Though they may all look similar to the unpracticed eye, kayak designs vary considerably, and even small variations in hull dimensions and shape can have large effects on boat performance. Each boat is designed and built for a specific use and for a specific type of paddler. No single aspect of hull design determines overall performance by itself; it’s the combination of dimensions and shape that determines the feel and performance of a boat.
In sizing up boats, it’s important to keep in mind the combination of design features that will produce the handling and performance you want. Seven features are critical: length and waterline, bow shape, width, cross section, chine shape, footprint, and volume in bow and stern.
The overall length of a kayak matters, but the length of the waterline is most important for boat efficiency. Other things being equal, a longer waterline results in a faster craft because it allows for more streamlined passage of the hull through the water. A boat with a long waterline also tracks better and rides its own bow wave more efficiently than a boat with a short waterline. In rougher waters, a properly designed kayak with a long waterline will be more efficient to paddle because it can span the waves instead of riding up and down in the wave action, allowing more glide. Longer kayaks are also more stable because the boat has more wetted surface, which results in a more stable craft. Carrying capacity is also greater with the extra length.
A shorter kayak will be more maneuverable and fun when poking around and often easier to handle both in and out of the water. Because the wetted surface of a shorter boat is small, the hull is often easy to move through the water at cruising speeds. However, at high speeds, the shorter boat will not be as fast as a longer boat.
Many kayaks have a distinctly upswept bow, often referred to as a “Greenland” bow. In flat water, a Greenland bow has little benefit. However, in rough conditions, an upswept bow lengthens the waterline of the boat, which allows it to cut through the waves more easily and keep momentum. The degree of lift that this type of bow gets in rough conditions is very dependent on how much flair there is in the bow of the boat.
A plumb bow — one the enters the water at nearly 90 degrees — maximizes the waterline of a kayak relative to its length, making the boat feel longer and paddle more efficiently. Plumb bows are often used on different forms of racing kayaks. Note that if a plumb bow is very thin, it will punch through waves and possibly dive and slow the boat. However, if there is sufficient flair and body in a plumb bow bow, then the boat can have a good balance of wave piercing and lift.
The width — or “beam” — of a kayak effects stability, speed, and overall fit, as well as carrying capacity. Given the same hull shape, a beamier kayak will generally be more stable than a narrower one, and have a higher volume for stowage. Wider kayaks may be preferred by those who simply prefer or need greater stability, or by taller paddlers, whose higher centre of gravity tends to reduce overall stability. However, a narrow kayak generally will be more efficient in cutting through the water. The appropriate beam for any individual paddler is most closely related to his or her body size or by the paddler’s skill and ability to feel comfortable with the degree of stability.
Width is not the sole factor determining feel and stability. It’s also important to consider the “cross section” of the hull. Imagine taking a kayak and cutting it in half crossways through the cockpit area. Now look at the shape of the hull that is revealed across the cut — that is what we talk about when we talk about the cross section of a kayak. The cross section is what creates the initial feel of stability or instability in a kayak. There are two extremes in cross section. A hull with a rounded cross section is extremely fast but it offers very little stability. A hull with a flat cross section feels very stable but makes for a slower boat. Most kayaks are designed around a compromise between round and flat to get the perfect shape for the boat’s intended use. In addition, the cross section may change as we move away from the hull towards the bow or the stern.
Vee-shaped and arched-hulls are quite common in touring kayaks. They give stiffness to the hull and improve tracking. The degree of vee or arch will determine how stable the boat will feel as well as how fast it is. Flared sides help to create good secondary stability and reasonable efficiency while straight sides will offer less secondary stability.
The chine is the transitional shape on the side of the kayak hull as it turns up toward the seam. The chine is critical for the way a kayak feels. As you lean a kayak over in the water, you can feel when it reaches a position of secondary stability. The shape of the chine determines where the buoyancy is in the boat, and hence where the point of secondary stability is. The more body and flare to the hull, the more secondary stability you will have.
Chines can be hard or soft. A kayak with a soft chine has a smooth transition between the bottom of the hull and the sides. Some soft chine kayaks can be quite flared and full, offering a lot of secondary stability in the kayak. Single chine kayaks have a well defined hard edge where the hull starts to turn up toward the side of the kayak. There are also multi-chine hulls that have several ribs as the hull turns up toward the seam. The difference in feel between hard and soft chine hulls is often minimal. Whatever the style of kayak, what is important is that the buoyancy is positioned to deliver the stability you want.
The plan view and footprint of a kayak refer to its general shape, and the way its length and volume are distributed either fore and aft — ahead of or behind — the cockpit.
The plan view is the view we have of a kayak looking down at the deck from above. There are three general categories of plan views for kayaks: symmetrical, Swede form, and fish form. A kayak that has its volume evenly distributed fore and aft, with the main body of the volume in the middle, is said to have a symmetrical hull. A symmetrical hull is nicely balanced and some of the finest all round sea kayaks are very symmetrical. A kayak that has most of the body aft of the paddler is called “Swede form.” This type of kayak has a longer, more slender hull entry giving easy touring speed and maneuverability. A “fish form” kayak is one that has more of the body forward of the paddler. A fish form kayak has a more full bow area and a slender exit, often improving the tracking in rough conditions. The fuller bow also creates a dryer ride with more lift when in big seas.
The footprint refers to what a hull might look like from underwater – imagine lying on the bottom of a swimming pool with a mask on and looking up at a kayak when it is above you. This is the footprint the kayak takes in the water. This footprint can change, depending on the weight in the kayak and often gives the best idea of the overall wetted surface and stability a kayak will offer.
A kayak hull that has full volume at its ends, right up in the bow and the stern, has more buoyancy and provides a drier ride. A boat that is too full in the bow and stern can be inefficient in rough conditions, as it does not cut through waves well. At the other extreme, a kayak with a very fine bow and stern may give the feeling of a fast sleek machine, though it will be quite wet as the bow cuts through waves instead of rising up. However, the speed may simply be illusory as a submerged bow will often slow the kayak down overall. The proper balance of bow and stern buoyancy is what enables a boat to ride up and through waves most efficiently.
Your Needs and Intended Use Budget and Materials Hull Design Additional Boat Features
Your Needs and Intended Use
Budget and Materials
Hull Design
Additional Boat Features
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