ARCHIVED - Blowing Away the Tailgate Myth
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May 07, 2007— Ottawa, Ontario
We've all seen owners of pickup trucks driving with their tailgates down. Lowering the flap at the back of the truck must improve aerodynamics and save fuel... right? Wrong!
In fact, driving with your pickup's tailgate down or off actually does the opposite most of the time, says NRC Researcher Emeritus Kevin Cooper, who has spent more than 35 years testing the aerodynamics of countless vehicles and other structures in NRC wind tunnels.
Cooper demonstrated that the tailgate-down myth was just that – a myth. Back in 1999, in between other tests in NRC's 9m wind tunnel in Ottawa, Cooper studied the aerodynamics of different makes and models of pickup trucks.
|Two pickup trucks being tested in NRC's 9m wind tunnel|
Such a drag...
His team's tests included trucks with different box lengths. They found that the shorter the box, the worse the drag becomes when the tailgate is left down or removed.
While lowering or removing the tailgate on trucks with an eight-foot long box may decrease the drag by a small margin (less than one percent), lowering it on a six-foot cab – like those typical of crew-cab trucks – increased the drag by five percent. Using a mesh tailgate cover raised it another five percent or more.
|His team's tests included trucks with different box lengths. They found that the shorter the box, the worse the drag becomes when the tailgate is left down or removed.|
"The end result is that having a closed tailgate is not nearly as bad as people think," says Cooper.
Here's why: Most of the drag on a road vehicle comes from its backwards-facing surfaces – on a pickup truck, these are the back of the cab and the tailgate. Some people try taking the tailgate off completely to eliminate the small amount of drag on the tailgate. Unfortunately, this increases the drag on the back of the cab, and they end up worse off than if the tailgate was left on.
NRC Truck Testing
NRC has a long history of testing and improving the aerodynamics and fuel efficiency of trucks. While Kevin Cooper's tailgate tests spanned only a couple days in the wind tunnel, NRC's work on heavy-duty (class 'A' tractor-trailer) trucks has added up to thousands of testing hours and decades of research.
These efforts have resulted in the innovation and development of many efficiency boosting measures that save fuel by improving aerodynamics, like roof-mounted deflectors, 'skirts' on the sides of truck trailers, and narrower gaps between the cab and the trailer.
In an industry concerned with massive fuel consumption and operating costs, Cooper is proud about the major difference that these aerodynamic changes can make. For heavy trucks that travel 140,000 to 200,000 kilometres per year, the annual savings can add up to 7,000 to 10,000 litres per truck.
Auto companies spend a great deal of time and money wind-testing vehicles, making sure air flows just above the tailgate of their pickup trucks. Lowering the tailgate throws all that effort out the window, Cooper says.
Cooper encourages truck manufacturers to let their customers know that the trucks are most aerodynamic with the tailgate up. The best way to further suppress your pickup's appetite for fuel is to add a fiberglass or vinyl tonneau cover. These covers reduce the air flow that circulates behind the cab―lowering drag for an even more fuel-efficient ride.
Saving fuel and the environment
Fuel efficiency is about more than saving money. Climate change and greenhouse gases are growing concerns for Canadians. Though it might seem like a small detail, keeping your truck's tailgate closed is an effective and easy way to both save fuel and produce less greenhouse gases.
So keep that tailgate up to save your pocketbook – and the environment.
Fuel Efficiency Tips
Small changes in the way you drive can also lower your fuel consumption and greenhouse gas production. If you cannot carpool or take public transportation, consider these tips for a greener ride:
1 – Relax. Aggressive driving―lots of fast braking and quick acceleration―burns extra fuel. A smoother drive will get you further and keep you safer.
2 – Stay on top of car maintenance. Make sure your vehicle is operating at its best and its tires are properly inflated to maximize your fuel savings.
3 – Plan ahead. Smart scheduling can keep you from making multiple trips or idling wastefully in rush hour traffic.
4 – Lighten up. Carrying unnecessary cargo will reduce your mileage.
5 – If you plan to purchase a new vehicle for city use, consider a smaller car that suits your daily needs instead of a van, sports utility vehicle (SUV) or large pickup. You'll save money and fuel.
6 – Ask yourself if you really need four-wheel or all-wheel drive capability. Sure you may be able to accelerate more quickly (even in bad weather), but you cannot stop any faster. Remember cars don't lose control, people do, says NRC's Kevin Cooper.
If you require a pickup truck, then take note of these three tips from aerodynamics experts.
1 – Keep that tailgate up! Lowering or removing it wastes fuel and can be more dangerous if you are carrying unrestrained cargo or if a vehicle is following you too closely..
2 – Don't use mesh replacement tailgates. These create extra drag in the back of the pickup and waste more fuel.
3 – Put a tonneau cover on your pickup truck's bed. The cover is the best way to reduce drag and save fuel.
- Aerodynamics Laboratory at the NRC Institute for Aerospace Research (NRC-IAR)
- Flow Measurement at NRC-IAR
- 9 m x 9 m Low Speed Wind Tunnel at NRC-IAR
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National Research Council of Canada
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