Quote:
Originally Posted by connorkeyser
so I should abandon my nose cone plans?? hmm.
|
*There's a couple schools of thought:
1) Do all the streamlining at the front and minimize the aft-body.Since 1974 I've only run across two studies where emphasis was concentrated at the nose.
*Eiffel studied what I call the Parisian ice cream cone (simply because it looks like one),with a convex hemispherical nose integrated directly into a conical tail,angled at 20-degrees to the longitudinal centerline.
*Dropping the cone tail first off his Tower,he measured Cd 0.18.
*Dropping it ice cream first,it recorded Cd 0.09.
*Baron Reinhard Koenig-Fachsenfeld,in the Technical University of Stuttgart's aeronautical wind tunnel studied a streamline body of revolution of L/D= 6:1.
*he ran it head-first and tail first.
*Tail-first it recorded Cd 0.55.
*Head-first it recorded Cd 0.45.
*As an automobile,running tail-first (or a reverse-Template),with wheels,it would have a drag minimum of Cd 0.142 with 'best' L/D ratio.
--------------------------------------------------------------------------
So it's possible to make a car of Cd 0.142 with most of the streamlining out front.The catch is that any windshield sloped to respect the tail-first contour would be slanted back so steeply that you'd never be able to see out of it.Something the HONDA HAWK team ran into at Bonneville during their LSR attempt.
The 1978 Volkswagen ARVW canopy delivered carnival 'fun-house' optical qualities for one auto journalist who drove it at VW's proving grounds.
And nothing in the published literature suggests that you could take any liberties at all with the nose.It would HAVE to be constructed exactly like a reverse-'Template'.
-------------------------------------------------------------------------
2) Conventional wisdom for sub-sonic bluff-body road vehicle aerodynamic streamlining is to have a convex-hemispherical nose-based forebody,combined with a long,tapering teardrop tail aft-body.
-------------------------------------------------------------------------
Wolf Heinrich Hucho was directly involved in the development of VW's Vanagon.In his book he has a drag table illustrating how little leading edge radius it took to achieve the lowest drag.Once they chiseled the clay a bit,no amount of further rounding produced any lower Cd.This was for zero-yaw of course.Later in his book he shows the 'bulbous' nose as the low drag champ for crosswinds,which is where we do most of our driving.
*The piece de resistance is in another table in which the entire drag of the nose constitutes a whopping 5.88% of the vehicles overall drag.Skin friction is 22%.The rest is aft-body drag.Over 72%.
-------------------------------------------------------------------------
This is an extremely long way of saying that your energies might be better spent working on the back of the car.
Today
Other popular topics in this forum...
