I learned the hard way about roof rack/ small car physics.
My civic's trans fought a valiant fight against strong prairie headwinds on a trip to Moab with three bikes on the roof.
It lost.
25%
My understanding is canopies do not offer as much of a benefit as you would think, but are marginally better than an open bed.
Essentially an open truck bed "collects" a mass of air behind the cab which lets the air coming off the cab smoothly reintegrate just behind the tailgate.
When you put a canopy on, you essentially create a giant low pressure area behind the truck which increases drag.
Best solution is a tonneau cover, but it's obviously hard to fit bikes under there.
I did a bunch of reading on this when I had a pickup. Can't find all the articles, but here's one about how aerodynamics work on a pickup.
http://www.nrc-cnrc.gc.ca/eng/achievements/highlights/2007/tailgate_down_myth.html
Cool. I totally assumed the canopy would be much worse. Thanks.
For those that are curious the Rocky Sprinter, a 3500 170 extended model, has about 90,000kms on it after 2 years and the average economy is around 11.5L/100km. The van is mostly always fully loaded up with 20+ bikes, tents, demo gear, etc.
QUOTE]I'm seriously keen on a Sprinter set up for riding and road trips. With a kid on the way it would be good for packing all the crap that goes with that too.
Jon-boy.
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