Trailer Aerodynamics: Ready for prime time

Trailer aerodynamic packages have been battling for acceptance for many years. Despite documented fuel savings by independent labs and fleets themselves, however, widespread adoption was still waiting for its breakthrough moment—until now. Thanks to regulations promulgated in the state of California and the likelihood of more complex federal regulations on big-rig fuel efficiency on the horizon, that moment may have arrived.

“Before [trailer] skirts were widely accepted, repair costs and long-term durability were always the biggest concerns,” explains Sean Graham, founder & president of Freight Wing Inc. “However, now that they are more common and a wider variety of trailer aerodynamic products are becoming available, it seems initial cost is now the biggest factor.”

He adds that the ability to quicken the return on investment of trailer aerodynamic devices is a motivating factor in the evolution of those products. “For example, we recently launched the 2012 version of our Aeroflex [trailer side skirt] product at a significantly lower cost and weight than our previous model. At 150 lbs., the weight has come down a lot due to the use of more advanced lightweight material, yet without sacrificing durability,” Graham says.

“I think the next step in the design evolution of trailer aerodynamic products will be to further refine the aerodynamic geometry of device combinations to maximize the overall fuel-saving benefits,” he points out. “Research sponsored by the U.S. Dept. of Energy will certainly help push the envelope in this regard in years to come.”

Other firms specializing in trailer aerodynamic systems agree with Graham’s outlook.

“The force behind the adoption of trailer aerodynamic technology is divided between two business drivers—fuel savings and government regulation,” says Mitch Greenberg, president of SmartTruck. “Many of the larger fleets are focused on ensuring they comply with the California Air Resources Board requirements, and it is clear California’s program has forced many fleets to investigate which [trailer aerodynamic] solution works best for them.

“On the other hand, many fleets are looking beyond the mandates and looking at finding the most valuable aerodynamic technology for their fleet,” Greenberg stresses. “They are defining value as a combination of price, fuel savings, durability and maintenance factors, and operational flexibility.”

To that end, he believes trailer aerodynamic developers will eventually create more integrated products where concepts are better incorporated into the initial design of the trailer.

“Keeping components inside the footprint of the trailer will grow more important, so the systems are not subject to damage, as well as minimizing installation times,” Greenberg points out. “The way we see it is that fleets need to worry about their trailers, not just their trailer aerodynamic systems.”

Trailer makers themselves echo that view.

“As a trailer manufacturer, we know that fuel economy has been a huge item for discussion in the past several years, especially when the price of diesel rises,” says Jamie Scarcelli, vice president & general manager at Wabash Composites, a division of Wabash National Corp. “California’s mandate definitely helped jump-start the demand for aerodynamic systems, although I think the industry would have gotten there eventually. What is an interesting trend is that even fleets that are not operating in California are starting to buy trailer skirts.”

Scarcelli adds, however, that as the population of trailer aerodynamic devices on the road grows, a “distinct concern” is beginning to be heard regarding durability. “We have the advantage of being both a trailer manufacturer and an aerodynamic device provider, [and] that unique perspective allowed us to design an aerodynamic device that not only provided fuel efficiency but also provided the durability required for everyday abuse and repairability,” he notes.

That’s why Scarcelli thinks the next design evolution of these devices will be first and foremost tied to improving durability. “Trailers operate in an abusive environment, and the trailer aerodynamic device makers need to take that into consideration,” he explains. “We have had a lot of new companies jump into this space without fully understanding that key requirement. I also think we will see requirements to truly prove fuel efficiency of these technologies not only on a track under ideal conditions but also on the road in real-life situations.”

Chuck Cole, manager of technical sales and product training for Utility Trailer Manufacturing Co., says that addressing the long-term durability and maintenance needs of trailer aerodynamic devices will become even more critical in the future.

“There are two reasons driving truckers to aerodynamics: regulatory compliance and fuel savings,” he notes. “The California regulation that requires either a 4 or 5% aerodynamic improvement on new trailers starting with the 2011 model year and also the retrofit of older equipment starting next year may be instances where a government mandate is actually good for the industry and will save the trucking community lots of money.”

In harm's way

Yet the still-unknown costs associated with annual maintenance of these devices is what’s worrying truckers large and small, Cole points out.

“Side skirts are located ‘in harm’s way’ and are subject to impact damage and will have some maintenance cost, which is still not 100% known. Indeed, at present, there are some 42 different side skirt models listed on the [Environmental Protection Agency] SmartWay-verified web page alone,” he explains.

“Some of these are probably more durable than others, with some ‘torture-tested’ to withstand severe impacts. With others, who knows? That’s why the buyer needs to know he has a reputable manufacturer and that the device has been structurally tested to ensure safe operation.”

Marty Fletcher, executive director of customer service and product development for trailer aerodynamic device maker Aerofficient, believes the evolution of such products will focus more intensely on durability and maintenance factors in the near term.

“When systems were first being deployed, initial price was the most important factor,” he says. “But now the evolution of aero devices is moving to total cost of ownership, which is reliant upon durability and reliability. An inexpensive system becomes very expensive when it must be repaired or replaced repeatedly, as there is no reimbursement for downtime or labor incurred. Additionally, system weight has always been an important aspect for consideration as well.”

Fletcher adds that trucking’s experience with existing trailer aerodynamic products demonstrates that they are challenged by the extreme work environments in which trailers must perform.

“Temperature extremes are causing warping and eventual cracking or delamination,” he notes. “Ground contact, most commonly in drop-down docks, is causing breakage while support struts are failing due to fatigue. Thus the design evolution must be to strengthen [trailer] fairings.”

At the same time, though, trucking customers want even greater savings from trailer aerodynamic systems, Fletcher stresses. “Existing fairings are good, but customers want improved aerodynamic performance,” he explains. “For us, that means optimizing fairings for refrigerated trailers, for trailers with fixed axles, even fairings that expand and contract when the trailer’s axles are moved to preserve the relationship between the fairing and the trailer’s tires.”

The key design strategy here is that fairings cannot remain static. “The one-size-fits-all approach of most current manufacturers will evolve to enhanced designs for customers’ common and unique needs,” Fletcher believes.

To help guide such improvement efforts, fairing and trailer makers alike are looking to research projects such as the Dept. of Energy SuperTruck program.

“A wide assortment of advanced trailer aerodynamic devices is being relied upon heavily by SuperTruck to contribute towards the program’s goal of a 50% more efficient tractor-trailer by 2015,” stresses Andrew Smith, founder & CEO of ATDynamics.

Proving Results

A major focus of the DOE project is to accelerate industry adoption of fuelefficient technologies by understanding and addressing fleets’ barriers to adoption,” he adds. “Also, ‘voice of the customer’ research pursued during this project has contributed to multiple design upgrades to our TrailerTail system to help speed up industry adoption. Most importantly, the project has broadcast the dramatic fuel savings to be reaped from currently available trailer aerodynamic technologies.”

Another benefit of the SuperTruck project, Smith believes, is that it’s allowed some of the world’s most renowned vehicle aerodynamicists, such as the researchers from Lawrence Livermore National Labs, to both study and confirm the on-road fuel-saving performance of these devices.

“The project has provided a great deal of resources to not only improve products, but just as importantly to validate their performance,” echoes Freight Wing’s Graham. “The opportunity to test products using several different methods, including computer simulations, wind tunnels, SAE J1321 track tests, and real-world fleet testing, has greatly increased our understanding of their potential,” he points out. “Proving results again and again with different tools and independent test partners has also enhanced the credibility of the data. I expect this validation will help convince a lot more fleets to try current and new trailer aerodynamic products for themselves.”

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