I recently discovered “Kayaking Joe” blog: https://kayakingjoe.blogspot.com
You can check out his double outrigger sailing kayak on the pages, including this page: https://kayakingjoe.blogspot.com/2013/07/ready-to-sail.html
No doubt lots of solo work went into putting this DIY boat together. Lots of conceptual thinking too.
Here are 2 short vids posted on YT…
He’s even got a horn if he gets into trouble :-)