S.U.P., Y’all

So I keep seeing people (not locals) paddling around on SUP’s here. Stand-up Paddle board interests me, so we borrowed one from a friend of my mom’s and played around a bit on the North Shore of Kaua’i. There was a Beautiful rainbow above and beautiful reef fish below.

[SIDE NOTE: You know that negative ion feeling you get when you paddle through a waterfall at night, and it puts out the candles, the bats scatter, and you start laughing your ass off like a crazy person and you aren’t sure why? In the Inland Northwest, I rarely get this feeling, mostly just on the lake near sunset/sunrise. On the windward side of Kaua’i, I feel this way whenever the wind blows.]

Anyway, paddleboards are cool, there’s no way around that. Conditions for learning to surf weren’t present where I was, but I had a good time. Just as I always do in storebought kayaks and canoes, however, I couldn’t help wondering about the intended function of the paddleboard, how to improve it, and how to fix it.

It’s a raft, like a trayboat. It doesn’t keep you dry, but then who cares, this is the tropics. These boards could be used in place of a “dish pirot”, or a bamboo raft, and probably paddle faster. I’m thinking that a SUP is a good raft AND should double as a surfboard.

There are a few problems with the design in most SUP’s though. First of all, the foil is wrong on the rails for most of these. If the curve was reversed near the back, like a 60’s “noseriding” board, it could surf well in tiny waves, even given the huge wetted surface area required by the buoyancy requirements. It would be crazy to expect a good fast big wave surfboard from one of these, but I think a useful longboard that is also like a raft is totally possible in the design.

How is it used and why? I think the first stand-up paddleboarders forgot this part. What I see everyone do, and I did at first, is akwardly stand up on the board, then reach down with a single bladed long paddle, and move forward with painfully slow, jiggyness. High center of gravity is good for surfing, because you have to make small and large changes in your weight placement very quickly. It is really bad for paddling a big surfboard though. The only advantage I can think of is that you can see farther. Balancing on one of these isn’t hard. I think the length to width ratio is lower than needed, but your weight moves around as you paddle, making the waterplanes terribly akward and slow on flat water. Where I was, there was no current, but there were sharp, urchinny reefs 5 inches below me, so getting waves or losing balance might have hurt a lot.

I did what anyone with an obsessive love of hull hydrodynamics would have done: I got a cheap kayak paddle and sat down. I scooted my weight a little forward till I had as much length in the water as possible. (this also prevents the spilling of beverages). By doing this, I was able to go way faster than paddleboards usually go, with way better balance and control. Somewhere around the topspeed for flatwater paddling, the bow picks up a bit. It IS, afterall, a big hydrodynamic foil. When that happens I lean forward and paddling fast feels pretty easy. It isn’t as fast as my little boats back home, but then those don’t surf.

If I had to go through big surf on this, then surf back in, I’m sure there would be challenges and a learning curve. I reckon one would have to dip the nose down and try sliding under the wave. I’m looking forward to learning a bit about surfing. The waves here are among the best in the world.

I probably won’t have time to actually build a paddlin board while I’m here, but I think I could learn a great deal about hydrodynamics and planing by building and using a surfboard.

The above pic shows what I look like chillin in the weird reefy shallows around 22.223373,-159.437107, Anini area. I’m way fatter now, because produce is cheap and fantastic here.

Oh look! Hull dynamics links for surfing! :



I have a few theories from watching surfers, all of which are useless compared to the actual act of surfing.:

A common misconception among surfers is that the lift and velocity of a board is caused by the flat plane being pushed perpendicular along the water by the wave. In truth, there is a gravitational force pushing the whole person and board down the face of the wave. (these faces change with weight, balance, angle of wave face, angle of board, etc.) This becomes forward momentum RELATIVE TO THE WAVE (which is usually way slower than the land speed). Lift on various surfaces of the board are planing lift AND foil lift from the rail shape. These lift forces all work in different directions and some are counteracted by the weight of the surfer’s balance. The weight of the human can equal and balance out several of these foil lift forces and planar lift forces, some of them can be redirected into forward motion down the wave face. Too much motion forward (again, this motion is relative to the wave shape itself, not ground, air, or water) will decrease the angle of the wave face. Too little forward motion will increase the wave face angle. This angle interacts with the surfers weight. The whole thing is a balance act between known and unknowable forces. Sounds like good fun, huh?

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