surfboard design

Guest · Oct 19, 2001

Hello Im seeking any information you could possibly give my in the area of boat design that you might think is relevant to surfboard design. Im doing an assignment on board design and would love some information of bottom curves. I have found it difficult to find any information that is specific to surfboard design. My main focus is to give reason for the different curves.
If you could help me in any way I would be most greatful.
Thankyou and happy sailing.
Toby

Guest · Oct 19, 2001

Take a look at http://scsurfers.com/boardpage.html :

Basically, rocker is the curve along the bottom of the board.

The newer blanks from Clark Foam have natural rocker built into the boards and generally the board doesn't need to be shaped down (see above comments on over-shaping) as much as the older-generation of blanks. Rocker is placed in a blank when the stringer is glued in. The blank is cut in half, insert the stringer and glue it back together.

Natural rocker simply means the rocker that the blank has in it without any adjustments, that is, the rocker that the shaper designed into the "plug" that made the mold at Clark Foam. All Clark Foam is blown using molds and the molds were made by the better shapers from Southern California (where Clark Foam is HQ'd). Clarks blanks are all named and usually contain an initial which indicates who made the mold. For example, the 10-1Y blank is from Yater, 9-10H is from Rich Harbour, 9-8S is from Bill Stewart, 9-4B is from Bruce Jones and so on.

Clark Foam has literally hundreds of rockers available for the most popular blanks, some available to everyone, some for certain shapers only. Look at a Clark Foam catalog and the "Clark Foam Extended Rocker Catalog" available at shops where you can order blanks like Monterey Bay Fiberglass on 17th Ave. There is also a partial version online at Bruce Jones Surf Shop.

When talking about rocker, you need to differentiate between nose rocker, midsection rocker, and tail kick. They all contribute to tuning your board for particular wave types and styles of surfing as they are blended together. The shape of the rail and vee also add into this equation.

Tail kick is pretty crucial as it has the biggest lever arm. To illustrate it's effect, you can remove your sidebiters and center fin, if you are using a removable fin system, and stand on the tail of your board on a soft surface. More tail kick really brings the front of the board out of the water when you stand on the tail. Small tweaks there have big effects.

Mid-section rocker is where your accelerator is placed, if it has one. Flat being faster. Most short board chips don't have flat speed sections because speed is generated by turning and pumping. They have much tighter turning radii for top to bottom, slash and burn surfing. You will find less mid-section rocker in boards designed for fast, down the line, point break waves.

Nose flip comes into play when dropping in, bottom turning, and slashing off the lip. Extra nose flip will allow you tosurf steeper waves and drop in late. Having soft rails in the "catch zone" in conjunction with a fair amount of nose flip makes a board more forgiving in these situations. If you have too much tail kick this is where you will feel it, as the board will most likely bounce or do a wheelie as you are setting up for your bottom turn. Fin placement, cant, size, profile, flex, vee, concave, rail tuck, volume distribution, thickness, width, length, weight are all parameters that can make or break that clean template. Dialing custom boards in, is a "touchy feely" thing that comes with years of experience and working with a shaper who can and will listen and then executes correctly. That's another subject, though.

What rocker does, one by one, comments geared towards longboards:

Nose rocker - more here makes a board resistant to nosediving or pearling. Less rocker here makes a board go faster and stall less, easier paddling as the board glides through the water, not pushing the water. Less rocker here is better for noseriding,
Rocker all the way through; generally slows it all down some, but makes a board turn well
Tail rocker; makes a board turn real well, easier drops into the wave for a speedier entry, and also aids in noseriding...but pays a large speed penalty due to drag both while riding and paddling
The best is a combinaton of all. Modern boards need to be able to turn to get speed, so tail rocker is important, and it's not exactly true that "flatter is faster" on a wave, maybe on flat water with a sailboard, but not on a wave.

From Bruce Jones, "If you are surfing the same sized wave as a smaller person on a smaller board (proportioned), then the rocker needs to be increased. And in general I do increase the rocker as the board gets longer, or the board will be to stiff. There is no set rule how to do this. I have a rocker list that I use for each blank within a certain model, as I change blanks as the boards get longer. This is just from experience."

The standard "Clark Foam" method of measuring rocker:
The board is bottom up on shaping racks (or something), you measure the center point along the stringer, that is center from nose to tail, so on a 6' board it would be 3' from each end. Then you would hold a long straight edge along the stringer, tangent to the mid point mark, and measure the gaps at the nose and tail. So a typical short board might have 5.5" of nose rocker and 2.5" of tail rocker, and on a longboard maybe 5" of nose rocker and 3" of tail rocker. You can take measurements anywhere along this line to get a more precise reproduction.

Or you can be more precise and make or get a "rocker stick", a tool that most shapers have, it is a way of holding a long flexible fiberglass batten in place so one can trace the curve onto a template.
Click to expand...

This is from http://scsurfers.com/boardpage.html

Also take a look at
http://www.brucejones.com/
http://www.boardz.com/98/oct98/powerspeed.html
http://www.easternlines.com/boardtypes.htm
http://www.jimbanksurf.com/Surfboardgallery.htm

And for quick surfboard cad programs:
http://www.viser.net/~anthwind/Software___CAD/software___cad.html
http://python.swan.ac.uk/surfing/datftp.html

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