hucho and Sovran:
repeats Hucho's comment from his 2nd-Edition book, December, 1986.
' lower ( Cd ) values are possible. Whether or not they are feasible for any particular car is more a question of consistency with the vehicle's design concept than it is of aerodynamic capability.
As of 1986, Hucho claimed Cd 0.07, as the floor for an automotive drag coefficient. Body elongation and integration of the wheels into the body would be the pathway.
Wing or half-body shapes would be our only two options.
'Laminar' bodies have insurmountable outward vision challenges.
The 'Morelli' form, failed to deliver lower drag, when put to the test of an actual motor vehicle.
My contention remains, that wing-like automobiles would be highly problematic with respect to internal packaging efficiency versus overall dimensions, leaving the half-body as the likely candidate.
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Old 02-12-2021, 05:54 PM   #34 (permalink)
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Quote:
Whether or not they are feasible for any particular car is more a question of consistency with the vehicle's design concept than it is of aerodynamic capability.
Verbose for 'use case'.

Quote:
The 'Morelli' form, failed to deliver lower drag, when put to the test of an actual motor vehicle.
There's no close [single] quote. Is this part of the citation?
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Old 02-12-2021, 06:18 PM   #35 (permalink)
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Morelli form

It's reported elsewhere, and I'm pretty sure it's here at EcoModder from many years ago.
They couldn't get the body below C d 0.161, whereas the half-body can do 0.08.
Adding wheels to the Morelli form jumped the Cd to 0.35. Only blending bulges around the wheels allowed Cd 0.201, as a 'production' car.
The half-body would begin at Cd 0.13 with skinny tires, and go up with increasing tire width.
Then wheel integration would whittle that back down to the tune of a 70% reduction of the wheel drag.
A 'wing' car might go to Cd 0.07 if you could get people inside it ( which you can't ).
Half-bodies, with active ground clearance and fairings would approach Cd 0.09.
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Old 02-12-2021, 07:39 PM   #36 (permalink)
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Quote:
It's reported elsewhere, and I'm pretty sure it's here at EcoModder from many years ago.

forschungsauto pininfarina gr __ Picture Added 05-22-2014 12:54 PM

Permalink #34 was about whether it was part of the quote, or commentary.
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Old 02-24-2021, 02:16 PM   #37 (permalink)
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contemporary literature

In December, 1986, Hucho wrote, on page- 201:
' To what extent basic bodies with high fineness ratios can be used as the starting point for vehicle development depends upon the value placed upon low drag in the future.'
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Today, 35-years in the 'future', the absence of basic bodies of high fineness ratio as starting points for vehicle development, published in contemporary aerodynamic literature, may simply reflect the fact that, no value IS placed upon low drag.
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Old Yesterday, 05:44 PM   #38 (permalink)
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Quote: "Today, 35-years in the 'future', the absence of basic bodies of high fineness ratio as starting points for vehicle development, published in contemporary aerodynamic literature, may simply reflect the fact that, no value IS placed upon low drag."

I guess it depends on the definition of "low drag."

My $20K Mazda3 has a Cd of 0.26, if you can believe the literature. I'm sure Mazda worked hard to achieve that aerodynamic value, but they could have done better by making it look like the model in Post 36.

However, I'm sure it would have cost more to achieve such a shape, and I'm also sure I wouldn't have bought it.
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Old Today, 11:51 AM   #39 (permalink)
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I always thought of low drag as below 0.3, but maybe that was "low drag" at the time I started following aero.

But it depends on the power source, easier to get low drag by using electric power, so maybe my definition of low drag has changed now we need less cooling.

For me: sub 0.3 = low drag, sub 0.2 = very low drag, sub 0.15 = ultralow drag.

"Half-bodies, with active ground clearance and fairings would approach Cd 0.09." aerohead, what do you mean by that? I remember a discussion on here essentially saying that around 15cm is "optimal" for a "normal" car. How low or high would it need to be for the optimal for a half body? I would think optimal is zero.

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