Boat Construction Page


	Boat Construction
	USK thanks Shawn Baker, one of our contributing members, for sharing his boat building passion with us. Shawn has written the following regarding boat construction. Shawn is a wooden boat enthusiast. You can visit Shawn's personal web site to see some of his delightful handiwork.
	Click below to jump to a construction material Plastic Fiberglass Kevlar Carbon Fiber Skin-on-Frame Folding Wooden (The Zen of Wooden Boat Building (Video or DVD) available at the USK Store) Plastic Plastic sea kayaks are generally tough, damage-resistant, durable, affordable, and often heavy. Most kayak manufacturers produce their entry-level kayaks in plastic, since it is the most affordable kayak construction material. However, some manufacturers produce higher-performance designs in plastic. These boats are prized by advanced paddlers who paddle in the surf zone or near rocky shores and sea caves. Plastic kayaks are most often made from rotomolded polyethylene(PE.) Variations include crosslinked, superlinear, or blowmolded polyethylene. Rotomolding is a process where polyethylene pellets are fed into a heated kayak mold, and the whole mold is spun and tilted in several directions to distribute the plastic evenly. Crosslinked and superlinear polyethylenes have a slightly different chemical structure than normal, which result in stiffer, and sometimes lighter plastic kayaks. Blowmolding uses the same polyethylene as rotomolding, but a blob of molten polyethylene is injected with hot air into a cold mold. When the blob contacts the cold mold, it cools rapidly and the plastic takes on a harder, stiffer finish. To get acceptable stiffness, plastic boats need to have thicker walls then their composite kin, and are resultingly heavier. PE is much cheaper than fiberglass, carbon fiber, Kevlar fiber, and composite resins, so the resulting boats are also cheaper. Plastic kayaks are highly durable, and will survive impacts with rocks or when dropped that would fracture a composite kayak. Plastic is susceptible to damage from dragging on hard surfaces, just as other kayak construction materials, but will stand up to a lot longer period of abuse than the others. While it can sustain a great deal of abuse and neglect, it is a difficult material to repair. Plastic is also susceptible to distortion due to heat or being tied down too tightly on a roof rack, so keep your boat out of the sun, away from the heater, and use good cradles that don't focus the rack pressure into a small dent-causing area. Plastic kayaks cost from $600-1,800. Fiberglass There was a time when all rigid sea kayaks were made from fiberglass. Now, only mid- to high level kayaks are constructed from fiberglass. Glass kayaks are relatively light weight, stiff, fairly durable, and moderately expensive. Fiberglass is one composite (composite: a combination of two different materials) construction material along with carbon, Kevlar, and other fabrics. Fiberglass is actually the glass fiber fabric that makes up the kayak. Sometimes polyester resin is mistakenly called "fiberglass", because it is the most common type of laminating resin. Polyester resin can be used in a Kevlar kayak without a single strand of fiberglass. Epoxy and vinylester are two other resins that can be used in composite construction. They are tougher, stronger, and more expensive than polyester resin. Most composite kayaks are covered with a layer of "gelcoat." Gelcoat is an opaque, tough, shiny layer of resin that is sprayed into the mold before reinforcing fibers are laid. Fibers are laid once the coating "gels", hence the name. Gelcoat also protects the reinforcing fabrics and resins in the completed kayak from UV light and abrasion. Fiberglass kayaks are either vacuum-bagged or hand-laid. Vacuum-bagged kayaks are produced by laying saturated fiberglass in a mold which is placed in a "vacuum bag" or "envelope." Vacuum pressure sucks extra air and resin out of the laminate resulting in a lighter-weight kayak. Hand-laid kayaks are made without the vacuum envelope, and are often slightly heavier due to excess resin, but are less-expensive because less equipment and labor are required. Fiberglass kayaks can either have thin, lightweight hulls, or thick, tough, heavy hulls, depending on their anticipated use. Glass kayaks are susceptible to damage from dropping or dragging, so treat your glass boat with care. Gelcoat will absorb most minor damage without