Many sets of plans state on them that the purchaser is granted a license to build one boat.Even if the plans don't say that I would assume that it's implied. So, if the license isn't used you can sell it and, of course, the plans.

: In the process of deciding which boat to build next, I bought plans
: for four kayaks. I plan to build only two of them. Is is legal
: and ethical to offer for resale the plans for the boats I will
: not be building? -Wes