Anatomy of a Canoe: Essentials of Good Design (Canoecraft Excerpt)
The following is an excerpt from Canoecraft by Ted Moores. Click here to order the complete edition.
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It is doubtful whether any first-class canoe is the result of any one person’s study. The builder’s shop is the mill, he is the miller. The ideas of others are grists. – J.H. Rushton
One does not have to be a naval architect to understand the basic principles of canoe design. They are relatively simple, yet vitally important – especially to the builder.
The curves of a well-designed canoe are its calling card – a proclamation of the kind of paddling it does best. At one time, the lines of the slender, double-ended craft were directly traceable to a particular locale or people. The curious profile of a Newfoundland Beothuk canoe was a far cry aesthetically, functionally and geographically from the sturgeon-nosed craft of British Columbia’s Kootenay people.
Within the limits of materials and technology, both native canoes and those built by the early whites were traditionally shaped to conform to the kind of water they plied and to the job they had to do. But with the advent of mass production, that connection was broken. In the post-World War II era, canoes were more often designed to conform to the demands of new materials than to function in a specific environment. Efficiency in the water took a backseat to efficiency in the factory.
Commercial designs have vastly improved in the past 15 years or so, as the emphasis has shifted back towards performance. Even so, by building your own canoe, you gain unique control; with the design and construction decisions you make, you can reestablish that perfect harmony among canoe, paddler, and water.
There is no point in expending energy to build a craft that is going to paddle like a barge. At the same time, every builder, designer, and paddler has his own version of the perfect canoe. The following section bares our personal biases; you can find others by referring to the books listed in Sources.
The key to sorting through the maze of designs is to determine what you expect of your canoe. Where will you most often paddle, for how and with what gear? Most paddlers face a range of circumstances. The challenge is to select a design that meets most needs most of the time.
If your experience in canoes is limited, go to the water to test these principles where they really count. Examine hull contours and paddle different canoes to discover what suits your style best. Your woodstrip canoe will be a thing of aesthetic beauty, but understanding design will assure that it is satisfyingly functional as well.
A Canoe in Perspective
When a canoe is taken out of its watery element and projected onto a drawing board, it can be reduced to three views – profile, body plan and plan view.
The profile view (see illustration) shows a canoe from one side, as if it were cut in half lengthwise. This perspective describes the accurate length and depth of the boat, its sheer-line (curve of the gunwale, or top edge), its keel-line (curve of the hull, or bottom edge), the shape of its bow and stern and its waterline length (hull length that is wetted when the canoe is in the water).
The body plan (see illustration) shows a canoe from the end, as if it were sliced crosswise at regular intervals, or stations, the shape and dimensions of which are each represented by a single line. Each cross section shows the accurate width and depth of the canoe at that point, as well as the shape of the hull bottom and the shape of the sides. A centerline drawn perpendicular to the waterline splits the cross section in two, but since each half is identical, only one half is shown in the body plan.
The plan view (see illustration) shows a fish-eye perspective of the canoe from directly underneath the boat, as if it were sliced end to end at regular waterlines. Each lengthwise section shows the true length and width at that level, as well as the contour from its maximum width to the point at each end. This describes the path the water must take at various levels as it moves from the entry line at the bow to the exit line at the stern. When the slices are superimposed over a common centerline, the plan view also indicates whether the canoe is symmetrical (bow and stern halves are the same shape) or asymmetrical.
The parts of a canoe are common to most watercraft.
The Elements of Performance
Each of the many physical elements illustrated by the three views has a profound effect on a canoe’s performance. Although they are discussed separately below, none of them acts in isolation. Each affects the others to some extend; in a well-designed canoe, they function in delicate balance.
The profile view shows a canoe from the side, sliced in half lengthwise, illustrating the top and bottom curves as well as the length and depth of the canoe.
On average, the center half of a well-designed hull provides 75 percent of its stability and carrying capacity, while the end quarters function primarily to part the waters at the bow and bring them back together at the stern. Obviously, a longer hull will carry more weight, but length also affects speed.
Generally, the greater the waterline length and the higher the ratio of length to width, the faster the canoe and the easier it is to paddle. This is partly due to the physics of waves and partly to the fact that, in comparison to a short, wide hull, a long, narrow hull rides higher, with less wetted surface, and thus generates less friction against the water. A long hull will also track (hold its course) better than a short one will, but it will not turn as easily.
