Great Dane offers a wide variety of aerodynamic products, including undertray devices, boat tails and gap fairings, as well as side skirts, which is its main aerodynamic offering. While these aerodynamic solutions can be very helpful for fleets, Great Dane’s Fetz advises customers not to let their expectations for fuel savings get too high. “From what I’ve been told by representatives of some of the biggest fleets, in a real-world situation, a truck with get about half of what the test numbers will claim,” he relates. “That’s not because the device isn’t doing its job, but because the real-world drive cycle is different, full of stop and starts, traffic issues, etc., so the drive cycle’s going to have different results than a 65 MPH test.”
Some may question whether the weight of aerodynamic components can be a burden on the trailer. (A set of skirts, for example, typically weigh about 175 lbs.). While that’s a valid concern, the benefits still outweigh the costs. “The weight of a trailer skirt doesn’t affect a truck’s fuel efficiency much—it is a factor, but a small one,” Great Dane’s Fetz says.
“In most cases, the drag reduction and fuel savings benefits of aero devices far outweigh the ‘cost’ from the added weight of the devices, subject again to the average mileage and speed the fleet is running in its operation,” FlowBelow’s Butler says. “Aero manufacturers generally make every effort to keep the device weights to the minimum required to deliver the highest functionality, efficiency and durability.”
“The weight addition is low enough that in the event that the trailer happens to be at max weight, the benefits should offset the weight increase,” agrees Fleet Engineers’ Roberts. “Removing 200 lbs. of freight to gain 5 to 6% in most cases makes economic sense.”
What the future holds
So what innovations are coming to the world of trailer aerodynamics? Our surveyed experts had a plethora of ideas about what might be coming to this segment down the road.
Laydon’s Acott mentions the possibility of larger trailer skirts and more use of boat tails; Andersen talks about the growing number of customers who combine Eco-flaps with other aero devices; and Aeroserve’s Smerdon hopes that the coming innovations will “closely examine device life cycle costs, weight and safety. The limits for aerodynamic improvement on the basic trailer ‘as-is’ are rapidly approaching and until it is redesigned, the limit may have been reached already.”
“We could see higher efficiencies, especially with GHG Phase II and the EPA SmartWay program coming,” Great Dane’s Fetz suggests. “We might also see greater durability, although these devices are already pretty durable. It’s also possible we could see more solutions for the rear of the trailer, although that presents its own set of challenges.”
“You are starting to see trailer manufactures using more adhesives. This allows them to eliminate some rivets down the side of the trailer. The rivets all create drag. I also think you will see some trailer manufactures start to cover up the cross members to reduce the drag,” Fleet Engineers’ Roberts says.
“Fleets will see more tractor-trailer design integration from the outset with the OEMs,” Butler of FlowBelow predicts. “The tractor and trailer should be viewed as a total system and the aerodynamic and other fuel efficiency enhancements added should be engineered to optimize the ‘system’ as a whole. Thus, more and more currently available aerodynamic ‘add-ons’ will be incorporated into the tractor and trailer design and engineering from the factory versus added later as aftermarket items.”