It’s been a long time since the majority of boatbuilders abandoned wooden boatbuilding for the faster-to-produce and less expensive material of fiberglass. Because of this transition, a great deal of development has taken place in the area of fiberglass hull construction, as boatbuilders and suppliers have devised ways to use the material more effectively. If any indication of this needed, just compare the brawny thickness of a fiberglass hull built in the mid-1960s, when fiberglass was still a new hull material, to the highly efficient use of fiberglass in a hull built today.
Similar work has gone into improving metal hulls. New anti-corrosion coatings for steel, for example, have made it a much easier material to maintain when used for a voyaging sailboat.
What about building in wood? The great tradition of wooden boatbuilding survives in the custom work of a handful of yards, and there are still interesting wooden projects being launched. And while wood building technology isn’t leaping forward, there is steady development going on, especially in the area of wood composite construction. “At this point in wooden boatbuilding, there is a slow refinement of the techniques and materials,” said Ryan Knight, technical advisor for Gougeon Brothers in Bay City, Mich., which markets West System epoxy products for marine use.
Prospective boat owners who have always wanted a custom-built wooden vessel seek out those yacht designers and boatbuilders that have developed a reputation for building in wood. Designer Bruce King has designed several large wood sailing yachts, including the 124-foot Antonisa, launched in 1999 and the 155-foot Scheherazade, expected to be launched in spring 2003, both of which were built by Hodgdon Yachts in East Boothbay, Maine. King says custom boats are still built using wood because, “the owner believes it is the best way to build a boat.”
The hulls of both Antonisa and Scheherazade have been cold molded: multiple layers of wood strips fitted together and bonded using epoxy. This technique results in a strong, stiff hull. And for owners of these custom vessels, the beauty of wood also enters into the equation.
“One of the big advantages,” King said, “is that every part of the structure can be developed to be aesthetically pleasing. You can’t do that with other materials.”
Tim Hodgdon, owner of Hodgdon Yachts, is a believer in wooden construction. “It’s a fantastic way to build a one-off hull,” Hodgdon said. “It produces a very stiff, high-quality structure.”
Another advantage that epoxy-wood construction offers is a bit more interior space compared to, say, the same boat built of aluminum. “The inside surface is the finished surface,” Hodgdon said of an epoxy-wood hull. An aluminum hull is usually sprayed with foam insulation and then an interior is framed out inside that. So the 155-foot Scheherazade has a thickness of 3 1/2 inches, as opposed to nine to 10 inches for an aluminum hull, said Hodgdon.While the basic concept of cold molding with wood and epoxy used today is essentially the same as that pioneered by Meade and Jan Gougeon in the late 1960s to build iceboats, the techniques and materials have advanced.
“There has been development in coring, in using Nomex cores and foam cores,” said Steve White, owner of Brooklin Boatyard in Brooklin, Maine. “There has been development in the epoxies used. Gougeon Brothers has developed different formulations to improve bonding and the speed of application.”
One way the process of using epoxy is easier for builders is through the use of preloaded cartridges. “We’ve gone to Pro-Set cartridges,” White said. “We don’t have to do the mixing and that improves speed. That’s what boatbuilding is all about — can you do it quickly enough to stay competitive?”
Hodgdon agrees that the state-of-the-art in wood-epoxy construction has advanced. “There are continuous ongoing advancements. There is a lot going on with composite reinforcements, in vacuum bagging, and in epoxy types. We use a hybrid version of Gougeon’s Pro-Set epoxy.” And when you’re building a 155-foot boat, you need plenty of epoxy.
One of the drawbacks to epoxy is its price: the chemicals used to formulate this material are more expensive than the standard polyester resin used for molding fiberglass hulls. And because so much less epoxy is made worldwide compared to the huge volume of polyester resin manufactured, epoxy resin is more expensive. Why not then build a less expensive wooden hull by using polyester resin? The trouble is that while polyester resin is an excellent binder for fiberglass, it performs poorly with wood. Oddly enough, polyester is air-inhibited — it doesn’t cure well with a filler material that contains air pockets. Because there are air-filled spaces in wood, polyester won’t cure properly.
