A kayak type is similar to the idea of species: all kayaks of the same type share certain common features of shape, size and construction, with room for variation. Two familiar kayak types are the west Greenland boat, and the Aleut iqyaq or baidarka. Zimmerly estimates there were 40 or so distinct kayak types in the arctic at the time of european contact.
The critical proportions and sizing of each type was passed along thru the use of anthropometric rules, which is another way of saying dimensions as expressed as units of the builder's body. These rules insured a properly dimensioned boat that remained within the acceptable range of length, beam, rocker and other critical parameters.
The actual appearance of the boat and it's construction details exist thru example and living memory. This is an important point. People are part of the information loop: Too long a break in continuity and something could get lost. This is unfortunately true in many cases, such as Aleut ideas on frame flexibility.
The use of types and anthropometric measurements meant that designs could be transmitted and preserved without the use of written records.
The idea of type is still valuable today. Since each type evolved to meet specific conditions and useages, type is a good way to find a boat to suit intended use. Kayak types are an excellent starting place for the modern builder, who may be looking for basic designs to modify, or work with.
Designers looking for raw material will find a wide variety of boats to look at. Although traditional kayaks are not always perfectly suited for recreational use, they provide a storehouse of ideas and basic forms, and a encylopedia of dimensions and proportions that will repay further study.
The best source of kayak types is in books - see our bibliography in the FAQ. Arima, Zimmerly and Adney are all good sources for lines drawings and photos of several different types.