You wrote:
What you want is called a "garvey". There are plans in the two books
by the late Thomas Firth Jones which you might find at the public
library or can purchase via his website at www.jonesboats.com if it's
still there...

FYI: Yes, the site is still there, and Carol plans to keep it going and
continue selling the plans as long as people are interested in them. Of
course, Carol cannot provide the level of support that Tom did, but she can
put buyers in touch with people who have used the plans before and who are
willing to share the benefit of their experience.