Kayak Buyer's Primer
Written by S.W. - Sailsport Marine January 1997
As of this writing, kayaking has become one of the fastest growing outdoor recreations in the country and we are lucky to be surrounded by some of the best and most beautiful paddling waters here in Northern Michigan. Hopefully this primer will help those of you who have just started thinking about kayaking or those who are confused by the huge array of different boats available that are called kayaks.
The first thing to decide when looking for a kayak is what you want to use it for. Kayaks can fall into three general types of use designations: Touring, Whitewater, or Recreational. Touring boats are for paddling in the open water and have enough volume to store gear for camping or day trips. Whitewater boats are made to be maneuverable and easy to spin around any obstacle. Recreational boats are designed for all-around fun, comfort and simplicity. Depending on what the boat's use is to be, it is designed around three basic design variables: length, width, and hull shape.
Length of a boat determines speed and maneuverability. Maximum hull speed of any displacement boat is determined by length. All kayaks act as displacement boats (unless they start surfing). A longer boat has a higher hull speed. A longer boat also has more resistance to being spun around, so it is less maneuverable and tracks a straight line better.
The width of a boat is the main factor for stability. A wider boat is generally more stable. Although stability in flat water and stability in waves are two different and opposing things, we will start on the premise that most beginning paddlers are going to start in calm waters. A wider boat is also going to have more wetted surface area, causing more drag, so it will be slower.
Hull shapes can determine maneuverability and stability too. Looking at the profile of a boat can give an idea of maneuverability. A boat with a curved or rockered shape is going to be more maneuverable than one with a straight bottom front to back. This also means it will not track a straight line as well.
We look at the cross section of a hull to determine stability. A flat bottom will give a boat greater initial stability, but less stability in waves. A more rounded bottom will give less initial stability but a smoother feel that is easier to keep upright in waves.
Now we can try to tie all these variables
together with the type of boat you are looking for.
Touring boats are generally made to go in a straight line quickly and efficiently in flat water or waves and wind. To track a straight line we want a less maneuverable boat: one that is long with little to no rocker to the bottom. You don't want your boat wig-wagging back and forth - that wastes your energy. A longer boat is not only going to track a straight line better, making it more efficient in the open water, but it is going to have a higher hull speed. To go faster we also want less wetted surface area on the hull. A narrow rounded hull section gives the least wetted surface. That rounded section also gives more control in wavy conditions. A crosswind will want to round you up into the wind so we want to minimize the surface area on the side of the boat by making the deck low for less windage.
The ideal touring boat would therefore
be long (20 ft) and narrow (19 in) with little to no rocker, a rounded
bottom, and a low deck for less windage. Of course not many people are
paddling boats like this because there have to be some tradeoffs for
comfort, stability, and ease of transport. The most common tradeoff is
in the hull section and width. We can still have a good touring boat
that is fast and stable enough for most conditions without having a
boat that will capsize the first time you turn to scratch your back.
Most people don't need a 20 ft long boat either. A boat 16 ft or more
will track a nice line, will be fast enough for most, and will still
fit in your garage.
If you want a boat to paddle on rapids
you need a highly maneuverable boat that you can control every move of.
This means a short, rockered hull with a flat hull so you can slide
sideways and surf, and little ends so that the current can't grab them.
Some whitewater boats are used for surfing waves too. For wave surfing
you want a boat that planes easily and will carve a turn. For that you
want a short maneuverable boat like a rapids boat but with a flatter
hull cross section and harder rails to carve the face of a wave. Some
also have a negative rocker towards the tail and a more buoyant bow to
keep it from diving.
There is a huge range of recreational boats from solo play boats to tandem sit-on-top boats. There are too many boats that fit into this category to describe here, but they are all made for fun in a wide range of conditions.
