I have a Yakima rack with 1" diameter round bars. The bars make really loud howling noises at any speeds over 50 mph. and it's really annoying when trying to groove to Sarah MacLachlan. I had the idea to build a pair of fairings for the rack, and finally got around to doing it today.
The airfoil that is most appropriate is the SD 8020 symmetrical, thickened to whatever is necessary to enclose the bars. I chose 4" long and 1" thick, so the airfoil is 25% thick. The front and back halves of the airfoil are hot wired out of Dow 60 foam, and coated with 3 ounce fibreglas all over. For now, they are held in place with full width duct tape, cross ways strapping tape, and cable ties. The cable ties go through 5/16" diameter carbon tubes (arrow shaft material) to prevent damage to the foam, and then wrap around the leading edge. I will make a set of velcro straps once the tape wears out.
Amazingly the bars are totally quiet, the only sound is a hissing associated with the towers and the bar ends which are not faired. This is the only application of my modeling tools and construction to a real life problem. Total cost is essentially zilch, scraps were used for all the pieces. Wait, the resin costs about $2.00.
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