“EkoStinger proves to be much more than a side skirt,” proclaims the heading on a press release from a company with that name in Rochester, N.Y. It’s not a side skirt at all, but an underslung arrow-shaped structure mounted ahead of a trailer’s tandem, and it diverts air flow around the axles, suspension and wheels.

Unlike most skirts that are stationary, the stinger moves with the tandem as it’s slid fore and aft, so it smooths air flow no matter where the tandem is set, said the system’s inventor and company president, Parr Wiegel, in a phone conversation last week.

The structure is mounted on tracks to enable the sliding, and it sits high enough – about 16 inches from the pavement -- to avoid contact with driveway aprons, railroad crossings and other obstructions that could cause damage, he said. The stinger is warranted against such damage as well as “driver error.”

The second part of the product is a long plastic sheet that covers the frame rails and crossmembers and reduces turbulence there. The underframe cover extends most of the trailer’s length, and is tightly sealed around its edges to keep salt spray and frozen moisture away from the undercarriage.

“We add a fluted polycarbonate cover to protect the beams from rot, plus you’re not carrying around extra weight from ice and snow. That can build up to be a thousand pounds or more,” he said. The under-cover and stinger also suppress water spray and improve rainy-day visibility for truck drivers and motorists.

“There are two things we tell people: Key-on to key-off, you’ll get 4 to 6% better fuel economy. Some fleets in the Northeast say they are seeing 10 to 15%, though they may be a bit enthusiastic. And in most cases, you’ll see increased stability of the trailer, and that requires some driver modification,” Wiegel said.

“Truckers driving along I-90 up here get crosswinds. Crosswinds coming off Lake Erie cause sway. This (the stinger and under-cover) reduces the sway, so the driver takes his foot off the throttle because he doesn’t have to compensate for sway. That saves fuel. One operator with double 48s running on the New York Thruway is getting 5%” better economy.

Wiegel doesn’t have a trucking background, but got interested in vehicle aerodynamics during his highway travels when he saw trailers with skirts, and he doubted their effectiveness.

“I own a hurricane protection company and we deal with 150 mph winds, and I’m always around wind tunnels. We make windows that will stand up to hurricane-force winds. We guarantee your window for the life of your house. We like to build products better than anybody else.

“So I called up some of my friends who are aerodynamicists and asked them to test some skirts. And they said, ‘They don’t work.’

“Skirts have flaws,” Wiegel insisted.  “A trailer has to be going 45 mph before there’s an effect.  And side winds actually hit more surface with the skirts in place. And with gaps for the tandem, you’re introducing wind back in. You almost have to run the tandem fully forward to get any savings. Then you have gaps behind the axles.”

A combination stinger and under-cover lists for $2,450, “but we have very aggressive discounts based on numbers,” he said. NationaLease and HD America Truck Pride outlets are distributors.

Of course, competitors who produce and sell trailer skirts would disagree with Wiegel’s pronouncements. They’d present their own wind-tunnel results, and customer testimonials, to prove they’re right.

To be sure, the EkoStinger is not the first underslung device that mounts ahead of a trailer’s tandem. There is at least one skirt product that moves to accommodate the tandem’s setting. And there’s been another under-cover (a sheet metal version was tried some years ago with good results, but never entered production, as far as I know).

But Wiegel’s product combines two or three features that add up to a different way to tackle the air-drag problem. May he and everyone be successful at cutting through the wind and saving fuel.