A Look at Kayak Hull Designs

| August 30, 2012 | 4 Comments

Before you start adding in the seats, skirts, mounts, pedal drives, cleats, bungees, hatches and all the other features you’ve come to love about your kayak, you have the hull. A kayak’s hull is its bare bones form and usually is dressed up before even leaving the manufacturer. But when you really look at them, you’ll notice that not one single hull looks the same. Ok, sure they sometimes look similar, but kayak hull designs can also vary drastically – and there’s a reason for this!

While each brand has its own unique style of designing kayaks, hull’s are really shaped to fit specific purposes. An obvious example would be comparing a whitewater hull (commonly short, rounded on the sides, and with a curving bottom) to a sea kayak hull (usually long, pointed and with a flattened bottom). It’s easy to tell that these kayaks are meant for different things, and you can probably guess some of the reasons behind the designs as well!

Hull Shapes

While basic hull designs are by no means limited to any set group, we do notice that there are four common types. These include rounded, v-shaped, flat and pontoon hulls, though it’s likely you’ve heard them referred to as other names in different places.

Rounded Hulls – These hulls, as their name implies, have rounded edges giving the kayak a ‘torpedo’ shape that results in increased speed because of less water resistance. Rounded hulls usually make for more maneuverable kayaks as well and commonly have more secondary than primary stability (more about this in a moment).

V-Shaped Hulls – Compared to rounded hulls, these hulls have a sharper ‘V’ shape that allows the hull to better cut through the water making them more effective at tracking in straight lines. These hulls are generally fast as well and sometimes considered ‘tippy’ as they offer more secondary than primary stability.

Flat Hulls - Flat hulls are used for a surprising variety of purposes ranging from play boats to fishing kayaks. The reason is, based on other factors like length, width and curvature, flat hulls combine stability and maneuverability. Flat hull also offer great primary stability.

Pontoon Hulls (AKA Tunnel) – Stability is the key feature of pontoon hulls. Kayaks with these types of hulls combine the primary stability of a flat hull with the secondary stability of a rounded resulting in the the greatest stability available. While these hulls generally lend themselves to decent tracking they aren’t known for their speed.

Primary Versus Secondary Stability

Other than the basic shape, kayak hulls vary in the ways that they curve (or don’t). This can be in either the sides or bottom of the kayak, and is referred to as chine and rocker, respectfully. These curves, or lack thereof, affect a number of factors when it comes to performance – the main one being stability.

Kayak stability is broken down into two sections: primary and secondary. Primary stability refers to the initial steadiness of the kayak on flat water, whereas secondary stability refers to a kayak’s ability to stay stable when tipped on its side (something useful in poor water conditions). Often kayaks that are very stable in rough water feel tippy in flat water and vice versa. Manufacturers tinker with a number of factors to find the perfect balance of primary and secondary stability for each boat’s intended purpose. For example, a kayak intended for coastal fishing will be designed to consider the primary stability needed to fish but also the secondary stability necessary to handle choppy waters.

Chine

Chine is best defined as the way the bottom of the kayak meets the sides and determines whether or not the kayak looks rounded or boxy. A hard chine means a more angular meeting compared to a soft chine which refers to a more rounded one. Harder chine hulls are known to track slightly better and offer better primary stability but also provide a flatter surface for choppy waters to push up against – thus these boats are more prone to tipping in bad water conditions. Hard chine hulls are also popular for play boats because the sharp edges catch waves better and make it easier to perform tricks. On the other hand, soft chine hulls are better at providing secondary stability and also are said to generally be faster. Of course, soft and hard chine are simply the extremes – an enormous number of multi-chine hull designs exist somewhere in between the two.

Rocker

Rocker is the curvature of the hull from bow to stern. The name rocker comes from the fact that the more rocker a hull has (more curvature), the more likely it is to rock from front (bow) to back (stern). More rocker allows for greater maneuverability because the bow and stern have to face less resistance as less of the boat is in the water. For this same reason, hulls with more rocker are less effective at tracking than hulls with less rocker. In fact, a kayak with a flat bottom or, in other words, no rocker will track best as the bow and stern will have most resistance in the water (of course preventing easy turning). Like a hull’s chine, kayaks can have any amount of rocker and can even have rocker only in the bow but not the stern or vice versa.

Is that it?

Design symmetry, weight positioning, hull materials, water entry line and other more specific features (like sponsons or keel lines) are just a few of the other factors that manufacturers take into consideration when designing a kayak. However, knowing the basics about hull shape should help you make a more informed decision on which kayak will best suit your needs and purpose. As always, if you have any comments or questions, share them below – we’d love to hear what you have to say or answer any questions you may have! Thanks for reading and happy paddling. – Joseph@ACK

 

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Category: Kayaking, Knowledge, Resources

Comments (4)

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  1. Rod says:

    Thanks Joseph, you have really explained the basic consepts very well. Where the manufacturers trick us with some of their designs is when they use combinations of these concepts in different parts of the hull. I was particularly interested in your explaination of primary and secondary stability. I had always thought primary stability was stability in the upright position and secondary stability was the kayak had better stabilty when it was leaned on a side. I suppose the result is the same.

    • jdowdy says:

      Rod,

      After reading your comment, I went ahead and reworded my explanation in the blog. Thanks for the feedback, glad you liked the article!

      Joseph

  2. Chris says:

    I want to build a “boat” strickly for fly fishing in ponds & small lakes, (No waves except from wind and no current.), It will be a one man boat and I want it as light as possible so I can use my truck and no trailer. I would like to be able to stand up to cast but be able to paddle with my kayak paddle sitting down, so I do not want it too wide. (Probably between 32 an 36 inches. I figure about 11 feet long. My question is what is the best hull design? I have had many boats and read alot about hull design but really would appreciate your advice. Thanks

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