After reading the
ToyotaNation truck forum freakout, I went searching for some solid info about truck bed aerodynamics. (This was when I thought I was going to sign up & edumacate the lot of 'em
.)
If you search the web for info about tonneau covers vs. efficiency, you find stuff like this:
That link (and many like it) refer to a report done by senior engineering students @ Western New England College, which not surprisingly shows that a tonneau cover improves efficiency.
But in the list of configurations tested for the report, the best results
weren't for the tonneau, but a "new cap design", which wasn't explained any further (at least on those pages that are mostly trying to sell tonneau covers
).
Long story short: intrigued, I wrote to an engineering professor @ the college. He knew of the report, and kindly made & sent me a copy.
NOTE: the students' report is online here Improving Aerodynamic Characteristics of a Dodge Ram Pickup Truck - including a photo of the aerodynamic "new cap design":
The observations/conclusions (from the above web link):
I was not surprised when I opened the report to see an image of the "new cap design" that looks an awful lot like the ones Phil, Brett & big_dave have made for their trucks. (Why this cap style isn't mentioned on all the web pages that reference this report, I don't know.)
I'll post more tomorrow, but that's the crux of it right there.