By Jim Twamley
Just how effective are those RV wind deflectors you see on trucks pulling 5th wheels and travel trailers? Though somewhat technical (what you’d expect from a Professor of RVing), this information could save you some serious cash.
Trucks pulling trailers lose a majority of their energy at highway speeds through aerodynamic drag. Using computational fluid dynamics, scientists study airflow as it interacts with test models in a wind tunnel. These studies have determined that in order for an RV wind deflector to work efficiently it must be within a few feet of the trailer due to the fact air flow created by the deflector closes in within a few feet unless it’s conducted by another surface. Cab extension gap seals and side fairings will help to make this possible. (From the article “On the Aerodynamics of Tractor-Trailers,” by M. Hammache and F. Browand.)
According to these scholars, the best place for an air deflector is actually on the trailer itself because that’s where the majority of the drag occurs. When you place a rounded “nose cone” on the trailer, you eliminate the gap of a cab wind deflector and the aerodynamic drag is significantly reduced. So, if you’re looking to save a bunch of money by installing one of these over-the-cab deflectors, make sure it’s as close to the trailer as possible and also install gap seals. If you don’t do this you’re throwing money to the wind.
In fact, if the gap is too large, it will end up reducing your fuel economy because you’re actually increasing the drag. The bottom line is that trailers like the Titanium brand, made with an aerodynamic nose, are more fuel-efficient than any aftermarket cab-mounted wind deflector. The more aerodynamic the trailer, the better the fuel economy. —Preventing the money from blowing out of your wallet —Jim Twamley, Professor of RVing