Quote:
Originally Posted by euromodder
Essentially, it works on the very same principle as a parachute: catch air and inflate, then generate a lot of drag.
While you may see an overall improvement because the appropriately-shaped parachute improves the lousy aerodynamics of the vehicle, you'll still lose a fair deal of the potential improvement to the drag the parachute needs to keep inflated.
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Nope.
Billows out because internal pressure in the bag is a bit more than external pressure.
Watch a motorycyclist's shirt billow out at speed--not because he has a parachute or uber-ventilated arm pits.
The NASA truck thing was simplicity itself, and was not so long as to droop and tangle in the wheels or gear when stopped or in reverse.
Somebody here on Ecomodders as I recall within the past month or two had pics of a stowage bag on the back of an SUV or station wagon, which partly filled in the draggy zone just aft of the back bumper. A self-inflating bag of somewhat larger size is what I have in mind, and would make a nice, streamlined protective envelope for, say, a bike rack (including bikes).
Also, hinged panels at the rear edges of box trailers have been reported on this website. On an SUV or Volvo wagon, such could cheaply and easily be made of Coroplast, with a Dacron panel to fill in, making a semi-rigid and rounded rear cap for the vehicle, with better aerodynamics and fuel savings.