Well. hre's my 2 cents on this.
My 93 Rodeo has all the farkles. Too many to list right now, but you can see from the picture that it's a heavily modified expedition vehicle.
Now about the question at hand. Look closely at my rack. It is a combination of Yakama, Virgin Records bargan basket rack, and homemade fold down light bars.
My wind fairing is an old aluminum door from an old travel trailer we dissasembled some time back. Why buy something expensive when you have materials at hand that will do the job. It has two Yakama mountain bike rails on the outside, a fold up kayack rack that allows stuff in the basket under the Kayack. The shovel and axe are mounted with gun rack holders on the side of the rack. And like I said the light bar folds back flat in front of the basket to allow me to park it in the garage.
Before I added the wind deflector the wind noise was terrible. The mileage suffered too! It doesn't really matter if you have stuff in the rack or not. Your going to add wind resistance just having the rack on top of your vehicle. Just stick you hand out the window of a moving vehicle to see how little it takes to try and break your arm off. It doesn't matter if you hand is open or closed. Turn your hand flat like a wing and you get less resistance. Play with it like you did as a child and all this willl make more sense.
That's what a fairing is for. It blends the rack into the aerodynamics of the body. Channeling air up over the open bars and load. With the wind deflector all those different bars are behind a vaccuum.
When you load your rack try and put smaller items up front and large stuff near the middle or rear. It will help if you try and load so that you continue a smooth bulge behind the fairing over the top of the truck. Now, if you can, try and taper off you load near the back edge to allow the deflected air to flow back down to the road. Too much vaccumm behind the vehicle can be a detriment too. Ever drafted a Semi Truck? Same thing! Airplane fuselages are smoth and curved for a reason.
Use a tight tarpoline, if you can, for long highway drives to help channel the air smoothly over the various contents of your roof rack load.
My Dad was an Airplane Airframe Mechanic and when we were kids he built a roof top carrier for the top of our 56 Buick Station Wagon that looked like a wing. It was covered by a very taunt tarp held in place by cords. I remember the front edge went all the way to the windshield. That thing could put a Greyhound Bus to shame with his loads. He was always concerned about areodynamics on the ground and in the air.
I realize that my Rodeo has the aeordynamics of a parachute, but, remember, every little bit helps. It gets about 15 miles to the gallon at or under 65mph as it sits.
Well, I know that's more than 2 cents worth but, ya'll can keep the change on this one.
Curtis in Texas
