View Single Post
Old 02-28-2012, 07:24 PM   #20 (permalink)
aerohead
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 16,228
Thanks: 24,375
Thanked 7,357 Times in 4,757 Posts
windshield

I stumbled onto some tasty little numbers when re-visiting Walter Lays wind tunnel work of 1933.
Lay tested a 'pumpkin seed' model car,which for all intents and purposes IS the 1987 GM Sunraycer,with matching Cd 0.12.
By installing a completely vertical windscreen with square edged header and A-Pillars he doubled the drag to Cd 0.24! Hucho refers to this in his book(s) when mentioning that no amount of boat-tailing will reap benefits if the forebody isn't 'clean'.
What's remarkable about Lay's research,is that by tilting the windscreen back only to 50-degrees from vertical,all the turbulence was killed,and the car was as low-drag as if it had the 'ideal' compound windshield.
Of course,this is only at zero-yaw,and the 'ideal' windshield WOULD have an advantage in a crosswind,but it kinda drives home Hucho's point,that most contemporary automobiles have adequate forebodies,from which to streamline from.
I think we'd be hard pressed to find any modern vehicle,except maybe Hummer H-1 and some Land Rovers,which didn't meet Hucho's criteria for acceptable forebody.
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
Frank Lee (02-28-2012)