Wind Deflector

I'm new to the 5W scene having just purchased a 2008 29RLBS to replace a 28 TT. I noticed bringing the 5W home from CT that my mpg was less than with the TT, which was not unexpected. I am wondering if a wind deflector on my truck might improve things a bit. Does anyone have any experience with defectors and 5Ws.

Thanks.

I have no direct experience, but have read about this a fair amount. The big rigs can benefit because they drive so many miles (hundreds of thousands per year); the few thousand most 5ers drive per year are not enough to get a return on your investment.

I doubt it is worth it. The front of the cat is already aerodynamic; not sure you would gain anything.

I used a deflector for a few years on a earlier truck and 5th wheel but sold it when when I traded up because it did not match the new truck color. I couldn't say it improved the fuel economy enough to measure. All it did was keep the bugs off the front cap in an area about half way up and the width of the truck cab.

Everything I've ever read about this subject also leads me to believe it's not worth the expense.

Mostly likely, you're seeing a difference in MPG based on weight, not aerodynamics.

TC

I come from 35 years of truck background as driver, manager and maintenance department. All the studies I have read show that in order for a roof deflector to work, the gap between the deflector and trailer must be less than 36" to make an improvement in fuel efficiency. More than that and the slipstream effect curls behind the deflector and creates turbulence between the two units. And don't forget that the front cap of your WC is already reasonably aerodynamically designed and does not create the solid wall that a semi-trailer presents.

I wouldn't recommend the expense unless you like the overall look of the deflector and/or want an expensive bug deflector.

An interesting newer aerodynamic change is the trailer skirts you see beneath semi-trailers on both sides in order to improve the flow of air. Rather than allow the wind to roil around beneath and create drag these skirts direct the wind out smoothly away from the unit.

But in all these improvements I agree with Glen in that it requires more miles than you will drive to justify the cost efficiencies of capital expense and fuel returns. You would probably have to be putting on 100,000+ miles annually to make it worth a thought.

Thanks to all. I appreciate your input.
I will be dropping this idea!!

Regards.

Now that we're on the dynamics of the front cap.....

Would raising the trailer from a 15" to a 16" tire cause more drag ? another inch higher ......
Seems like the lower to the ground you could keep it the better off you'd be ?

Any time you present more real estate to the wind it will cause more drag. But half an inch is of no concern; don't worry about it. The torque from your Power Stroke won't even notice it.

One advantage of a taller tire/wheel is that the RPM's will decrease somewhat because of the taller tire/wheel and theoretically the bearings will last a "little bit" longer. But again I wouldn't go to the expense and trouble for only that reason. However, if that fancy shiny new 16" wheel has caught your eye it's a heck of a good justification to your significant other why it's an absolute necessity!

Also, it's only half an inch because the difference between 16 and 15 is across the centre of the hub so it only creates a half inch lift.

If my limited understanding of aerodynamics is correct, you're more likely to see change from the air sweeping UNDER the trailer than over it.

Even at that, I don't think that an inch or so would make any real difference.

TC

Figure this one out. The new Cameo is basically flat on the nose and looks much less aerodynamic than the old Cat. I get the same if not better mileage pulling the Cameo. It weighs in at 13K while the Cat was ~9.5K. All I can figure is that the extra weight gives more momentum.