Monday, October 14, 2013

Kayak Hull Designs.

       I often get asked about different kayaks by people interested in kayak fishing. Most of the fear about kayak fishing is tipping, or flipping over on the water. While I maintain the "tipy" feeling will go away with time; the shape of the hull will affect the movement of the kayak through the water. This week Joe Dowdy of Austin Kayak writes about kayak hull designs. 

Types of Kayak Hull Designs

            Before you add all the fun accessories like seats, mounts, skirts, cleats, bungees, hatches, and other goodies you've come to love about your kayak, you have the good ole hull. A kayak’s hull is really its bare bones form and is usually dressed up before it even leaves the factory. When you really take a deep look at them, you’ll notice that no single hull looks the same. Often, they look similar, but kayak hull designs vary drastically and there’s a reason behind it!
           Though each and every brand has its own unique style of kayak’s, hulls are actually shaped to fit specific purposes. An evident example would be comparing a whitewater hill to a sea kayak hull. A whitewater hull is commonly short, rounded on the sides, with a curving bottom and a sea kayak hull is usually long, pointed, and with a flattened bottom. It’s pretty easy to tell that these kayaks are meant for different things and probably pretty easy to guess the reasons behind the designs as well.
Hull Shapes
Generally, there are four common types of hull shape designs. These include rounded, v-shaped, flat and pontoon hulls—though, it’s possible that you’ve heard them referred to as other names in different places.
Rounded Hulls – These hulls have rounded edges (wonder where they got their name from) giving the kayak a ‘torpedo’ shape that results in increased speed because of less water resistance. These round shaped hulls make for more steerable kayaks as well and commonly have more secondary than primary stability (more about this soon enough).
V-Shaped Hulls – Differing from the rounded hulls, these hulls have a pointed ‘V’ shape that allows the hull to better slice through the water making them better at tracking in straight lines. These hulls are generally fast and sometimes considered ‘tippy’ as they offer more secondary than primary stability.
Flat Hulls - Flat hulls are pretty universal because they have a 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 unfortunately aren't known for their speed.

Primary Versus Secondary Stability
Aside from the kayak’s basic shape, the hulls vary in the ways that they curve or not. This curvature can be in either the bottom or sides of the kayak, and is referred to the rock and chine, respectfully. These curves can affect a wide variety of factors when it comes to performance—the biggest factor being stability.
Basically, kayak stability is broken down in two sections: primary and secondary. Primary stability is the initial steadiness of the kayak on flat water. Secondary stability is the kayak’s ability to stay stable when tipped on its side. Secondary stability is extremely useful in bad water conditions. Often, kayaks that are extremely stable in rough water feel unstable in flat water and vice versa. Kayak manufacturers fiddle with a number of factors to find the right balance of primary and secondary stability for each kayak’s intended purpose. For example, a kayak built for coastal fishing is designed to take primary stability into consideration for fishing, but also secondary stability for when water gets choppy.
Chine
Chine basically means the way the bottom of the kayak meets the sides. The shape of the chine determines whether or not the kayak looks boxy or rounded. A hard chine means a more angular meeting compared to a soft chine, which has a rounded meeting. Hard chine hulls are known to track slightly better and offer more primary stability because it can swiftly cut through water. However, it provides a flatter surface for choppy waters to push against, making them more prone to tipping in poor water conditions. Many people like to use hard chine hulls as play boats because the sharp edges make it easier to perform tricks. Soft chine hulls, on the other hand, are better at providing secondary stability and are generally known to be faster. It is important to remember that soft and hard chines are simply the extremes. There are an enormous number of multi-chine hull designs that exist between the two polar ends of hard and soft.
Rocker
Rocker is the curvature of the hull from bow to stern. The term 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 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.
                                                    



About the Author:
Joseph is an avid kayaker based out of the central Texas area. He has spent many a weekend and holiday on the Texas coast attending sea kayaking events or just having some fun with a kayak or paddleboard. He’s currently employed at Austin Canoe and Kayak (ACK.com) and loves that he gets to spend time working with his favorite toys. 





       With all the hype over wide slow stable kayaks these days I still don't recommend cutting speed for stability like so many do. You will understand if you are ever trying to get up river to catch up to a friend in a skinnier kayak. Don't get me wrong, if a slow stable kayak is what it takes for you to enjoy the water then don't mind me. The best way to find out what you want it to research and try out different kayaks.

Thanks for reading,

Dan


2 comments:

  1. There is also Tim Neimier's California Hull. It's a cross between a flat and V. Take a look at the Ocean Kayak photo at the beginning of the post, and you'll see the California Hull/

    ReplyDelete
    Replies
    1. Good eye. There are other combo hulls out there as well, such as the pontoon/V on the new Old Town Predator. Thanks for reading and commenting.

      Delete

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