As I've mentioned on another string, I've been trying to figure out which sea kayak to get once I have the dollars. That search has lead me back to a few boats from the Prijon range which are absolutely everything I wanted and currently on sale - so great value.
Having sold plastic fishing kayaks previously I thought I'd come across all the available methods formaking plastic boats only to find that the Prijon HTP boats are different again. They're blow molded. From there, it wasn't a stretch for me to fall over this video clip which demonstrates the process. It's a bit of a sales pitch but still very interesting - for me at least
I find that clip bloody interesting too. Obviously substantial set-up costs, but once the mould is made, you could pump them out pretty quickly.
On the topic of plastic boats, there is a company called Finn (not Fenn) that makes a plastic ocean racing ski that apparently weighs in at about 14kg!! Hard to believe, but my brother, who is over in Perth and has an Epic V10, reckons they're pretty good - particularly if considering taking them down some rapids (eg. Avon Descent). I was recently over in Perth and saw one on the roof of a car - looked the goods, but couldn't pick it up to see how heavy it was.
