Flow
Rocker – The bottom curve of the surfboard. This curve is most apparent when the board is laid upon a flat surface. Function: Rocker is probably the single most important factor, which determines how a surfboard works. The curve of the rocker will carve a particular arc when the board is leaned over in a turn. If the rocker is very full or round, the board will turn a tight, sharp arc. If the rocker is straighter or flatter, the board will carve a larger radius or more drawn out turn. Some shapers design the rocker to be a very smooth continuous curve, whereas other shapers fit the rocker that will perform best when the surfer is standing over a particular portion of it. Where one stands on the surfboard determines what part of the rocker is engaged with the wave. This is why boards have a sweet spot–a place which, when stood over, feels comfortable and allows for ultimate maneuvering.
Flatter rocker is faster, paddles easier, and catches waves earlier. Flatter rocker creates a longer, more drawn out turning characteristic with down the line drive. Flatter rocker makes a board more difficult to turn and easier to pearl. Fuller rocker is slower, paddles worse, and catches waves later. The more pronounced curves pushes the water ahead of it like a plow rather than skimming up on top of it. Fuller, rounder, rocker creates a shorter, tighter and rounder turning characteristic. Fuller rocker creates a looser turning characteristic and is more resistant to pearling. Usually as the length of the board increases the rocker increases, and as the length of decreases the rocker decreases. Shorter boards can get by with less rocker for several reasons; their shorter length allows them to turn easily; they fit into a tighter curve in the face of the wave without pearling; and they are more responsive to front/rear weight transfer.
A board with too much rocker will be inherently slow, with a very loose turning characteristic. Boards with increased rocker work best in steep, fast, powerful waves. A board that doesn’t have enough rocker will be inherently fast, with a very stiff turning characteristic. Board with decreased rocker work best in slow, mushy waves. Thin boards can get by with less rocker for they will actually flex (increasing their rocker) when they are pushed through turns yet maintain the benefits of flatter, faster rocker when unweighted. Bill Barnfield utilizes a technique for measuring rocker that is used throughout the industry: Turn the board bottom side up, measure it’s total length and divide this measurement in half. Mark the exact center point of the board. Balance a straight edge that’s longer than the board and extends beyond both nose and tail directly upon your center mark. Set the straight edge directly over the stringer. To accommodate a glassed on rear fin, shift the straight edge to one side for clearance, keeping it parallel to the stringer. Measure from the tip of the nose to the bottom edge of the straight edge (the edge resting on the board) to record the nose rocker. Measure from the tip(s) of the tail to the bottom edge of the straight edge to record the tail rocker. It is important that the straight edge is true and straight, for any sag will throw off your measurement. If you have trouble getting the straight edge to balance directly over the center mark, gently wedge a pencil under the straight edge to adjust the point where it touches the board. For a more detailed record of the rocker take a measurement every six inches. Nose Kick – Nose kick refers to the upward curve or rocker in the front third of the board. Nose kick helps keep the board from pearling, and is the transition point that introduces water to the remainder of the bottom curve. Insufficient kick will cause the board to pearl while excessive kick will push water and slow the board down. Tail Kick – Tail kick refers to the upward curve or rocker in the rear third of the board. The amount of rocker curve in the tail often increases noticeably immediately beyond the fins. This feature allows the surfer to bring the board around in a tight radius if necessary because the accentuated curve will carve a tighter arc with less resistance. if a shaper uses a straighter faster rocker in the middle of the board for speed, he can still give the surfer an option of turning very sharply by shaping accentuated kick into the tail. Interestingly, tail kick has more influence on pearling than nose kick does. By shifting the weight to the rear, a surfer can keep the nose of the board extremely light to prevent pearling. Tail kick facilitates rearward weight transfer.