The body plan is an end view of the canoe, sliced crosswise at regular intervals, bow to stern, with the contours superimposed in sequence over a common centerline. It illustrates the canoe’s depth and width.
The plan view shows the hull from below, sliced lengthwise at regular waterlines. It illustrates the hull shape and the canoe’s width and length.
This is the maximum width of a canoe. With a narrow beam, less effort is required to push the water aside, and less friction is created by the hull surface. But, although a wide canoe generally paddles slower than a narrow one does, it has greater carrying capacity and is more stable when loaded to its design capacity.
Beam may be the same throughout the depth of the hull, in which case, its sides are plumb (see hull contour, below). But if the maximum beam occurs at the gunwales, the hull is flared. Most often found on narrow hulls, flared sides afford good “final stability.” The hull becomes more stable when it is loaded down, because it becomes wider the lower it sits in the water. Flared sides also deflect waves.
When the gunwale beam is narrower than the maximum beam, the sides are tumblehome (they “tumble home”). Tumblehome is usually found on wider hulls: the reduced gunwale width allows the paddler to reach over the side easily without sacrificing good carrying capacity. The arcing sides also help stiffen the hull. Although tumblehome does not affect initial stability, it can result in very poor final stability when too extreme, especially in combination with a wide, flat bottom.
Determining the depth of the canoe: Freeboard, the distance between the gunwale and the water, varies with the load the canoe is carrying.
The depth of a canoe is measured amidships from the gunwales to the bottom of the hull. This can range from 10 inches in a little solo canoe to more than 24 inches in a freighter. Depth is also measured at the bow and stern, from the top of the stem to the lowest point of the keel-line.
Freeboard, another measurement of depth, is the distance from the water to the gunwales. Freeboard affects the seaworthiness of a canoe: high sides will make it susceptible to wind, reducing speed and controllability, whereas low sides will render it susceptible to swamping in whitewater and waves.
Predicting the freeboard of a design when the canoe is fully loaded can be done several ways. When “capacity” is listed in canoe specifications, it usually refers to the weight that can be loaded into the canoe while retaining 6 inches of freeboard. “Design displacement” refers to the weight that will lower the canoe to its design waterline. As you study different plans, watch for figures that indicate pounds per inch of immersion. Ultimately, this is more meaningful than capacity is and will give you perspective on how a particular hull will handle loading.
Top: Up to half the length of a well-designed canoe is devoted primarily to parting the water at the bow and returning it at the stern. The longer the canoe, the faster it is. Above: The placement of maximum beam on the side of the hull determines the shape of the sides and the canoe’s stability, speed, and carrying capacity.
More important than depth, beam or length is the way these measurements are drawn together to form the hull contour. How this shape moves through the water is the key to canoe performance.
A canoe has a displacement hull. It is basically a moving trough, dividing water at the bow and replacing it at the stern. Its efficiency depends on the amount of friction created by the hull surface meeting the water and the smoothness with which the water is displaced around its form.
The contour of the hull below the waterline determines the efficiency of the canoe as well as its stability in rough water.
A semicircular, or round-bottom, hull produces the least wetted surface, but its tippiness makes it practical only for flatwater racing shells.
A flat-bottom hull has the greatest wetted surface and is capable of carrying large loads. It can also turn quickly in every direction, making it appropriate for whitewater, where high maneuverability is a priority. This skidding action, however, means tracking can be difficult in anything less than glassy waters, and even then, flat-bottom hulls are slowed by high friction.
Since it is buoyant over a large surface, a flat-bottom hull feels the most stable when first climb in but remains so only in calm water. In rough water, the flat, buoyant hull follows the profile of the waves and can turn turtle suddenly when tipped past the sharp turn of its bilge. A flat bottom may be justified in freight canoes but is unsafe in recreational craft on anything but flat water.
The shallow-arch, or semi-elliptical, hull contour is a good compromise between the round and flat bottoms. Its domed shape helps stiffen the hull, which is especially important with lightweight construction techniques, and reduces instability in the bilge area. In addition, waves tend to slide under the boat.
This hull feels “canoey,” with good initial and final stability. Because such hulls take less abuse from heavy waters, naval architects often characterize them as “sea kindly.” A shallow-arch hull will also track better than will a flat hull. Because of its seaworthiness and average tracking and turning ability, this contour is the starting point for most general-purpose touring or cruising canoes.
