I was always bothered by the wind noise from my Thule square bar rack. I have had fairings on my car racks for years, they help but usually crack after four years or so from the UV. For the van, I felt even the widest fairing was not going to do much and it was pretty pricey.
I was all set to go to TAP plastics and have them make up a unit when I came across a posting about a wrapping solution. The suggestion was to wrap cording spirally around the bar from side to side. This is supposed to create /induce vortex shedding (for all you engineers). This breaks up the airflow around the bar and minimizes/eliminates the noise created by the bare bar.
Bottom line, does it work? I was so skeptical and yet so frustrated with the noise that I thought I would try it out on our trip to Yosemite a few weeks ago. It works and it works great!!! Not completely silent but at least 80 to 85% quieter. The bonus is less frontal area (I know, really marginally less) due to no fairing, and 100 "van units" to be deployed elsewhere.
So if noise from the racks is an issue, this is worth the effort. I used a multi-strand cording that will likely last a couple of years. Next time I will find a better cording for UV exposure.
Apologies if this has already been covered on SMBforum, could not find it in a search. I would love to hear feedback of your experience.