Wooden Boats
(Updated on 16/03/07)


Wooden Boats UK

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Not surprisingly there are a number of different building techniques used by wooden boat builders, each with distinct advantages.

From Dugout Trees to Cold-Moulded Racers

The first wooden boats were built by our distant ancestors, who built watercraft by shaping and hollowing logs, with the aid of fire and simple stone tools. Over time these wooden boats were improved, with planks added to increase the boats' capacity and seaworthiness. From such simple beginnings a fascinating variety of wooden boats evolved, but all shared several features; planks were edge fastened, typically with pegs or splines, and each was unique in shape, with the boat's form determined during construction through a combination of tradition, the builder's skill, and the nature of the wood available. Prior to the widespread use of fibreglass, such edge-fastened craft accounted for most of the world's small, locally built fishing and trading craft. The technique is still in use today in some remote areas, with boat builders who have never set eyes on a designer's drawings producing lovely, seaworthy wooden boats.

Several wooden boat builders in northern Europe developed the edge-fastened vessel to the utmost, using thinner planks and lapping them to provide extra strength. The Norse longboats proved themselves over the centuries on the rough North Sea, and the building technique has stood the test of time as well, remaining essentially unchanged as today's lapstrake planking. As capable and beautiful as they are, lapstrake boats do have some limitations, among them constraints in the boat's shape, and the difficulty in building really large boats.

Today's wooden boats are almost universally built to carefully drawn plans, but the tradition of smooth hulls with edge-fastened planks lives on. Strip planking, where nails and glue join the planks, and a keel replaces the original log, is the modern equivalent.

Larger Wooden Boats

As European trade and military forces expanded some 500 to 600 years ago, so did the demand for larger and more burdensome vessels. It led European builders to develop a construction technique where each plank was independent of the next, being supported by an internal skeleton rather than by the adjacent planks. This revolutionary technique was adopted for use in smaller craft, and came to be known as carvel planking. Among other advantages, it allows the builder to maintain precise control over the shape of a boat during construction. The majority of wood boats afloat today are carvel planked.

Modern adhesives such as resorcinol and epoxy have led to new construction methods, including the use of plywood for planking, and cold-moulding, where thin veneers are glued together to form the boat's skin. These, together with strip, lapstrake and carvel planking, form the five most common methods of building wooden boats, and, more than likely, any wood boat you encounter was built using one of them. There are many variations in how wooden boats are constructed, even if we restrict ourselves to one basic method, such as carvel planking. But one of the most important distinctions between wooden boats remains the way in which the planking is fastened. Is it fastened only to the framework, as in carvel planking, fastened to the framework and its neighbouring planks, lapstrake and strip planking, or glued up from thin veneers, creating an almost one piece hull, as in cold-moulded and some modern plywood hulls? This is important not just from the standpoint of building wooden boats, but also largely determines how repairs should be carried out, and suggests what one should look for when evaluating the condition of an older boat.

Is there a best technique? Are all carvel or strip-planked boats created equal? And is there a reason to consider anything other than the latest epoxy-glued cold moulded hull? Let's look at the alternatives available to wood boats builders.

Carvel Planking Construction by Wooden Boat Builders

The structure of a carvel planked hull is easily understood if you imagine yourself building such a boat. In the past, the keel, stem and stern post were usually sawn to shape from large timbers that were then bolted together. With large timber becoming scarce, they are more often laminated up from thinner stock. Although many small dinghies and open wooden boats are built upside down, almost all larger carvel planked vessels are built right-side up. When braced upright, this backbone mimics a child's drawing of a boat, outlining the shape from the bow, down along the keel, and up to the stern. To define the shape of the hull a ribcage is added to the backbone. This is done first with moulds, which can be thought of as temporary bulkheads spaced every few feet for the entire length of the boat. Ribbands, or longitudinal stringers, are then fastened over the moulds, spaced every 6 to 12 inches. The moulds and ribbands together form a rigid framework over which a carvel hull is built. Although sawn frames are sometimes used, most small to medium sized wood boats employ steam-bent or laminated frames. Frames can be installed either inside or outside the ribbands; the former method is most common on the east coast, and the latter on the west. Floors, which serve to connect frames to keel, are also fitted at this time. Floors can be of wood, plywood, steel or bronze. Frame and floor spacing varies with each design, and the size of the boat, but a spacing of 8 to 12 inches is typical. Planking is applied over the frames, using nails, screws, or rivets to hold each plank in place. Planks are fastened wherever they touch on the hull's framework, at the stem, along the keel, at the stern, and to each frame, but not to each other. Instead, when planking is complete, the hull is caulked, usually with cotton, which will act to seal the seams as the planks swell after the boat is launched. By forcing each plank against its neighbour, caulking also helps makes a boat's structure more rigid.

