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Board Design Seminar Related links Board Shapes: There are lots of factors that affect how a board performs. One must be careful about a particular design characteristic, as the overall performance of a board depends on the whole package, not just one characteristic of a board. Following are some basics of board design, and their effect on the performance of a board. I have organized them in the general order that I use when designing and shaping a board. Volume: The volume of a board determines how much floatation the board will provide when it is not moving. If a board has 80 liters of volume, it will displace 80 liters of water, and as a result provide 80 kilos (isn’t metric nice) of floatation. If you subtract the weight of your rig, and the weight of your board, you can figure out how much floatation your board will provide to float the sailor. Keep in mind, this figures that the whole board would be submerged. The factors that effect the volume most are thickness, then width, then length. If you add 1” of length, you really aren’t adding much volume, but if you were to add 1” of thickness, or 1” of width, you would be adding quite a bit of volume. To get an idea of the volume of boards, you can use this chart we put together. It assumes a lot of things, but it does help determine the sizes of boards. Tail Rocker: The flatter the rocker in the tail, the quicker the board will plane. If you have too much flat area of the board, your top speed can suffer, as there may be too much board in the water causing additional drag. Less tail rocker also can make the board less turney. Finding a compromise between too much and too little is the challenge of the board designer. Nose Scoop: A board needs enough nose scoop to keep it above the water line. A wave board designed for small waves would need more than a slalom board because on a wave, you may be riding straight down the face, which is curved, making the nose more likely to pearl (become submerged). A wave board designed for smaller waves will have more nose scoop than one for bigger waves, as the smaller wave has more curve than the bigger wave. Excessive nose scoop serves no real purpose, and can cause problems like damage to the sail, or person. Putting too much nose scoop in a board can also affect the location of where the water contacts the board making it harder to plane. The board designer’s task is to find the correct amount of nose scoop. The scoop/rocker line is one of the most important aspects of board design. Width: The wider the board, the more surface area there will be to propel the sailor onto a plane. Too wide though, and the board suffers at high speed. It becomes harder to control, bounces too much, especially when jibing. Too narrow of a board makes it hard to get planing, and also can make the board difficult to turn, especially at slower speeds. Location of Wide-point: Moving the wide-point further back started the trend of the “no-nose” design. As you move the wide point back, it makes the rails on the back of the board more curved, which makes the board turn more quickly. This can be great for lighter winds, and bigger boards. But, this can have a negative effect on smaller boards or boards that are designed for speed and stability. For example, someone who sails a board at high speeds like in the gorge, or on a big wave, would want not want the wide-point too far back, as it would make the board more difficult to control. For that reason, sailors who are riding very large waves are using “gunnier” boards (boards with straighter rails in the back). This provides the stability that is desirable when riding down a bumpy large wave. On big waves, the last thing a sailor wants is a squirrelly board! Over-all width, tail width (measured 12” from tail), and wide-point all work together to help determine how loose, or stable a board will be. Board Thickness: A thicker board will provide more floatation. Lots of floatation is great for light winds, or to get planing, but once the board is moving, that extra floatation can get in the way. It can make it hard to handle in higher winds. Rail thickness: Rail thickness works in conjunction with overall thickness, and tail thickness, as after all, the rail needs to blend into the middle of the board. If the rails are too thick, submerging them may be difficult, especially on a gunnier board. This can be a problem when wave sailing, or even high wind sailing, as if you have a board with too thick of a rail, it can be difficult to submerge it to get enough resistance off the bottom of the wave to propel you to the lip of the wave. But then again, you don’t want it too thin, because this can cause problems with catching on each small ripple on the face of a wave. Too thin a rail can also make the board difficult to get planing. Vee: If you put a straight edge across the bottom of a board, the amount of space between the straight edge and the opposite rail is the “vee”. Vee in different places in a board can have a big effect on performance. Vee can affect turning, stability, and planing. Most boards have the most vee towards the tail of the board. Usually the vee is fairly slight in the front, and generally increases towards the tail. More vee makes it easier to go from rail to rail. If the vee increases towards the tail, it makes the rail have more curve, yet doesn’t radically effect the overall rocker line. The increased rocker in the rail makes the board turn better. Some boards have more vee in the middle, which would displace more water. I have found that too much vee up in the middle makes the board a bit sluggish. Rail tuck: Rail tuck is the distance the chine line is tucked under the board (from 0” to ¾”). Most slalom boards have less rail tuck than do wave boards. The more tuck a board has, the less likely the board will “catch” a piece of chop when jibing, or turning. More tuck = more forgiving, less tuck= sooner planing. Rail tuck and chine are closely related. Chine: Chine is a boat building term, but has found its way into windsurfing. Chine is the sharpness of the rail. Hard chine is sharp, soft chine is rounder. Virtually all boards have a fairly hard chine in the tail. This is to provide a nice exit for the water off the tail of the board. If the tail had a soft chine, water would try to remain attached to the board, increasing the drag. Virtually all sailboards have a hard chine in the tail, so when people refer to chine in a board, they are often speaking about the front and middle of the board. The softer (or rounder) the rails are in the front, and middle part of the board, the more forgiving the board will be, but a softer rail will be slower to plane. Most slalom boards have a harder chine than wave boards. The harder chine makes the water release off the board at a slower speed, which helps the board plane earlier. This isn’t as critical for most high wind boards, as control is more important than planing at slow speeds. Board design is a series of compromises. There is no such thing as a board that can do everything. The combination of the characteristics above determines the overall feel of the board. One trendy feature on a board isn’t going to make a bad board good. And alternately, a particular feature may not ruin an otherwise great board (although it might). I hope this information is helpful to you. If you have some comments, I would like to hear them. -Brian Carlstrom |
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Windance 108 Hwy. 35, Hood River, OR 97031 |
