Back in the 70's, the Univ of MD did a real great study of that sort of
thing. They determined that if you could eliminate the gap altogether, you
would have a MUCH better efficiency.

They had a system of complex levers and springs and stuff on moveable panels
that eliminated the gap on top and sides, right down to the road almost.

Try that on your pickiup and your wickiup. - NOT!

Really, if you can get as close to eliminating the gap as you can, the only
problem will be the sides. The top can be a piece with a concaved-shaped
edge on the truck, a convex-sort of sheet on the trailer, with the *center*
of the arc approximately over the hitch-point.

The OTR trucks have side-fairings on the cabs that are sometimes two feet in
length, but they work that way because the pivot of the fifth wheel is over
the axles, about 4 or 5 feet behind the front of the trailer. When the
trailer turns, the corner of the trailer is up between the fairings.

Really, just eliminate as much open distance as you can. If you had a "fifth
wheel" trailer, you'd be further ahead.

Flash





"Andy Asberry" wrote in message
...
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-----