Wooden Boats - Simple Repairs

Repairing carvel-planked wooden boats is simple in some respects because planks are fastened only to the framework, and not to each other. Once the fasteners are removed, this being easiest with planks that are screw fastened, a damaged plank or two can be removed, replacements made and then fastened in place, all with a minimum of fuss. Old planks can be used as patterns, though the technique of spiling, used to determine the shape of a plank when no pattern exists, is not difficult to learn. But the quality of the wood and the work must be good. Vertical grain timber should be used for planking stock, and fits must be precise. Major structural repairs on carvel hulls can be difficult, as the interior of the boat must often be dismantled in order to reach and replace damaged frames or floors. And while a few cracked frames on a strip-planked hull can often be ignored, cracked frames on a carvel hull should be repaired, as they provide the planking with its only support. On the other hand, major repairs to stem and stern are eased by the fact that planks can be removed quite easily, giving access to the damaged backbone. Generally speaking, the independence of the various parts of a carvel hull must be maintained: planks swell and shrink and the entire structure moves, and repairs must take this into account. The exception to this rule is the rather radical fix that is sometimes done to older hulls, and which involves cold moulding several layers of veneer over a conventionally planked hull. The laminated outer skin has sufficient strength to resist the movement of the original planking, and the result can be a new lease on life for a tired old wooden boat.

Wooden Boats - Lapstrake Planking

Lapstrake hulls generally use a backbone similar to that of a carvel planked boat, but from there the construction differs. Planks are lapped over each other and fastened at each lap, giving even an unfinished hull considerable strength. This allows lapstrake hulls to be framed after they have been planked, rather than before, meaning that ribbands can be dispensed with when setting up. Moulds are erected on the backbone as with carvel planking, but these are usually more widely spaced; small wooden boats may even be built using only one midships mould. The fewer the moulds, the more the shape of the boat will be determined by the bending characteristics of the wood.

Once the moulds have been trued and faired, planking can begin, starting with the garboard plank, which is secured to keel and stem. Subsequent planks are fastened at the stem or transom and where they lap over their neighbours; rivets or clench nails are commonly used, and the laps are often glued as well. Frames may be sawn, steam-bent or laminated, and these and any floors usually installed after planking is complete. Repairs are largely similar to those on carvel hulls, except that there are also fastenings between planks to worry about, and the fit of the planks is even more critical. Plywood can be used as planking stock, and if the original construction featured glued plank laps new planks could be fixed in place with epoxy, easing the work of the builders of wooden boats somewhat.

Strip Planking Construction by Wooden Boat Builders

Strip planking bridges modern and traditional building techniques. In its traditional form it might be thought of as a modified type of carvel planking, where the frames are a bit more widely spaced, and additional fastenings, usually nails, join each plank to its neighbour. The backbone, set up, and construction technique would otherwise mirror that used with carvel planking, and the planking would be fastened to the backbone and the frames in much the same way. In its modern form, strip planking has more in common with cold-moulding; today strip-planked hulls are typically glued up with epoxy, and may be built without frames, with glass cloth or other reinforcing, set in epoxy, providing the necessary athwartship strength. Backbones are almost always laminated, using an inner and outer stem that simplifies both setting up and planking.

