Shawn Baker who used to post here and who is a very good kayaker has this on his web site. I have used it and it makes a very good, light seat.
http://www.geocities.com/shawnkayak/seat/
best don
: I would like to build a cedar-strip seat similar to the one detailed in
: Nick's article dated Thursday 20th August. How do you generate the pattern
: for the internal form? I have thought of a few options but they all
: involve sitting in something sticky thick and wet and waiting for it all
: to go hard! What about builders plaster in a thick polythene bag? You
: could make up a strong wooden frame, place the bag and plaster inside the
: frame, change into a pair of tight fitting underpants or swimming trunks
: and, with a good explanation for those close to you of what you are trying
: to achieve, and the help of a good long book, some good music, some beer
: or wine, something good to eat, a charged mobile and a few very good
: prepared reasons as to why you are presently unobtainable, sit on the bag
: with knees slightly raised and wait without the expectation of an
: exothermic setting reaction, for it all to go hard! How long would you
: have to wait? Quick setting cement may be another option but probably the
: most hazardous! Plaster of Paris may be a bit safer if the bag should
: burst! Once the form has "set", a profile copier made up with
: wooden dowel rods in a support strip could be used to copy the profile
: onto strips that would form the seat. Any other options? A
: three-dimensional digital copying unit? Perhaps I should stop thinking
: like this!