A few years ago I created a design for a kayak made out of XPS foam insulation board. I built the first one and after flogging it for months, released the design for anyone to build, all I ask is a picture of the finished boat, along with the general area you use it in. Over 20 have been built at this point, and I pictures of new boats almost every month. I've gone on to build 7 more, selling two and giving three to relatives. Two weeks ago my son and I launched two new sawfish kayaks, my 12 yr old had built his over the past winter as I taught him to, and I launched my tandem Sawfish.