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Click on a link below to read about a topic or download the entire Rich Harbour's Surfboard Information document here.
Surfboard 101
SURFBOARD 101 A surfboard is a type of fulcrum, where lift is provided by the fin, rail and outline shape, and the weight of the surfer in front of this lift creates the surfboard's forward motion. When the board traverses on the face of the wave, the speed increases because you are no longer moving just towards the beach, but somewhat parallel to it. The tighter the line that is drawn to the face of the wave, the faster you go. The speed of the board will increase as the surfer moves forward on the board, until his weight overcomes the volume of board beneath his feet. This place of maximum speed, which is about 1/3 from the nose, is sometimes referred to as the [full] trim spot. Conversely, the closer one places his weight to the fin area, the lift action will begin reducing, stalling the board. NOSE RIDING Nose riding is affected by several design characteristics. Some surfers seem at home on 15 1/2" noses, but nose width helps stability. Several other factors play at least as much in importance. One is weight: the heavier the board the better. Board length is also very important. Longer boards simply nose ride better, mostly because of their longer rail line. A straighter or more parallel outline will give more tracking, as will 50/50 rails. Some tail lift in the rocker is also important. Water flowing up over this tail will give downward pressure at the tail, adding some nose lift. Super long, wide, heavy surfboards don't turn very easily, but these are features that enhance the nose ride. FINS All fins: The wider the board in the tail, the longer the fin needs to be. Increased fin base traps more water for lift and drive. Volume above the [immediate] base will reduce side drift. Increased fin rake (a term for the amount of base overhang) ads drive, but resists board rotation. Single fin: More base, more drive. With less base, you get less resistance when pushing through a turn. Increased fin depth adjusts for both tail width and the surfer's weight. Increased fin depth creates more grip on turns (harder to turn) and decreases premature tail release while nose riding. More volume will also decrease premature tail release. HP fin: This Harbour designed [single] fin went through 22 design changes before arriving at its current form. Unique in shape it utilizes a rather full base with a sickle shaped cut-away and long, raked tip area. Instead of vertical flex typical of most designs, the raked tip has wag. This wag bends with the turn, and generates snap when exiting the turn, driving the surfer forward. Easy turn with more drive - what more could you want? Multiple fins, 2+1: This is the term for one medium sized center fin that is usually 6 to 7 inches deep, and the two smaller front fins called side bites. The side bites are normally 3 ½ to 4 ½ inches in depth. Most side bites are in a fixed position, and most center fins are adjustable. Moving the center fin forward decreases the rotational resistance, making turning easier. Moving it too far forward will begin to force the surfer forward to get any lift for motion across the wave. When the center fin is increased in size it creates more drive and less side drift, which will make the board harder to turn. Side bite design: The less rake, (overhang from the base) the more rotational action. More rake will give more directional drive. Tip flex is important important. This is accomplished by tapering the thickness vertically from the base to the tip. See the Harbour/Stamps design from O'Fish'L fin company. Single vs. 2+1: Tri fins tend to turn more off of the rail while single fins find more of a pivot type of turn. This is mainly because the side fins, are usually very close to being under or in front of the foot that is putting pressure on the rail that is being sunk into the turn. These side bites are generally angled in towards the nose and this also assists in initiating the turn. The single fin, on the other hand, usually is under or a little behind the pressure foot. With a single fin turns are more of a pivot. The surfer lifts the nose up and rotates the board on the tail rail. Better surfers can lay a single fin board on a rail and power a turn. Good luck with this maneuver, as most just dig a rail! ROCKER Rocker is the term for the curvature of the board from nose to tail. There are three primary areas of rocker - nose, middle and tail. Increasing the nose rocker will cause less water splash in the face while paddling, and decrease the chance of catching the nose while dropping into a wave or while turning. However, while paddling into a wave, increased nose rocker can ad water entry resistance when combined with increased nose width. Additional nose rocker can also cause the tail to release prematurely while on the nose. Excessive nose rocker will push water instead of gliding through a good nose ride. Increased rocker in the middle of the board will give less drive, and slow the paddling. Too flat of a curve will make the board stiff. A key area of rocker is the area between 12 and 24 inches from the tail. There should be a bend there with a straighter curve forward of this bend. This joining of tail curve and flatter area are one of the key