Sit-on-top kayaks are becoming very popular because they are very simple and less intimidating. There is not the sense of being enclosed in a cockpit and if you do tip over you can simply climb right back on. There is no water to bail out. They can be made quite comfortable and maneuverable with add on seat backs and thigh straps. The drawbacks are that they are wetter and they need to be wide to compensate for the fact that you have to be sitting above the waterline, moving your center of gravity up and making the boat less stable.
If you think you may want to try paddling for fun or exercise, there is sure to be a recreational boat just for you, and your whole family.
There are four main elements to consider when looking at different hull materials: weight, stiffness, durability, and cost.
Weight is a factor to consider both in and out of the water. Obviously if a boat weighs less it is going to be easier to tote around and get on and off your roof rack, but it is also important in the water. A lighter boat displaces less water as it moves, making it easier to move through the water. It is going to make a boat more responsive to each input of the paddler.
Stiffness is a factor to consider for longer touring kayaks. A stiffer boat is a more efficient boat. If you paddle a boat that flexes under you as you paddle, that flexing is using energy that you would rather be using to propel you forward.
Durability is a very important factor for most kayakers. Nobody wants to invest a lot of money in something that won't last. Ideally you want a boat that you can accidentally drop off of your roof rack or bash into a submerged rock without worry. It goes without saying that cost is a factor in everyone's buying decision, but depending on what you intend to use your boat for, you may find that a less expensive boat is better for you.
Now we can look at the different hull materials builders are using and why. There are at least six different types of construction being used by major manufacturers: Polyethylene, Composite, Wood, Skin-on-frame, Inflatable, and ABS laminates. Rotomolded polyethylene has become the most popular material as technology has led manufacturers to stiffer and more durable plastic make-ups. Rotomolded boats are formed in a mold that is rotated over high heat. The heat melts the plastic while the rotation forces the plastic to the outside of the mold. Rotomolded boats have two of the most sought after qualities, especially for beginner and recreational paddlers. They are extremely durable and they are inexpensive. Rotomolded boats are supremely impact resistant and they will take the abuse of any beaching. They are used almost exclusively by whitewater paddlers and touring / rental fleets because of their durability.
Composite boats can be made from a variety of cloths set in a resin matrix to make a hard, tough shell. The two main cloth types are fiberglass and Kevlar. A colored gelcoat outer skin is used to protect the fiberglass form UV rays and abrasion. It also gives it a very smooth shiny finish. Most boats are hand laid -up in two molds, a deck and a hull, then joined together. This is a labor intensive operation, but boats can be made with differing amounts and types of cloth to make up a hull that can be stiff in places and light in other. It is the preferred construction for longer boats because of it's stiffness. Composite boats are extremely light, stiff, and durable, but they can be about twice as expensive as Poly and they are not as impact resistant. These boats are performance oriented and the only choice for most serious touring paddlers.
The other construction materials are not as common. Wood boats are very esthetically pleasing and can be very light and stiff, but they require quite a bit of care and maintenance. Skin-on-frame boats are the originals. The Eskimos built kayaks by this method and there are still kayaks made this way. Todays boats don't use bones and seal skins, but usually use aluminum or wood frames with a fabric skin. Some can be broken down and packed in travel bags, but these are very expensive. Inflatable boats can be good for travelers too but they are not very durable and tend to sit high off the water creating lots of windage. ABS laminates are very durable but tend to be even heavier than poly boats. Most of these constructions are used for a specialized purpose and are not nearly as common as rotomolded or composite boats.
All this points toward the the conclusion that rotomolded boats are best for beginners and recreational paddlers and composite boats are best for more serious touring paddlers. This is true in most cases, but there are some plastic boats that could satisfy the most experienced paddlers and there are some great recreational composite boats. Whatever your needs there is sure to be a boat for you.
This brief guide should help you narrow down your choices from the multitudes of boats on the market. When you are ready to choose between a couple of boats the best thing to do is paddle them to see which fits and feels best for you. The way a kayak fits you personally is a big factor in making you feel comfortable and confidant on the water.