A shallow-vee contour takes the hull deeper and sharper into the water and produces slightly more wetted surface. Like the shallow-arch hull, the shallow vee affords a high degree of final stability. But it tracks better, since the vee shape functions like a keel, keeping the canoe on course. It is less responsive in turning, however. Because the shallow vee cuts cleanly through waves, with little pounding or skidding, it is especially appropriate for sailing and lake canoes.
Most hulls employ a combination of these forms. For instance, a cruiser might have a deep-vee bow to part the waters efficiently, opening gradually to a shallow vee, then a shallow arch to pass the waves cleanly along the hull, then narrowing back into a deep vee at the stern. Such a design would combine seaworthiness and directional stability with good maneuverability. It would also offer reserve buoyancy – extra width at the vee sections when the canoe sits deeper in the water.
Separate keels are the subject of some controversy in canoe design. They do add a measure of stiffness and protection to the hull bottom and will be much appreciated when paddling through a crosswind on a lake, but that same keel will be roundly cursed when you try to maneuver through rock-strewn rapids.
As a general rule, a shoe keel (a keel generally 3/8 inch deep by 2 to 3 inches wide) is a good idea for protection on a river boat, while a deeper keel is appropriate on a lake canoe, where maneuverability is less important than tracking ability. Keels should be avoided on whitewater canoes, since they get hung up on obstructions and inhibit the sideways movement critical to dodging through rapids.
The keel-line of a canoe also affects maneuverability and directional stability. A straight keel-line from stem to stem produces a fast, easy-paddling canoe that tracks exceedingly well but turns poorly.
Even without a keel, the profile of a hull bottom strongly affects performance and the way the canoe rides out rough waters. Keel-lines range from the razor’s edge of a racing cruiser to the extreme rocker of a slalom canoe. Recreational canoes fall somewhere between.
A keel-line that curves upward from the middle towards each end of the canoe is said to have rocker. Essentially, rocker allows the canoe to pivot on its midpoint. The more rocker on the keel-line, the shorter the canoe’s waterline length and the easier it turns and rises over waves. Too much rocker forces the center of the canoe to support most of its weight, driving it deeper into the water, increasing displacement and friction and decreasing speed.
Rockers can range from moderate lift in a cruiser to the banana-like profile of a competition slalom canoe. Poorly made or old canoes sometimes develop reverse rocker, or hogged keel-lines, which inhibits performance.
Rather than a fully rockered keel-line, a canoe can have a slight uplift just at the stems. In a loaded boat, this allows enough of the hull to ride in the water for good tracking, but with the bow and stern riding slightly above the waterline, maneuverability and reserve buoyancy are improved.
The profile of the bow affects performance as well as the line of the hull body. Some bows rise vertically or on a slight incline, yielding a fairly straight sheer-line and maximum waterline length. This inclined, or plumb, bow forces the sides of the canoe to flare. The greater the incline, the more the sides must flare.
Most traditional canoe bows, however, rise up out of the water and curve back slightly towards the paddler. This recurve, a logical extension of the rockered keel-line, reduces the area exposed to the wind for a given waterline length. But as the bow curves, it puts tumblehome into the sides, reducing reserve buoyancy.
To compensate for this, extra height is often added at the stems. Extreme recurve, with a sharply rising sheer-line, makes the canoe more susceptible to wind and adds some unnecessary weight, but the trade-off may be worth the beautiful sweeping lines.
The entry line of a canoe – the shape of the forward point of the bow that cuts the water – plays a large part in its efficiency. The smoothness with which water is displaced around the hull affects both speed and the amount of effort required to attain it.
A canoe that carries its fullness well into the ends must quickly push aside a large volume of water, which tends to slow down as it moves along the hull. Thus the canoe tends to plow through the water.
On the other hand, a hull with a fine entry line moves the water aside more slowly. Because the displaced fluid has more time to get out of the way, the paddler exerts less of his own force to move it. The fine lines part the water neatly, producing little spray and a small set of waves that accelerate naturally along the hull.
Fine entry lines are desirable under all conditions, albeit in varying degrees. A flatwater cruiser should have the finest entry, whereas a whitewater canoe must have its fullness carried as far forward as possible, without disturbing the fine entry.
