SECTION IX C - COMPOSITE CORED CONSTRUCTION

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Many high tech one-off custom boats are built with epoxy resin and exotic fabrics such as Kevlar and Carbon Fiber laminated onto cores of vinyl foam, balsa, or thermoplastic honeycomb. Phase Two epoxy is System Three Resins’ preferred material for this type of construction. These boats are built on male or in female molds in a variety of ways.

The chief structural difference between this and more common wooden boat construction is that in wooden boat construction the wood acts as the “core” and is structural. The fiberglass/ epoxy skins protect the wood against the elements rather than strengthen the wood core to any great extent. In composite cored construction the opposite is true. The skins carry most of the structural load and the core, by separating the skins, provides stiffness and enables the builder to produce a very strong, lightweight hull. This not so obvious difference dictates very different requirements for the matrix resin used. A resin well suited for a wooden boat will not be good for a composite cored hull. Those who tout their products for both types of construction are robbing Peter to pay Paul and penalizing builders of both types of boats in the process.

Almost all serious racing sailboats and powerboats are composite cored. The materials used to build these boats are expensive. Generally, the lighter the hull the more it costs. Lightness comes at a high price if strength is also a requirement. The reason for the extreme push towards lightness is that with limited horsepower (sail area or engine size) a lighter hull will move faster.

Proper design and engineering of these boats is essential if they are to be lightweight and still hold together. Because the materials used in composite cored construction are exotic and expensive a proper shop with the right environmental control is a must. These hulls are almost always postcured. That is, after the laminate hardens the entire hull is raised to an elevated temperature for several hours to finish curing the matrix resin. Phase Two epoxy requires this post cure to achieve its ultimate properties and it is folly to use a product like Phase Two unless it will be post cured.

If you are interested in learning more about composite cored construction ask for System Three Resins’ publications “Two Phase Epoxy Systems for Composite Cored Construction” and “Using Phase Two Epoxy Resin”.

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