View Single Post
Old 03-15-2008, 05:52 PM   #25 (permalink)
LostCause's Avatar
Join Date: Feb 2008
Location: California
Posts: 504

Thunderbird - '96 Ford Thunderbird
90 day: 27.75 mpg (US)
Thanks: 0
Thanked 7 Times in 7 Posts
Originally Posted by trebuchet03 View Post
All of these are wheeled land based and close enough to experience the ground effect (at least, they are designed to work with that - except for the Diablo which was just sculpted - tested later). I'm only showing human powered ones because a great deal of effort has been put into achieving ridiculously low cDA values

Generally, it's not a good idea to place limits on "best" 400 years from now, when the star trekian force field is perfected - we'll have the ability to have cD values of .0001 and under etc.
Very, very true. I suppose I shouldn't have claimed 0.15 to be the lowest possible value ever, but I still stand by that it is a realistic (not unbreakable) lower limit for conventional automobiles.

I intended the number to be used more as a guideline, to have people who are at 0.25 realize that the curve is shallowing out as you get closer to practical limits. 0.35 to 0.25 is relatively easy. 0.25 to 0.15 will be much, much harder for any conventional car to acheive. 0.15 and less will either require one-off innovation or the loss of conventional characteristics (i.e. tandem seating, severely reduced occupant space).

My eyes are opened a little wider, though. Thank you. In 400 years, I'll be hoping Scotty will be around to beam me places. cD 0.0001 will be horribly high...

Just wondering, how do you guys calculate cD for your HPV? Scale model, moving road surface windtunnels? CFD? Road tests? I know at our school we have a supersonic wind tunnel with a subsonic in the works...definately nothing full scale, though. Do you guys have time at nearby windtunnels?

- LostCause
  Reply With Quote