Dugout Boats After simple rafts and reed barges, dugouts are man's most ancient form of boat. They are also the most unstable unless fitted with one or more outriggers. The scarcity of suitable trees has led to a decline in the number of new dugouts being built and the skilled labor to select, fell and hollow out a suitable large tree is not being passed on to new generations. The process of hollowing out a log is appropriate only in areas where there is an abundance of timber as it is an extremely wasteful way to harvest timber. Generally softer timbers are preferred as this makes the work of hand carving the hull much easier. The disadvantage of using lighter timber is that it is not durable and it is common for dugouts to be serviceable for only 5 years, or less. Failure is normally caused by cracking of the ends of the canoe where very soft sap wood forms these highly stressed components. Dugouts are rarely decked and the crew must bail constantly to keep the water level down. Traditional dugouts are often highly refined and they can perform well. The structures can be reasonably light as they are designed to be paddled or sailed down or across wind. "Modern" dugouts are heavy because the hull must be thick enough to deal with the stress imposed by powerful motors and beating into head seas. Often dugouts are modified with planks added to offer higher freeboard and ribs bolted in place to support these planks. Steel nails are used and these corrode rapidly causing what is know as "fixing sickness".

			Planked Boats True  Eastern traditional boats used only hard wood pins to secure panks both to each other and to frames. Western or European boat building relied on copper or bronze fixings to avoid fixing sickness but these materials are very expensive or simply not available to artisanal fisher communities. Even galvanized steel is almost impossible to find and boatbuilders use cheap electroplated "boat" nails or mild steel bolts. The result is predictable and very wasteful of both timber and human resources. Boats must use very thick planks because the fixings are prone to corrosion. The hulls become heavy and need more power to drive them. This in turn only increases stresses on the hull and the fixings. "Modern" planked boats in Indonesia generally last less than 7 years and they perform poorly at sea. Well built traditional boats can be found in a few parts of the country but timber shortages and rising fuel prices are likely to see a loss of boat building skills and a deterioration of quality. Some traditional builders are finding they can build and market pleasure boats and this may keep ancient skills from disappearing totally. Unfortunately most fishing communities can no longer afford the large engines and high fuel consumption needed to keep heavy planked boats at sea. image courtesy of Australian artist Pete Tillack

			The most popular material for pleasure boat building worldwide has not enjoyed universal success in developing nations fisheries. While the material lends itself to production moulding to produce large numbers of identical boats with a high standard of surface finish, the material has many structural and performance limitations that have resulted in a mixed reception by Artisanal fishermen. GRP is made from 100% imported materials and is subject to import duties and taxes as well as merchants mark-ups. The result is that GRP in developing nations is often over twice as expensive as in industrialized regions. The high price tends to result in boat builders trying to combine wood and plywood into hulls to reduce the volume of imported material and to reduce skin thicknesses to dangerous dimensions. The resins used to bond the glass fiber in GRP are not waterproof and over time the laminates soak up water and rot any timber reinforcing. The boat becomes heavier, flexes more and gets weaker in a matter of months or at best a few years. Many GRP boats are built in backyard situations and there is no attempt to control moisture content of materials or to ensure low humidity during the laminating process. The result is that moisture is trapped in the laminate reducing bond and hence compromising the final strength. Laminating techniques are almost always "low tech" and this results in very high resin to glass ratios. This makes the composite heavy, weak and brittle and wastes expensive resin. Repairs to GRP boats are simple in principle but are rarely carried out correctly. Power grinders are usually not available and often materials sold to fishermen are dumped because they are old or substandard. The catalysts used in Polyester resin are very toxic and there is evidence that the fiber dust that results from the use of power tools and surface sanding is a serious health hazard. High temperatures make if very difficult to enforce the use of masks, goggles and filters as they are very uncomfortable. Skin irritation and discomfort make working with GRP an unpleasant job and it is likely that long term exposure may cause cancer in some workers. GRP production of components for fishing boats may still prove to be the most appropriate method in some situations but an air-conditioned space will be required to minimize the hazards outlined above. Large scale fabrication of boats using GRP is not considered appropriate nor feasible given fishing communities limited buying power and access to credit.

			GRP Sheathing over Planked Boats Catastrophic failure of GRP boats is common and traditional boat builders prefer to use it as a sheathing over a conventional planked boat. Even in these cases, the sheathing is never applied to dry wood and thicknesses are inadequate to deal with the stressed of expansion and movement of planks. Polyester resin forms a very poor bond to anything other than itself. It traps fiber mechanically in composites rather than bonds. The bond between the sheathing and the hull relies on steel cladding nails and these corrode away in a few months. Failure occurs at seams usually results in the force of the water peeling off large sections of GRP away and boats often then face foundering due to the large volume of water that passes through open plank seams so exposed. Maintenance of the timber planking and caulking of seams is impossible so these boats can be considered to be time bombs that have a much higher chance of drowning the crew than do traditional planked boats. Sadly the method is often used to extend the service life of an exhausted planked hull and this is a very poor investment with an even shorter fuse.

