philh wrote:
JaxDad wrote:
As a pilot with a degree in aerospace engineering I can tell you that “parasitic losses” can manifest themselves in many weird and wonderful ways. Likewise the gains created by eliminating them, witness the little air tabs (originally designed for aircraft) that can measurably increase fuel mileage on a coach.
In this case, I’d say an overloaded suspension created excessive (even if you weren’t aware of it, the slow creep is imperceptible) motion which created the losses you’re now recouping.
At Motorcoach speeds, parasitic losses on a brick aren't going to amount to much. OP said 1.5 to 2 mpg improvement. There was either something very seriously wrong with the alignment or the OP's calculations are a bit off.
On he contrary, any improvement in the aerodynamics of a ‘brick’ result in pretty substantial gains. Bear in mind also that as speed increases the drag does NOT increase proportional to the gain. According to Bernoulli's equation, drag is proportional to the SQUARE of THE speed.
Look up “AirTabs” and the gains that can be made by just adding some little plastic stick on tabs to a ‘brick’ and changing the vortices that form BEHIND it.