elements of surfboard design that must be coupled with outline and rail shapes. It takes years of knowledge to know how much and where to put it. More tail rocker will ease turning and increase tip time. But it will slow paddling, down line speed and decrease drive out of the turn. Decrease the tail rocker and the board becomes stiffer in maneuverability, but the forward drive increases. I have spent over 40 years developing a good blend of rocker curves and they work. There are no [tip] numbers (people are always asking how much rocker is in a particular board, and quite frankly I don't know and don't care) that are as important as the relationship of the previous curve to the next. Numbers taken at the end of a surfboard cannot represent the total rocker curve. Lay a snow ski on a flat surface and you can see why. RAILS There are two basic styles of rails. One is the down turned rail that was popularized in the nineteen seventies, and the traditional 50/50 rail that was carried over from the wood board days. 50/50 rails are sometimes referred to as egg rails. They are shaped just like their namesake. A 50/50 rail would have the apex of the curve dead center in relation to the center thickness of the board, although there is no logical way to qualify this (and most are probably slightly below). The surfboard's bottom is generally somewhat flat through the center twelve inches, then blending into the rail. They are smooth riding and many claim they nose ride better. Down turned rails are about 75% down at mid ship, with a soft roll, quickly blending into a flat bottom. They usually change to full down turned rails about 20 to 24 inches from the tail. This is the area that the outline shape makes the transition into the tail curve. The hard edge [in the tail area] of the down rail board will grip the water while the 50/50 rail lets some slip by. With the 50/50 you must capture water somehow so you increase the fin area or move the fin aft for more leverage. A fin needs to be of less volume on a board with down tail rails than on a board with 50/50 rails. This is because the edge on a board with down tail rails is acting in concert with the fin while gripping the wave. 50/50 rails feel somewhat smoother - they have that glide feel. They find a slightly lower line on the wave, and seem to nose ride with a little more control. Boards with down tail rails and the soft low mid rails, will initiate cut-backs better due to the fact that water isn't being trapped by wrapping the rail. They give more tail lift, and this makes them seem to accelerate faster which is sometimes referred to as drive. This rail design is not well suited for heavier boards. Rails will set into the wave to a depth relative to the rider's weight. Heavier surfers need more volume so it can either be put into thickness, which increases the rail size, or length or width, which allows for thinner rails. CURING (Note: all degrees are Fahrenheit) Many things have been said about how long a board needs to cure before it is ridden. For the first 48 hours resin is very soft. Severe dents will occur wherever pressure is applied to the surface. Most boards are laminated one day, hot coated the next day and sanded the following day. Severe denting is generally not a problem with glossed and polished boards. The gloss and polish process usually takes an additional several days, making about 5 to 6 days from the day it was laminated. The lamination process is the application that most needs to resist denting. If you wait an additional week after polishing the board will be reasonably cured. This time estimate is based on a typical 70-degree ambient temperature. If it is the dead of winter, and days and nights are very chilly, the waiting period can double or triple. Conversely, heat can greatly accelerate the curing process. Your board, exposed to about 115 degrees heat for several hours, will be adequately cured. Reliable sources tell me that this rapid cure actually increases the strength. Surfboards that are already cured cannot be made stronger by this process. Be very careful not to let the board get over 125 degrees. Polyester resin actually begins to soften at about 150 degrees. See our page INFO/HEAT for more on this. STRINGERS Stringer is the common name in surfboard construction for the piece or pieces of wood that divide the foam blank. The stringer is glued in after blank is removed from the mold. Stringers both give the blank rigidity for shaping and the finished product. They also provide the shaper a sight line to use while shaping. Colored glue can be used to decorate the lamination. Harbour Surfboards uses colored glue to give a better site line when shaping the lighter colored basswood. Basswood: (Tilia americana) is a very clear grained hardwood that is easily shaped. It is light, with a specific gravity of just less than 0.4. To compare, Balsa (Ochroma pyramidalis which is also a hardwood) is 0.15 and Spruce 0.4. Lignum vitae, the heaviest wood, has a specific gravity of over 1.2. (This stuff doesnÍt even float!) Cedar: Due to redwood being over harvested, I have chosen to use cedar (Thuja plicata) a wood that visibly resembles redwood. Like redwood, cedar is almost 25% weaker than basswood. I recommend cedar only in three stringer boards or T-bands. T-bands are described in the surfboard business as more than on