Patent Application
20070218787
This invention relates to surfboards and similar recreational boards for water sports. More particularly, the present invention relates to high strength, lightweight, durable surfboards and to the construction of such surfboards.
The popularity of surfing and water sports in general has increased significantly in recent decades and includes not only the use of surfboards but also body boards, water skis, and wind-surfing craft. Because of the increased interest, the demand for improved construction has likewise increased. Accordingly, one general object of this invention is to make a lightweight and durable surfboard so that the rider will have a board that lasts longer and will enhance his performance on the waves.
The first surfboards, it is believed, were originated by Polynesians and were made of wood from trees found on their islands. They were carved and shaped by hand and stained and finished with natural oils. The early boards were 12 to 20 feet long and weighed 100 to 200 pounds.
Before the days of widespread availability of polymeric materials and fiberglass, surfboards continued to be constructed of wood, particularly lightweight wood, which was laminated in order to provide strength; that is, a board of wood that was advantageously lightweight usually would not have sufficient strength to withstand the force of waves if it were constructed from a single piece of wood. Subsequently, laminated wooden boards and then molded fiberglass boards appeared. Next, fiberglass covered surfboards were developed having lighter weight and enhanced performance. Wooden board cores began to be replaced by lighter weight polymeric foams, particularly polyurethane foam cores. However, foam cores alone did not possess enough material strength to maintain the structural integrity of the board for long periods of strenuous use and, consequently, the foam cores required additional structural support which, in some designs, was in the form of wooden stringers to provide the necessary strength for a successful board. Unfortunately, this type of construction limited the number of designs that were sturdy enough. In addition, foam surfboards generally did not last more than a season or two with frequent use. One drawback was that an air bubble tended to form between the fiberglass and the foam thus destroying the structural integrity of the board.
One example of a surfboard body molded around a longitudinal stringer is shown in U.S. Pat. No. 4,798,549 to Mark Hirsch.
Another construction for strengthening the core is shown in U.S. Pat. No. 5,514,017 to William J. Chimiak wherein the core is a honeycomb of a polyamide for increased strength and rigidity. The Chimak patent mentions the application of multiple fiberglass scrim covers and also mentions that reinforcing carbon filers may be woven in the scrim.
Still another honeycomb construction is shown in U.S. Pat. No.6,800,006 B1 to Mark T. Itnyre, et al. Longitudinal reinforcing stringers are shown in this patent. Another design using fiber reinforced resin on the top of a board is described in U.S. Pat. No. 6,790,402 to Richard Greven.
A patent showing a multi-layer core construction reinforced between layers and having longitudinal stringers is U.S. Pat. No. 5,944,570 which issued to J. Randolph Appleby. The foregoing mentioned patents show the desirability of the longitudinal reinforcement of a surfboard. These prior designs can provide high performance and a minimum weight of five to eight pounds, high strength, tough dent and puncture resistance skin, strong side rails, and an attractive high gloss finish with a slick surface to enhance speed: The designer's goal is to provide all these features at a relatively low cost. Another general object of the present invention is to provide an improved surfboard incorporating the desirable features described above.
A further object of the present invention is to increase the strength of a fiberglass covered surfboard while keeping the increased cost to a minimum.
Still another object of the present invention is to provide increased strength of the surfboard without adding to the weight of the surfboard.
The foregoing and other objects of the present invention can be appreciated by the description below under the heading Summary of the Invention.
In one aspect, the present invention is a surfboard or similar recreational board for surfing and other water sports which comprises an elongated, shaped core, said core having an upper surface, a lower surface, and a longitudinal axis; a skin or skin layers completely covering said core, at least one skin layer comprising a woven fiberglass fabric having a multiplicity of reinforcing strands woven into said fabric and extending the length of said board parallel to the longitudinal axis, said strands increasing the rigidity and strength of said board. The core of said board is preferably a foamed polymer which may be polyurethane or polystyrene. The core may be of a honeycomb polymeric construction or a light weight metal honeycomb such as aluminum; or, it may be wood, a wood laminate, or foam and wood composite. The skin is preferably adhered to the core with a polymeric resin, the bottom of the core having at least one skin layer and the top or deck having at least one of the reinforced skin layers and preferably a plurality of such layers.
The fiberglass skin fabric is woven from either a C or E fiberglass and the reinforcing strands may be either S Glass, S-2 Glass, quartz, carbon or aramid fibers or may be a blend of these fibers with each other. In general, S-2 Glass or quartz reinforcing strands are preferred for their bright white appearance and ability to be woven readily with other glass fabrics.
The multiplicity of reinforcing strands define a band having a preferable width from about six inches to about twelve inches that extends the length of said core when the skin is applied to the core. Rather than a band, every other longitudinal strand may be a reinforcing strand.
