Sea Kayaks: There is No Such Thing as Secondary Stability

Surfing the breakwater at the Great Lakes Sea Kayak Symposium. P&H Capella 163.

Tippy kayaks are tippy. Stable kayaks are stable. Seriously.

Secondary Stability and Seaworthiness 
Flip through a sea kayak catalog, read a book on sea kayaking or click through a website and you’ll soon come across the concept of secondary stability. The idea is that the stability of a kayak can be judged in two ways: how stable the hull feels while upright vs how stable it feels when leaned over on edge. Initial stability is upright stability. Secondary stability is resistance to capsize when the kayak is put on edge.

For example: a certain kayak might feel tippy when sitting upright, but more stable on edge. Such a kayak would be said to have light initial stability and good secondary stability. Another kayak might feel very stable sitting upright but offer little resistance to capsize on edge. Such a boat would be said to have good initial stability but poor secondary stability.

Resistance to capsize is pretty helpful when it comes to paddling in rough water, so secondary stability is generally thought to contribute to seaworthiness in a kayak. This means that another way to think about the concept is to say that boats with good secondary stability are more stable in rough conditions, while those with good initial stability are more stable on flatwater.

The whole idea does get a little bit squishy at times, with the term secondary stability alternately used to refer to seaworthiness and to stability on edge.

For instance, round or V-shaped hulls are typically less stable when upright than flat hulls. They have light initial stability. Many of these hulls do firm up on edge–good secondary stability. Since secondary stability is generally associated with seaworthiness it isn’t too much of a leap to think that V or rounded hulls are inherently more seaworthy than flat hulls. The logic doesn’t follow perfectly, but it is close enough to be sticky.

Put another way it could be said that boats with light initial stability are more seaworthy than those with high initial stability. The way this is typically explained is to say that hulls with light initial stability are easier to hold upright in rough conditions because they are easily put onto edge. Flatter kayaks with good initial stability are though to be more difficult to control in these situations because the flatter hulls are more difficult to put on edge.

This sort of reasoning is usually accompanied by illustrations showing cross sections of kayaks on waves. These invariably show the V or round bottomed boats remaining upright on the face of a wave, while the flat bottom boat tips over.

The whole thing is further complicated by the fact that kayak manufacturers are in business to sell kayaks. The idea that boats with light initial stability and good secondary stability are inherently more seaworthy than flatter, more stable kayaks is a good way to convince somebody to buy tippy kayak. If all you have to sell are tippy kayaks, you’ll need to come up with a good explanation for why tippy kayaks are superior to stable kayaks.

The combination of all these factors has created a persistent meme in the sea kayak world. Conventional wisdom has it that boats with rounded or V hulls and light initial stability are easier to control in rough conditions than those with flat hulls and high initial stability.

For a long time I bought into this idea, but the longer I paddle the less sense it makes to me. After years of paddling and selling sea kayaks I’ve come to the conclusion that the whole discussion of initial and secondary stability isn’t really all that useful. It’s a distinction without a purpose. Kayaks are either stable, or they’re not.

Questioning Conventional Wisdom
Back in the late 90’s I had the chance to go over to Nigel Dennis’ place in Wales as part of a dealer meet put together by Great River Outfitters. GRO imported Nigel Dennis Kayaks and Valley Canoe Products, and had put together the rendezvous for a few key dealers so they could paddle the boats in real world conditions to learn how they performed. I was out with a group in Trearddur Bay, swapping in and out of different kayaks and catching rides on the surf rolling in off the Irish Sea. I’d had a chance to surf the new Nordkapp Jubilee and switched into an NDK Greenlander Pro to see how the two boats compared.

The Nordkapp is a classic, British style sea kayak with a V-hull, fine ends, and a reputation for tippiness. I had an earlier version of the Nordkapp myself that was less stable than the Jubilee, so I was comfortable in the boat and caught a few good rides. What shocked me is what happened when I switched over into the Greenlander Pro. On the same break, with the same size waves I felt massively more stable and in control. This despite the fact the the Greenlander has a much flatter hull than the Nordkapp.

Making time in a Nordkapp Jubilee. North coast of Unalaska Island 2001. Photo: Stan Chladek.

When I hit the beach I talked to a few people about my experience. Most were puzzled that the Greenlander felt more stable to me. Conventional wisdom held that, with its lighter initial stability, the Nordkapp should have been more stable in rough conditions. The flatter Greenlander Pro should have been pushed around by the waves more and felt less stable. My experience was the opposite.

Tippy Kayaks
A few years earlier I had a chance to paddle a very unstable sea kayak for a few months. I was looking to find a faster kayak to replace my 16-foot NDK Romany and a friend up in Marquette, MI told me I should check out his Vyneck. On my initial test paddle of the boat I landed on a rocky beach and damaged the gel coat. I offered to repair the damage and James told me to take the boat home and paddle it for a while to see if I could get used to it. I never did.

The Vyneck is a Nigel Foster design with zero rocker, a round bottom and virtually no felt-stability. It’s a truly tippy kayak. The Vyneck has very light initial stability and no secondary stability. It doesn’t feel more stable on edge. It heads toward the edge and keeps on going. The boat is also a little hard to roll. Once it’s upside down it likes to stay that way. Some kayaks have good initial or secondary stability, the Vyneck has tertiary stability.

I paddled the Vyneck for several months and did some trips out of it. In rough conditions I had to keep an active paddle blade in the water at all times. I could NEVER take my hand off the paddle. I remember one occasion when I reached up to take my hat off and capsized. Forget about accessing the dayhatch. Unloaded, loaded, rough water, flat water it didn’t matter. The boat was unstable.

After the gelcoat repair, I returned the Vyneck and ordered up a Nordkapp HS. For several years I paddled this boat almost exclusively. The Nordkapp was a little tippy, but at the time there weren’t a lot of options in fast expedition kayaks. I accepted the tippiness as a tradeoff for increased performance, and set about learning how to paddle.

Eventually I learned a few tricks that improved my comfort. The most important of these was relaxing my lower body in rough water.

The original Nordkapp has a distinct feeling of twitchiness in reflecting waves and turbulent water. You can get the boat to settle down if you drop your knees away from the deck and relax your lower body. This technique is very useful in a boat with light stability. Dropping your legs away from the thigh braces allows your upper body to move independently from your lower body, lowers your center of gravity, and prevents you from over-compensating with your knees to try to keep the boat bolt upright. In weird reflecting waves it makes a big difference.

Dropping your knees is a huge help if you’re trying to stay on top of an unstable kayak in rough conditions, but the fact you need a special technique in a boat like this gives lie to the conventional idea of secondary stability. If a tippy boat was naturally more sea-kindly you wouldn’t need a special technique to keep it upright in rough water.

NDK Romanys on the beach near Lake Superior Provincial Park, Ontario.

NDK Romany and Explorer–Narrow and Stable
The Vyneck and Nordkapp are both narrow boats, but that’s not the reason that they feel tippy. There are plenty of narrow sea kayaks that offer good stability. For example, the Valley Anas Acuta is a half inch narrower than the Vyneck but is dramatically more stable. Likewise, the NDK Romany and Explorer are only slightly wider than the Nordkapp, but much more stable. The difference between stable narrow boats and tippy narrow boats comes down to hull shape. The stable designs are flatter.The Anas Acuta, Romany and Explorer share a flat hull cross section that contributes to solid stability in rough water.

There’s a good reason that all three of these boats share similar stability and hull profiles. The Romany was designed by Nigel Dennis and Aled Williams back in the early 1990s. Nigel wanted a boat that would be good for introducing paddlers to rough water paddling around Angelsey Island in North Wales. If I remember correctly, Nigel had a mold for the Anas Acuta at his kayak center and had been making a few of these kayaks on site. The Anas Acuta was stable enough for beginners, but it had a small, round, traditional cockpit that was difficult to enter and exit during landings and rescues.  Nigel approached Frank Goodman at Valley and asked if he could modify the Anas to create a new boat for his center. Frank agreed and the result was the Romany, a 16 foot sea kayak with a fairly flat hull, keyhole cockpit, rear dayhatch and sloping rear bulkhead for ease of rescues.

[Nigel told me that Goodman called him back a few days later and said that Valley wanted to work on an update of the Anas Acuta as well. The result was the Pintail. The Pintail and Romany are distinctly different boats but both are evolved from the Anas Acuta].

A few years after the Romany was introduced in the US, NDK launched the Explorer: a 17’6″ version of the Romany for expedition use. I’ve had the chance to paddle the Explorer and Romany over at Angelsey in big tide races and surf, and all over the Great Lakes region. They are two of my favorite boats.  Both boats are 21.5 inches wide and have a flat bottom with a slight V. Both are stable on flatwater and in rough conditions despite their narrow width and flat hull profile.

Surfing the Quest in the Triangle. 2003. Photo Nigel Law.

P&H Quest–A Little More V, A Little Less Stable
In August of 2003 I headed down to Tybee Island, Georgia to work for a few months at Sea Kayak Georgia. On the way down I stopped into Asheville, NC and picked up a P&H Quest from the US distributor, Pyranha US. I hadn’t paddled a P&H boat before, but I was between kayaks and Jim at Pyranha was gracious enough to loan me a boat for a few months. P&H was just being reintroduced to the US market and Pyranha US was hot to get the boats into the market and in front of potential buyers.

At 22 inches, the Quest is a half inch wider than the NDK Explorer, but it has a more sharply V-shaped hull and finer ends. I paddled the Quest for a couple months down at Tybee and spent a lot of time out in the Triangle surfing the boat and playing around. I also loaned the boat out to a on guided multi-day tour, so I had a chance to see how stable it was for an inexperienced paddler. The Quest was fast and straight tracking, but less stable in rough water than the Explorer. The sharp ends and deep forefoot of the Quest made it difficult to surf, and the V hull felt less secure in lumpy conditions. It was a fun boat to paddle but I didn’t think it was as well balanced or versatile as the Explorer.

Toward the end of my time on Tybee I had an experience in the Quest that confirmed my opinion of the boat’s stability characteristics. At the end of BCU Week that year I took my BCU Level 3 Coach exam in the Quest. One of the exam’s tests was to throw away your paddle, pull out your spare, assemble it and retrieve your primary paddle. Out in the Triangle I tossed away my paddle, reached for my spare, and capsized with half a paddle in each hand. The Quest didn’t have the kind of stability I needed for coaching in rough conditions.

P&H Cetus–Flat and Eye Opening
I wasn’t the only one who had trouble with the Quest. Most of the team guys who paddled for P&H around this time found the boat to be less stable and less maneuverable than they would have liked. P&H had two boats that were extremely popular with coaches and team paddlers: the Capella 163 and Capella 161. These were flat bottomed stable kayaks that were easy to coach out of and fun to paddle in rough conditions. Unfortunately, they were too short to load up for an extended trip. The guys wanted a more stable expedition boat from P&H. Something like the Capella but longer. Something like an Explorer.

Teaching at the Door County Sea Kayak Symposium. Capella 161. Photo Jim Pippit.

Pyranha/P&H owner Graham Mackereth went to work designing the new boat. When the Midwest guys saw the first pictures we thought he had it all wrong. The boat was was Swede form (widest behind the seat) and we had hoped it would be fish form (widest toward the bow) or at least symmetrical like an NDK Explorer. The sea kayak scene in the Great Lakes had been heavily influenced by Stan Chladek, owner of Great River Outfitters and Stan was a big proponent of the fish form designs from Valley Canoe Products. GRO also sold Nigel Dennis’ symmetrical Romany and Explorer designs, which were hugely popular. We had all come up in these boats and were more or less convinced that there was only one right way to design a kayak. Boy, were we wrong.

The Cetus very much looks like a stretched out Capella 161. It has a flat hull cross section that is widest just behind the cockpit, and very little rocker in the stern. This combination of features lets the Cetus do things that I didn’t think were possible in one design. The Cetus is both stable and easy to edge. It has good initial stability AND good secondary stability.  It tracks straight when upright but turns nimbly on edge. It is very fast but not at all tippy.

The stability of the Cetus is probably the most shocking part of the design, especially for someone who is used to paddling boats like the Nordkapp or Quest.

The first time I paddled the Cetus was on a sales rep tour of New England in 2009. By this time I was working for P&H as a sales rep and making the rounds of shops in the territory to introduce myself.

I met up with John Carmody and joined him and a class for a foggy paddle near Popham Beach on the coast of Maine. A half hour or so into the paddle we were all playing a game that involved throwing a sponge as close to the rocks as possible and then going in after it. The sea was a little bumpy and there were 3 foot, reflecting waves bouncing off a low cliff face. I chased after the sponge, threw it for someone else and noticed that I was completely comfortable in the boat. Stable. Not twitchy. Sitting still with my paddle across the spraydeck. Looking back over my shoulder at the game. The boat was shockingly stable.

At 22 inches, the Cetus isn’t much wider than a Nordkapp or Explorer, but is flatter than either, and it feels more stable than both. The Cetus feels stable on flat water. It feels stable in rough water. It feels stable while surfing. The Cetus’ rough water stability is superior to any round or V hulled kayak I’ve paddled. And I’ve paddled quite a few.

Over the last 25 years I’ve had a chance to paddle a lot of sea kayaks. In addition to the  Nordkapp HS, Vyneck, Romany, Explorer, Quest and Cetus Classic, I’ve spent significant cockpit time in the Valley Pintail, Nordkapp Jubilee HM, P&H Bahiya,  Capella 163, Cetus MV and HV, Aries and Delphin. Along the way I started to suspect that there was more than a little hype associated with the whole concept of secondary stability. The Cetus pushed me over the edge. This was the design that convinced me once and for all that boats with flat hulls were more stable in rough water than those with rounded or V hulls.

Cetus MV. Grand Sable Dunes. Pictured Rocks National Lakeshore.

Rough Water Stability
After hundreds of hours of paddling in more than a dozen different sea kayak models, I’ve come to the conclusion that a sea kayak is either stable or it’s not. A design’s felt-stability on flat water is directly linked to its rough water stability. The factors of hull design that make a kayak feel rock-solid stable on flat water also contribute to a feeling of stability when things get lumpy. Flat water and rough water stability are so directly linked that it isn’t really useful to draw a distinction between them.

This means that there really is no such thing as secondary stability. At least not when it comes to seaworthiness.

What, then, makes a kayak feel stable in rough water? I think it boils down to two main factors: predictable motion and ease of edging. Predictable motion is provided by a flat hull, and a flat hull is easy to edge if the kayak is narrow.

Predictable Motion
Predictable motion is probably best defined as what a kayak feels like as a wave passes under the hull. This is most dramatically felt when the wave comes from the side or quartering from the rear. As the wave passes under the hull, does the hull feel like it wants to capsize or not? If the hull reacts to the wave, does it react abruptly, or slowly?My experience suggests that V or rounded hulls tend to have a more active and abrupt motion in these sort of conditions. As the wave passes under the hull it tips first one way and then the other. A flatter hull has much less of a tendency to snap quickly from one gunwale to the other and feels more stable.

The more predictable motion of a flatter hull allows the paddler to be more relaxed, which in turn contributes to even more felt-stability. A hull with an abrupt, twitchy motion from side to side frequently causes a paddler to tense up and over-correct in an effort to keep the boat upright. Increased tension at the thigh braces locks up the torso and makes it more difficult for the paddler to keep his body over the top of the kayak. This exaggerates the motion of the hull and makes the kayak feel tippier still. It’s a feedback loop that can be hard to break. I know, from personal experience. After an epic beatdown in my Nordkapp one November I was so rattled that I didn’t know if I would ever get comfortable in the boat again.

Ease of Edging
Predictable motion leads to confidence and increased real stability in rough water. Ease of edging becomes important as waves steepen.

Unlike larger boats, sea kayaks have a dynamic center of gravity. If you’re in a flat bottomed john boat and a big wave hits you from the side there is little that you can to to keep the hull level and prevent capsize. Likewise, if you are in a wide, flat bottomed recreational kayak on a steep wave you’re likely headed for a swim. In these scenarios, the diagram of the wave flipping the boat becomes very real.

If you are in a properly fitted sea kayak you have complete control over the angle of the hull as it meets the wave and the position of your body over the kayak. Not only can you keep your body (center of gravity) in balance over the hull, you can also edge the hull toward the wave with your lower body to resist the rotational motion of the wave and keep your boat upright. As waves steepen and eventually break, the ability to edge a hull toward the wave is a critical part of avoiding capsize.

Round and V-bottomed hulls are easy to edge because they are tippy when upright. With a paddler in the cockpit, these hulls want to fall over toward their gunwales rather than sit upright in the water. The best of these designs begin to resist capsize as their gunwales near the water. The worst of them keep on going, like the Vyneck.

Flat bottomed kayaks feel more stable than rounded or V-hull boats, but that doesn’t mean they are hard to edge. Some flat hulled designs, like the Cetus, are extremely easy to edge, and respond to subtle shifts of weight in the seat, despite their very flat hull cross sections. In the case of the Cetus, edging is made easier because the widest point of the hull is just behind the cockpit. This asymmetric shape also contributes to the overall feeling of stability that the Cetus provides.

The key to edging a flatter hull lies in correctly fitting the kayak to the paddler’s weight and height. A flat bottomed boat that’s too wide will be difficult to edge. For most folks, a kayak under 22 inches will get the job done. Lighter paddlers will need narrower boats. Heavier paddlers will be able to edge wider boats with no trouble and will benefit from the added stability of a wider hull. Many manufacturers now offer different widths in popular models in order to accommodate a wide range of paddler sizes. The best way to know which size is correct for you is to paddle the designs side-by-side.

Sea Kayaks are Either Stable or Tippy
The combination of predictable motion with ease of edging creates a kayak that is stable in rough conditions. Narrow, flat bottomed kayaks tend to have a more predictable motion than those with distinctly V or round shaped hulls. Narrow, flat bottomed kayaks are easy to hold on edge, particularly if they have an asymmetric plan design. Boats like this are stable. Period.

The concept of secondary stability and associated ideas about hull design are more applicable to boats that have a fixed center of gravity or cannot be edged by the paddler. Modern performance sea kayaks with flat hull profiles have a dynamic center of gravity and can be easily edged, so there is little benefit to rough water stability from a V or rounded hull. In fact, the opposite is true: in narrow hulls, a V or rounded cross section contributes to a decrease in felt stability in rough conditions.

What this means is that if you test paddle a kayak in calm conditions, and find it to be stable and easy to hold on edge, you can reasonably expect it to remain stable in rough conditions. If it feels tippy on flat water it will feel the same or worse in rough conditions. If its hard to hold on edge in flat water it will be difficult to edge in the rough stuff and, consequently, more difficult to control. Flatwater performance dictates rough water stability.

If a kayak is stable, its stable. Don’t worry about secondary stability. It isn’t even a thing.

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