The strips themselves are often specially shaped, concave on the top and convex on the bottom; strips are also available that incorporate a tongue and groove. Most builders fasten the strips with both glue and nails, and the best builders use square copper or ringed bronze boat nails. Strip planked hulls move very little, due to the multitude of fastenings and glue joining the planks. This makes it possible to glue replacement plank sections directly in place. But the fastenings between planks must all be cut when removing damaged or rotten planking, and this can be a frustrating job. In addition, it is impossible to back the planks off the stem, stern or keel as one can do with carvel and lapstrake hulls. As a result, backbone repairs on strip-built boats must be managed with planking in place. Typically, new wood must be scarfed or laminated onto the existing structure, a procedure that can be very difficult if the repair is extensive.

Laminated Construction by Builders of Wooden Boats

Although the technique of cold-moulding far predates the epoxy era, it's with the advent of epoxy that laminated hulls, constructed of thin strakes or veneers, have become commonplace. Epoxy is a high strength adhesive that bonds well to most woods; what's more, it can provide an excellent moisture barrier when used to coat or sheath timbers. These properties have made it possible to build lightweight laminated boat hulls that absorb a minimum of moisture as they age.

Cold-moulded hulls are set up in much the same way as their carvel cousins, although almost always inverted, with moulds and ribbands defining the hull's shape. On some hulls the ribbands may become part of the final hull, serving as stringers. Thin veneers are laid over this framework, usually starting at 45 degrees to the keel, with each subsequent layer set at 90 degrees to the former. Framing usually consists of bulkheads and stringers, though it is increasingly common to build frameless hulls. An excellent way of doing this is to combine strip planking with cold-moulding. Moulds are set up, the hull is planked with a layer of thin strips, and then several layers of veneer are laid over the strip planking. This eliminates the need for ribbands or stringers, and the resulting hull is very strong.

Repairs to cold-moulded hull planking are carried out by laminating new wood directly in place, having bevelled or stepped back the edges of the damaged area. If the damage is extensive, temporary internal framing may be required to help define the shape of the hull, and to support the new planking as it is being glued and fastened in place. If a cold-moulded hull has many internal stringers and these are damaged, they must also be repaired. As with the repair of frames on a carvel planked hull, gaining access is often the most difficult task. With cold-moulded hulls damaged frames and longitudinal stringers can be cut back and new wood laminated directly in place. Backbone repairs on these hulls generally have the same complications as do those on strip planked hulls.

Plywood Construction by Builders of Wooden Boats

Plywood does not enjoy a good reputation as a boat building material, and its use is generally limited to decks, joinery, and small craft. But fine wooden boats can be built with plywood, providing the material is of good quality, marine grade is best, and it is properly protected. Older boats, usually v-bottomed, were often planked with plywood over a substantial framework of sawn frames and longitudinal stringers. They were usually sheathed with fibreglass cloth set in polyester resin. Boats built in this way may still be sound after 25 or 30 years, but polyester resin's poor adhesion to wood, and plywood's tendency to rot when saturated with moisture, makes this far from certain. Ensure that you have an especially thorough survey done if you are contemplating the purchase of an older plywood boat.

Modern plywood construction almost always incorporates epoxy. If hull planking is laminated from two or more layers of thinner plywood, the result virtually mirrors cold-moulded construction. Plywood's primary limitation is its inability to bend in two directions at once, and some designers have adopted a radius chine to overcome the disadvantages of a chine hull form. Designs for stitch and glue construction are also becoming increasingly common. These generally require no lofting or setting up, and need little interior framing, making them much faster to build. Plywood is also finding increasing use as a planking material for lapstrake hulls, usually with the laps bonded with epoxy. It's an excellent construction method that can produce a beautiful, strong, low maintenance wooden boat.

Repairs to plywood planking are relatively easy, and involve bevelling or stepping back the plywood at the edge of the damaged area, and scarfing in a new section. On older hulls, where the plywood has not been epoxied to the backbone, backbone repairs can be tackled fairly easily after removing any necessary hull sheathing. On newer hulls constructed with epoxy the usual complications arise.


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