If you’ve test paddled a sea kayak at any time in the last 20 years, you’ve probably heard about secondary stability. The concept is much discussed, particularly within the world of performance sea kayaks. Often, a sales clerk will mention the term to reassure someone in a seemingly-tippy kayak during a test paddle. “This kayak has light initial stability, but it has excellent secondary stability,” they’ll say reassuringly.
The idea of secondary stability is so ingrained in the world of sea kayaking it’s hard to imagine the concept isn’t valid, but I’m here to tell you it doesn’t hold water in the real world. It’s complete bunkum.
Before I make this case, we have to agree on definitions so we’re talking about the same thing. For this discussion, let’s agree secondary stability—as distinguished from initial or primary stability—has two distinct meanings. The first is the tendency of a hull to resist capsize as its edge or deck nears the water. With this definition, a tippy kayak with light initial stability might be said to have good secondary stability if it feels more stable on edge than upright. The second meaning of secondary stability is usually conflated with seaworthiness. The same tippy kayak with light initial stability might be thought to have good secondary stability in rough conditions. According to this theory, a narrow and round hull or V-hull causes a feeling of tippiness on flatwater but will be less affected by choppy waves than a flatter, more initially stable hull.
Both these concepts are widely accepted—and both are completely wrong.
The problem isn’t that secondary stability doesn’t exist. It’s just it only exists in theory, in nautical computer models and flat-bottomed jon boats, not in the real world of sea kayaks. Here’s why.
Let’s unravel our first definition. If a boat has a round or V-hull, it is likely to feel unstable when held directly upright on flatwater. With a good design, such a hull will feel more stable as it tips onto its edge, as long as the paddler can keep his body over the hull. This is the crucial bit and where the whole idea of secondary stability goes right out the window. This kind of secondary stability depends on paddler skill. As soon as the paddler shifts his shoulders over the water, the boat will capsize. No amount of secondary stability will prevent this from happening.
The problem with the second definition of secondary stability stems directly from the first. A boat which feels unstable on flatwater will have quick motion from side to side. Such a boat feels like it wants to fall over on edge rather than sit upright. In rough conditions, this creates a snappy motion many paddlers find unsettling. The natural reaction to this motion is to firmly grip the thigh braces with your legs and hold on for dear life, trying to keep the boat upright. If you do this, you’ll find the boat begins to feel very unstable, very quickly.
The quick motion of a narrow and round or V-hull kayak makes it very easy to overcompensate in choppy conditions. Firmly locking your legs to the cockpit rim makes it impossible for you to let your body hinge at the waist. This makes it nearly impossible to keep your shoulders above the hull. As your shoulders pendulum from one side to the other, the feeling of snappiness in the hull is exaggerated. Experienced paddlers drop their legs away from the thigh braces in these conditions to prevent this sensation. Again, we sell paddler skill as the key element in the feeling of stability, rather than secondary stability inherent to the hull design.
By way of these two examples, we can see the concept of secondary stability isn’t particularly helpful when it comes to sea kayaks.
Any sea kayak will tip over if you put your shoulders over the water, regardless of how it scores on some theoretical computer test of secondary stability.
If a kayak feels tippy on flat water, it will also feel tippy in rough conditions. Given these realities, it doesn’t make any sense to talk about secondary stability. In the real world it doesn’t exist.
If good secondary stability isn’t the key to stability and seaworthiness in a sea kayak, what is? Predictable motion and ease of edging.
Predictable motion is the opposite of a feeling of quickness from edge-to-edge. It’s provided by a boat mostly flat under the cockpit, carrying flatness most of the width of the hull. The sensation of stability is enhanced if the widest part of the kayak is near the seat. A flattish hull feels stable when upright and lacks the tendency to shift quickly onto its edge. It has a predictable motion. This predictable motion helps any paddler at any skill level to be more confident, more relaxed and better able to remain in balance.
You might be tempted to believe such a flat hull would be pushed around or even tipped over in rough water. This might be the case if you’re rowing a jon boat or paddling a wide recreational kayak, but it isn’t true in a properly fitted sea kayak. If your kayak is narrow enough, it will be easy to hold on edge, even if it has a flat hull. A kayak that can easily hold an edge will not be tipped over by choppy waves. Instead, such a kayak will allow the paddler to shift her weight in the seat to keep the hull upright as the wave passes under her kayak. With the kayak upright, it is easier for the paddler to keep her body centered above the hull for maximum stability.
So, there you have it. Stable kayaks are stable and tippy kayaks are tippy. Secondary stability doesn’t enter into the equation. If you test paddle a kayak on flatwater and find it stable and easy to hold on edge, you can reasonably expect it to remain stable in rough conditions. Despite conventional wisdom, secondary stability isn’t a useful concept when it comes to sea kayaks. Forget about it.
Contrarian Brian Day has been paddling sea kayaks, teaching kayak skills and sharing unsolicited opinions about outdoor gear since the early ’90s. Please direct your rebuttals to [email protected]
Secondary stability isn’t a useful concept when it comes to sea kayaks. Agree or disagree?| Photo: Kevin Light