View Single Post
Old 12-16-2008, 05:39 PM   #8 (permalink)
aerohead
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 16,272
Thanks: 24,394
Thanked 7,363 Times in 4,763 Posts
kammback

Quote:
Originally Posted by CobraBall View Post
Kammback creates drag. It doesn't reduce drag.

To make an object stable while in motion, the center of gravity must be forward of the center of pressure. This is true for high speed automobiles, airplanes, rockets or javelins.

Kammbacks are used in Top Fuel Funny Cars for two reasons. 1. to keep downforce or pressure on the rear tires. 2. To increase drag aft of the CG.

In the movie World's Fastest Indian Burt Munro did a stability demo with a pencil, the pencil became stable when the CG was moved forward of the CP. Burt wanted to add weight to the front end of his Indian MC to shift the CG forward of the center of pressure, thus make it more stable.

IMHO, dams, wings, spoilers, kammbacks are "thangs" that are used to overcome bad aero design. Anything and everything that has mass and moves in a fluid creates drag.
The Kammback citing may have been used in the context of separation-free flow up to the point where the car body was chopped off.And with Cd0.37,the K-cars were remarkably "cleaner" than their contemporaries.And yes,the K-cars did have cross-wind stability problems.The up-shot is that Dr.Morrelli solved that one back in the 1980s,so we're better protected from those challenges.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote