Regular mud flaps add drag to a typical tank trailer, but specially perforated Eco Flaps reduce it and save fuel, the company says. However, note the long fender, with a downswept rear that acts as a drag-producing sail.
 - Photo: Eco Flaps

Regular mud flaps add drag to a typical tank trailer, but specially perforated Eco Flaps reduce it and save fuel, the company says. However, note the long fender, with a downswept rear that acts as a drag-producing sail.

Photo: Eco Flaps

Tank trailers seldom get aerodynamic treatment. Is it because their basic cylindrical shapes look like they move smoothly through the air? That might not be correct, as there’s still a lot of surface area to grab at air molecules, and ladders, walkways, and the tank’s blunt rear end all add to the drag. So do the fenders positioned above a tractor’s drive wheels (more on this in a bit).

Nonetheless, the makers of Eco Flaps, the perforated guards that allow air to pass through but still control splash and spray, thought their devices could be useful on tankers. So, in April the company commissioned a study with Exa Corporation, a developer and distributor of computer-aided engineering (CAE) software.

Exa engineers used computational fluid dynamic simulations to analyze air flow over a typical tanker surface, along with the effects of Eco’s “fly swatter” mud flaps compared to regular flaps.

The study concluded that Eco Flaps could indeed reduce drag and save fuel, said Bren Marshell, vice president of sales. The analysis simulated four different configurations in order to understand how the Eco Flaps splash guards performed when installed on a day cab tractor and tanker trailer. They were:

  • Baseline with conventional mud flaps on the tractor, tanker trailer, and fender
  • Eco Flaps splash guards on the tractor, trailer, and fender
  • Eco Flaps installed on the tractor and trailer, but conventional mud flaps on the fender
  • An equipment setup with no flaps used

The results showed a 2% improvement in drag at highway speeds when Eco Flaps were on the tractor and trailer, but conventional mud flaps remained on the fender. The use of Eco Flaps on the tractor, trailer, and fenders indicated a 2.8% improvement in drag. The total fuel savings from the full swap out is estimated at 1.4%.

 “This analysis from Exa Corporation shows that utilizing Eco Flaps on all sections of the tanker truck provides drivers with the greatest fuel savings,” said Marshell. “At these numbers, drivers can achieve ROI within just three months.”

Owner of this dry-bulk tanker removed its fenders to cut drag, and relies on the tractor-mounted fenders to protect the tank from splash and spray. 

 
 - Photo: Tom Berg

Owner of this dry-bulk tanker removed its fenders to cut drag, and relies on the tractor-mounted fenders to protect the tank from splash and spray. 

 

Photo: Tom Berg

OK, but regarding tanker fenders:  Doing away with them makes sense because they act as sails, catching high-speed air and pulling backwards on the trailer. That was the finding of fleet managers at Air Products & Chemicals, based in Pennsylvania. They removed the fenders and installed tractor-mounted polyurethane fenders over the drive wheels. These protected the tank above from splash and spray, and also weighed less than the metal fenders.

There was a fuel saving and while I can’t recall the percentage, it was enough to make the equipment change worthwhile. Building tank trailers without fenders also saved a few bucks.  

Anyway, for more information about Eco Flaps, go to www.ecoflaps.com.

Author

Tom Berg
Tom Berg

Tom Berg

Journalist since 1965, truck writer and editor since 1978. CDL-qualified; conducts road tests on new heavy-, medium- and light-duty tractors and trucks. Specializes in vocational trucks and trailers of all types.

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Journalist since 1965, truck writer and editor since 1978. CDL-qualified; conducts road tests on new heavy-, medium- and light-duty tractors and trucks. Specializes in vocational trucks and trailers of all types.

View Bio
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