Surfboard Construction & Care

The Making of a Blank

The surfboard begins at the blank factory where two chemicals are mixed together to form a rigid polyurethane foam which is poured into a concrete mold. It dries and when removed from the mold it is known as a surfboard blank. Available are numerous blanks of various lengths and proportions to fill the many needs of the surfboard industry. One or more strips of wood, known as stringers are inserted to make the blank rigid enough to shape them to sizegenetics and strong enough to resist breaking. These stringers are pre cut to a lengthwise curve known as the rocker. We at Harbour have created private rocker templates available to only us. With a pencil, a skilled craftsman at transfers the Harbour rocker template onto a piece of wood and cuts it out to that line and it becomes the stringer. During the gluing, the blank is bent to the curve of that stringer, and when the glue is dry the blank now has the rocker that the stringer has.

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Shaping the Blank

Computer Shape

  • Always searching for a new design concept, periodically new surfboard shapes are created by Rich on his computer using special surfboard designing software.
  • A blank is then attached to a table that has special vacuum cups to hold it in place.  Using a grinding bit made of thousands of tiny carbide particles, a CNC cheap software machine makes an exact copy of Rich’s computer creation. The finish computer shape is rough and has no rail shape on the bottom rail edge, leaving some ability to fine tune each board. However it does have the exact foil, outline, deck crown, channels, concave, tail “V” and any other design features that the original had.
  • Hand finishing one of these computer shapes takes a great deal of skill and about 45 minutes time.
  • The advantage of a computer prepared board is that it is next to impossible to hand shape identical surfboards. This technique is excellent for reproducing a model, keeping the consistency at a maximum.
  • We now have the ability of making specific changes to any existing shape or creating a shape from existing foils on our computer database. There is an additional charge for this option.

Hand Shape

  • Blanks are ordered with a specific rocker glued into the deck of the blank. The shaper removes the skin of the blank from the deck. Any irregularities that may have developed in gluing are addressed at this time.
  • The blank is then turned over and proportioned, creating the blank’s foil, and then it is brought to thickness.
  • The appropriate outline is drawn and cut out.
  • The rails are roughed in.
  • The board is finish sanded.

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The Glass Job

Coloring by Foam Spray

  • This technique must be applied now
  • Areas of the finish shaped blank are covered with tape and masking paper to create a design. Water based acrylic paint is sprayed onto the exposed areas of the blank.

The Lamination

  • Two ways to hand laminate (called a lamination) are:
    • Free Lap
      • Fiberglass cloth is pulled over the entire length and width of the finished blank’s bottom. The cloth is trimmed by scissoring about 1 1/2” below the rail’s center line all around the blank. The Harbour logos that have been silk screened onto rice paper are placed beneath the glass. Polyester laminating resin is catalyzed and poured onto the glass and the resin is spread evenly with a rubber squeegee. The fiberglass is wrapped around the rail, with the squeegee pressing it tightly to the foam blank.
      • When dry, the edge where the glass ends is smoothed and the entire lamination process is repeated on the deck.
    • Cut Lap
      • The deck is taped off about 1 ½” from the rail. Then masking paper is applied to the inside edge of the tape to form a wide barrier.
      • Fiberglass cloth is pulled over the entire length and width of the finished blank’s bottom. The cloth is trimmed by scissoring about 2” below the rail’s center line all around the blank. Polyester resin is catalyzed and poured onto the glass. Pigments may be added at this stage to create transparent or opaque colored boards (this technique must be applied now). The resin is now spread evenly and the glass is wrapped around the rail and past the masking tape with a solid rubber squeegee.
      • When the resin is in its final stages of hardening, the board is turned deck up and a razor blade is used to cut the excess glass that goes past the masking tape.
      • The Harbour logos that have been silk screened onto rice paper are put onto the surface glass beneath an additional layer of glass that extends slightly beyond the logo.

The Hot Coat

  • The rough texture of the finished lamination needs to have a smooth finish to sand. This is known as the hot coat, getting its name from the fact that this coat is heavily catalyzed to get a quick cure and this high catalyst content typically warms the resin. Laminating resin has catalyst and surfacing agent added and it is spread over the deck of the board with a brush.
  • Repeat the hot coat on the bottom.

Fin Box

  • A jig is attached and a hole is routed into the bottom near the tail to accept the fin box.
  • Glass cloth is cut to wrap around the bottom and sides of the fin box.
  • Catalyzed resin is poured into the routed hole and the glass and fin box are plunged into the hole.


  • The entire board is power sanded using sandpaper attached to a soft rubber sanding pad.
  • The rails are hand sanded.
  • The entire top and bottom are block sanded.
  • The entire board is again sanded using a fine paper.


  • The center of the rail is taped with the under side of the tape hanging free. A special blend of resin called glossing resin is brushed on the deck and the excess resin runs off of the tape on the rail onto the floor.
  • Repeat glossing on the bottom.


  • A bead has been formed on the rail where the deck and bottom gloss coats overlap. This is carefully removed and the board is then completely dry sanded by machine with a soft sanding pad using 400 then 600 grit sand paper. Then the rails are wet sanded.
  • Finally the board is polished, with first a coarse polishing compound and then an ultra fine compound.

