Does a fiberglass camper shell/topper reduce or help aerodynamics
 

I installed a fiberglass camper shell on my truck a few months ago and have not recorded any noticeable increase or decrease in gas mileage, in theory, should my shell/topper help or hurt my gas mileage and aerodynamics? My truck is a 1998 nissan frontier king cab XE.

camper shell/mpg
 

So far,only one report,a 2009 Masters Thesis,by Feysal Ahmed Adem reported an mpg loss when a 'traditional' camper shell was installed on a pickup.
Other reports and testimonials claimed modest improvements.
The added weight could aggravate urban mpg.
On the open road any weight addition from the shell would be a wash with respect to mpg.The reduced rear lift offered by a shell would be an inducement to keep it even if it did nothing for mpg.
Every pickup should be considered on a case specific basis.

Depends on the shell, probably hurt around town because of the weight, maybe help a little on the highway with no cross wind if designed well, but if just a simple cab high with a flat back probably no better then a flat bed cover.

My '87 Toyota has a cab-high topper, it's almost exactly the same height as the roof of the truck. I noticed a modest improvement in fuel economy when I installed it, about 5-10%.

For various reasons, storage space chief among them, the topper stays on the truck about 99.44% of the time. It only comes off for very large construction projects or major firewood opportunities.

If I ever find myself in that magical confluence of surplus time and surplus money, I would like to make a nice whaleback topper like others here have made. With careful driving I can push 40mpg, I think with a whaleback I could hit 40mpg even with careless driving.

I too would like to some day explore building an aero topper.

My fiberglass canopy comes off during the summer; it is used mostly for keeping things dry during the winter [November 1 to April 1, studded tire season] as well as for weight over the drive wheels. It's not the most aerodynamic canopy as the side windows stick out .5" from the sides. It spends it summers stored in the garage.

Ninja edit: image added:
http://i983.photobucket.com/albums/a...psdf6836f3.jpg

My own experience, with '88 Toyota 4WD and the cab-high shell that was on it when I bought it, is that I got a 1-2 mpg increase (from about 26 to 28 mpg) after taking it off. Not really scientific testing, though, as it was just whatever driving I was doing.

Another relatively scientific test: topper hurt efficiency
 

Tested:

• bed cap on
• cap off, tailgate down
• cap off, tailgate up

http://ecomodder.com/imgs/ford-f150-cap-on.jpg


http://ecomodder.com/imgs/ford-f150-cap-off.jpg

1994 Ford F-150 XLT with an 8 foot bed, 5.8L V8, automatic

See: http://ecomodder.com/forum/showthrea...p-off-601.html