What is the hull of a kayak?

The bottom of a kayak is called the hull. This “floating surface” forms an interface between the kayak and the water, and thus plays a primary role in determining how the boat will perform. Ultimately, the design of the hull of a kayak is the main factor in whether or not a kayak is right for you.

An educated buyer can look at a kayak hull design and estimate how the boat will perform in the water. Different kayak hull shapes will have different paddling characteristics; speed and glide, tracking and manoeuvrability, and stability are all directly influenced by kayak hull shapes.

In general, kayak hull design boils down to two things:
First, rocker. That is the upsweep of the kayak’s hull from bow to stern that establishes the balance between tracking and manoeuvrability. For example, whitewater kayaks feature plenty of rocker to assist agile handling in rapids, while sea kayaks have minimal rocker to enable easier straight-line travel, that is tracking.

Second, the cross-section of the hull determines stability.  That is as if a slice were taken from the kayak from side to side.  The way various kayak hull types influence stability is discussed at length in the next section of this article.

Kayak hull types

Pontoon hull kayak

This type of hull is often also called a “double hull kayak,” “tunnel hull,” “dual hull design” or “catamaran hull kayak.” This kayak hull type prioritizes stability, at the expense of speed and manoeuvrability. Like a pontoon boat, a pontoon hull kayak is designed to sit flat on the water and resist rocking from side to side. It’s a common kayak hull design for beginner sit-on-top kayaks and fishing kayaks. The large surface area of this kayak hull type makes it slower to accelerate and requires more effort to maintain a cruising pace.

Pontoon hull kayaks track well; that is, they tend to move straight through the water and are more difficult to turn. Choose a pontoon hull kayak if you’re a beginner paddler looking for the ultimate in stability. However, be aware that this type of kayak hull design will also limit your ability to perform more advanced paddling techniques, such as edging the kayak (which increases manoeuvrability in single-hull kayaks).

Tri hull kayak

This type of hull is often also called a “cathedral hull kayak,” “kayak dihedral hull design,” or “multi-channel hull kayak.” This kayak hull design is commonly used in sit-on-top kayaks (especially those manufactured by Ocean Kayaks). A tri-hull kayak provides the reassuring stability of a catamaran hull with the enhanced tracking of a well-defined keel line—that is, a V-like structure running along the bottom of the kayak from bow to stern.

Manufacturers of tri hull kayak designs can also achieve more manoeuvrability than pontoon kayaks by adding rocker (curvature) to the outer hulls, which allows the kayak to turn more easily yet still feel supremely stable. Look for a tri hull design if you want a higher performance beginner sit-on-top kayak.

Displacement hull kayak

All recreational, touring and sea kayaks feature what’s known as a “displacement hull.” This means the kayak pushes (or displaces) water as it moves (in contrast, a “planing hull,” often identifiable by a flat bottom, will plane or skip across the water with minimal resistance—once it reaches a certain speed. Think surfboards and surf-inspired stand up paddleboards).

Flat hull kayak

A flat hull kayak is defined by great stability. That’s because the paddler is effectively floating atop a larger, flat surface that resists rolling from side to side in the water. Flat hull kayaks are great for beginners, and commonly used in recreational and touring kayaks. This kayak hull design is often paired with a wider-than-average width, to further enhance stability and support larger paddlers. Flat hull kayaks feel most stable on flat water, a phenomenon known as “primary stability.”

However, they can feel tippy and less reassuring to the paddler when waves or current rock the kayak from side to side. In these circumstances, flat hull kayaks are said to have poor “secondary stability,” and are more prone to capsizing than kayaks with rounded hulls. Flat hull kayaks also tend to be slower because their boxy shape moves through the water with greater resistance than rounder hull designs.

Round hull kayak

In contrast to a flat bottom, a round hull kayak has greater secondary stability (more resistant to capsize in waves, chop and current). However, a round hull has far less primary stability (that is, it feels more tippy when sitting flat on the water); therefore, this kayak hull design is less suitable for beginners. More advanced touring and sea kayaks tend to have rounder hulls, which makes them faster in the water than flat-bottom kayaks.

Planing hull kayak

Planing hulls are found exclusively in whitewater freestyle kayaks. These small, sub-seven-foot-long kayaks are meant for surfing on stationary river waves. Planing hulls are flat, like a surfboard. This allows an advanced paddler to “skip” on the surface of the water to perform acrobatic manoeuvres.

Planing hulls feel stable on the water. However, their larger surface area makes them slower and feel more cumbersome for downriver paddling.

V  hull kayak

A V-hull kayak features a pronounced keel line (that is, a shallow V-shaped ridge running from bow to stern along the bottom of the kayak). This allows the kayak to hold its course (or track) better than a flat bottom kayak, since the V-shape of the keel line resists turning more than a flatter hull. The flipside to solid tracking, however, is reduced manoeuvrability.

More advanced paddlers overcome this tendency by performing turning strokes with the kayak on edge or tilted (under control) to lift the V-shaped keel out of the water. V-shape kayaks feel less stable when sitting flat on the water, with a tendency to rock from side to side. However, this translates to greater stability in waves and current—another desirable attribute for more advanced paddlers.

