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How to Choose a Canoe - Part 2: Canoe Design

Posted by Darren Bush on 5/29/2013 to Canoe

There is a bewildering variety of canoes available out there—how do you ensure that you pick the one that’s right for you? We have broken choosing a canoe into three parts. Part one is general information. This section helps you think about, how you will use the canoe, and what type of canoe is best for your use. Part two is on canoe design. Part three is about which canoe material will be best for your budget and use. Be sure to check out our other articles on canoe materials, too.

The Shapes in Canoe Design

Length is an important determinant of canoe performance, having a large part to play in both efficiency and in tracking. A difference of as little as six inches can have a remarkable impact on the feel of the boat. In terms of efficiency, longer hulls (all other aspects held constant) will be faster, and shorter hulls will be more maneuverable. For a given width, a longer hull will be more streamlined. This means that it can be paddled at higher speed with less effort.

But now it gets tricky. What counts as “high-speed” is different for each hull. In general, for longer, narrower hulls this speed will be faster than for shorter, wider designs. At lower speeds, however, you may find paradoxically that the long, fast boat feels slower. That’s because you’re rubbing more boat on the water, and that friction is only counterbalanced when paddling at higher speeds. In short, fast does not mean efficient—fast is a Corvette with a V8, efficient is a Volkswagon Bug (like my first car, a ’57 beetle, all 40 hp).

Not that you’re likely to, but don’t forget about width, or as we sometimes call it, beam. When you look at canoe dimensions, keep in mind that the gunwale (rhymes with tunnel) width and the maximum width are often not very relevant to this aspect of performance. You need to look at the waterline width. As you look at canoes, it is easy to forget that the shape of the waterline is not what you see when you look down on the gunwales. Most manufacturers of performance canoes will list the waterline width, and now you know how to use it. Speaking of the waterline width, it’s also the dimension that has the greatest effect on the stability characteristics of the canoe, with wide waterlines generally featuring more stability.

However, that is an extreme simplification, and the shape of the hull in cross-section has a lot to do with stability. The cross-sectional shape of a canoe hull plays an important role in how the canoe performs. The shapes on the extreme ends of the spectrum are round and flat, and most hulls are somewhere in between. The most common shapes are shallow arch and shallow V.

Some of the concepts that will come into play in this area are speed and stability. Many people do not care about speed, but most people do care about efficiency. The two concepts are related. In most cases, a hull that is more efficient will travel farther than another for a given amount of exertion. Put another way, a more efficient hull will require less effort per stroke to keep up with its less efficient counterpart. But remember that potential hull speed is not actual hull speed. Buy a boat that matches your speed.

Stability is an important concept for a potential boat-owner to understand. There are actually three types, usually called initial (or primary) stability, secondary (or final) stability, and finally, dynamic stability.

Initial stability is the feeling of steadiness that a hull has when it is sitting flat in the water. It is what most people mean when they talk about stability. If you want to be able to stand up to shoot or cast in your boat, you want high initial stability. Secondary stability has to do with how the boat handles when it is leaned. It is a function of how much energy it takes to keep a leaned boat from going all the way over. High secondary stability means a boat can be held on edge with little effort, and low secondary stability means that it takes lots of energy (powerful bracing strokes) to hold it up without letting it tip all the way over.

If you will use your boat in rough conditions, you can have too much initial stability. This is because hulls with high initial stability want to ride flat on the water. When you encounter wavy conditions, you may find that the surface of the water pitches up and down at steep angles, angles which your boat will try to mimic. This means the boat will be rocking from side to side on the faces of the waves. Lower initial stability will help alleviate this problem, and high secondary stability will ensure that you remain comfortable with your boat held at an angle to the surface of the water. It is possible to create hulls which get high marks in both types of stability, but they have to be quite wide. This creates problems of a different type, since a wider boat will tend to plow rather than slip through the water. You can make the boat longer to counteract this, but then you end up limiting maneuverability. The long and short of it is that most boats are a compromise between initial and secondary stabilities, and you will have to do some thinking about what is important to you.

The last, dynamic stability, is difficult to measure. It basically refers to the fact that boats moving through the water have more stability than boats at rest. Anyone who has ever paddled an Olympic kayak or round-bottomed rowing shell knows that the boat is very twitchy and uncomfortable at rest, but seems to “settle down” when the boat starts moving through the water. All boats have some dynamic stability, but it is not that essential in most non-racing hulls. So forget I said anything about it. FYI only…

Round-bottom hulls are extremely fast, but have very low initial stability. They gain their speed from having a very small amount of wetted surface (the amount of area in contact with the water) for the volume that they displace. Because there is no inherent stability in a round-bottomed hull, they are used primarily for racing, where when combined with a narrow and long boat, the end result is a very fast top speed.

