All depends on the type of kayak as said. I have built a fair few kayaks over the last few years. Depending on where you are we could show you some of the molds we have and use and how to build them with little effort. If not o will post up some of the pictures of the boat builds.
You will learn that kayaks are built in an unconventional way compared to a lot of other Composite parts as they are also built to be light and strong. Most racing boats are built with 2x 200g layers and some type of core. More reinforcement around the seat and ends.
Tom