Rocker has traditionally been labeled as the single most important component or design element in a surfboard. But it's unrealistic to try and isolate one aspect of a surfboard -- a complex combination of compound curves -- and claim that one component as the single most important design feature. It's the marriage of all the curves, hopefully working in harmony to produce the magic.
When it comes to talking about surfboards, we think -- and shapers tend to work -- step-by-step, in a 2D world and by the magic of process, it all gets woven into a wonderful 3D, functional, sculpture.
How many of you have bought a new board that looks like it's the one -- magic -- but it's not quite right? It's fast as you'd want, but doesn't turn, or it's super loose but bogs on the flats -- or it works at Spot X and dogs at Spot Y.
The centerline, the spinal chord, is the easiest to quantify. The rail rocker and all the transitional pathways radiating out from the spine towards the perimeter (outline) are infinitely more difficult to measure and quantify. The relationship of the perimeter rocker with the center is what determines bottom shape.
Wireframes provide a glimpse into the complexity of how all the curves interact.
Can you ride a door? Over the years in a few films and videos, we've seen some pretty good surfers take a stab at it. Maybe a narrow one with soft rails and a little flex might be the go. Alaias are flat but they bend. So do bodyboards. It's so nice to be able to adjust the curve of your ride to fit the occasion. If it's thin enough, depending on what it's made of, you can bend rocker into it as you ride. What's good about a bodyboard? You bend it to fit. Cheating!
Flex can be and is built into a surfboard. Then there are issues about the quality of the flex; how efficiently will it return to its original shape? Where do you position yourself? How hard can I, or should I, press and when, and where do I need to stand?
So rocker is not the defining component. But -- unlike all other design elements -- it is in a state of flux. Your outline, thickness, rail shape, fins, and fin position won't change as you ride a wave but your board rocker, your bottom curve will, depending on construction, weight, force, etc.
The juxtaposition of rail-rocker and bottom rocker create bottom contours. Image: Steve Coletta/ naturalcurvesboards.com
Shapers worry about fractions of an inch, but in reality, blanks sag and bend on the shaping racks, or the glassing racks. Other factors come into play: during lamination, resin shrinking as it goes off can pull rocker into or out of a blank, or cause the blank to twist slightly, resulting in asymmetrical rocker. Epoxy runs roughly 2% and polyester about 6%. Reaction time or how hot the batch is affects the shrinkage too. Or, how a board is stored can affect the final outcome. Rocker can be affected in the process of building a board after it leaves the shapers hands. What we shape and what ends up as the finished product always has a variance.
Rocker on the front end of the board is cosmetic, to a large degree. The first six inches or so. The entry, the guts, and back third, the business end, is what really matters. The overall flow is nice from an aesthetic standpoint and to certain degree, performance. But really, you could lose the front three, six inches and still end up with something that gets the job done. Miss the back third, the command center, by a few hundredths of and inch, and it becomes an issue. Good or bad, it's all subjective and heavily dependent on the waves you ride and how you want to ride them.
How do we measure rocker?
Most shapers I know use some sort of straight edge placed on the center point of the bottom. The blank or board is placed bottom up on racks, the top of a trash bin, sawhorses, or some thing that provides a reasonably stable, level surface.
Photo: Sean Brody
Mark the center of the board. Use a beam as a tangent. Crude, but if you find a light firm straight edge, you can create a close proximity to a tangent. Some shapers will use the straight edge of a half template. I like three-sided aluminum window track. If you can find something with about ½" walls, eight feet long and straight, it's gold. It's light, rigid enough, and doesn't influence the blank with its weight or sag within a reasonable degree. An eight-foot incandescent bulb actually works pretty well too.
Photo: Sean Brody
Shapers use a very light, one-finger touch on the rocker beam. When measuring a finished board, incurring flex and distorting the measurement isn't as much of an issue. Using the light finger press, in theory the blank or board could be on its side or upright. It shouldn't matter if the beam is pressed against the center point. If you are using something shorter than your actual board length, like a 6-foot beam (easy to find at any hardware store) mark the center of the beam. Place it on the center of the board. Press lightly and measure a point within the half-length of the beam, like the 12-inch mark. Establish what the rocker is at that point and then find something about ½" to ¾" thick you can use as a shim underneath the beam, slide it underneath the beam until it makes contact, then slide the beam to the full length of the end of the board and make sure your reference point is consistent with the previous measure, then go ahead and measure the rest of the board. When I'm shaping longer boards, like guns, longboards and SUPs, this is the method I use to make an 8-foot beam cover anything up to almost twice its length
Putting your board belly down on the ground to measure rocker doesn't work because the balance of the board is affected by the distribution of mass so your net number might be in the ball park -- but the (tangential) end numbers that most shapers use will be off.
Measure the tips and one foot in from both ends and you will get numbers that are probably consistent with in 1/16th of an inch to what your shaper is coming in with.
