Thanks to Deadshaper for turning me onto this one. I’m going to approach this one from two angles. Board and fins. Firstly fins. Would I be correct in assuming that fins act a little like the wings of an airplane generating lift and hold? Secondly, something that probably generates a lot more wind resistance, your board. The faster you are going the less area of the board that is actually touching the surface of the wave leaving the next obstacle, wind resistance. Jet boaters would probably know an awful lot more about this one but aerodynamics is not something I’ve heard a lot about on this forum. Or does eveyone feel that surfboards are too slow to warrant worrying about this?
Wonder where the “beak” nose shape of the 70s came from? It was supposed to act as the leading edge of an airplane wing, thus lifting the nose out of the water… At least that’s what I read at the time… Theoretically true, but really effective?
Nice. But I’d take things a bit further…
As metaphor, aerodynamics is seductive, all those flowing and pointy shapes and bits, but at best its limited. The problem arises when you consider the fact that surfing occurs at the interface between two mediums of significantly different densities. Actually that’s just for starters, but perhaps it’s enough.
Fins and or other totally immersed structures are different of course and one might be able to get some inspiration from aerodynamics, say the acclaimed propulsive attributes of a funnel fin or a tapered bottom contour?
I would not suggest that it’s your problem, but it is my impression that many (at least) look at surfboard and see a ‘whole’. You might think, ‘of course they do’, but we know that most of the time ‘functionally’ an awful lot of the board isn’t doing much of anything, or possibly symmetric elements are doing different things. The pointy bits up front, board volume, the rail that really isn’t interacting with the fluid in the same way as the waveside rail, etc. all suggest something less than a ‘full immersion’ kind of treatment.
Yes, its getting old, but the only (analogous) body of theory out there seems to be with regard to hydrodynamic planing. Of course the problem with the literature on planing is that it tends to deal with vehicles that have ‘engines’ attached. In this respect Surfing is unique. (And please include body, sponge, knee, etc. in that, it’s why I capitalized ‘Surfing.’)
It’s not likely to happen anytime soon, but a more proper term would be ‘surf planing.’ Not very attractive, and it’s not likely to impress the chicks (or whomever), but technically it is accurate. Its not all that happens during a ‘ride’ but it is what makes the activity unique.
Analogies are a great source of inspiration, but they can be dangerous.
kc
Let me chime in with my neighbor kc on this…
The thing is that sea water is something on the order of 1000 times more dense than air at sea level(http://en.wikipedia.org/wiki/Density_of_air - I looked it up, memorty not being all that great ) . And so the effects of hydrodynamics are gonna be that much more pronounced than those of aerodynamics. Put it another way, a little wax smeg on the bottom is gonna have as much effect as, say, the shape of the nose or more importantly the stance of the rider who has a lot more surface area.
Now- you do point out something quite interesting:
Quote:
The faster you are going the less area of the board that is actually touching the surface of the wave …
I happened to get the Riding Giants DVD out of the library last week and I was noticing that even on those quite small tow-in boards there is damned little of it actually in the water at speed.
How much? Well now, that’s a very complex question indeed.
doc…
The speed of a surfboard in air is not going to be enough to really generate any real aerodynamic forces, except for maybe dropping in in offshore winds when you get that air flow coming up under the board holding you back. The surface area of a board at that speed just isn’t going to be big enough to overcome your weight.
As a comparison of the differences in water and air flow we recently were contracted to do some testing on swimsuit materials by Speedo. In order to accurately simulate a water flow of 2 m/sec we had to run the wind tunnel at 28 m/sec due to the density difference.
The greatest aerodynamic drag in surfing, occurs when you, the rider, stand up and present your body and chest to the ‘‘displacement wind’’ moving up the face of the wave.
did you do this using reynolds scaling?
surfboard design is a complicated subject but i’m sure aerodynamics is the least of our worries.
I think the comment about a surfboard being unique as it is a planning craft without an engine is insighful. What is more interesting though is that even when ‘gliding’ it is tilted with repect to the water surface (which is also curved) and in fact spends little of it’s time with both rails in the water.
I think aerodynamics when I crouch lower on a windy day and stay below the lip to cut the amount of wind my body is picking up (or in the tiube - there’s not much wind there!)
I do know guys who maintain that they use their deeep concaves to capture air on big floaters and ride the air cushion down, but I think hydrodynamics are the determining factor in board performance
(mind you, I have a 'beak" on my face, so maybe that contributes to cutting through the wind).
I’m not an aero engineer but I am pretty sure that that is how the did it. Running fabric samples isn’t practical in our “other than air” wind tunnels due to the cost of their use so yeah, you just crank to wind speedup to get the numbers of molecules going by at whatever rate you want (or something like that).