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Aerodynamics – Saving Money Today

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Talk to commercial vehicle operators these days about cutting their carbon footprint and minimising the environmental impact of their vans and trucks and the conversation is likely to revolve around alternative fuels. After that it may go on to encompass the use of onboard driver behaviour monitoring systems designed to discourage speeding and harsh braking.Kuda Aerodynamics

Does that mean the benefits of aerodynamics have been forgotten? Not exactly – but there may not be quite the focus on them so far as some fleets are concerned that there once was.

Improve Existing Vehicles

“I wouldn’t say there is less interest but aerodynamics treatments are not always as close to the top of the pile as they should be,” says Tim Vincent, commercial director at Kuda. “A lot of operators seem to be looking at the next trucks they are going to acquire and which alternative fuel they will be powered by while forgetting how they can improve the performance of the trucks they have already got.”

Kuda markets its air kits under the iAM – improved Air Management – banner.

“Bear in mind that if you fit an aerodynamic kit then the fuel savings it can offer mean that it can pay for itself in six months,” Vincent says; and if you burn less fuel then that’s good news for your bottom line as well as for your carbon footprint.

He stresses however that a lot depends on the sort of work an operator is on. Air kits bring their biggest benefits if you are a high-mileage haulier with a tractor unit and high-volume semi-trailer that tackle a lot of motorway work.

“If they do 100,000 miles a year then you’ll certainly see your money back,” he observes.

In those circumstances the most important aerodynamic aid to fit is a cheese-wedge-shaped cab-top spoiler that bridges the gap between the top of the unit’s cab and the top of the semi-trailer says Vincent. That can bring you a fuel saving of roughly 3.5%, he estimates.

“Remember that every 200mm of trailer bulkhead shown above the cab increases aerodynamic drag by 3%,” he says.

Fit side collars to the rear of the cab and you can increase the total fuel saving to 4% he observes, then boost it to 5% if you equip the tractor unit with side skirts. Further savings should be garnered if you fit your trailer with side skirts too.

All these items can be fitted to rigid chassis as well; to 18-tonners for example with box bodies. “You probably won’t get a 5% saving but you won’t be far off.” he remarks.

How about mounting a vortex generator on the roof? “It can bring a saving – maybe 0.5% to 1% – but although it probably helps, it’s hard to prove,” Vincent observes.

It should perhaps be stressed that aerodynamic treatments work to their best advantage on box and curtainsider bodies. They will be far less effective if a tractor unit is for example hauling a low-loader laden with an excavator given the lack of smooth surfaces that can be worked with.

A full-height roof spoiler may not always be practical if you are hauling a big-volume semi-trailer using one of the small day-cab tractor units favoured by some of the major supermarket chains. “What you can also do in that case is mount an aerodynamic spoiler on the trailer’s front bulkhead,” Vincent advises.

Automatic Spoiler Adjustment

If you are going to specify a cab-top spoiler and your tractor unit hauls different heights of semi-trailer then you should opt for one that is height-adjustable he says.

Kuda spoiler

Match the height of the spoiler to the top of the body

The best approach is to select one that comes with a system such as Kuda’s LaserEye. It adjusts the spoiler automatically when the unit reverses up to the trailer.

That means drivers do not have to do anything. Most importantly, they do not have to climb up onto their vehicles to adjust their spoilers manually.

Climb onto a vehicle and there is always the risk that you will fall and be injured; and the Health and Safety Executive takes a tough line when it comes to falls from height in the workplace.

So what does all this kit cost?

“A cab top spoiler and collars will set you back £1,100 – they only weigh 70kg in total so there is next to no weight penalty – plus a further £600 if you want LaserEye,” Vincent replies. Add LaserEye and the package will take a further two months to pay for itself.

“I’m always amazed by the number of incorrectly-adjusted spoilers I see on my travels,” says Craig Poacher, sales manager at Hatcher Components. Hatcher too offers a cab-top spoiler that automatically adjusts itself to the trailer’s height under the Smart Spoiler banner.

“Without it it’s difficult for drivers to fully align the spoiler to the trailer’s height,” says Poacher. “Smart Spoiler removes the guesswork.”

It is of particular benefit to hauliers whose trucks go to both retail outlets and distribution centres, he contends.

“Often that involves using a standard trailer during day retail drops but a tall double-deck trailer at night,” he says. “If you require that operational flexibility then Smart Spoiler is just what you need.”

Boat-Tail Trailers

Rear-mounted wings – sometimes referred to as boat-tails – can be fitted to truck bodies and trailers as well, although operators may understandably worry that they will be damaged if the driver forgets they are there when reversing up to a loading dock.

Last year saw Montracon unveil an aerodynamic refrigerated DAF CF 18-tonner which should be capable of delivering a 10% reduction in drag.

Air management features include rear boat-tails 500mm long. As it meets the collars at the back of the cab the front of the body tapers to minimise any air turbulence between the cab and the body while allowing sufficient space for the truck’s fridge unit.

Dramatically-sculpted or sloping roofs on curtainsider and box bodies can reduce drag and thus fuel usage.

A sloping front roof distinguishes each of the three 15.6m step-frame double-deck box van longer semi-trailers built by Tiger Trailers and delivered to Howard Tenens earlier this year. Deployed on a distribution contract Tenens has with tool supplier Toolstation, they can transport up to 87 roll-cages apiece; that’s 38 on each deck with another 11 on the trailer neck.

The trailers transport stock between Toolstation’s distribution centres in Redditch in Worcestershire, Daventry in Northamptonshire and Swindon in Wiltshire. The hydraulically-operated moving upper deck can handle loads totalling up to 7.0 tonnes.

Fitting an aerodynamic package to a rigid vehicle can result in a potential average fuel saving of around 6% says Kevin Hawes, aerodynamic specialist at Hilton Docker Mouldings. However cutting fuel consumption is not the only reason why operators should consider investing in air kits, he contends.

Installing them will demonstrate that you care about the environment, he points out. “You will be perceived as being eco-friendly,” he observes.

He believes such kits can benefit residual values and goes on to suggest that rental companies that decide to install them could end up enjoying a competitive edge because of the fuel economy benefits they can bring to their customers.

“Your vehicle’s stability and handling will improve, reducing wear and tear on the steering and tyres,” he says. “Furthermore, good under-body side skirts can channel water spray and reduce over-spray.”

That will benefit other road users following your truck in heavy rain on the motorway; and improve your company’s public image no end.


About Jason Hodge (1361 Articles)
Editor of Commercial Vehicle Dealer Magazine, Jason has worked in the commercial vehicle industry since leaving university over 20 years ago.