Surfboard Outline Design - Greenlight Surfboard Design Guide
Surfboard Outline Design
- A surfboard’s outline, or planshape, is the most conspicuous feature of a surfboard. The overall planshape of any board is generally determined by the normal board specs you are used to seeing – length, nose width, wide point width, and tail width.
- Both nose and tail width are measured 12 inches from either the end of the board, and are most accurately measured using a square placed along the center of the stringer and multiplying by two.
- The wide point of a board is most often not at the mid point of the board, so care must be taken to identify where the wide point is before you make your measurement.
- Length is measured on the deck side, from the tip of the nose to the tip of the tail, with the tape measure stretched taunt.
Wider noses (greater than 11 inches) are typically used on shortboards for smaller waves, inexperienced riders, or on designs intended to be flatter and/or shorter, than the typical shortboard. Both the retro and modern fish, along with many other single and multi-finned retro boards, use this nose template. On shorter boards, any increase in nose width helps make up for an overall decrease in board volume, which relates to flotation and ease of paddling. Wider noses on flatter boards help create more lift, as lift created under the nose is directly related to surface area: more area means more lift. This is an important consideration particularly at lower speeds, like when paddling or riding small, weak surf.
Once up on plane, however, the function of nose width changes. Wider noses tend to put more rail in the face of the wave than pulled noses. This gives wide-nosed boards more of a tendency to “catch” along the forward rail than pulled-nose boards, particularly in critical parts of the wave where the face is steep and the water is moving fastest, most noticeably in the tube. Narrow noses create a curvier forward rail line that helps fit into the pocket of a wave better than the rail line created by wider noses, and creates a shape that is less likely to catch in steep sections of the wave, or on later, steeper drops. But the reduced surface area of a narrow nose also means less volume forward, and an increased tendency to pearl. Board designers compensate for this drawback by adding more nose rocker to raise the entry point of the nose and increase lift under the nose.
One beneficial effect of a wider nose and an increase in wetted rail is a board’s ability to carve very powerful but more open turns, as the increased length of a deeply set rail can hold and drive firmly through the turn. What this profile lacks in release it makes up for in power.
Wider tails (greater than 14 inches) are most often found on boards designed for smaller, weaker waves, and boards with four or more fins. Wider tails provide the planing area needed to keep a slow-moving board on the water surface, and allows for an earlier take-off. Because buoyancy is a function of displacement, and displacement is a function of volume, the added volume in the tail increases the buoyant force acting on of the back third of the board. This increase in buoyant force results in a greater and more immediate acceleration of the board as the board and paddler are lifted by the approaching wave just before take-off. The greater the acceleration before takeoff, the sooner the board speed will match the speed of the wave. Only when the board and wave speed are equal will the rider be able to take off and make the drop.
But added tail area is generally a disadvantage in larger surf. At the speeds a rider attains in large surf, wide-tailed boards tend to get “skippy,” or lack control, particularly when used in combination with flat bottoms. Under these conditions, the board can become overly stable, and a large amount of force is required to put the board onto a rail to initiate a turn. Wide tails tend to resist penetrating the water’s surface as they generate more lift than narrower tails… they want to stay flat at speed.
Narrow tails are typically found on boards designed for larger, more powerful surf. The reduced surface area in the back third reduces lift, and allows the tail to sink deeper into the water when the surfer’s back foot is weighted. Sinking the tail increases drag, which, under these conditions, is desirable, as it provides control at speed and a faster response to rail-to-rail transitions. At lower speeds, narrow tails give the rider a “squishy” feeling under the back foot, meaning the rider often feels the tail penetrate the water surface deeply during snappy type turns, rather than resist that penetration and drive through the turn along the water’s surface. At the lip, where the wave is thin, a narrow tail can push straight through the wave and out the back, giving the turn a more tail-slidy, “fins free” flair.
Wider boards (19 inches or more) carry more volume and bottom surface area than narrower boards, all other things being equal, which increases buoyancy and ease of paddling. Wider boards are also more inherently stable, as are wider tails, so they are generally suited for weaker, smaller, or less experienced surfers, as well as weaker or smaller surf.
Wide points are often found behind center on performance shortboards, and ahead of center on many retro boards, longboards, and guns. Pulling the wide point back puts the apex of the rail curve outline closer to the midpoint between the surfer’s feet. Having the widest point between the surfer’s feet shortens the turning radius of the board, but compromises drive. The wide point is often thought of as a pivot point around which the board turns. While this analogy is not entirely accurate, pulling the wide point back minimizes the amount of rail that is sunk in the aft section of the board when the board is surfed off the back foot, as most performance boards are surfed. In other words, the wide point serves as a break in the rail curve. When the board is put on a rail, the curve ahead of the wide point arcs up and out of the water. Pulling the wide point back gets more of the board up and out of the water sooner, concentrating all of the force of the turn into a smaller area of the board’s bottom. Because the focus of all of that force is now further back, more centered between the rider’s feet, the sensation the rider feels is that of a “pivot point” beneath him/her.
