View Single Post
Old 12-09-2009, 05:49 PM   #304 (permalink)
MetroMPG
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
Quote:
Originally Posted by aerohead View Post
How the front of the car divides the airstream,and the forward architecture determines the local velocity and available kinetic energy of the flow at any given point.
Typically,the nose scoops more over the car and the energy there is greater than the sides and can sustain the most "bending."
I don't have Hucho's later book and I don't know if he goes deeper into side flow.
Jaray's/Klemperer's/Fachsenfeld/etc. work suggest that if you respect the teardrop form,as a half body of revolution,we can curve the sides just as we would the top.
But the teardrop doesn't have a "roof." And I'm more conservative,allowing only half what might work over the roof.No good science there,sorry!
Good explanation, thanks.

I also basically guessed at side angle. I arbitrarily chose 10 degrees, and then eyeballed it by holding up a cardboard triangle with a 10 degree angle while laying out the strings.

One interesting result of my imprecise construction techniques that resulted in the boat tail being skewed somewhat to the passenger side: I've effectively tuft tested two different side angles. I haven't measured them yet, but will this week and will report back.

FYI, I measured the bottom angle: it's 4 degrees from the undertray to about a quarter of the way along the length of the boat tail, where it transitions to 7 degrees. And we saw from the tufts that it had attached flow to the end.
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
The Following User Says Thank You to MetroMPG For This Useful Post:
TEiN (12-10-2009)