Rails

I love Saturday mornings. Because I work in the finance industry (that’s how I really make my living), I work some brutal hours (5am-1:30pm PT). However, Saturday and Sunday mornings I get to sleep in a little and spend the morning with my significant other (Richard). Most weekend mornings Richard has been working, which means he’s been writing—a lot. Right now he’s working on a book with the Mingei International Museum about the history of surf craft and design. I really like being around Richard when he’s working, because he throws down some serious knowledge. I get to soak it all in; and since I’ve only been surfing for a few years, I have a lot to catch up on.

So Richard has been extolling the genius of Bob Simmons since I’ve met him, but I didn’t “get it” for a very long time. I think it’s a lot of information to take in all at once—hydrodynamic lift, Bernoulli, Lindsay Lord, planing hulls. And then being new to surfing, I didn’t even understand the basics—rocker, rails, outline, fins, thickness, volume, etc. Over the past few years, everything Richard has taught me has slowly been percolating and taking up some serious storage in my cerebral database. The past few years have been a slow accumulation of knowledge, which has brought me here today. I have to admit, Richard still stuns me when he goes into professor mode. Sometimes I write about my free lessons. Mind you, these are ramblings are unauthorized synopsis, but I feel I at least get the gist and hope I’m getting the facts down correctly.

So today I’ve been thinking a lot about rails. I think a lot of people take rails for granted. So basically, rails works a lot like an airplane wing. Airplane wings have a specific curve design (“airfoil”) that lifts them into the air. The top of the wing has a vertical (v. horizontal) component to it (described as “upper surface curved” in the image below) so that the wing’s curve pushes air up and over the wing. This air that is flowing on the upper surface is moving faster, and is a lower pressure, than the pressure on the bottom surface, where it is moving slower. The pressure difference creates a net aerodynamic force. It’s sort of like when you squeeze a watermelon seed through your fingers.

airplane wing

So surfboard rails function the exact same way as airplane wings, except instead of air, water is flowing above (and below) the foiled rail. The curved surface of the rail going through water is where you get your dynamic “lift” and is what speeds you through the water/down the line. So when you are surfing, you are really surfing on your rails (that is, if you are riding the face of a wave and going down the line. Going straight on white water doesn’t really count as surfing).

Well, Bob Simmons knew this a long time ago (1940s). Simmons was the first to foil (curve shape) his rails. Prior to that, rails were squared off planks, which don’t really have a lot of hydrodynamic elements to it. The other critical thing Simmons knew was to put a fin on each rail—thus, the dual fin (v. single fin) set up. Ingenius really, because you get speed through your turns on the rail, which is where you would want a stabalizing fin. It’s in the  bottom turn (surfing on the foiled rail) where you get dynamic lift to get you to the top of the wave, and it’s in your bottom turn you are generating the most speed. You are NOT generating speed going straight; you generate speed pumping on your rails. The other thing Simmons knew was that a straighter rail, or straighter outline, is going to be more hydrodynamic than a curved outline. A curved outline is going to flow through the water less efficiently than a straight line rail. This is a little harder to explain without an image, but I pulled this image below from Richard’s surfboard site (http://surfboardsbyhydrodynamica.com/hulls) to explain. Basically, with a curved outline (white outline below), there is going to be less area (less rail) of the board in the water. The longer your rail, meaning the straighter your rail/outline, the more surface area to plane on. These are the elements of a hydrodynamica planing hull: straighter rails + more surface area.

curved outline

So what Daniel Thomson has figured out with his Tomo designs, is how to shape hydrodynamic designs and apply them in a modern surfboard. His boards have more planing surface and a straighter outline.  Daniel does this very consciously. His designs are very thought out. He knows the history and elements of good design and put them into his modern planing hull. Btw, you get speed on your board from the dynamic lift of the rails, which is how Daniel gets his sick airs. From speed.

On a seperate note, foiled fins are another ingenuity to design. Larry Gephart is probably the finest fin craftsmen out there. If a fin is not perfect, Richard says he’ll throw it out. I’m positive this is why Richard has loyally used Gephart fins on all his Hydrodynamica boards. Gepharts cost a little more, but are totally worth it. Then there are the aesthetics. His fins are just beautiful pieces of craftsmenship.

And one little rampage as I sign off today. I think it’s totally retarded when you’re writing about surfboard design and history to only show images of the front of the surfboards. How can you tell anything from just the front of the board??—that only shows the outline. What about the fin set up? The rocker? The rails?—these are the most critical pieces of the surfboard. I was searching all over the internet for a boxed plank rail image (which I couldn’t find).  All I found where the front of boards. Surfing Heritage Cultural Center is an exception. They did a great job of showing boards on their site.

Thanks for reading. –MB

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