Flat-bottom hulls have the highest initial stability, like a floating dock or pier. The drawback is that they have a high wetted-surface area, and are therefore less efficient at both lower and higher speeds. Choose a flat-bottomed boat if initial stability is very important to you, and you don’t mind giving up a bit of speed and rough-water capability for it.

Shallow arch hulls are a compromise between the speed and efficiency of round bottoms and the initial stability of flat ones. There is a lot of variation within this family, with some hulls rounder (less initially stable and faster) and some flatter (more initially stable and slower), so you can pick a point along the spectrum where you are comfortable.

Shallow V hulls are also a compromise between round and flat. In terms of initial and secondary stability they have very similar characteristics to shallow arches. However, the shallow V has a bit higher wetted-surface ratio, so it is, theoretically, not quite as efficient. Advantages of the shallow V include enhanced tracking and performance in carved turns, and a great degree of comfort and stability when leaning the boat. The shallow V also helps to stiffen the boat. This is not generally required in composite boats, but it can be helpful in some Royalex hulls.

External keels deserve to be mentioned in a discussion of cross-sectional shape. They are typically absent in performance designs because they increase the amount of wetted surface and therefore decrease efficiency. However, in recreational canoes where initial stability is very important, sometimes a keel will be included in order to keep the boat from blowing sideways in a crosswind or to keep it paddling straight in the hands of less-experienced paddlers. External keels can also help to stiffen a boat that is made of one of the more flexible materials.

Also relevant to hull cross-section is the shape of the sides of the canoe. They can feature flare, tumblehome, or straight sides. Flare means that the canoe continues to get wider above the waterline, reaching its maximum width at the gunwales. Flare plays a big part in keeping waves from breaking into your boat, and it has a positive effect on secondary stability. However, flare can make it difficult to reach the water with your paddle, since you will have to reach out over the gunwale. If you are reading a catalog and notice that the gunwale width and the maximum width of a boat are the same, the boat has flare.

Tumblehome means that the widest point on the canoe is not the gunwales. In cross-section, the sides of these hulls appear to pinch in a bit at the top. This means that the paddler doesn’t have to reach as far out to get the paddle shaft vertical in the water. This is especially useful in solo canoes, but tripping canoes can benefit from it as well. They can have extra beam for cargo capacity, but the tumblehome makes it easier for the paddlers to reach the water. If a canoe’s measurements indicate that the gunwale width is less than the maximum width, the canoe has some tumblehome. Most designs will feature a combination of flare and tumblehome. Flare in the ends makes for a dry ride, while tumblehome in the midsection allows for easier paddling.

Straight sides offer something of a compromise between the two extremes. Since flare and tumblehome each have distinct advantages, most designs will go one way or the other. Straight sides, on the other hand, are typically found on all-purpose recreational and sporting canoes. If the waterline width, the maximum width, and the gunwale width of a canoe are all the same, the canoe has straight sides.

Rocker is the amount of curvature along the length of the keel-line of a boat. The runner of a rocking chair is the perfect demonstration of extreme rocker. The function of rocker is to increase maneuverability. When this happens, the ability to track with minimal effort is decreased proportionate to the amount of rocker — the more the rocker, the harder it is to make the canoe go straight. Once again, you will have to find the balance that suits your needs. Whitewater boats feature lots of rocker so that they can spin on a dime. Cruising boats typically have little of no rocker so that they can cover long distances efficiently, without the need for corrective strokes.

Depth is also important, especially in determining capacity. There are actually three measurements of depth—bow, center, and stern. The one most commonly referred to is the depth at center. This measurement gives you an idea of the relative capacity of the hull. Deeper boats will generally carry more weight. Depth also adds seaworthiness, since it helps keep the water where it belongs (that is, out of your boat). The down side is that depth increases windage and may interfere with comfortable paddling. Once again, figure out where along the scale you are and look at boats that meet your criteria. Carrying heavy loads on rivers and lakes with ferocious chop calls for depth, while cruising and day tripping on small, wind-swept lakes does not. Likewise, bow and stern depth add seaworthiness (but not much capacity). Bow depths tend to be greater than stern depths because oncoming waves are more likely to spill into the canoe than are following seas.

Part 1: General Information
Part 3: Canoe Materials

Well, that’s about it in a nutshell. Call us at (800) I – PADDLE if you have any more specific questions about information in this article or if you just want to talk about boats. We like talking about boats.

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