Hi Rien,
there was quite a link between us K designs builders here in New Zealand.I was following Rodney, who built Sparta, from when he started work, and I was also going to build a KD650. I changed my ideas when Bernd came out with the Duo 480 plans and built that instead. Rodney modified the construction jig of the rudders, and then gave it to me when he was finished with it. I recently gave it to David Thatcher who is building the Eco 6 . I also followed Hamish's build with his Eco 5.5 but I cant remember exactly our discussions about the foil construction. What we were finding was that the original angles worked sometimes with the plywood but other times would fail. I dont think the plywood now is as strong as it was maybe 20 years ago.
I have not sailed my boat much the past couple of years as I have got involved more seriously with competition archery. But in any case my boat sits comfortably in my barn with no maintenance to be done. I like the look of the Eco 6 and hope you get a lot of enjoyment from her. I have not been coming on this site as much lately but I saw the images Bernd posted on Facebook of your boat
cheers
