SLICK STUFF: Boat tails on the rear and side skirts on the sides were incorporated into this experimental Great Dane trailer, designed for Wal-Mart.
TORONTO, Ont. – Nobody has ever accused the traditional van trailer of being an aerodynamic piece of equipment.
The front wall of a 53-foot van serves as a sail of sorts when travelling down the highway.
Most truckers have resigned themselves to the fact that about 65% of the energy used to power a heavy-duty truck down the road at 70 mph is being used to overcome aerodynamic drag.
But with the continued volatility of fuel prices, some fleet managers are beginning to explore ways of making their trailers more aerodynamic.
There are options out there, although very few of them are widely used in Canada or the US – mostly due to practicality issues.
One way companies can improve the aerodynamics of their tractor-trailer units, is to reduce the gap between the power unit and the trailer.
Cab extenders, or gap seals, can be added to the tractor to reduce the space between the rear of the tractor and the front of the van body.
The Smartway Transport Partnership program (run by the US Environmental Protection Agency), recommends truckers spec’ wheelbases and fifth wheel settings that position the trailer as close to the rear of the cab as possible.
The organization points out that reducing trailer gap from 45- to 42-inches can improve fuel mileage by 2%.
Gap fairings for the front of the trailer are also an option. These direct the airflow around the edges of the front wall of the trailer.
Further back, side skirts are another option for improving trailer aerodynamics.
The skirts reduce the amount of air that flows underneath the trailer where it interferes with axles and wheel assemblies. Trailer side skirts can improve fuel mileage by up to 6%, according to manufacturers.
One such manufacturer, Freight Wing, says its belly fairing has been proven to improve fuel mileage by 4% – a claim that’s been backed by SAE-approved testing.
The side skirts generally attach to existing I-beams.
The rear of the trailer is another area where aerodynamics can be improved.
Devices called ‘boat tails’ can be attached to the back of the trailer to improve airflow. The boat tails form a cavity and improve the way air flows off the rear of the trailer.
A Clarkson University research team found that boat tails allow a typical tractor-trailer to achieve a fuel mileage improvement of 0.6 mpg – or more than 10%. Unfortunately, there are regulatory barriers in Canada which currently do not allow for the use of boat tails on trailers.
Recently, Great Dane manufactured a trailer for Wal-Mart that incorporated several aerodynamic devices including boat tails and side skirts. (For more on this story, see pg. 49).
It appears fleet managers are finally beginning to explore opportunities to improve trailer aerodynamics in more detail.
“I don’t think there’s any question aerodynamics on trailers works and saves fuel,” Charlie Fetz, vice-president of research and development, recently told Truck News.
“To me it boils down to practical issues and whether the economic trade-offs balance out properly.”
Time will tell whether the traditional van trailer will undergo a facelift in the years to come.
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