causing structural harm. These kayaks are easy to repair with fresh resin and glass, provided the damage isn't too extensive. Glass kayaks cost from $1,000 to $2,500. Carbon Fiber Carbon fiber kayaks are extremely stiff, lightweight, beautiful, brittle, and expensive. Carbon fiber isn't used extensively in sea kayaks, but is often used in finer racing and Olympic boats. Carbon fiber kayaks are constructed with the same resins and methods as fiberglass kayaks. Carbon fiber is extremely stiff. This results in a very stiff kayak that doesn't require much hull thickness. This stiffness also results in a brittle kayak that should be treated gingerly. Like fiberglass kayaks, carbon fiber kayaks can repaired quite easily, but the carbon fiber fabric for the repair will cost more. CF boats often cost $2,000-4,000. Kevlar Thanks to the US space program, we have Kevlar as a kayak building material. Kevlar kayaks are stiff, lightweight, yet extremely tough, and expensive. Kevlar is the stuff bulletproof vests and flak jackets are made of. Kevlar is slightly less stiff than fiberglass, but much tougher and lighter weight. Kevlar kayaks are made in the same manner as fiberglass and carbon fiber kayaks. Often, a little fiberglass or carbon fiber will be combined with the Kevlar cloth in a kayak to give a little added stiffness. Kayaks constructed from kevlar are very, very tough. Because the fiber itself is so flexible, the kayak will absorb a serious impact and spring back. A collision with a rock that would hole a fiberglass or carbon boat might result in only cracked gelcoat on a Kevlar kayak. Kevlar fibers are very tough, and difficult to sand or cut, so repairs are slightly more difficult than fiberglass. Kevlar boats cost $2,000-$3,500. Skin-on-frame Skin-on-frame, or SOF boats include both rigid-framed kayaks and foldable kayaks (see below). Traditional Aleut and Inuit kayaks were sealskin over driftwood frames lashed together with animal ligaments. Modern skin-on-frame kayaks are very inexpensive if you build it yourself, lightweight, flexible, fairly durable, and quite pleasing to the eye. Frames are generally made of wood that is glued, lashed, or doweled together, or aluminum tubing lashed together. Skins can be made of canvas, nylon, or polyester, and waterproofed with urethanes, Hypalon, or even house paint! SOF fans feel that their boats have better handling in big, choppy waves, since the frames flex slightly and give with the water, rather than forcing the water to move like a rigid-hulled boat would. A handmade skin-on-frame kayak can be had for $150-300 using your hands, or $1,000-3,000 if built by the hands of an expert craftsman. Folding Kayaks Folding kayaks are easily-transportable, durable, and very expensive!! Popular with world travelers, folding kayaks can be folded into bags the size of a duffel bag and flown anywhere in the world. These kayaks have frames made of wood, plastic, and aluminum. Skins are generally made of nylon or polyester fabric with a Hypalon or rubber coating. Due to the folding mechanisms, size constraints, or the paddling needs of traveling kayakers, most folding kayaks are not produced in high-performance designs. These kayaks command costs from $2,000 up to $4,500 for a fully-outfitted double folder. Wooden Kayaks Wooden kayaks are lightweight, relatively durable, very inexpensive or extremely expensive, and drop-dead gorgeous! Wooden kayaks are built with either marine plywood panels glued together ("Stitch and glue"), or edge-glued softwoods ("Strip-built.") Once the hull shape is defined, they are protected inside and out by one or several layers of epoxy resin and fiberglass. The epoxy and fiberglass disappear when wet, resulting in a beautiful, glossy wood finish. Stitch and glue kayaks can take from 60-120 hours to build, and "Strippers" will require 150-350+ hours. Most wooden kayaks are made by "backyard builders" and can be fabricated for as little as $200 by scrounging your own materials, to nearly $800 for a full-featured kit. Showroom-quality kayaks built by expert craftspeople can cost as much as $4,000-$6,000. Summary It really doesn't matter what type of boat you paddle. Any type of material choice is a tradeoff. You need a boat that will meet most of your needs, with as few of the drawbacks you feel are important. Most importantly, the kayak does not make the kayaker. Just get out and get wet!!

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