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WEST SYSTEM epoxy and our wood/epoxy boats |
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What does it mean when we say, "Built with WEST SYSTEM® epoxy?" |
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WEST SYSTEM is the brand name for marine epoxy products produced by Gougeon Brothers, Inc. These products include the base resin, several hardeners with differing properties, fillers, and supplies. We use WEST SYSTEM epoxy products exclusively in our shop. We use these particular products because we think they are the best epoxy products for wooden boat building.
Epoxy resin, as pioneered by the Gougeon Brothers, has revolutionized wooden boat building. Modern wood boats, built with new techniques and incorporating epoxy resin systems, are now more durable and require less maintenance than fiberglass boats. These modern wooden boats are sometimes called "wood/epoxy boats" or "WEST SYSTEM boats." I will attempt to briefly explain some salient points about the modern wooden boats we are building. Wood as an engineering material Wood has several physical properties that make it an excellent choice for wooden boatbuilding. Stiffness, light weight, and resistance to fatigue give wood advantages over other materials for boatbuilding. However, wood also has disadvantages. It is subject to rot, it shrinks and swells with changes in moisture content, and it loses some of its strength and stiffness with increasing moisture content. All these disadvantages are related to the absorption of moisture by a boat's structural members. If we can keep the moisture out of those structural members, all these disadvantages go away. We use epoxy coating to keep the moisture out.Why our wood boats don't rot For wood to rot, it needs three things: a particular moisture content, a range of temperature, and oxygen. Over the range of temperature we have no control. However, we can use epoxy coating to keep the moisture and oxygen out. We use only kiln dried wood in our boats. Kiln drying will bring wood down to a 6% to 8% moisture content. Wood only rots at about 20% moisture content. That's a lot of water that would have to enter the wood to bring it up to that moisture content. With our epoxy coating and careful construction techniques, we can keep the moisture content very close to the content it had when we epoxied it. Even if there were to be some breach in the coating, that would only be a local breach. Damage to the boat would be confined to the immediate area, allowing time for repair without any real damage occurring. Rot will not be a problem if you get the damage repaired within a reasonable time. That said, we have never had a case of rot in any epoxy coated boat we have built. None. Part of the credit for this must go to our clients, who love their boats and take good care of them.Keep it still The second disadvantage mentioned above is the way wood can shrink and swell. Epoxy coating prevents that from happening by keeping the moisture content nearly constant and at a low level. Seasonal changes or travel can cause small variations in moisture content, but these are minor. The wood stays where we put it. Seams don't crack. Paint doesn't peel. More importantly, glue lines don't fail. Glued joints are the secret to propagating stress properly through the structure without failure.Strength If we are to use wood as an engineering material, we also must have some solid numbers we can assign to it for compressive strength, tensile strength, sheer strength, and stiffness. We need it to be as strong and stiff as it can reasonably be. We use kiln dried wood that is dried to a known moisture content. Thus, we know how strong the wood is, when we purchase it. Before we incorporate each member into a boat's structure, we epoxy coat it. Then we know it will keep that strength indefinitely.Stiffness It's relatively easy to make a boat strong enough. We only have to use enough material to provide an adequate safety margin against material fatigue and unforeseen loads. Beyond this, the strength of the material becomes unimportant. Stiffness, however, is always important. Stiffness is the ability of a structure to resist deflection. Stiffer is better. The stiffer a boat is, the less it will fatigue, and the more solid it will feel and sound as it moves through the water. Generally speaking, the strength and stiffness of a hull can be increased by increasing skin thickness. Unfortunately, weight also increases with skin thickness, so that skin weight alone becomes the major factor in determining overall boat weight. The primary goal then is how to gain maximum stiffness with the least amount of weight. The answer is to begin by using wood. We continue by using craftsmanship. Because our custom wooden boats are built piece by piece, we can incorporate relatively complex construction techniques like our stringer frame system of hull and deck construction. This further increases hull and deck stiffness and saves even more weight. Wood fiber alone is a good structural material for boatbuilding. However, it has limitations which are overcome by mating wood with epoxy resin to form a new composite material.How we use WEST SYSTEM epoxy We use these products in five basic ways:1. As a glue. Our boats are almost entirely glued together with WEST SYSTEM epoxy. I say "almost" because wear members like skegs, skids, and guards are installed with a marine bedding compound so that they can be more easily replaced if necessary. 2. As a coating. We epoxy coat our boats inside and out. In our dories and work skiffs, epoxy coating is an option. In our V-bottom boats, it is standard. Epoxy coating keeps the wood dry. 3. In combination with fiberglass. This is really just a way to make the coating very thick and strong. We glass the outside of our V-bottom hulls, decks, and cabins. Glass and epoxy is an option on our dories. 4. As a putty. We add fillers to the epoxy resin and hardener mix. We fill screw holes, build up corners, and use it as fairing putty. We very seldom have to use fairing putty, since our boats are built almost perfectly fair to begin with. 5. For fillets. We add fillers to produce a filleting putty which we sometimes use to join plywood panels. Since our boats are fully framed, we seldom use fillets, but they do come in handy for building iceboxes and things of that nature. |
We are located on the Snohomish River in the Pacific Northwest, about 20 miles north of Seattle.
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