How it all works

Each Airtab® produces two vortices of air, each approximately 4 to 5 times the height of the Airtab® and several feet in length. These tight swirls of air "bridge the gap" between tractor and trailer and lets air flow more smoothly into the vacuum at the rear of the vehicle.	This images shows how the vortices are created.
Aerodynamics of Trucks The first aerodynamic drag reducing devices were introduced to the trucking market in the early 1980s. To date these devices have been applied almost exclusively to the front of the vehicle in the form of air deflectors or fairing. Airtabs™ are unique in that they target two drag producing areas - the tractor/trailer gap and the rear of the trailer, box van or RV.	This image shows the airflow and high drag areas around an unfitted unit. Airtabs™ target and reduce drag at two locations: the gap between tractor/trailer and the rear of the trailer.
The Tractor-trailer Gap If this gap is larger than approximately 0.5m or about 18 inches, unwanted airflow spirals into this area creating extra drag and reduced fuel economy. The operator has two options; move the 5th wheel forward to reduce the gap or use side extenders to shield it. Both these options have drawbacks. Moving the 5th wheel forward reduces maneuverability for city or yard work and it also places more weight on the steering axle. This increases driver "work", steering tire and steering gear wear and tear. Side extenders are expensive and must be flexible in order to maintain maneuverability. Airtabs™ allow an operator to set the 5th wheel "to spec" or to the optimum position and not incur extra drag or steering gear wear penalties and eliminating the need for side extenders. The savings realized by increased steering tire wear alone makes a substantial return on the cost of Airtab® .
The Back of the Trailer Airtabs™ reduce drag at the trailer rear in two ways. They radically alter the airflow pattern from a vertical one to a horizontal one. This eliminates the formation of large eddys, stabilizes the "ride" and increases fuel economy. By smoothing out the airflow, by making the airflow more streamlined, Airtabs™ artificially taper the rear of the trailer. Put another way, Airtabs™ make the airflow behave as if the trailer is narrower than it really is. This drag reduction results in less fuel consumed. Look closely at the image.. This is a very accurate depiction of the airflow behavior surrounding a moving trailer without Airtabs™ as viewed from above. Notice how large vertical eddys of air (like small tornadoes) alternately form and "shed" making room for another to form on the opposite side. Although not visible here, there is an additional eddy that rolls off the top of the trailer as well. These eddys tumble into the partial vacuum formed by the moving vehicle.
These large eddys cause the trailer to sway. Any cross wind (According to NASA studies, there are always cross winds) or any air disturbances from passing vehicles causes larger eddys to form and increase the trailer's tendency to sway. This swaying increases driver work and fuel consumption in exactly the same way as an airplane will burn more fuel on a "bumpy" flight than on a smooth one of equal distance. The lack of streamlining causes turbulent air to tumble into the vacuum left by the large "back end" increasing drag and fuel consumption. Streamlining the trailer by tapering it is the best solution, but that option is not practical. Tapering by lengthening the trailer is not legally possible. Tapering and keeping the same length reduces capacity. Both these options would involve massive changes to docking and loading facilities. Attempts to reduce drag at the rear of trailers to date have involved cumbersome, expensive and labor intensive devices including inflatable cloth "sails" or foam "boat tail" extenders.

Wind Tunnel Test Photos

The photos below show results from a wind tunnel trial with smoke generators used to track airflow patterns.

Without Airtabs™ the smoke indicates airflow into the tractor/trailer gap. This creates drag.

With Airtabs™ fitted, the unwanted airflow into the gap is all but completely eliminated

Spray reduction

Drivers report an improved view to the rear and sides in wet or snowy weather. They can see other vehicles behind them more clearly, and see if it is clear to pass (or be passed). All drivers of vehicles fitted with Airtabs, even 18 wheelers, report improved stability of handling of the vehicle. Drivers of RVs fitted with Airtabs report consistently better handling when being passed in the same direction by large vehicles. -Improved Safety- Improved stability also means less driver workload to keep the vehicle under control, especially in crosswinds.

Road Grime Reduction

Because Airtabs™ alter the airflow out past the rear of the vehicle, the accumulation of road grime or snow is reduced. This reduces weight buildup, tail light and reflector obstruction in snow. Less road grime means advertising information on the back of the vehicle remains more visible and the company's image is enhanced by a cleaner vehicle. [Read]