Canoe - Hull Design

Hull Design

Hull design must meet different, often conflicting, requirements for speed, carrying capacity, maneuverability, and stability The canoe's hull speed can be calculated using the principles of ship resistance and propulsion.

• Length: this is often stated by manufacturers as the overall length of the boat, but what counts in performance terms is the length of the waterline, and more specifically its value relative to the displacement of the canoe. Dispacement is the amount of water displaced by the boat. It is equal to the total weight of the boat and its contents, since a floating body displaces its own weight in water. When a canoe is paddled through water, it takes an effort to push all of the displaced water out of the way. Canoes are displacement hulls: the longer the waterline relative to its displacement, the faster it can be paddled. Among general canoeists, 17 feet is the most popular length, providing a good compromise between maneuverability and speed.
• Width (beam): a wider boat provides more stability at the expense of speed. A canoe cuts through the water like a wedge, and a shorter boat needs a narrower beam to reduce the angle of the wedge cutting through the water.
• Depth: a higher-sided boat will stay drier in rough water. The cost of high sides is extra weight and extra wind resistance.
• Stability and bottom shape: the hull can be optimized for initial stability (the boat feels steady when it sits flat on the water) or final stability (resistance to capsizing). A flat-bottomed hull will have high initial stability, while a rounded or V-shaped hull will have high final stability. The fastest flatwater canoes have sharp V-bottoms to cut through the water. But they are difficult to turn and have a deeper draft which makes them less suitable for shallows. Flat-bottomed canoes are most popular among recreational canoeists. At the cost of speed, they have shallow draft, turn better, and more cargo space. The reason a flat bottom canoed has lower final stability is that it the hull must wrap a sharper angle between the bottom and the sides, compared to a more round-bottomed boat.
• Keel: an external keel will make a canoe track (hold its course) better, and can stiffen a floppy bottom, but it can get stuck on rocks and decrease stability in rapids.
• Profile, the shape of the canoe's sides. Sides which flare out above the waterline deflect water but require the paddler to reach out over the side of the canoe. If the gunwale width is less than the waterline width or the maximum width the canoe is said to have tumblehome. This makes paddling easier.
• Rocker: viewed from the side of the canoe, rocker is the amount of curve in the hull, much like the curve of a banana. A straight keeled canoe, with no rocker, is meant for covering long distances in a straight line. The full length of the hull is in the water, so it tracks well and has good speed. As the rocker increases, so does the ease of turning, at the cost of tracking. Native American birch bark canoes were often characterized by extreme rocker.
• Hull symmetry: viewed from above, a symmetrical hull has its widest point at the center of the hull and both ends are identical. An asymmetrical hull typically has the widest section aft of center line, creating a longer bow and improving speed.