Having the wide point at the midpoint of the board is often referred to as “neutral.” This design yields a compromise between drive and responsiveness, and is often used on “utility” boards… those boards that work well in both smaller and larger surf, but are not ideal in either, and barely work in the extremes.
Pushing the wide point forward means more rail remains in the water during a turn. The force of the turn is spread out over a larger area of the bottom, extending more noseward, and the center of that force is necessarily shifted forward. For the rider, this draws out the turn, but conserves much of the drive that would be otherwise scrubbed off by the stalling effect of the tail if the wide point were further back. This is why so many retro shortboard designs have their wide points ahead of center. They are meant to be surfed “old school style” with more weight on the front foot, which facilitates longer, more swooping, drawn out turns. While this style no longer wins contests, few will argue the aesthetic of such a timeless surfing style when combined with the delicate balance of grace and power that was once the ideal.
CURVEY VS. PARALLEL OUTLINES
While truly straight, parallel rails – rail lines that run parallel to the stringer (and also each other) for any significant length of the rail – are not the norm on modern surfboards, curves that are nearly straight and symmetric are often referred to as “parallel,” and are found at least to some degree on many designs. On most boards where parallel rails are used, the length of the parallel section of the rail is restricted to the immediate areas adjacent to and along the wide point of the board, sometimes extending perhaps an inch or two ahead of and behind that area. In general terms, parallel rails facilitate speed, stability and trim, and are most often found on guns, long-boards, and funboards. Parallel rails elongate the wide point of the board, effectively increasing the surface area of the bottom that would otherwise
be trimmed away by a more curvy outline. Designs that use extended parallel rails therefore lend themselves to more open turns, rather than snappy, short-radius turns, and are therefore not typically suited for modern performance shortboarding.
Specialty longboards, however, designed for noseriding, use relatively long sections of parallel along the wide point and extending noseward, as form drag (drag induced by turbulence caused by changes in a body’s form) is minimized along the straight sections of rail. Long parallel sections forward of the wide point on noseriders lengthens the distance of wetted rail that penetrates the wave face, and stabilizes the board as the rider makes subtle adjustments of weight and footing to keep the board locked in the pocket in an effort to increase tip time.
Curvy outlines are more the norm when it comes to modern shortboards. These boards have a more or less continuous curve from nose to tail, and provide the release needed to loosen up the ride. Release is facilitated as the curve goes from subtle or parallel at the wide point, and accelerates toward the ends, pulling in the nose and tail. While many designs use smooth, elliptical curves that run the entire length of the board, some boards use more asymmetrical curves along with bumps, wings, or hips to change the overall curve to meet specific rider needs. More on this later…
Because a continuous rail curve minimizes the amount of rail imbedded in the wave face, these boards are not designed for extended trimming. Rather, they are designed to be surfed rail-to-rail, constantly being pumped and turned to generate speed and work in tandem with a variety of complex bottom contours and fin configurations.
WINGS, BUMPS, & HIPS
An effective way to dramatically change width is to create abrupt contour changes to the planshape. Hips, wings and bumps, used in the back third of the board, create a break in the rail line curve that serve a number functions simultaneously. By reducing width, they reduce lift in the tail, allowing the tail to penetrate the water more deeply, eliminating the need for a lot of curve through the middle of the board. The rail ahead of the wing and through the middle of the board and can stay straighter for a more parallel outline, but tail width is bumped down quickly for release.
Similar to our earlier discussion regarding wide point, some people refer to the wing or bump as creating a “pivot point” for turning. More accurately, however, the wing actually serves to create more of a “release point” than a pivot point, by changing the distribution of lift force under or near the back foot. Because most modern surfing maneuvers require the back foot be placed over the front fins for turning, if a release feature (usually a wing or bump) is placed behind the back foot, in line with the trailing edge of the front fins, water will not release from under the board until after it has passed the fins. The rail line through the middle and into the back third is lengthened, and the board becomes more drivey, but less responsive. Wings and bumps are common in wide-tail designs, like fish, and on quads - both of which are known for having heaps of drive (lots of fin area helps, too!).
A hip, or break in the curve of the rail line, is most often used forward of where a bump or wing might be placed. Placed at the leading edge of the front fins, this “corner” in the outline places the release point either ahead of or directly under the surfer’s back foot. The rail line is shorter through the middle, and the board responds faster to rail-to-rail shifts in pressure. Many high performance shortboards use varying degrees of hip in their planshapes. What this design loses in drive it makes up for in responsiveness. That responsiveness is put to use as the rider pumps the board down the line to generate drive, rather than having drive be intrinsic to the design.
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