Aerodynamic...but not aircraft

Andy Asberry wrote:
3/4 ton extended cab pickup towing a 24 foot travel trailer. Fuel
mileage is effected much more by wind than weight.

I want to build a camper shell that will be cab high at the front and
direct the airflow smoothly over the trailer.

There is about 4 feet between the front of the trailer and the rear of
the proposed camper. For some reason, I believe the camper should be
higher than the trailer. But how much higher? Should the angle be
constant? Convex? Concave? A different exit angle?

About a foot from the top of the trailer, the front slopes back at a
45 degree angle. All opinions are welcome but educated calculations
will be given more weight.

--Andy Asberry--
------Texas-----

I'd be betting against making the camper higher than the trailer. At
least on a/c, drag is reduced if the trailing body is slightly larger
than the object ahead of it. Ailerons with leading edges that are
slightly fatter than the wing trailing edge come to mind. If you can't
make a smoothly faired transition to a smaller cross section, the drag
will go up a lot. Think round gear leg vs one with a teardrop shaped
fairing.

Take a look at big tractor-trailer rigs. the air dams on the tractors
aren't higher than the trailers.

Charlie
I'm not an aerodynamicist, but I do know one. :-)