piece of wood glued with another. However most people refer to T-bands as two alternate colored woods glued together in a pattern (e.g. cedar-balsa-cedar). Clark foam can put together just about any combination of stringers that you want. Be advised that these requests can, at best, double the time of production. When using basswood, we use 1/4" width for the thicker boards and 3/8" for the thinner, high performance models. Shorter boards may have even narrower stringers. The word hardwood and softwood have nothing to do with the wood's hardness. All trees are members of the plant kingdom that are spermatophytes or seed plants. This kingdom is further divided into two broad groups (separated by how the seeds are born). Gymnosperms are naked seeds and comprise all trees that produce softwood lumber. Angiosperms are covered seeds (like walnut, pecan etc.) that make up the hardwood group. DEFLECTION AND BREAKING
DENTING Dents are a natural Bi-product of surfboards. The old balsa boards, when whacked really hard, will dent. I have been in this business since 1959 and have seen no production foam boards with more than a total of 20oz of glass per side. When using contemporary resins, the real problem in denting is the substrate or foam. Even with the early 60's when foam weighed about 3.9 lbs. per cubic foot, surfboards still dented. Think of this: put one layer of 4oz glass on concrete and you will not dent it. To make a surfboard of reasonable weight, we cannot apply enough layers of glass to make it ridged enough to be dent resistant. Today's longboard typically is made of CLARK "supergreen" foam. This name has nothing to do with anything but a name for foam that is approximately 2.44 lbs. per cubic foot. Supergreen is the standard of the longboard industry. Foam is not the same strength from surface to core. The surface of the deck is the strongest part of the blank, but rapidly loses its toughness as you shape deeper than 1/8". We do not carve rocker into the blank. This will cause what is known in the industry as overshaping. Harbour Surfboards orders the desired deck rocker which is pre-glued into each blank. It is then barely skinned, resulting in a deck that is as strong as materials will permit. If you must knee paddle, get a standard glass job with supergreen or classic ) foam and go knee paddle it for a couple of sessions. Now strip the wax off where you kneel and you should find 4 dents where your knees and insteps have depressed the glass and foam. The glass is now being stretched and is still trying to bond to the foam. Take your board to a qualified repair center and ask them to put several layers of 4oz glass in the depressions. The new glass now will conform to the curvature of the dent and hold the old glass down. You have just added strength to your exact balance points, with very little weight to your board. This concept also applies to any other concentrated dents on the board. Failure to repair deep dents may result in delaminations. HEAT Surfboards are very sensitive to heat. Most polyester resin begins to noticeably soften at only 150 degrees. Foam becomes very unstable at about the same temperature. I have seen surfboards get amazing twists from improper storage or exposure to heat. More than one customer has brought back a fin that is severely warped. I have to inform him that the fin and surfboard have been exposed to excessive heat; usually in a car while it is resting on the fin. This fin is not ruined! Heat a large pot of water to 160 degrees. Using tongs, immerse it for about 30 seconds. Pull it out and, using potholders, bend it straight (it should be as soft as salt-water taffy). After it cools it is as good as new. A heat twisted board can be fixed with offset weights clamped outside the rail on the two high ends of the surfboard. I made a set of clamps from a pair of one by one pieces of wood about 24" long with 4" screws and wing nuts at each end. On a warm day, put the board inside of a car. Ad the weights to the appropriate ends and clamp with the screws. Close the car and wait till it gets about 160 degrees inside. Take the board out with clamps and weights still in place. Put it on a set of level saw horses and lower the temperature with cool water. Check the twist. You may have to repeat this process or, if luck is with you, that is it. DINGS Fix any ding that exposes the foam to water. A ding on the rail will make the board susceptible to breaking. If it gets into a stressful situation, the stress will focus on the weakest point - the ding. You now have a broken board. Don't let a split in the glass on the bottom go unchecked. I have seen the entire bottom glass ripped off because water was forced into a small split in the glass. Dents in the deck, which are commonplace with today's surfboard construction, should have a couple of layers of glass put in the dent before it delaminates. Delaminated glass is far more expensive to repair than reinforcing the existing glass. All shatters will take in a minute amount of moisture. Large shatters may need some maintenance. While working with the clear silane glass, a really good repair person can virtually make a shatter disappear Volan cloth will always show a little bit where the repair has been made. STRENGTH
WEIGHT The weight of two identically ordered surfboards can vary as a result of several variables.