			Plywood is a sandwich of wood veneers and filler material held together by adhesives. There are many grades of plywood, but generally, marine plywood made with a waterproof adhesive is required for boatbuilding. Lower grade plywoods can sometimes be upgraded for marine use if they are coated with a polyester resin. Plywood is very adaptable to small boatbuilding operations. It is light, can be cut to any shape, and is easily bent. Since sections are cut from large plywood sheets, there are fewer seams than in planked boats. Plywood construction involves building a framework for the hull from planks and then attaching sections of marine plywood to this frame. The plywood hull is held together by nails; marine glue is used to seal the seams. Plywood boatbuilding can be quick, inexpensive, and easy. As long as the surface, and especially the edges, of the plywood are treated with epoxy resin or another sealer, the boat will have a long life. However, the use of plywood does restrict the hull to hard chine shapes, such as flat or V-bottomed boats. Moreover, its resistance to chafe is not high. Plywood skiffs have wide acceptance throughout the world as inexpensive, rugged work boats. In southern New England (United States), plywood skiffs are extremely common and are used for lobstering, trawling, and gill netting. With good waterproof adhesives, these skiffs can have a 15-year service life. Marine plywood is also used in the stitch-and-glue technique (figure 1.7). Precut sections of plywood are wired together with galvanized wire; the seams are then sealed with epoxy resin. The final connection is made by bonding the epoxy resin glue with glass fiber. Once the resin has set, the wires can be cut and a finish applied. The product can be a strong, light boat with a life expectancy at least as good as traditional timber vessels. Boat construction by this technique is easy and fast. PrecutD sections of marine plywood may be assembled in a village workshop without sophisticated equipment. Skilled carpenters are not required, but it may be necessary to import the epoxy resin and glass fiber. This boatbuilding technique has been introduced at the Muttom Cooperative Boatyard in Tamil Nadu, southern India, in cooperation with the Intermediate Technology Industrial Services of England. A number of different designs have been constructed to satisfy coastal conditions, crowded beaches, and the need for more space to carry nets.

			Wood Laminates The Gougeon Brothers of Bay City, Michigan did the pioneering work on cold molded wood epoxy composites used in boat building. They also did research and developed components for other cold molded epoxy-based laminates used, for example, by National Aeronautical and Space Administration (NASA) in research programs on wind generator blades. Their NASA research proved that cold molded wood/epoxy composites are not only very strong but also competitive when cost is a factor. Natural fibers such as wood and bamboo behave differently than manmade fibers such as fiberglass. Wood (and bamboo) have degrees of structural integrity before resin impregnation whereas fiberglass does not. The Gougeon Brothers proved that wood fibers used as reinforcing material in advanced structures will show high stiffness, very high strength-to-weight ratios and excellent fatigue resistance.  They report, “Wood (epoxy composites) may begin with less ultimate strength than either carbon fiber (epoxy composites) or fiberglass (polyester) composites, but it (wood) maintains a higher percentage of its original strength through a million (fatigue) cycles than either of the other materials . . .. At 3.5 million average fatigue cycles, the polyester (fiberglass) laminate retains less than 19% of its original strength.” Boat structures have to take hard knocks. They are pounded by waves and suffer rapid reversals of load from tension to compression.  They bang up against rocks and reefs and shore. They are dragged up beaches,  stomped on, jumped on and landed on.  They are fried by the sun sometimes over 150F. on the exposed surfaces and then chilled by cool sea water. All these factors causes flex or differential movement and that in turn causes fatigue.

				Bamboo Laminates The fiber of preference in US and European veneer laminates tends to be wood. Little experimentation with bamboo in laminates occurs in the United States. One reason, of course, is relative unfamiliarity with bamboo on almost any level. A second has to do with availability of bamboo to work with. Some work, however, has been done in Asia. Bamboo plyboards and chipboard have been or are made in China, India, Vietnam, Indonesia and the Philippines with varying degrees of success and achievement of market position. These products have, for the most part, been made with urea-formaldehyde and phenolic adhesives that require heat and pressure. These substances are known carcinogens and therefore allegedly dangerous to workers and end users.

			Combinations Combining wood veneers and bamboo shows great promise. Denser bamboo has enormous tensile strength so it can be bonded either side of less dense timber or on the external layer of the hull skin for ease of finishing and fairing.

