[freebeard]

a huge reduction in drag ( about 35%)

Not possible.

Trucks and trailers generate aerodynamic drag in four main areas: front of the tractor, gap between tractor and trailer, underside of the trailer, and rear of the trailer. Here are a few of the ways engineers have targeted these areas, along with Wood’s rough estimate of the percentage each idea is said to reduce drag: Top row: wake boards, 7%; vortex strake, 7%, high-momentum mudflaps, 3%; fairing, 3%. Bottom row: passive porosity, 4%; boattail, 5%; side skirts, 2%; and vortex traps, 7%.

This from Richard Wood "who chairs the Society of Automotive Engineers' (SAE) Truck and Bus Aerodynamic and Fuel Economy Committee and is a member of the American Trucking Association's (ATA) Engineering and Technology Policy Committee and the Technology and Maintenance Council (TMC) Future Truck Committee".

With misinformation and factually incorrect statements swirling, Richard Wood is out to ease the turbulence