Trailer Aerodynamics and Fuel Efficiency

Tags: Fleet management

Aerodynamics plays a big role in determining your car’s fuel efficiency, and an even bigger role when we’re talking about semi-trailers. When trailers are designed to move smoothly through the air, they create less drag, which saves fuel and the environment.

This is important not just for truckers but for everyone in the supply chain. From manufacturers to retailers, everyone benefits when trucks use less fuel because it can help reduce costs.

Better fuel efficiency is a win-win for everyone. For truck drivers, it means spending less on gas and being able to go further on a single tank. For businesses, it leads to lower shipping costs, which translates to lower costs for consumers. And for the environment, it means fewer emissions. Improving trailer aerodynamics is a smart move that helps the whole supply chain work more efficiently and responsibly.

What Are Trailer Aerodynamics?

Trailer aerodynamics focuses on how trailers are designed to move through the air more efficiently. It’s about shaping and designing trailers to slice through the air with less effort. 

The principles of semi-truck aerodynamics in trailer design involve understanding how air flows around large objects. Designers increase a trailer’s aerodynamics by adding features like rounded corners, flat panels, and streamlined edges. 

Fewer sharp edges and more curves on a trailer’s body work together to reduce air resistance, known as drag, by helping air glide over and around the trailer more smoothly. Smoother, more efficient airflow reduces turbulence and increases efficiency.

By reducing drag, trucks can maintain higher speeds without more fuel, making transporting goods more efficient and environmentally friendly. This design approach not only saves fuel and money but also contributes to reducing the transportation industry’s carbon footprint.

What Causes Drag on Tractor Trailers?

Drag on tractor-trailers is like a force that pulls back on the truck as it moves forward. It’s caused by air hitting the truck and trailer, creating resistance. The bigger and boxier the trailer, the more air it pushes against, and the harder it is for the truck to move forward. This resistance can really add up, especially at higher highway speeds, making the truck use more fuel.

The Science Behind Drag

Drag is a force that opposes an object’s motion. For tractor-trailers, drag is the resistance caused by air as the vehicle moves forward. Aerodynamic drag is a combination of two main components: 

• Form Drag: This type of drag results from the object’s shape. For tractor-trailers, the boxier and less aerodynamic the shape, the higher the form drag. Air needs to move around the vehicle, creating areas of high pressure in front and low pressure behind, which slows the vehicle down.

• Skin Friction Drag: This type of drag occurs due to the friction between air and the truck’s surface. Air creates resistance as it flows over the truck’s surface. The smoother the surface, the less friction and less drag.

Contributors to Drag on Trailers

Several factors contribute to drag on tractor-trailers:

• Shape and Size: The larger and less streamlined the trailer, the more air it has to push through. This is why the design of the trailer is so important. Sharp edges and flat surfaces create more drag.

• Speed: The faster a truck goes, the more air it has to push out of the way. This means more drag and more fuel used to maintain speed.

• Wind Conditions: Windy conditions can increase drag, especially if the wind is blowing against the direction the truck is traveling. Crosswinds can also create additional drag by hitting the sides of the trailer.

• Trailer Gaps: Spaces between the tractor and the trailer and between the trailer and the road allow air to get trapped and swirl around, increasing drag.

• Load Weight: Heavier loads require more power to move, increasing drag, especially when going uphill or accelerating.

Main Points of Drag on Trailers

Three areas of a semi-truck rig produce the most drag.

• Front of the Trailer at the Gap: Behind the cabin in front of the trailer, a low-pressure area is created, resulting in high levels of drag.

• Trailer Undercarriage: Air passing under the bottom of the trailer around the wheels causes high drag.

• Back of the Trailer: A low-pressure zone is created as air passes around a trailer. That low pressure results in significant drag.

The trucking industry is always looking for ways to improve tractor-trailer aerodynamics, and these factors are key to achieving a more streamlined, eco-friendly supply chain for everyone.

How Drag Impacts Semi-Trailer Fuel Efficiency

Drag is a significant factor affecting fuel efficiency in semi-trucks. As a truck moves, air resistance, or drag, works against it, requiring more fuel to maintain speed and momentum. The more drag a trailer experiences, the harder the engine works, leading to higher fuel consumption. This is where trailer aerodynamics play a crucial role.

