Quote:
Originally Posted by Frank Lee
Yeah, in theory. As a practical matter I'd say vehicles operate in cross-wind almost all the time, so hardly ever would the rear wheels on a quad truly be shrouded by the fronts.
Look at a trike and a quad at about a 15 degree offset from the front. I see more shadowing with the trike.
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You're like many pilots, who are always flying into a headwind and for whom every landing is a cross wind landing.
Assuming 60 mpg, where aero drag predominates, then 15 degrees means a 90 degree cross wind at 16 mph. The national average wind is 8 mph. Wind direction and speed and vehicle directions and speeds are always changing. Therefore, streamlining (the portion focused on drag reduction) makes little to no accommodation for relative wind direction, although studies have been done to evaluate such things. It's hard enough to just get the car working well in a wind tunnel with straight-on flow.
(I'd guess that the national average car while at highway speeds, spends 10% of its time with the apparent wind coming from more than 6 degrees off the nose, and 90% of its time with angles less than that. I've driven in a lot of snow storms, watching the apparent angle-of-approach of snowflakes.) (Craig Vetter seems to worry about 30 mph headwinds.)
Vehicles are, however, designed aerodynamically to deal with crosswinds from a vehicle stability standpoint. Its better to have the "sail area" in the back rather than in the front if stability is what you are looking for. In general it is also better (for stability) to have a boxier shape