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Originally Posted by Fubeca
First tank with the aerocap - 15.4 MPG - dismall!!
[sarcasm] I don't know why the aerocap didn't help[/sarcasm]
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Thanks for the laugh!
(And for showing an understanding of "testing" that seems to escape so many.)
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Quote:
Originally Posted by ChazInMT
Just curious, do you ever consider the fact that when the airflow that is leaping over the roof of the truck, reaches the rear of the cab, it is already headed downwards at a 5 - 7 degree angle?
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Air doesn't "leap" over the front of the cab roof and "fall" down again at the back.
Watching rain spray on the highway might give a person that impression (because displaced rain droplets are vastly more massive than air, so don't follow the same trajectory). In fact, air flow over a modern pickup's cab roof is parallel (tangental) to the roof surface. You can see this in smoke trace photos/videos.
Quote:
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So I ask, is this “12 degree roof line rule” based on a super streamlined shape?
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I think it's based on established research results. Which apparently works reasonably well by properly applying the teardrop template that you see in this and other threads.
Nobody's suggesting it's a perfect approach. I'm no expert, but my guess is there's probably some wiggle room of a couple of degrees. But knowing how much work it takes to make a mockup, much less a "good" version of an aerocap, Kamm back, or a boat tail, I'd err on the side of a conservative slope that is
likely to work, rather than end up with a shape that goes "a bit too far" and suffers detached flow, rendering my work useless.
Why re-invent the wheel? But if you really want to experimentally investigate what slope/arc works best, by all means go for it!