By improving the design and adding aerodynamic devices to trailers, drag can be significantly reduced. This leads to smoother airflow around the trailer, decreasing resistance and, consequently, the amount of fuel needed. 
The relationship between drag and fuel efficiency is direct: as drag decreases, fuel efficiency increases, making aerodynamics an essential factor across the logistics industry.

Semi Trailer Aerodynamic Devices

The trucking industry has developed various aerodynamic devices to combat the drag that semi-trailers face. These devices streamline the trailer, reducing air resistance and improving semi-truck fuel efficiency.

Here’s a look at some of the key features of an aerodynamic rig:

Truck Trailer Tails

Truck trailer tails are attachments that go on the back of the trailer. They look like folded wings and work by smoothing the airflow as it leaves the trailer. This reduces turbulence and drag at the rear of the trailer, which is a primary source of resistance. By using trailer tails, trucks can see a significant improvement in fuel efficiency.

Airflow Trailer

An airflow trailer is designed with aerodynamics in mind from the ground up. Its shape is more streamlined than traditional trailers, with curved edges and a design allowing air to flow smoothly over and around it. This reduces drag significantly, making the trailer much more fuel-efficient.

Trailer Fairings

Trailer fairings are panels attached to the trailer’s sides and bottom. They help guide air smoothly around the trailer, reducing the drag caused by air getting trapped under or around the sides. Fairings are particularly effective in reducing the turbulence and resistance created by the wheels and undercarriage of the trailer.

Trailer Door Gap Cover

The gap between the trailer and the tractor can create a lot of drag. Trailer door gap covers are designed to bridge this gap, smoothing the airflow between the tractor and trailer. This reduces the turbulence and drag that occurs in this area, improving the overall aerodynamics of the semi-trailer.

Wheel Covers and Mud Flaps

Wheel covers and mud flaps streamline the wheels and rear of the trailer. Wheel covers smooth out the airflow around the wheels, while aerodynamic mud flaps reduce the drag caused by air hitting the back of the trailer. Both of these devices help reduce the overall resistance faced by the trailer, contributing to better fuel efficiency.

The Importance of Trailer Aerodynamics

The importance of trailer aerodynamics cannot be overstated for modern trucking. As we’ve seen, aerodynamic improvements to trailers can lead to significant reductions in drag, which directly translates to improved fuel efficiency. This helps cut down operational costs for trucking companies and contributes to environmental sustainability by reducing fuel consumption and greenhouse gas emissions.

Investing in aerodynamic features like truck trailer tails, airflow trailers, trailer fairings, door gap covers, wheel covers, and mud flaps is a smart move for any fleet. Companies can enjoy long-term savings and contribute to creating a more sustainable future. We recommend readers consider these aerodynamic solutions to enhance their fleet’s performance and efficiency.

Frequently Asked Questions on Trailer Drag

What percentage of fuel can be saved by using aerodynamic trailers?

Using aerodynamic trailers can lead to significant fuel savings. On average, improvements in trailer aerodynamics can result in fuel savings of about 5% to 10%. This percentage can vary based on the specific aerodynamic features used and the type of routes typically driven.

How much does aerodynamics affect MPG?

Aerodynamics can substantially impact a semi truck’s miles per gallon (MPG). By reducing drag, aerodynamic trailers can improve a truck’s MPG by several points. The exact improvement depends on factors like the truck’s design, speed, and the aerodynamic devices used.

Does trailer height affect MPG?

Yes, trailer height can affect MPG. Taller trailers present a larger surface area to the wind, increasing drag and potentially reducing fuel efficiency. However, the overall impact of trailer height on MPG also depends on factors like trailer design and aerodynamic aids. Matching the height of the tractor to the trailer maximizes fuel efficiency.

Get the Latest Aerodynamic Trailers with Hale

Visit Hale Trailer for more insights and information on trailer aerodynamics, fuel efficiency, and the latest in trailer technology. For the latest and greatest aerodynamic trailers for your shipping needs, explore our inventory online or see our fleet in person at one of our locations.