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Airtabs™ are patented, unique wishbone shaped vortex generators designed to increase vehicle aerodynamic performance and fuel economy by reducing aerodynamic pressure drag at two key locations; the tractor-trailer gap and the rear facing surface (the base area) of any commercial or private square backed vehicle or trailer that routinely attains highway speeds. Drag reduction and fuel economy benefits from Airtab® application is not limited to commercial trucking operations. Airtabs™ enhance aerodynamic performance equally well on cube vans, straight trucks, expeditors, SUVs, RVs, buses, horse, toy and utility trailers, faired "bob tail" tractors, flat beds and tankers. The results may vary somewhat with vehicle type but the aerodynamic theory and principles are the same for all.

Airtabs™ are mounted 3 per linear foot, or every 4 inches on center. Take the number of feet to be covered and multiply by 3 to give the number of Airtabs™ required.

Each Airtab® creates two tight swirls of air or vortices that combine to reduce the suction and drag at the rear of vehicles traveling at speeds above approximately 35 mph or 55kmh. Airtabs™ are also effective at the rear roof lines of automobiles that have a rear window slope of greater than 30 degrees.

Airtabs™ offer several safety benefits as well.  They improve vehicle stability by altering the airflow at the vehicle's rear. The large random eddies at the rear surface are changed to an array of small vigorous “stream wise" vortices. The majority of users comment immediately on the improved vehicle handling performance, especially in gusty cross wind conditions or when passing (or being passed by) other vehicles. This increases driver safety margins by reducing wandering and sudden adjacent lane incursions. Mirror visibility in rain or snow is also improved as the Airtabs™ help suppress precipitation and spray patterns. Safety is improved through better mirror visibility yielding safer lane changes as well as improving the visibility conditions for other road users. By reducing the suction and aerodynamic drag at the rear of vehicles, the tendency to accumulate snow and road grime at this location is reduced. This helps to improve corporate image and reduce cleaning time and expense. It also enhances safety by keeping conspicuity tape, tail and brake lights cleaner and helps the bottom line by reducing snow and weight build up in winter.


Aerodynamics Research Revolutionizes Truck Design
Originating Technology/NASA Acknowledgement


Originating Technology/NASA Acknowledgement
t-6The last 35 years have seen a sea change in the design of trucks on America’s highways, reflecting extensive research into vehicle aerodynamics and fluid dynamics conducted by NASA engineers. Thanks to the ingenuity of a Dryden Flight Research Center researcher bicycling through the California desert and a team of engineers in Virginia, the shape of rigs and recreational vehicles (RVs) today owes as much to the skies as it does the open road. Bicyclists, motorcyclists, and even pedestrians feel a push and pull of air as large trucks pass. The larger a vehicle is and the faster it moves, the more air it pushes ahead. For a large truck, this can mean a particularly large surface moving a large quantity of air at a high velocity—its blunt face acting like a fast-moving bulldozer, creating a zone of high pressure. The displaced air must go somewhere, spilling around the cab into swirling vortices. The air traveling along the side moves unevenly, adhering and breaking away, and sometimes dissipating into the surrounding air. At the end of the cab or trailer, the opposite effect of the high-pressure zone at the front develops; the airflow is confronted with an abrupt turn that it cannot negotiate, and a low-pressure zone develops. The high pressure up front, the turbid air alongside and under the vehicle, and the low pressure at the back all combine to generate considerable aerodynamic drag. A study published in Automotive Engineering in August 1975 found that a tractor trailer unit moving at 55 miles per hour displaced as much as 18 tons of air for every mile traveled. In such cases, roughly half of the truck’s horsepower is needed just to overcome aerodynamic drag.

t-7In 1973, Edwin J. Saltzman, Dryden aerospace engineer and bicyclist, noticed the push and pull of large trucks at highway speeds while riding to work. As a tractor trailer overtook him, he first felt the bow wave of air pushing him slightly away from the road and toward the sagebrush; as the truck swept past, its wake had the opposite effect, drawing him toward the road and even causing both rider and bicycle to lean toward the lane. Saltzman mused about ways to mitigate the bow wave and trailing partial vacuum, and resolved to help trucks glide through air instead of push through it, and, in the process, decrease drag and increase fuel efficiency. NASA colleagues at Dryden were working on the effects of drag and wind resistance on different kinds of aircraft and the early space shuttle designs, so they transferred their considerable knowledge to the design of large trucks.