Tape comes in handy so you don't have to mark up the blank or board. Photo: Sean Brody
Since the early days, many shapers have used rocker templates. The female curve that fits to the bottom of the board. Curves that fit that middle third, or half of the board. Curves that fit the entire length are more difficult to generate and require many more physical copies for a full spectrum of equipment. The guts of the board are critical -- eyeballing the interior three to four feet of a board takes a very experienced eye. The flow on the ends is fairly easy to pick up on with the front foot of board somewhat cosmetic, the back foot or so, extremely important.
Photo: Sean Brody
Rocker templates for the entry to exit, or the middle third, or half of the board are critical. The curve through the few feet of the middle is very important because it influences the numbers out towards the ends. A little change or variance in the mid-section magnifies the numbers, proportionately, as the measurement moves away from the center.
If a spreadsheet was compiled from a few dozen good boards of various sizes, I believe the numbers for mid-section curve would be remarkably consistent.
Adjustable "rocker jigs", or a tools to capture the bottom, or deck, curve and transfer it to another blank or some material to make templates, have been around for decades.
This rocker profile jig was designed and built by Stan Pleskunas 20 plus years ago. Image: Rusty
There are similar jigs available through some surfboard-building suppliers.
These are very useful tools that will nest onto the bottom of your board -- or any board that captures your interest -- and holds a flexible baton or strip of plastic in place with a series of adjustable spars. This type of tool allows you transfer the curve to some sort of template material or a blank you or your shaper is working on. These tools are great because they really get a good impression of the transitions.
The flow out of the exit of the board is something that should jump out at any experienced shaper -- and to a certain extent, a surfer who has owned more than handful of boards or a least looks at a lot of boards.
Looking at and seeing the differences:
Place your board in front of you, tail in your hands, bottom up. Slowly raise and lower the board so you can see the transition from the very end of the board up to the mid section. Move it off to one side and raise and lower it a few more times. Centerline. Rail line. Do this a few times to get an impression. Then go through the same process with any other boards you may have or get together with a few friends and check out their boards as well. The more boards you look at and try, the more you will start to understand what the different curves look like; you will register finer increments of change. You will start to make the connection between the arc you are looking at and the arc you make on a wave.
Ironically, electric "power" planers, the shaper's primary tool, are something borrowed from carpentry. A tool designed to take down thickness whilst keeping the surface as flat as possible. It ends up they can remove a lot of foam and are good at blending curves. An experienced shaper feels the curve underneath the tool; blending and smoothing the transitions as if the tool were the actual water flowing over the surface.
Carving in rocker by hand with an electric planer is an art and a science.
Computers have given us the capability to reproduce the things we want to with a very close degree of tolerance.
I have lots of stories about good accidents in the hand-shape world: boards that get bumped and need some post-shape cosmetic surgery, or some sort of dyslexic mishap that results in a magic board. On the flipside, computers do what they are told. So if a shaper wants to get creative, he can. And, if by some good fortune or well thought through idea, the board works, it's repeatable.
Magic boards shaped by hand are an act by the accidental purist. Or an accidental act by the purist. If a draw-knife had soul, a Skil 100 Planer is the Holy Grail, where does that place the CAD program and CNC machine? It's a logical step forward and the reason why overall board quality and consistency has improved greatly in the last 10 or so years. More than ever, understanding what you need or want is so important because the numbers part of it is so doable with CAD design.
There is no right or wrong. The role of rocker is to fit the curve of a particular wave you are going to ride and the lines you want to draw.
Try to visualize a cross-section of the wave, wave height, shape, and contemplate the speed it s traveling and the power behind it and create a curve to fit it or create a curve that has an element of resistance, plus or minus, so that you might have leverage or control to personal standards that fits that curve.
At the end of the day a 5'2" fish would probably nest right into the guts of a 10'4" gun.
A 6'8" for Pipeline, if cropped to 6'2" for Big Rock, might be too flat. The wave and the arc you want to draw are the key defining elements for the arc or radius of the curve of your board.
Every wave is different and every surfer plays it with his or her own touch. Take any given spot on any day given day and each and every different surfer will draw slightly different lines.
Flow and balance: A brief history of Rocker
Since the early days of longer boards, a surfer visualized riding waves a certain way and a shaper would blend the curves to make the vision happen.
As surfing evolved, and the lines drawn became more diverse, the curves of the boards evolved. New understanding of how all the elements complement each other: rocker, width, outline curve, foils, bottoms, flex, fin size, placement, angles. It's a give and take. Change one facet to try to achieve a particular feel and there are many ways to compliment or enhance the change so other performance aspects don't get compromised.
Mini-guns of the late '60s and early '70s saw heavily kicked noses to make the drop but straight, narrow tails for drive and hold. These were single fins; with wide points up and narrow, straight, tails; outline curves reflect the bottom curves.
Brewer was one of the most influential shapers during the shortboard (r)evolution. Exploring different types of rocker early in the shortboard era, many of Brewer's designs inspired shapers around the world, myself included. At the time, this ski influenced "Disc" was very forward looking...in retrospect, an example of an imbalanced curve.
Reno Abillera and his blue disc.