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  • Fiberglass comes in many weights. Some of the common ones used in the surfboard industry are 4 oz., 6oz. 7.5 oz., and 10 oz. There is no realistic strength difference between Silane (the clear glass) and Volan (the greenish colored glass) finishes of the same weight.
  • Twist weave carries more resin than flat weave.
  • S-Glass has great memory, but this may be its undoing. It won’t stay bonded to the foam as well when severe denting occurs.
  • The amount of MEKP (methyl ethyl keytone peroxide also known as jeux de sims France) has an influence on the strength of polyester resin. The resin manufacturers recommend adding less than 2 percent catalyst. With such a minimal amount, the gel time would more than an hour, and the foam would absorb large amounts of resin making it extra heavy. In very cold weather, some surfboard glassers have been known to use up to 10% MEK to achieve the desired eight-minute gel time.

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  • The weight of two identically ordered surfboards can vary as a result of several variables.
    • Foam is mixed by weight for each particular blank. Since it is about the consistency of waffle batter, getting the same amount into the mold from the mixing bucket each time is difficult at best.
    • The stringer, being a natural wood product, can vary in weight due to what part of the tree it comes from. The amount of moisture it has will also affect the weight. Stringers glued in the summer will always have less moisture content.
    • The viscosity of the resin changes with the seasons. The resin used in the winter is always thicker.
    • Color in the lamination or a volan glass job requires extra resin to protect the cut lap. This extra resin can add weight, up to a pound.

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  • There are several ways to color a surfboard. These are listed in order of appearance in the industry.
    • Resin pigment. This is pigment added to resin and applied by brush after the board has been laminated, hot coated and sanded.
      • Due to the amount of pigment added to the resin, it becomes quite soft, and a clear coat must be applied over it. This makes a long board 2-4 pounds heavier. It is a very labor intense application and only a few glossers in the world are any good at it. With the extra layer of resin, this is the strongest and heaviest glass job.
    • Color in the lamination. When a board is fiberglassed, the fiberglass is pulled from the roll the entire width and length of the board. It cannot be sectioned, as this would cause a week joint. The only exception to this is when a colored panel of glass is placed inside of the bottom’s overlap line. When this is done, another layer of glass is applied over the entire deck to seal that joint.
    • During the fiberglass lamination process, pigment is added to the resin. It may be either transparent or opaque. The board must be taped off where the glass ends to form a clean, cut line. The lamination does not have to be volan glass, as silane with the color impregnated into the fiberglass and a razor cut line will produce the same look. Color in the lamination can only be applied on a complete side and rail wrap, or as an inlay that meets the rail wrap from the other side. Tail blocks and nose blocks are subsequently covered, so opaque laminations will cover the blocks and transparent laminations will cover them in that transparent color.
      • This and the resin pigment mentioned above are the most delamination resistant color processes. It is also labor intense, but not as much as Resin pigment.
      • The hot coat, which is the clear coating of resin that follows the lamination process, must be put on thicker with color in the lamination. This acts as a buffer, so the sander does not sand into the cut overlap. This extra thickness will cause the board to be heavier.
      • Because it takes a given volume of resin to laminate a surfboard, any foreign substance – and in this case pigment – displaces the resin. Pigment has no structural value so the strength of the lamination is diminished by the percentage of pigment added.
    • Pin lines. Ink lines and acrylic pins on the hot coat are applied after the hot coat is sanded. A single line of tape is placed down and an ink pen is dragged against it, using the edge of the tape as a straight edge.
      • Acrylic pins use two lines of tape and the acrylic paste is squeezed out of the tube between the tapes.
    • Foam spray. After the blank is shaped, the requested design is taped off and all other areas are covered with masking paper. Acrylic color is sprayed in the unmasked areas of foam. Pin lines can be applied using the foam spray method.
      • Paint does not bond to foam as well as resin. Observe the flap of glass on the next broken board you see, and note the paint on the flap, not the foam.
      • This is the most delamination prone of all color processes. However, it still is a most acceptable technique if the owner periodically checks the board for dents in an area that gets a lot of wear.
    • Acrylic spray. After the hot coat is sanded the surfboard is masked off to the desired design. Acrylic paint is sprayed onto the unmasked area.
      • Resin does not bond to acrylic paint as well as resin to resin. Large sprayed areas of acrylic paint may possibly delaminate. Acrylic paint on the rail is difficult and should be avoided because it is very easy to polish through. To avoid this, glass shops usually put on extra layers of resin. This adds weight.

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(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. Foam begins to get unstable at 130 degrees.

