In surf there are right ways and wrong ways to do things. A wetsuit for example – front zip or back zip – there’s one way to put it on. You wax the top of your surfboard, not the bottom. These are just a few of the functional norms that when violated by an unassuming beginner often provoke laughs among seasoned surfers (see also: Kook of the Day).
But in some cases, the most common way to do something doesn’t serve a discernible purpose compared to another way it could be done. For example, when I strap my 9’6″ single fin to the top of my rig, I always do so tail first. Why? If I’m being honest, I have no idea. Probably because that’s how everyone else does it. No one told me to do it that way exactly, it sort of just became the way I do it. There’s likely a lesson on social norm formation in there, but that’s beside the point.
In my estimation, the number of surfers that strap their surfboard to their car tail first far exceeds the number that does so nose first. But being a tail first advocate, I wanted to find out if there was any merit to it. So I decided to bother an expert with way more important things to do with my silly question – which is more aerodynamic, tail first or nose first? Staring at the crude illustrations of the different options I sent him (tail first on top, nose first on bottom), Dr. Paul Dimotakis, John K. Northrop Professor of Aeronautics and Professor of Applied Physics at Caltech, was kind enough to humor me with the following response:
“My opinion is that your bottom configuration [nose first] is preferable. If there’s any side wind, having the tail in front would increase drag more than having it in the rear because the flow would separate at the fin and it’s better for it to do that aft.
“If the bow faces forward, it’s also important that the board tip is down (as you’ve sketched), again to minimize flow separation since the flow has an upward component as it’s going over the car and one would like the board to conform with that to the extent possible.
“I’ve sometimes seen boards with their tips pointing up and that’s not a good idea.”
To emphasize that he didn’t have the time to spare for my frivolous question, Dr. Dimotakis made sure to conclude by saying he wasn’t available for follow-up. Noted.
So is this scientific breakthrough going to change the way I throw my board on my car? Not a chance. Surfing is anti-establishment right? And what’s more anti-establishment than knowingly increasing the wind resistance of your car in the face of scientific expertise all for the sake of pulling up to your beach parking lot and not standing out? Nothing.