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Old 09-28-2023, 11:45 AM   #1 (permalink)
aerohead
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'There is no single best aerodynamic shape for.....'

' There is no single best aerodynamic shape for a road car.'
Julian Edgar, from Vman455's thread, about R.H. Barnard and the template, recently found at page-29, here at the Aero. Forum.

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I'll take a stab at this, within the context of streamlining, and very low drag, as is my interest, and why the aerodynamic streamlining templates were offered as a tool.
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Caveat:
* this has nothing to do with corporate committees which decide the technical specifications for production road vehicles. It has only to do with off-the-shelf technology, and the feasibility of producing passenger cars with a drag coefficient in the neighborhood of Cd 0.07, to Cd 0.09, as per Hucho, December, 1986.
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1) There IS a single best shape for a road car of Cd 0.07, to Cd 0.09.
2) ' The perfect aerodynamic shape is the teardrop... The design of a perfectly aerodynamic car would need to head in this ( teardrop ) direction.'
Dr. Teddy Woll, Daimler-Benz, Mercedes-Benz.
3) ' The 'ideal' form for a road vehicle is... a cambered version ( of a half-teardrop )...' Dr. Richard H. Barnard
4) ' The teardrop has the shape that air can flow around with particularly low resistance- round at the front and tapered at the rear, so there's no 'wake' and no drag against the direction of travel.' Marcel Straub, Porsche.
5) ' A teardrop-shaped body offers minimal drag.' Rick Voegelin, MOTOR TREND.
6) ' The ideal teardrop shape, for example, has a long tail.' Rich Taylor, Popular Science.
7) 'A teardrop shape has a minimal wake-the streamlines come together at the end of the long tail.' Julian Edgar, p.127, 'Modifying.................
8) ' Aerodynamic experts say that a car with the best- streamlined shape will look like a teardrop.' HT Auto Desk
9) ' Optimum shapes are 'streamlined' bodies having a very slender rear part.' Dr._Ing, Dietrich Hummel.
10) ' the longer the tail, the less wind drag occurs.' Professor Herbert J. Carver.
11) ' The coupe-like roof form and tapering rear end are also designed for ideal aerodynamic performance.' Daniel Scharfscwerdt.
12) ' When vehicles developed for the lowest drag coefficient are evaluated for Cd vs length, the correlation is discerned and expected trend is in fact confirmed.' Hucho.
13) ' A long tapering rear is still good for a vehicle's aerodynamics.' Dr. Teddy Woll.
14) ' the drag reduction from an elongated tail varies almost linearly with the reduction in cross section area.' Dr. Jeff Howell et al.
15) ' High base pressure explains low drag.' Julian Edgar, p.80, 'Modifying...
16) ' Steep tapering ( of the rear contour ) is limited as the resulting flow separation increases air drag.' Hucho.
17) ' our data suggest that road vehicles do ( have optimum fineness ratio values ). William H. Bettes
18) ' For well-designed forms ( of bodies of revolution ) the drag coefficient may be as low as 0.04.' Richard Von Mises
19) The lowest friction and pressure drag sum for a streamline body of revolution, Cd 0.04, occurs with a free air fineness ratio of 2.5:1 ( re: Hoerner )
20) ' With refinements in aerodynamics progress is towards the ( streamline) body of revolution.' Hucho.
21) ' the optimum shape ( of a road vehicle ) in terms of drag is a ( streamline ) half-body, which forms a complete ( streamline ) body of revolution together with its mirror image- produced through reflection from the roadway.' Hucho.
22) '(T)he drag of the basic ( Cd 0.07 to Cd 0.09 ) body (of revolution-derived vehicle ) is achievable. To what extent this can be approached in the development of a production vehicle is therefore more a question of the balance of the requirements of the specification, than of technical feasibility.'
Hucho, December, 1986.

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Last edited by aerohead; 09-28-2023 at 11:49 AM.. Reason: add data
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