Under-fairings and other streamlining aids are highly debated topics.
We did do a far more complex exercise in conjunction with Piper and expended great resource to develop the most aerodynamic solution.
Regrettably, commercial vehicles are subject to considerable stress - particularly on the rear and sides.
Underskirts are practical and we provide full wrap-round skirts, but even these get damaged.
Tail-fins, skirt extensions (lower than 400mm from ground) and other aids regularly get damaged thus nullifying any fuel benefit attributable to their aerodynamic efficiency.
Covers over the wheels are not practical as wheel nuts are regularly checked and inspectors will not go through the process of removing a panel.
Under-belly smoothing is something we have been testing, with the inclusion of a venturi duct running under-chassis. Contrary to initial beliefs, actual fuel savings were not forthcoming and this method was dropped. "Fill-in" has also been discussed, but this makes maintenance very difficult (servicing usually every 10 weeks)
The most exciting
development is that of eliminating the gap between tractor and trailer by using a seperate bogey. This will allow us to maximise the Teardrop profile without undue separation.