Mid- to late-'70s; Parrish and Barnfield take modern single fins to a new threshold: Beautiful, parabolic, clean uninterrupted rockers.
Geoff McCoy challenges template proportions and gives us all a glimpse of the future. He pulls in the nose and widens the tail, rethinking the proportions needed to surf more intimately than ever. Surfers want to be as deep and tight as possible.
1981 Simon gives us three fins.
Pat Rawson takes his Brewer foundation (he also credits Barnfield with teaching him how to measure rocker) and makes early tri-fin guns for the North Shore that turn heads and set new standards for performance in THE testing ground. Part of the magic is a break in the rocker line in the control center...between the feet...the business end of the board.
"Staged rocker" or curves with breaks still have their place. On longer boards the change in curve creates a fulcrum for turning. The breaks are usually located in conjunction with an outline break -- a "hip". The more exaggerated the break is, or the interruption of flow is, the looser the board becomes. The downside is an increase in drag.
In more modern designs, there are still plenty of shapers who use rocker breaks but they tend to be very subtle. With the much lower relative volume of modern designs, the rider isn't as much of a passenger and can overpower the board more readily. The role of the fulcrum has diminished with today's thinner, narrower, shorter boards.
The '80s saw more curve in the back of the boards, drive provided by the tri-fin setup. Front fins allow for wider tails, create lift and hold. The 3rd fin off the tail provides drive and additional hold.
Early '90s rockers are pushed to what are arguably modern extremes.
Templates change, less outline curve, gunnier, thinner, bendier, more rocker; boards are deeper in the water, committed to rail arc and flex. With more rocker, drive has to be built back in somehow. Straighter outlines, deeper concaves, bigger fins, straighter fin angles. Narrowness lends to quickness from rail to rail.
Boards have crept up in length, largely due to the increase in bottom curve in the '90s and early into this millennium.
You could chop off a couple of inches from the nose and a half an inch and change from the tail and have a shorter board that still rode the same or possibly better without all the baggage on the extremities.
I stopped someone at the beach the other day. He had a typical performance shortboard from a big label. The front three inches of his nose were missing. I asked how long it had been like that. "A month or so." Can you tell the difference? "Not really."
What are the symptoms of a board that doesn't fit?
In small, gutless surf, getting on top of the water, planing and linking sections is always a challenge. The solution is an increase in area and volume and a decrease in bottom curve.
Conversely, as you step into venues that have more powerful, hollower surf, generally speaking, you'll want more curve. Visualize the curve of the wave, its power, and the length of ride or arcs you are looking to draw.
Flow is important.
The more the water has to bend around a curve, the more drag incurred: more curve requires or enables shorter arcs, quicker response from the rider, less glide, more effort. The rhythm of the wave and rider need to be in sync.
Balance of the curve
Most boards have a very similar curve thought the midsection.
When turning a board, a good solid rail turn, it's important to visualize the waterline arc of the board and see how it's going to run through the water. An imbalance at either end of the board will create drag. If the front part of the curve doesn't feed the back part of the curve efficiently and creates conflict on the line you might be trying to draw: the board doesn't flow or follow itself through turns.
Too much rocker in the nose won't prevent pearling or poking if the tail is too straight. The back part of the board needs to fit the canopy of the wave.
A low entry may paddle well and catch waves early but it might not fit the curve of the trough of the wave and it will also set an arc (lack of curve) that fights the change in curve in the back of the board.
-A 9'8" gun may have 7" in the nose and 3" in the tail
Greg Long winning the Eddie on a 9'8" x 10 3/4" x 20 1/2" x 10 5/8" x 3 1/8" by Christenson. Photo: Klein
-A 6'8" pipe board may have 5.5" in the nose and 2.75" in the tail
-A 6'2" hot-dog board may have 5" in the nose and 2.5" in the tail
-A 5'6" fish may have 3.8" in the nose and 1.05" in the tail
Some CAD programs will let the users "ghost" in another board for comparison.
The end numbers are fairly common knowledge or at least somewhat consistent from shaper to shaper. If your shaper doesn't provide them for you, it's easy enough for you to start tracking your numbers. Use of a straight-edge and measure 0, 3, 6, 12, 18, 24 from the ends.
Width and thickness are fairly easy to track as well.
More and more shapers are using machines these days and there are some shaping CAD programs that are available online in a beta version for consumers to play with.
Numbers are good. These beta versions of shaping programs will allow you to play with curves and start to understand transition numbers and sequences that flow. Keep in mind, however, the proof is always in the water.
One of my biggest shaping influences was Bill Barnfield. In the late '70s, Bill taught me the importance of tracking numbers. Lot's of them: numeric control long before CAD shaping.
Ask for your numbers from your shaper and learn to measure your boards.
Check out your friend's boards.
Building a base of reference helps you understand what your needs and solutions might look like.
Your next magic board might be the one already under your feet -- with a ¼ inch change in tail rocker.
Talk to your shaper and learn to speak his language. Knowledge is king and if you put in the effort, the reward is yours.