The first formal experiment involved a Ford van retired from delivery duties at Dryden. Mechanics attached an external frame which was then covered with sheet aluminum to give the van flat sides all around and 90-degree angles at all corners. The vehicle looked like an aluminum shoebox on wheels, simulating the cruder motor homes of the period. The Dryden engineers measured the vehicle’s baseline drag and then set about modifying the shape of the van: First rounding the front vertical corners, then the bottom and top edges of the front, then the edges of the aft end, and finally sealing the entire underbody of the van including the wheel wells, with tests run after each modification. Rounding all four front edges yielded a 52-percent drag reduction, while sealing the bottom of the vehicle gained another 7 percent. The engineers estimated the potential gain in fuel economy to be between 15 and 25 percent at highway speeds.

t-8During the following decade, Dryden researchers conducted numerous tests to determine which adjustments in the shape of trucks reduced aerodynamic drag and improved efficiency. The team leased and modified a cab over engine (COE) tractor trailer, the dominant cab design of the time, from a Southern California firm. Modifications included rounding the corners and edges of the box-shaped cab with sheet metal, placing a smooth fairing on the cab’s roof, and extending the sides back to the trailer. Rounding the vertical corners on the front and rear of the cab reduced drag by 40 percent while decreasing internal volume by only 1.3 percent. Likewise, rounding the vertical and horizontal corners cut drag by 54 percent, with a 3-percent loss of internal volume. Closing the gap between the cab and the trailer realized a significant reduction in drag and 20 to 25 percent less fuel consumption. A second group of tests added a faired underbody and a boat tail, the latter feature resulting in drag reduction of about 15 percent. Assuming annual mileage of 100,000 driven by an independent trucker, these drag reductions would translate to fuel savings of as much as 6,829 gallons per year.On the other coast from Saltzman and his Dryden team, Dr. John C. Lin and Floyd G. Howard of Langley Research Center with Dr. Gregory V. Selby of Old Dominion University, Norfolk, Virginia, conducted a series of research projects in the late 1980s and early 1990s focusing on controlling drag and the flow of air around a body. One study conducted in 1989, “Turbulent Flow Separation Control,” explored controlling airflow—flow separation—to decrease energy expenditure and weight in airfoils, inlets, and diffusers and improve aircraft control and decrease drag. The study employed vortex generators, aerodynamic surfaces protruding from a body that draw faster moving air to the surface of the vehicle and disrupt the slower moving boundary layer air around a vehicle, the use of which can be traced back to research conducted by the National Advisory Committee for Aeronautics (NASA’s forebear) in the 1950s. The generated vortices “energize” the slower-moving boundary layer and thereby reduce drag and, in aircraft applications, increase lift.Subsequent studies in 1990 and 1991 continued vortex-generator research with an exploration of various active and passive methods for controlling two-dimensional separated flow. These studies quantified and characterized the behavior and performance of a variety of large-eddy breakup devices for turbulent flow separation control.

Answering the charge given by the U.S. Congress in the National Aeronautics and Space Act of 1958 to disseminate newfound technologies and discoveries to the public, NASA makes the results of its research and expertise of its scientists and engineers available through a variety of means. Sponsored by the Innovative Partnerships Program, these include published studies, NASA outreach, the Small Business Innovation Research and Small Business Technology Transfer programs, technology transfer offices at each NASA field center, and the Space Alliance Technology Outreach Program (SATOP). The aerodynamics studies at Dryden have been made publicly available, and Aeroserve Technologies Ltd., of Ottawa, Canada, with its marketing arm, Airtab LLC, in Loveland, Colorado, applied these studies, the aerodynamic work at Langley, and the patented Wheeler vortex generator to the development of the Airtab vortex generator; designed to reduce drag and improve vehicle stability and fuel economy. Of the devices tested, the Wheeler showed the least parasitic drag, and Aeroserve optimized the Wheeler design for ease of installation and application to any vehicle.

