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Modern Wood/Epoxy CHAPTER Composite Boatbuilding 2 This chapter is new to the 5th edition. It presents an overview of the shift in design, materials, and fabrica- tion techniques made possible through using wood/epoxy composites. The Shift from Traditional Boatbuilding The Gougeon Brothers on Boat Construction: Wood and WEST SYSTEM Epoxy focuses on boat construction in which wood and WEST SYSTEM® epoxy are used as the primary engineering materials. Mating wood with WEST SYSTEM epoxy forms a composite that has physical characteristics superior to either component by itself and is stabilized from the effects of moisture. Thus, wood/epoxy composites become a material which has significant advantages for boatbuilding. The new fabrication techniques depart in significant ways from traditional boatbuilding. Traditionally, wood has been viewed as a dimensional material, each piece seen as a finite building block. To build a boat, you took boards and planks and shaped, fit, and assembled them with fasteners. Traditional boatbuilding evolved as a set of building techniques and material choices informed by centuries of experience in the unforgiving marine environment. It revolved around two things: l. Thematerialproperties,rotresistance,anddurability of wood species. 2. The mechanical fasteners used to join components together. Inherent in traditional boatbuilding is equilibrium in the choice of wood species and the techniques used to assemble wooden parts into a boat. That equilibrium was disturbed by the introduction of new coating and adhesive technologies during World War II. By the 1960s, the use of wood as a boatbuilding material had declined rapidly, victim to its susceptibility to rot, peeling paint, instability, swelling, and warping. The introduction of epoxies for boatbuilding between the 1960s and the 1980s radically changed this. The development of wood/epoxy composite structures revolutionized the use of wood as an engineering material. Whereas traditional boatbuilding approached wood as a dimensional material to be shaped, fit, and assembled with fasteners, wood/epoxy composite con- struction approaches wood from a different perspective. It views wood as a fiber that can be bonded with epoxy into the shapes and forms needed for boatbuilding. Thus, wood can be used as a reinforcing material like fiberglass. But unlike fiberglass, which has little struc- tural value until it is incorporated in resin, wood fiber is an excellent structural material on its own. As a result of the use of epoxies, designers and builders now have great latitude in the diverse and creative ways to approach design, materials, and fabrication. The introduction of new coating and adhesive technologies allowed boatbuilding to draw on aircraft construction techniques and the broad use of non-wood materials such as foams and fabrics. Builders are no longer bound by the durability of particular wood species if they can coat wood for moisture protection. They can eliminate the high point loading of traditional fasteners if they can spread loads over large surface areas by gluing. So the modern boatbuilder is no longer limited to traditional wooden boatbuilding methods based on durability of wood species and construction details based on fastening techniques. He or she can choose woods based on a wider set of mechanical properties and construction details based on adhesion and effec- tive coating maintenance. Using wood in a composite with epoxy makes the most of wood’s structural advan- tages and overcomes its limitations. Epoxy Resins Epoxy resins are a broad family of materials, which are among the most versatile of thermoset plastics. Like polyesters, epoxies begin an exothermic polymerization reaction when resin and hardener are mixed. They then thicken, get tacky, and, when the reaction is complete, form a hard, solid plastic. Unlike linear chain polyesters,PDF Image | Gougeon Brothers on Boat Construction
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