TAMPA, Fla. — Great Dane demonstrated its aerodynamic trailer, developed for Wal-Mart, at the Technology and Maintenance Council (TMC) meetings here recently.

The company tackled drag in key three areas to improve airflow over the trailer, explained Charlie Fetz, vice-president of research and development with Great Dane.

One area we attacked is the frontal area. This trailer is only 12-feet, six-inches tall, Fetz told Truck News on-site. The other area we worked on is the underbody drag. The traditional way to reduce underbody drag is to use skirts these particular skirts are retractable. In normal operations, below 35 mph they would be folded up. The brake system can sense the speed of the vehicle and at 35 mph they deploy. The rear of the trailer has a boat tail or cavity back with the door inset two feet. It creates an increase in pressure behind the trailer. A trailer wants to drag air along with it. If you can do something to raise the pressure behind the trailer, thats a good thing.

There are also wheel covers that prevent air from entering through the wheels and becoming trapped under the trailer.

Each section of the trailer that was addressed by Great Dane accounts for about one-third of the drag a typical van trailer encounters, Fetz explained. While the trailer is lower to the ground, the cubic capacity remains the same. The suspension can raise the trailer to the traditional dock height for loading and unloading. A minor drawback is there are wheel boxes inside the trailer that forklift operators would have to be mindful of.

Nonetheless, Fetz said the trailer balances practical issues such as dock height and cube weight with aerodynamics.

Great Dane paired the trailer with an International tractor to find out just how aerodynamic the combination could be. Wind tunnel testing showed the trailer was 7% more fuel efficient than traditional van trailers. When coupled with a device that closes the gap between the tractor and trailer, a further 2% fuel economy improvement was realized. Wal-Mart is expected to implement the aerodynamic trailer into its fleet.