Product Outcome
t-9The Surface Transportation Assistance Act of 1982 required states to permit trucks with trailers as long as 48 feet on both interstate and intrastate highways; the previous length limit of 55 feet had applied to the tractor and trailer together. As the previous regulation made the COE tractor a dominant choice, owing to its decreased length regardless of aerodynamic or fuel efficiency shortcomings, the new regulations opened the door for a renaissance of the “conventional” cab. While COE designs place the cab directly above the engine, minimizing length and producing a cube-like tractor, conventional truck designs place the engine ahead of the cab. Though longer as a result, a protruding nose offers truck designers an inherently more aerodynamic shape from which to work. In 1982, COE trucks constituted over 65 percent of the market for the Peterbilt Motors Company, with similar numbers for other manufacturers; the cab-over design represented only 1 percent of sales for Peterbilt by 2004. Streamlined cabs and fairings are now a common sight on our highways, and the once-prominent cab-over design has been abandoned in virtually all applications except small-capacity urban-oriented trucks where length remains a premium. The modifications tried by the engineers at Dryden were adopted by the truck manufacturers, as the same principles the NASA engineers demonstrated with COE trucks applied to conventionals. In addition, the cargo boxes of most delivery trucks today have rounded corners and edges, a direct application of the research conducted at Dryden on the “shoebox.” Today’s trailers, on the other hand, are little changed from the last few decades. For livestock haulers, a key factor is that individual farmers have been the predominant owners of trailers, and these owners are difficult to convince about the costs of redesign versus the savings of superior aerodynamics. However, more and more livestock trailers are sporting boat-tail designs that ease the flow of air past the end of the trailer and minimize the low-pressure wake. Conventional trailer manufacturers have resisted change more so than others, in part because the aft end of such a trailer needs to be easy to manipulate at loading docks, where the optimal shape for superior aerodynamics—the boat tail—is impractical.

Effective on any vehicle with more than a 30-degree slope to the rear, Airtabs see many applications in addition to trucks.

Likewise, the gap between the cab and the trailer can create a significant amount of drag as air swirls in the space between. Two conventional means to address this issue are problematic: Adding side extenders (to decrease the exposed gap) is expensive and might impede maneuverability; moving the fifth wheel forward (to shorten the gap) places more weight on the steering axle—which is legally regulated and limited—and reduces maneuverability while increasing driver effort and wear on steering tires and steering gear.Addressing both of these dilemmas, Aeroserve’s Airtabs garner the benefits of the airflow found in a boat-tail design with the practicality of a squared-off end for loading and unloading, and see additional applicability smoothing the airflow between cab and trailer. Airtab vortex generators create a controlled vortex to reduce truck and trailer wind resistance and aerodynamic drag. Each Airtab produces two counter-rotating vortices of air, each approximately four to five times the height of the Airtab and several feet in length, that smoothly bridge the gap between tractor and trailer or control airflow past the rear of the vehicle. Airtabs thus allow an operator to set the fifth wheel to the optimum position without incurring extra drag or steering gear wear penalties and gain some of the aerodynamic benefit of side extenders. At the back of a trailer, box van, or RV, Airtabs radically alter the airflow to reduce drag in two ways: Shifting the airflow pattern from vertical to horizontal to eliminate large eddies, and smoothing the airflow to artificially simulate a tapered rear of the vehicle. In fact, Airtabs have been shown effective on any vehicle with more than a 30-degree slope to the rear; the potential benefits stretch across vehicular applications and could thus benefit a considerable number of vehicles.Smoothing the airflow results in markedly improved fuel economy without compromise to design utility, and additional benefits have been realized as well. The vortex generation reduces spray; users have reported improved rear and side view in wet or snowy weather, increasing safety and offering a clearer view of surrounding vehicles. Also, because Airtabs alter the airflow around the rear of a vehicle, the accumulation of road grime is reduced, keeping tail lights and reflectors clean and allowing less snow to build up, a significant safety benefit in foul weather. Less accumulation of road grime also means advertising and safety information on the back of a vehicle remains visible.Perhaps most importantly, drivers of vehicles fitted with Airtabs have reported improved stability and handling and dramatically reduced fishtailing of trailers—an effect where the trailer sways or slides from side to side independent of the tractor, potentially causing catastrophic loss of control—effects that are especially important with the double trailers found in North America and the famous quad-trailer “road trains” in Australia. Increased stability also means that the trailer does not scrub on the sides of the road as much, increasing the life of tires. Drivers also report better handling when being passed in the same direction by other large vehicles. Cummins Rocky Mountain LLC, a diesel engine and generator wholesale and distribution company in Broomfield, Colorado, recognized these benefits and agreed to promote and sell Airtabs after internal testing and customer feedback indicated that Airtabs brought immediate safety and fuel economy benefits when running equipment at highway speeds. The company noted additional benefits included ease of installation, minimal maintenance, and low price.As more NASA research and development is adapted and introduced to the market by companies like Aeroserve, the vehicles populating our highways and interstates will likewise continue to evolve. Practical solutions to aerodynamic challenges, exemplified by the Airtab, offer increased stability, safety, and economy to airborne and surface vehicles alike, and NASA is proud to contribute tangible and current benefits to both fields of transport and travel.Airtab® is a registered trademark of Aeroserve Technologies Ltd.

