Thread: SUV Kammback
View Single Post
Old 09-29-2014, 10:44 PM   #39 (permalink)
UnicycleDan
EcoModder In Training
 
UnicycleDan's Avatar
 
Join Date: Jul 2014
Location: Cleveland, Ohio
Posts: 20

BigBlue (UnicycleDan) - '03 GMC Envoy XL
90 day: 20.55 mpg (US)
Thanks: 13
Thanked 3 Times in 2 Posts
Quote:
Originally Posted by aerohead View Post
You can see that it is perfectly integrated into the body with seamless transition.The air needs this 'perfection' in order to protect the boundary layer,which determined whether or not you'll have separation.
You all are frustratingly right. My tail design in my head and on paper is getting increasingly complicated and more difficult to build with every time I post something and one of you makes another really great point/observation. Thanks for being frustrating.

Quote:
Originally Posted by aerohead View Post
Your cardboard mockup is more like a box-cavity,and for it to work,it needs to be as low as the bottom of your bumpers bottom,and it needs a 'floor'.It cannot be open on the bottom unless there is a back on it,and the back is airtight.
I'm going to need some good clarification on this statement, as it will determine some key design choices as I move forward and piece my tail together. I understand the concept that closing the bottom would be useful to the flow from underneath the car if the sides extend to the bottom of the bumper. I understand that it would be better to extend the sides down to the bottom of the bumper so that all of the air around the car sides decelerates together and merges smoothly, not just the top half, and therefore, less turbulence. Extending down that far would significantly increase the work I need to do, though. Some questions:

1) If I don't extend the sides any further down than they already are, is a bottom still useful? If yes, please explain.

2) How does a closed back replace a closed bottom? Just to make a stagnant pocket of air that "blocks" airflow, as if it had a solid bottom panel?

3) You use the phrase "for it to work". Why wouldn't 2/3 of the kammback produce at least half, if not fully 2/3 of the benefit?

4) Would a front air dam and side skirts negate the benefit/usefulness of adding a bottom to the kammback?
__________________
"On the 8th day, God created kammbacks. And God saw that it was good."
-Genesis 1:32

Last edited by UnicycleDan; 09-29-2014 at 10:50 PM..
  Reply With Quote