I do not have completed instructions and drawings for a tandem kayak at this time. I hope to have tandem plans available sometime next summer. As soon as they are available they will be listed on my web page.
However, I have a number of people who are adapting one of my single kayaks into a tandem at this time. They buy the solo kayak plans and I provide (at an additional cost of $30) a set of scaled and proportioned stations for a tandem kayak, with drawings suggesting the location of cockpits and hatches. I have not set up and faired these forms beforehand so there may be a little fairing necessary. Also I have not faired the lines in the deck between the cockpits. If this doesn't scare you then you can start working on a tandem of any of my single designs now.
I can put your name on the list for notification when the tandem plans are completed if you wish.
Below Tandem Georgian Bay built by Steve Gay, photos Steve Gay.
Building time ran about a year and a half (Georgian Bay tandem). It was worth the time spent and everyone who sees it thinks it's a work of art.
Steve Gay, Shoreline, WA