Although traditional canoes are generally symmetrical in shape, some modern designers have abandoned that principle. In an asymmetrical design, the beam is placed slightly aft of center, creating a longer bow. Paddling and tracking becomes easier because of the fine entry of the long bow and the extra buoyancy in the stern quarter.
Top: A plumb bow forces the canoe’s sides to flare, while traditional recurved bows result in tumblehome sides. High recurve is traditionally attractive but can make the canoe susceptible to wind. Above: Fine entry lines part the waves more smoothly than a blunt-nosed bow that plows the water. The result is greater speed with less paddling effort.
Compromises and Conundrums
Between the extremes of the blunt-nose, flat-bottom freighter and the stiletto racer, infinite variations in canoe design are available. At the same time, however, there is no ideal form. Each of the principles discussed above can be manipulated for specific results, but the gain of one advantage inevitably entails the loss of another. If you opt for tracking, you will sacrifice maneuverability, while the extreme rocker that offers optimal maneuverability will rob your canoe of tracking ability.
Even within each design variable, there are no absolutes. Final stability is a prime concern if you are out for a paddle with the kids, but it is a low priority if you delight in the solo canoe “ballet” of Bill Mason. And finally, no matter how function a well-designed canoe may be, it must also be visually pleasing, balancing practicality with beauty of lines.
The flexibility of canoe design, however, is its own reward. All these disparate elements can be orchestrated in several different ways to produce a variety of canoe prototypes well suited to different requirements. If there is no such thing as the perfect all-purpose canoe, there are individual types that do specific jobs very well.
A cruising, light-tripping or general-purpose, canoe should have a keel or vee end sections, a fairly straight keel-line and a fine entry line for good tracking and efficient paddling. It should have a shallow-arch or shallow-vee hull with low stem profiles. Asymmetrical designs are appropriate. Overall length can range between 14 and 18.5 feet, with at least a 12-inch depth and a beam between 30 and 34 inches.
A wilderness, or tripping, canoe must meet all the challenges of extended bush travel – large lakes, shallow streams, whitewater and portages – and still be able to carry sufficient gear. The hull should be as full as possible towards the bow and stern without disturbing the fine entry, with a slight uplift or rockered keel-line for maneuverability in rough water and a shallow-arch contour. A bit of tumblehome in the sides is ideal. The hull should be keelless or shoe-keeled, and weight is a definite consideration. Competent wilderness canoes are at least 16 feet and as much as 18.5 feet long, with a 12-to-14-inch depth and 34-to-36-inch beam.
A whitewater, or downriver, canoe should have a shallow-arch to flat-bottom hull, well rockered for easy turning and with a good lift at the ends so that it can ride through heavy rapids without taking water. Moving the bow seat back somewhat will improve this ability. Keels are undesirable, unless a shoe keel is considered necessary for protection. In any case, a whitewater canoe has to be strong enough to withstand inevitable encounters with rocks. Decks should be long and gunwales wide enough to shed water, with tumblehome sides to accommodate the beam. The consideration of weight has to be balanced against durability. Dimensions are similar to those for a wilderness canoe, although depth should be about 14 inches.
The design of a solo canoe depends on the individual canoeist’s paddling technique. A traditional Canadian-style solo canoe, paddled heeled over, is 14 to 15 feet, with a symmetrical shallow-arch hull. Widths range between 25 and 34 inches, with a slight tumblehome to the sides.
The traditional American Rushton-style solo canoe, on the other hand, is paddled flat with a double blade. It is typically narrower (24 to 30 inches) and shorter (10 to 14 feet), with a shallow arch/shallow-vee hull. The paddler sits on the hull bottom, supported by a backrest.
The contemporary Gault-style solo canoe, a new design now fashionable in the United States, is paddled well heeled over. It is also narrow (24 to 30 inches), with shallow, flared sides and an asymmetrical hull 13 to 16 feet long, with a rounded-vee bottom and soft bilges.
After digesting this chapter, you may not be ready for the world of custom design, but you should be able to set your own personal performance priorities. As one builder exclaimed after mastering the mysteries of canoe design: “I’m not trained, but now I certainly can tell an ugly canoe when I see one, and I have a pretty good idea about how poorly it must handle.” In the next chapter, you will find plans for a range of canoes that are as sweet in the water as they are on the shelf.