Airtabs™ are unique, Vortex Generators (VG) that have been specially designed for trucks. They work by creating a controlled swirl of air, or vortex, which actually reduces wind resistance (or aerodynamic drag). Aerodynamic drag has long been a target for fuel economy on trucks.

Airtabs™ Dramatically reduce the 'fish tailing' on trailers and have made tremendous impact on the handing of double trailers in Australia and North America.


Here you can see Airtabs™ fitted to the tractor, (these can be painted to match the color of the truck). In this area, the vortex prevents air from entering the gap and creating turbulence.



Streamlined cabs and fairings have made improvements, but there is still the problem of the large flat area at the back of the vehicle and, for tractor-trailer units, the gap between the tractor and trailer.


Here you can see Airtabs™ fitted to rear of the cab, this reduces the airflow into the gap between the tractor and trailer.




At the back of the vehicle is an area where the air has to rush in to fill the space left by the vehicle. Since the air has to make a sharp bend around the squared-off back of the vehicle, this creates a lot of drag and turbulence. The drag from both areas takes engine power to overcome, and therefore fuel.

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.

They work on RVs too click here!


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.


badairflow This image shows the airflow and high drag areas
around an unfitted unit.

goodairflow Airtabs™ target and reduce drag at two locations:
the gap between tractor/trailer and the rear of the trailer.

The Tractor-Trailer Gap

The gap size is an important aspect of fuel economy in trucking operations and should be minimized as much as loads allow.  If the gap between the trailing edges of the tractor fairing and the front of the trailer is greater than about 18 inches (1/2 meter) increased drag in this region begins to reduce fuel economy.  For every additional 10 inches of gap size above about 30 inches, aero drag will increase 2% and fuel economy will decrease by 1%.  The operator can reduce this gap with side extenders and/or moving the 5th wheel forward.  However, moving the 5th wheel forward can reduce maneuverability and can place more weight on the steering axle increasing steering gear and tire wear.  Through the use of side extenders and Airtabs, operators will have the flexibility of setting the 5th wheel more precisely for the load, not add weight to the steering axel and avoid a reduction in fuel economy by using Airtabs to reduce gap turbulence.



The Back of the Trailer

Airtabs™ reduce drag at the trailer rear by changing the dominant flow pattern from vertical to horizontal.  Airtabs™ change the airflow from the alternating formation of large vertical eddies to a line of dozens of small vigorous horizontal ones.  This reduces vehicle sway, improves stability in gusty cross wind conditions and increases fuel economy.  By altering the airflow in this manner, Airtabs™ artificially taper the trailer and make the airflow behave as if the trailer was slightly smaller than it actually is.  This results in drag reduction and an increase in fuel economy.


Click on image to view animation

vortLook 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.  Click on image to view animation

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.


A lack of trailer streamlining causes a partial vacuum to form at the rear of the trailer at highway speeds.  This causes turbulent air in the form of large vertical eddies to tumble into the partial vacuum and the large alternating eddies cause the trailer to sway.  Disturbances from passing vehicles or obstacles temd to amplify these eddies and increase the trailer's tendency to sway, increasing driver work load and fatigue, increasing drag and lowering fuel economy.  Streamlining the trailer by tapering would be the best solution but is not practical due to a necessary reduction in trailer capacity and massive changes to docking and loading facilities.

Other functional after-market devices that will reduce drag at the rear of trailers do exist.  These are usuall devices that physically alter the trailer rear by using inflatable sails, foam boat tail extenders or rigid metal panels that extend to taper the trailer rear.  However, these devices can be combersome, expensive, heacy and prone to collision damage.  These devices can also interfere with loading operations.


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.


tunnel2 With Airtabs™ fitted, the unwanted airflow into the gap
is all but completely eliminated.


The pictures above were taken in a low speed wind tunnel facility looking down on a simulated tractor-trailer gap.  Notice how in one photo the smoke reveals how turbulent air enters the gap and increases aerodynamic drag.  The second photo shows how Airtabs™ reduce the amount of smoke, turbulence and drag entering the gap under identical controlled wind tunnel conditions.

* These photos supplied courtesy of the Cranfield University Atmospheric Boundary Layer Wind Tunnel



Spray Reduction and Stability
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 at the rear of the vehicle, the partial vacuum there is reduced.  There is less accumulation of road grime or snow.  Less road grime means advertising remains more visible and the company's image is enhanced.  Less snow means less weight to haul and less snow build up that can obscure conspicuity tape reflectors and low heat LED tail lights.

Airtab® is a registered trademark of Aeroserve Technologies Ltd. US and Canadian Patents


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