Cd 0.075 (the impossible just took a little longer)

[aerohead]

At the "Fuel-Efficient Vehicles-Now!" website,aerodynamics appendice,table of photos and drag coefficients,at the top of page,is the pac car II Shell Eco-Marathon competition winner.They claim Cd 0.075 for the car.A few years ago this would have been the claim of a madman! At the pac car website,they offer the "shape" of the car in CAD form for 100 Euros.----------- This is remarkable! Contemporary wisdom had it that Cd0.10 was the lower limit for a vehicle on the ground.----------------------------------- The web address(lets see if I can do this without screwing it up) is ETH - PAC-Car II - Welcome to the PAC-Car II website! This really raises the bar for aero-modding potential.

[MetroMPG]

Quick, someone call Aptera and tell them they've got it all wrong!

Some photo galleries from the PAC II web site itself:

PAC-Car II in Nogaro 2005
Nogaro 2005
PAC-Car II in Ladoux 2005
PAC-Car II Miscellaneous
PAC-Car II Technics

There are a couple of wind tunnel and CFD images in the last gallery.

And I just figured out what it is about this car that looks familiar... to me, its "stance" looks like that of a bear.

[trebuchet03]

At what velocity?

[Big Dave]

It's a well-faired, slightly powered street luge.

[donee]

Hi Big Dave,

Yes it is. But the shape still has a .075 Cd. Imagine a Pickup truck shaped like that !

[diesel_john]

0.075 X 40 sq. ft is still a small number.
Dave, how bout a full size pickup shaped like the Pac. i am talking sit up straight with a ten gallon hat on.

[Tango Charlie]

That's weird. I can't see any pictures on that website. Doesn't appear that Firefox is blocking anything...

I really wanted to see the 'technics' page!

[Big Dave]

Don’t get me wrong, the street luge is the absolute indisputable champ when it comes to moving the human shape along the ground with the least wind resistance.

You look at this car and the VW 1L you see a world of similarity. Both are essentially hot-dog (others may use a more pornographic metaphor) shapes. The VW 1L hugs the ground where this car uses wheel pants and lifts the car up out of ground effect a la Aptera. But the basic shape is similar.

Rather than a pickup truck, I look at this and think about using the same basic shape and put the driver in a more comfortable seating position. I couldn’t imagine driving this thing more than a few miles. OK making the driver more upright and maintaining the shape will require the vehicle to be longer. That’s not a bad thing for a 2f1r trike. A longer wheelbase will make it more resistant to ground looping.

This shape beats the VW 1L in that it looks most resistant to high centering. As with the later-version Aptera, the wheel pants will have to be chamfered back a bit both on entry and departure angles, but that is a small concern.

[almightybmw]

I like how it's on a running track. Just needs hurdles to complete the image.

Practical? no. Cool? yes. I'd like a recumbent bike with an aero shell like this. Only thing I'd change is the wheel entry/depart angles, for curbs and the like. I remember reading a while ago the fastest aero-shelled bike hit 80+mph, human powered. I'd be happy with 40mph.