Wind deflectors
Does anyone know if those wind deflectors have any effect on gas mileage .. Will these deflectors give you better gas mileage and if so how much
Forum Discussion
In order for a wind deflector to be effective, it has to be mounted to the trailer as close as possible, like within a few feet, and it has to be angled properly or it will create additional drag. The problem is that most setups don't allow for mounting in a place for the deflector to become effective to begin with. The trailer gap is much too large and exposed. What ends up happening is that part or all of the airflow falls off the edge of the deflector and down into the trailer gap where it becomes drag. Also the deflectors are not large enough. There's just not enough surface area to adequately deflect enough of the airflow. When faced with a 96" wide trailer cap, a 48" deflector can only address half of the airflow over the top the trailer in a perfect world. The other 48" is out in the open. The deflectors only address a small amount of airflow going to the trailer. There's still tons of airflow hitting the exposed sections of the trailer and entering the exposed trailer gap. All of this air entering the gap creates a turbulent flow which creates drag. At the end of the day deflectors ends up being mostly ineffective. Most who've tried will tell you that they are not worth their money, unless you need a really expensive bug shield. If you could seal the trailer gap then that would have a much greater impact.
On the other hand, modern semis have a much better design than our combos. They have huge condo sleepers that meet both the height and width of the trailer. The top of the sleeper end up becoming a quite effective wind deflector. There's several inches of additional side fairings behind the sleeper. This works as vertical deflectors, redirecting air around the gap and to the trailer sides. You end up with a trailer gap that experiences very little airflow and almost eliminating 25% of the drag the unit experiences while traveling down the road.
On the other hand, modern semis have a much better design than our combos. They have huge condo sleepers that meet both the height and width of the trailer. The top of the sleeper end up becoming a quite effective wind deflector. There's several inches of additional side fairings behind the sleeper. This works as vertical deflectors, redirecting air around the gap and to the trailer sides. You end up with a trailer gap that experiences very little airflow and almost eliminating 25% of the drag the unit experiences while traveling down the road.
