I’m about to go on vacation and I bought one of those car-top cargo containers to go on the roof. It comes with soft pads to sit directly on the metal surface or it can be fastened to the roof rack.
I did the latter, since I don’t want to mar my paint, but from an airflow point of view, is it better to have the gap under the box or have it sit directly on the roof?
My best guess would be that overall wind resistence would be better with it raised off the roof, on the rack, since the air has four sides to go around rather than three. However, the air under the cargo box has to compress to fit underneath so there’s energy wasted there.
Anybody want to hazard a guess?
-B (with just enough aerodynamic smarts to be dangerous)