CONCAVE AND NOSE CHANNELS These are nose riding embellishments to add lift when riding on the nose. The concave is a traditional technique in shaping to enhance nose riding. This style was popularized during the mid-sixties at the peek of the nose riding craze. There are many ways to carve it into the nose area and we believe it is most successful by continuing the scooped out area fairly close to the rail and leaving a smooth exit line at the rear. This takes some of the drag out that is generally attributed to concave noses. The other style is nose channels created by Rich Harbour. Originally they were a pair of nose channels on each rail that followed the rail outline. These proved very difficult to fiberglass so the inside one was removed from each side with no noticeable change in performance. For several years they were made 2" from the rail. A board for a team member was being shaped when the sandpaper block hooked into a freshly carved channel. It had to be moved closer to the rail resulting in what the team member called the best nose rider ever. They are all now 1 5/8" from the rail. The differences in feel of the two styles are slight but noticeable. The concave is a more of a stalling style, making it smooth and stable ride. The nose channels don't slow the board down when in the trim spot about 1/3 back from the tip. Many better surfers claim to be able to climb and drop with them. We have applied each style to an appropriate shape in our line of boards. Enjoy! OUTLINE The outline, or plan shape is the curve that forms the outer edge of the board when observing from the top or bottom of the board. Measurements are taken one foot from the nose, at the widest point in the center section, and one foot from the tail. These places of measurement give only a general idea of the board's shape because the location of the apex of any curve of the outline cannot be told with just these three measurements. Although much of the board's riding characteristics can be attributed to the outline, one must realize that it is simply one element in a much larger table of contents that makes up the final shape. Each of the three measurements provides it's defining contribution to the board's performance. For instance, as the nose becomes wider, it becomes more stable to stand there. The down side of this is there becomes more volume of material or swing weight in front of you while turning, so the turning aspect diminishes. When dropping into a wave, a wider the tail will capture more water, thus causing better lift. But as the tail gets wider it becomes more stable and difficult to tip on an edge to turn. Boards with a three-fin set up typically have a tail width of 13 1/2 or less. This is because the fins start getting too far apart with a wider tail, reducing the rotational effect needed to turn. Boards that are wider in the mid section are more stable but are more difficult to turn because they don't tip up on a rail as easy as their narrower counterpart. The three measurements work in concert, and as one grows or reduces, it affects the others. For instance: if the nose and tail remain the same and the center width increases, the outline gains curve that enhances the turn. Conversely, if the nose and tail increase in width and the center remains the same, the rails become more parallel, complimenting the nose ride but decreasing the maneuverability. Increase the nose width and leave the other dimensions alone and it moves the wide point forward, reducing the center curve, making it more difficult to turn. When the tail width is left alone and the nose volume decreases it will make for great turns, but the board will be slow and a poor nose rider.
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