: jep, I do know that, allready made one!
: now we are thinking for a semi whitewater canoe , rocks and so on.
: So still searching for the right plastic ( a bit more weight , w'll take
: that)

: gr
: jos
Here's what your up against. Plastic is man made. It's composed of very long molecualr chains and tends to be very dense so there may be no chance to limit the weight to "a bit more".
A majority of the canoe and kayak market is composed of plastic boats. Manufactuers love it because it's so cheap but none of them has ever come up with a truely lightweight hull. They would if they could but they haven't so far. Part of the problem is plastics tend to have low stiffness so wall thickness has to be adequate to prevent oil-canning.
By going to plastic strips you are increasing the difficulties enormously. At various points you'll have to glue the pieces together. A lot of plastics won't take glue at all. One guy said that didn't matter. He would use "plastic welding" to hook all the pieces together. No news on that to date.
If you really need an indistructable plastic boat, buy one. They are very cheap.