			Wood Core Materials Surian or Indian Cedar/Burma Cedar/Philippines Mahogany is readily available in West Sumatra and the resource is harvested by mountain villages for domestic consumption. Very little is exported and the difficult terrain makes extraction by manual labor the only option. It is fast growing and being widely replanted in highland low grade cleared land and so it will be available long term. Here is an extract from a tropical timber blog <http://www.nafi.com.au> that sheds some light on its properties: According to our information, surian is another name for the timber more commonly known as calantas (also spelled kalantas). Calantas is a true cedar, the same as South American cedar, Queensland red cedar, etc. These true cedars have a similar durability (rot resistance) to western red cedar, but may be a little more prone to cupping during drying.  Surian is a fine furniture timber, but we have little data on its durability (rot resistance) when it is exposed to water. In the absence of specific data, we would expect it to give similar service to Australian red cedar which has a good reputation for durability. (The two are similar botanically, ie. Cedrela species). If you are using the wood epoxy saturation technique (WEST), or some version of it, then the durability of the timber is not so important. Likewise, if the boat is taken out of the water after use and stored under cover, then the durability of the timber is less important. In any event, we would be expect surian to give similar service to mahogany. Surian is readily available but will need to kiln dried carefully and of course it must be encapsulated in epoxy.

			Curraghs are among the most ancient vessels and their use by artisanal fishers is restricted to Eskimo tribes in remote parts of Alaska and Siberia. The building method is only suited to small craft and it evolved in areas where timber was precious and scarce. Modern fabrics used in tensile structures have overcome many of the problems that limited the popularity of curraghs and there now a growing market for portable framed boats that can be assembled or disassembled for portage or storage.  Modern curraghs are light and easily powered by sail or small engines and have proven to be very seaworthy fishing platforms.

			The only successful use of high performance marine grade aluminum for Artisanal fish boats has been in Samoa. The FAO designed "Piah" was originally made using alloy hulls and timber crossbeams and decks. More recently the boat builders have switched to stitch & glue plywood and epoxy methods to reduce costs. The high price of marine grade alloy makes it unlikely to see wide use.

			Polyethylene powder can be loaded into a fully enclosed metal mold which is then rotated at low speed and heated in an oven. The plastic melts and the rotation coats the inside of the mould. Thickness can be controlled by varying the amount of powder or by using foaming PE additives. Local thickness can be controlled  by tilting the mould on its axis while rotating or by changing the speed of rotation or the temperature. Boat hulls can be produced very quickly using this method. The largest PE boats in production to date are made in Jakarta in a factory built with the help of the NZ team who perfected the techniques required to achieve bonding between the opposite skins in the mold ie between the outer hull and the internal floors and stringer beams. One mould can produce 3-4 boat hulls per day (one shift) and this does help to offset the substantial investment required in plant and equipment. The biggest cost is the design, fabrication and trail-and-error modification of the metal molds for the boat hulls. To date the largest boats possible are 6.5m overall in length and naturally the manufacturers have focused on the most lucrative markets first. Speed boats for government agencies are now produced at prices that are substantially higher than poorly built Indonesian GRP boats but somewhat less than GRP boats built in other countries in the region. The key issue is to ensure that the volume of sales is very high to recover the development costs. Over time costs will be reduced as more is learned about the design of these new "one piece" boat hulls. Once the design challenges have been overcome and prototypes modified for optimal performance, PE boats have many advantages. The impact resistance of PE is enormous and the material is virtually maintenance free. It does not need painting and is self lubricating when dragged over rocks or reef. It can be abraded over time but hull thickness is normally greatest in the areas where contact is most likely (along the keel and chines) If the boat is damaged beyond repair, the material can be recovered, ground to powder and recycled. Repair is possible using plastic welding tools. Training and investment in the equipment are needed to support any large fleet of PE boats. Transport to remote areas is another inherent disadvantage with this method at least until the manufacturers recover the R&D costs to date and decide to build smaller production facilities closer to markets in West Sumatra. The transport cost for boats recently delivered to Padang exceeded Rp3,000,000 per boat based on stacking 3 boats on one truck. Recent fuel price rises will cause a dramatic rise in freight costs. The boats are heavier than new GRP boats but they do not absorb water. Keeping water out of the cavity between the skins is more difficult than expected because every time a fitting is screwed or bolted into the hull a potential leak is created. The material floats and the double skin concept makes the construction of near unsinkable boats feasible. The weight of the boats and their flex makes them safe and fairly comfortable at sea but the boat designs to date all require large powerful outboards and correspondingly high levels of investment and very high running costs.