Smooth sail­ing

Un­der­stand­ing how aero­dy­nam­ics af­fects your rig.

Motorhome & Caravan Trader - - Tech Talk - Words

When you’re tow­ing a bluff, full-size car­a­van around, aero­dy­nam­ics seems to be the least of your wor­ries. With the drag of an ex­tra set of wheels or two to pull along and, of course, the ex­tra weight in­volved, it would ap­pear that high fuel con­sump­tion goes with the ter­ri­tory for car­a­van­ners.

Yet, noth­ing could be fur­ther from the truth. Know­ing about ba­sic aero­dy­nam­ics and how they af­fect your rig is re­ally im­por­tant, not only for fuel con­sump­tion, but also for wear on your tow tug, and the sta­bil­ity and safety of the rig as a whole.

Au­to­mo­tive en­gi­neers be­came in­ter­ested in aero­dy­nam­ics and their ef­fect on ve­hi­cles in the early-to-mid 1900s, as cars be­came a reg­u­lar fea­ture in so­ci­ety and their abil­ity to travel at speed in­creased. En­gi­neers be­gan work on the most ef­fi­cient shape for a car body, which was found to be a teardrop shape. An early ex­am­ple of such a car is the 1921 Rumpler Tropfen-auto, with a low aero­dy­namic co­ef­fi­cient of drag (Cd) fig­ure of .27, as good as the bet­ter cars of to­day.

The teardrop shape didn’t ex­actly take off, so the cars through the ages that have been com­mer­cially ac­cepted are also a more con­ven­tional shape. Such cars in­clude the 1935 Chrysler Air­flow and 1955 Citroen ID/DS se­ries.

Later on, de­tail im­prove­ments be­came im­por­tant

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