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Deflection and Breaking

  1. Surfboards are a foam sandwich. The deflection rate of this sandwich is a mathematical formula. Thickness cubed delivers a relative number. For example: a 2″ thick board has a deflection rate of 8 while a 3″ thick board has a deflection rate of 27. The 3″ board is 1/3 thicker but more than three times stronger! The closer your feet are to the actual bottom surface, the more sensitivity and leverage you have. Thinner is better to surf on, but more subject to breaking.
  2. The surfaces of this bending foam sandwich are one side tensile and one side compression, much as a deck of cards. Most fiberglass that covers surfboards is split – 50% going lengthwise (warp) and 50% crosswise (weft). The fibers that cross the board do little to reduce deflection. Their main function is to reduce denting.
  3. The width of a stringer has the expected proportional effect; 1/4″ is twice as strong as 1/8″. However, increase the length by one-quarter and you double the deflection. Surfboards need to get thicker as they get longer.
  4. The combination of the stringer and fiberglass surfaces form an “I” beam. Increasing stringer size or fiberglass weight will decrease the breakage potential of the surfboard.
  5. Stress fractures are the hairline cracks that are the result of a surfboard going into an extremely stressful flex. The films of resin above and beneath the glass cloth are usually both cracked. This is a difficult repair job, as most of the cloth must be ground away but not removed. A batch of resin that has been diluted at least 50% is forced through the remaining cloth. When dry, several layers of very light cloth are applied over the damaged area making sure to cut the ends in a wedge. This disperses the load if the board again gets too much bend.
  6. Salt water weighs 64.3 lbs. per square foot. An unsupported section of surfboard will be at risk when exposed to the force of a wave.

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  • 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 polyester 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 foam that weighs somewhere between 2.5 and 3 lbs. per cubic foot.
  • Heat is probably not the cause of most deck delaminations. The main cause is that fiberglass just does not stretch. The shortest distance between two points is a straight line. A dent makes the distance between the edges of that dent greater. As the dent increases in depth so does the distance between the edges of that dent. Repetitive pounding in the dent causes slippage in the bond with the foam. This movement deteriorates that bond and accelerates the separation. The fiberglass, which has little or no elasticity, has no choice but to release from the foam. Deck dents delaminate primarily because of the constant pounding in one spot, and the lack of elasticity of the fiberglass. Failure to reinforce deep dents may result in delaminations.
  • To reinforce a dent:
    • Before the dent delaminates, remove the wax and sand the area thoroughly with 60 grit sandpaper, leaving absolutely no shine. Sand about 1 ½” onto the flats. Using a catalyzed batch of resin, apply 2 layers of 6 oz. glass to the dent. The key to this is to cut the glass so that it just overlaps onto the flats, making sure that the weave direction matches the same direction as the glass when the board was constructed. This technique will make the glass disappear. The object here is not to fill the dent, but to create more strength in the dented area, and to have a new layer of fiberglass that forces the old glass to hold the new shape. Hot coat all of the way to the edges of the sanded area. Do not use any masking tape. Free stroke your brush strokes, feathering at the edges and get out of it quick. Resin has a wonderful way of self leveling if you give it a chance. Sand the area when the resin has kicked off with 60 grit paper. Just blend the edges onto the flats so there is no lump. I finish the sanding with 120 grit paper, wax it and surf. Unless you are going to remove the wax when you eventually sell the board, the only person that will know that it hasn’t been glossed and polished is you. This is absolutely the simplest repair, and every surfboard owner should know how to do it.

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  • The delamination of glass from foam can have several different causes:
    • Fiberglass does not stretch. The shortest distance between two points is a straight line. A dent makes the distance between the edges of that dent greater. As the dent increases in depth so does the distance between the edges of that dent. The repetitive pounding in the dent causes slippage in the bond with the foam. The fiberglass, which has little or no elasticity, has no choice but to release from the foam. Now there is an air pocket and the heat of the sun will cause this to swell.
    • Glass weight can contribute to denting. High performance boards typically have a lighter glassed deck than their cruiser counterparts. A lighter glass job and lighter foam is necessary to get the performance that performance driven surfers demand. High performance boards are going to be more prone to denting.
    • Foam weight can also be a source of denting. The less dense foam that is found in higher performance boards is more prone to denting.
    • Heat can cause a board to bubble. Fiberglass begins to soften at around 150 degrees. Its’ bond to the foam begins to deteriorate and is then subject to delamination.
    • Foam spray: Acrylic paint sprayed on foam does not have as good a bond as resin directly to the foam. The difference between the two applications is minimal, but if a laboratory were to conduct a test a clear board will win the bond contest. Color in the lamination cannot be as strong as a clear because the pigment has displaced some of the resin. Pigment has no strength so the amount of strength lost will be the percent of pigment added. However in laminations with color the hot coats are thicker, so there may be no measurable difference in the final product.
  • Some surfers just seem to be harder on their boards than others. If you are one of these, extra caution must be exercised, both at the time of your purchase, and after use.The real problem with delamination is the uneducated public. A customer purchasing a high performance board should not expect it to be as strong as a classic nose rider. Surfers should strip the wax from their boards – at the minimum – with every change of season, if only to keep up with the proper temperature of wax. During this cleaning, a thorough study of the condition of the dents is in order.

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  • Surfboards are very sensitive to heat. Most polyester resin begins to noticeably soften at only 150 degrees. Foam begins to become unstable at about 130 degrees. A dark colored board can reach these temperatures in just minutes. 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 pot holders, 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. Add 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.

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  • 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 and may cause the board to break. 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. Delaminated glass also exposes the board to breakage, as the foam sandwich construction has been compromised.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.

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