“Polyester has some problems,” said Ryan Knight, technical advisor at Gougeon Brothers. “Polyester is designed to chemically bond to itself, but it doesn’t stick to wood. And it’s brittle; it only works when there is reinforcement.”
Epoxy has a chemical structure that makes it tough and more resistant to failure than polyester resin. “If you start a crack, the epoxy will stop it,” said Gougeon’s Knight. “It won’t allow the crack to propagate.” Both polyester and epoxy are polymers. That is, they are materials composed of light, simple molecules that have been formed into repeated linked units. What makes epoxy such a strong, crack-resistant boatbuilding material is that it is not merely a long chain of linked molecules, but a cross-linked matrix of linked molecules. When the two parts (the diepoxy part and the diamine part) of an epoxy are mixed, they lock arms to form one big molecule. It is this internal structure that lends epoxy its strength and toughness.
The other element in a wood-epoxy hull is, of course, the wood. The workability, beauty and adaptability of wood made it the material of choice for centuries. Scheherazade’s hull, for example, is made of Douglas fir and western red cedar. The wood was supplied to Hodgdon by a small company called Pacific Western Timbers, located in Port Orchard, Wash. All of this wood was cut from old growth trees that have been blown down or fell down in the forests of Washington’s Olympic Peninsula. Peter Wagner, co-owner of Pacific Western Timbers with his brother John, explains that because the trees grow on land that is mostly rock and gravel, their roots tend to spread out and gather nutrients on the surface, rather than sinking deep into soil. “The root ball spreads out instead of putting down a tap root,” Wagner said.
But this doesn’t seem to limit them: they can grow to incredible size, some as large as nine feet in diameter. They may fall when the base of the tree rots, or when a big storm loosens up the ground.
“You have these monsters hanging out on the hillside and a wind storm comes along and topples them. Sometimes one will push others and a slide will occur,” Wagner said.
Often the fallen trees will have been down for years when Wagner finds them. According to Wagner, the wood often will get covered with moss and dropped material from standing trees. Since these are dark forests that don’t get much sunlight at ground level, the covered trees get wet and then never dry out. The wet material keeps oxygen from getting to the wood, and parts of a downed tree will stay rot free for years — sometimes for decades.
“Nothing is set in stone,” Wagner said. “But [a downed tree] could be lying there for 10 years or even 50 years. Given the right conditions, a red cedar log could be preserved for hundreds of years.”
To recover this wood, Wagner and his crew go into the forest and assess the downed trees for the quality of their timber. They determine the best harvesting techniques and extract the useable logs, abiding by state and federal environmental laws. Sometimes the log removal is done using big, twin-rotor chinook helicopters, due to their heavy lift capability. “That’s where the difficulty comes. You have to calculate the weight to be able to pick them up,” Wagner said. When log length needs to be preserved, Wagner and crew will rip the logs lengthwise in the woods before they are flown out.
The logs are stored at Wagner’s Port Orchard facility and only cut when Pacific Western has an order. “Everything is custom cut,” Wagner said. Wood from Wagner’s company is used in residential and commercial construction, in historical yacht restoration, and in building the hulls of custom one-off yachts like Scheherazade.
The first layer of Scheherazade’s hull is vertical grain Douglas fir, 7/8-inch thick, running longitudinally. This is followed by four diagonal layers of 7/16-inch western red cedar. The final layer is more 7/8-inch thick Douglas fir, again set up longitudinally. The final outer layers are two layups of fiberglass cloth and epoxy. This fiberglass jacket is important both for abrasion resistance and because it provides, according to Tim Hodgdon, “a cosmetic scrim” on which to put down the final paint layers.