[deejaaa]

Originally Posted by Angib

The real textbook on how to make a van more aerodynamic was done by NASA Dryden back in the 1970s/80s:

A Reassessment of Heavy-Duty Truck Aerodynamic Design Features and Priorities
(Oops, first post, so can't link to file - google 88628main_H-2283.pdf and it will get you to their report.)

This has lots of scientific testing of real-world(-ish) aero mods which will teach anyone something - for example they tested a full boat-tail and a truncated one with precious little difference (Cd=0.242 v Cd=0.238).

looks like a good read. here's the link:
http://www.nasa.gov/centers/dryden/p...ain_H-2283.pdf
from the Abstract:
"The demonstrated increase in base drag associated with forebody refinement indicates that the goal of a 0.25 drag coefficient will not be achieved without also reducing afterbody drag. A third configuration of the test van had a truncated boattail to reduce afterbody drag and achieved a drag coefficient of 0.242.
These results are included here and references are identified for other means of reducing afterbody drag."