That’s the warning from Schmitz Cargobull’s UK technical director Derek Skinner (pictured), who says that far from reducing fuel costs, additions such as vortex generators and side skirts could even increase them.
Aerodynamic add-ons add weight, and depending on how each trailer is used, that extra weight could negate any aerodynamic fuel-saving benefits. The operator may even incur additional fuel costs to run a trailer that looks efficient, but actually produces more CO2 because of the impact of that extra weight.
Skinner says: “There is a prevailing school of thought that you should specify aerodynamic add-ons simply because it makes a trailer look more economical and environmentally friendly to the unassuming general public, without any reference to the actual financial or environmental argument.
“In most circumstances, you’ll save more money simply by specifying a trailer with a lighter chassis.”
Calculating the impact of add-ons is complex, he explains, and often requires knowledge of the mass density of air, drag co-efficients and their relation to object geometry, skin friction and form drag. It’s no surprise, therefore, that some fleet operators choose equipment that looks like it will do the job, without checking the numbers.
Using research methodology developed by the University of Huddersfield, Schmitz Cargobull says it can simplify this calculation and determine the exact profiles of where a trailer will benefit from add-ons.
“The science shows that a trailer with full aerodynamics ends up being less economical than a standard Schmitz Cargobull trailer when its motorway miles drop below 65 to 75%. If your trailer’s mileage on the motorway is sub-optimal, add-ons are probably a waste of time and money,” declares Skinner.