In another aspect, the single central band of reinforcing fiber may be divided into two bands, one on either side of the longitudinal axis that continues to the respective edges of the board; or, four bands or more may be used. In addition, transverse reinforcing bands may be incorporated in a skin layer. There may be one central band about midway of the surfboard or there may be two bands, one at about one-third the length of the board and the other positioned at about two thirds of the length of the board.
In a still further aspect, a skin with a multiplicity of reinforcing strands may be positioned only on one surface of the board which may be either the upper or lower side.
In yet another aspect, a multiplicity of bands may be positioned on both the upper and lower surfaces of the board. There can be more reinforcing strands on the upper surface than on the lower or vice versa.
These and other aspects of the invention can be further appreciated from reference to the description of the drawings and detailed description which follow.
The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings which form a part of the specification and are presented by way of illustration and not limitation and wherein:
In a typical or representative process of forming a surfboard, the foam core or blank is formed in a large, cement mold roughly the desired shape of the finished surfboard. The mold is constructed in two halves, and the two halves are clamped together and heated. Liquid polyurethane containing a foaming agent is introduced into the mold, the heat initiates the foaming reaction, and a dense, white foam is produced. After the foaming is completed, the mold is opened and the foam core is taken out and allowed to harden. Once the core is hard, it is cut in half vertically from the nose to the tail. A thin wooden stringer is glued between the two halves. The core is then clamped back together to dry. The stringer provides longitudinal stiffness and strengthens the board.
Next, the outline of the finished board is traced onto the rough core and the outline is cut out with a saw. Starting with the bottom of the core, the surface is smoothed and contoured to its final shape with a planer. When the bottom is finished, the board is turned and the top is shaped. A sander removes any ridges left by the planer, and the stringer is contoured with a plane. Rough sandpaper is used to shape the sides, or rails and then the core is given a final sanding with fine paper. The shaped core is now ready to be covered with fiberglass and resin to form the hard, outer shell of the surfboard. First, the core is blown clean with compressed air. If the board is to be colored or have a design on it, paint is applied directly to the foam with a spray gun or airbrush. When the paint is dry, fiberglass cloth that forms the skin is laid over the surface of the core and cut to fit. The top of the board, or deck, is laminated first. A polyester laminating resin, is mixed with a catalyst. This initiates cross-linking that will cause the resin to harden in about 15 minutes. The resin is poured over the fiberglass and spread evenly. All of the fiberglass must be covered without leaving too much or too little resin in any spot. When the deck is finished, the board is turned over and the process repeated on the bottom. The board is then turned once more, and the deck is given a second layer of fiberglass and resin for added strength and wear resistance. The laminating resin remains slightly tacky and rubbery when dry. Additional skin layers may be applied at this point if desired.
A second coat of resin or filler coat or sanding resin, is applied next. The filler coat fills any surface imperfections left in the laminating resin. Sometimes, this coat is called a hot coat resin and contains wax and contains a slightly different polymer mix which causes it to harden completely. The deck is coated first and then the bottom. When dry any excess resin is carefully sanded away. After sanding the board is blown clean with compressed air to remove any residual sanding dust. A final coat of gloss resin is then brushed onto the board. Like the other two layers of resin, this final gloss coat is mixed with a catalyst and will harden within about 15 minutes. After the gloss coat has completely hardened, as a final step, the board may be wet sanded with very fine sandpaper, then rubbed, buffed, and polished.
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A comparison of typical compositions of glass and quartz is presented in Table II below:
As can be seen, quartz and S Glass have about twice the tensile strength of E glass but the cost difference is significantly greater. Accordingly, one of the objects of the invention is achieved by using the higher strength material in a band down the center of the surfboard where it is more effective in adding strength and controlling the rigidity of the surfboard. The cost is lower since the higher price material is used only where it is most effective. Carbon fibers may also be used but their cost is even higher. The quartz and glass fibers have the most attractive appearance. Some manufacturers weave carbon fibers uniformly in a fabric but this tends to increase the cost and the carbon detracts from the appearance of the material. Applicants' invention lowers costs and maintains attractiveness.
In all of the embodiments, the surfboard core may be covered with a fiberglass scrim before the outer cover is applied. The first layer may be provided with the woven center band and the outer layer may also be provided with or without such a band. The woven fiberglass with the high strength fiberglass bands gives the board an attractive bright, white appearance and is a preferred material.
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Although the above description applies to surfboards, windsurfers, sailboats, water skis and other boards for recreational or water sport use, it will be understood that the invention is not limited to such applications as modifications may be made by those skilled in the art particularly in light of applicants' foregoing disclosure. Therefore, such modifications and embodiments may be made to be included within the spirit and scope of the following appended claims.