Comparing different hull types

Flat Bottom vs V-Hull Kayak

There are two main differences between flat bottom and V-hull kayaks: tracking and stability. A V-hull kayak will tend to hold its course (or track) better than a flat bottom kayak, since the V-shape of the keel line resists turning more than a flatter hull. Meanwhile, a flat-bottom kayak will feel more stable on the water than a V-bottom, which has a tendency to rock from side to side on flat water.

However, the stability characteristics of flat bottom and V-hull kayaks are opposite in waves, chop or current: in these conditions, a V-hull kayak will feel more stable and resistant to capsize than a kayak with a flat bottom. In general, V-hull kayaks are more efficient to paddle, with better speed and glide than flat bottom kayaks. V-hulls are typically associated with more advanced kayak designs while flat bottom kayaks are more suitable for beginners and flatwater conditions.

Planing Hull vs Displacement Hull

The question of planing hull vs displacement hull pertains exclusively to whitewater kayaks. (Recreational, touring and sea kayaks always use displacement hull designs.) A planing hull whitewater kayak (or “freestyle kayak”) is meant for surfing stationary waves. Its flat surface feels stable and, for advanced whitewater boaters, allows the kayak to skip (or bounce) on the wave to enable aerial freestyle moves.

However, a planing hull is slower, less responsive and more cumbersome to paddle downriver. In contrast, displacement hulls are typically used on river running kayaks and creek boats. This kayak hull shape is more predictable, faster, versatile and easier to paddle—but less suitable for performing freestyle manoeuvres.

Hulls by kayak type

Recreational kayak hull design

Recreational kayaks are made for beginners and stability is the primary objective of recreational kayak hull design. In this category of kayak you’ll find flat bottom hulls for maximum stability and comfort in flat water conditions. Some manufacturers further enhance stability with pontoon or catamaran kayak hull designs. Sit-on-top kayaks often feature tri-hull (also known as “cathedral hull kayak,” “kayak dihedral hull design” or “multi-channel hull kayak”) designs that are both stable and extremely easy to paddle in a straight line.

The large surface area of recreational kayak hull designs make these types of kayaks feel slow and sluggish on the water. The greatest drawback of most recreational kayak hull design is poor secondary stability; that is, the kayak will feel more tippy and offer less forgiving performance in waves, chop and current.

Sea kayak hull design

Sea kayaks are meant for more advanced paddlers than recreational kayaks, so you can expect that sea kayak hull designs are meant for greater performance. You will find some flat bottom sea kayaks (generally boats meant for larger paddlers), but the majority have rounded or v-shape bottoms for better efficiency and manoeuvrability—and enhanced stability in rough water (a feature known as “secondary stability”).

Novice paddlers who are more familiar with recreational kayaks will immediately notice the “tippiness” of a sea kayak. However, this feeling is quickly replaced by sensations of speed and glide as the paddler develops their skills and becomes more comfortable in the boat.

Sea kayaks are longer than recreational kayaks and with greater length comes more glide and speed. These characteristics are enhanced in kayaks with straight keel lines (that is, kayaks with little upsweep in the hull from bow to stern, A.K.A. “rocker”).

Some high-performance kayaks, including those manufactured by Epic and Stellar, feature plumb (near-vertical) bow and sterns which further lengthen the keel line and contribute to greater speed and efficiency. The trade off to a long keel line is less manoeuvrability; shorter kayaks, and those with more rocker, or upsweep to the keel line at the bow and stern, tend to be easier to turn.

Racing kayak hull design

As a rule, racing kayaks feature displacement hulls with long, straight keel lines. The bow and stern of racing kayak hulls are plumb (nearly vertical) to lengthen the waterline. A longer waterline equates to more speed and straighter tracking, both of which are definite attributes in a racing or fitness kayak.

However, these characteristics severely hinder manoeuvrability. As a result, most fitness kayaks feature rudders for easier handling and turning. Racing kayak hulls have round cross-sections to minimize surface area for less resistance and optimal glide.

Sit-on-top kayak hull design

Sit-on-top kayaks are designed to be stable, a characteristic that’s built into sit-on-top kayak hull design. Basic sit-on-top kayaks achieve stability with a flat bottom. This hull design offers great stability but has unremarkable paddling performance in terms of glide and manoeuvrability. Some sit-on-top kayaks use pontoon or catamaran hull design, essentially creating two round hulls on either side of the kayak, to maximize stability with a slight reduction in drag.

The best sit-on-top kayaks use a cathedral hull design, which capitalizes on the stability of a catamaran but adds a center v-shaped keel line running from bow to stern for better tracking, as well as rockered side panels for manoeuvrability. Expect to find these hull designs in Ocean Kayak sit-on-top kayaks.

Whitewater kayak hull design

Whitewater kayak hull design is divided into two categories: Displacement hulls, which feature round or arched bottoms for a blend of paddling performance (manoeuvrability, glide, ease of handling) and stability; and planing hulls with flat bottoms and some upturn at the bow and stern and hard, boxy edges (where the sides of the kayak meet the bottom).

Displacement hulls are predictable for use in river running and creek boating situations, while planing hulls can skim, skip and bounce on a stationary wave to enable acrobatic freestyle kayak manoeuvres.

The bulk of this article appeared in Paddler Magazine as s part of that publication’s “Buyer Guide.
Paddler Magazine is published by Rapid Media of Palmer Rapids, Canada.