For a general overview see: http://en.wikipedia.org/wiki/Kayak and http://en.wikipedia.org/wiki/Whitewater_kayaking
Parts of a Kayak
Choosing a Whitewater Kayak
Original By Ken Whiting, Illustration by Paul Mason
Photo by Paul Villecourt Images and Text Added on this Blog
The days of long, skinny kayaks shaped like logs with a hole carved into the top of them are gone, and along with them the performance characteristics that a log offers! Boat design is now a sophisticated process that makes use of professional designers, athletes, flashy software packages with digital simulations, and multi-prototype trial runs. Today's boats are shorter (from 1.5m to 3m, or 5 ft to 9 ft), wider (about 40 cm, or 25 in), flat-hulled, and far more thoroughly outfitted than their predecessors. These fundamental changes have afforded the paddler with substantially increased manoeuvrability, stability, and control.
The first thing we're going to do, is look at the characteristics that have the most effect over the way a whitewater kayak handles.
Rocker
Rocker is the curvature from bow to stern, as viewed from the side. As a general rule, the more rocker a kayak has, the more quickly it will turn. It will also travel through rapids more easily and surf waves with greater ease because the ends won't get caught by the incoming water.Notice the smooth and continuous rocker of this Dagger Axiom river runner . . .
compared to the extreme rocker at the bow and stern of this Liquidlogic Biscuit playboat . . .
and compared to the almost complete lack of rocker in this Dagger Zydeco recreational touring boat.
Hull Shape
There are two types of hulls that you'll find in a whitewater kayak. There are planing hulls and displacement hulls.
Planing Hulls are flat hulls that create a very wide footprint in the water. They are the most common form of kayak hull because they are the most stable, and surf waves incredibly well. The edges of the "planing" hull are bevelled up to the sidewalls at varying angles of aggressiveness; the more bevel, the "softer" the edge, and therefore the more forgiving and less tippy the boat will be when its side is exposed to the current. Displacement Hulls are rounded hulls. These were once the standard for whitewater kayaks, but have been largely replaced by the preferred planing hull. Displacement hulls track most effectively and are easily tilted on edge, but they aren't as stable or as manoeuvrable as planing hulls.
Boats designed specifically for playboating (surfing and performing various other acrobatics) will typically be shorter, have wider planing hulls, larger sidewalls, and more aggressive edges to maximize performance and manoeuvrability. These boats will also tend to have less volume in the bow and stern to allow the ends of the boat to be forced under water easily when desired. Boats designed for more all-around river running are typically a bit longer for increased speed. They also have narrower hulls that carve a better track in the water, more bevelled (and therefore forgiving) edges, and more volume in the ends (to prevent them from submerging). As you can see, your intended use for the boat is important in making a choice.
Playboating
River Running
One of the most remarkable areas of progress in design has been the inside of the boats. Specially contoured and adjustable seats, thigh hooks, foot braces, and lower back support systems have become the norm in all new models. It used to take us so long to outfit boats with mini-cell foam, a grater and soppy cement that we'd have a party and make an evening out of it! Today, you can unwrap your boat, make some minor adjustments, and paddle away--too easy!
In concept, the snugger you are, the more responsive the boat will be to your every movement and the better your posture will be. In reality, there's a comfort/control tradeoff and each individual has his limits. You will figure out your own soon enough!
The Range of Whitewater Kayaks
by Luke Kornbluh
Newcomers to the sport of kayaking are greeted by a bewildering array of terminology used to describe a spectrum of specialty designs that make up the overall range of whitewater kayak styles. The easiest way to organize them is according to length.
Designs have changed radically in recent years, a change often called the "short boat revolution." All types of whitewater kayaks are relatively much shorter than in the past. The differences between the types of boats listed on the continuum above are relative to each other.
At the long end of the spectrum we find racing boats and the high-speed designs they inspire for non-competitive river running. Examples of these longer but not specifically racing kayaks are the Dagger Green Boat and the Pyranha Speeder.
All-River kayaks are a recent development in the kayaking world. Jackson Kayak's "All-Water" model is an outstanding example and sometime lends its name to the entire genre. These boats are usually 9-10 feet long and they feature displacement hulls, low to moderate rocker, and many are equipped with a "drop skeg" to improve tracking on calm water but which can be retracted in whitewater situations. These "do-it-all" designs give up the best features of dedicated whitewater and touring designs, but they offer one-boat versatility to buyers not prepared to purchase two or more specialty boats. This type of kayak would be a good choice to a recreational paddler interested in getting into their first Class I-II rapids.
Creek boats are really a sub-category of river runner. These boats give up the surfability and crisp maneuverability of planing hulls for the bombproof secondary-stability of a displacement hull. This type of hull also allows creekers a better chance to glance off the rocks that define creek boating. In addition, they feature lots of rocker to aid in obstacle deflection and spin-ability in tight creek beds. Creek boats are high-volume and have peaked decks to make them resurface quickly after deep-plunges from high drops. Creek boats are sort of the "off-piste" kings of river running.
River-runner is a catch-all category for a wide-variety of kayaks. By experimenting with different blends of rocker, hull-profile, chines, and volume manufacturers have been able to produce a wide variety of designs. Each has its own subtle character and appeals to brand loyalists and certain niches of paddlers. For example, the now-famous Dagger RPM had a low-volume tapered stern that made it a characterically "surfy" and "snappy" river runner. Others, like the Wavesport Diesel combined harder-chines with high-volume ends to offer a blend of both creek-boat and river-play designs. These kayaks hope to offer whitewater paddlers a one-boat solution for all types of river.
River-play describes another sub-category of river runner, but unlike the creeker these hybrids are closer to their play boat cousins. Flat-hulls and hard chines dominate this species and the emphasis is on offering the paddler the comfort and down-river speed of larger river runners with the features necessary for true play-boating along the way. Kayaks like the Wavesport Fuse or Pyranha Rev are good examples.
Play-boats are the shortest and nimblest of all kayaks. They are designed not only to surf well, but to have their low volume ends submerged easily. The recoil of the buoyant ends allows the paddler to flip and roll the kayak in the air above the waves and holes that make up their playground. While many paddlers choose playboats even for river running, they simply too small to allow enough gear for overnight and expedition-style paddling.
