That's a nice boat, Paul… but not a Tjalk in a looong way. By my knowing a Tjalk is a flat-bottom, round bilge boat whereas this is a Vee-bottom with additional chine. Also, tjalk is a sailing vessel.
You might want to give the archive of the dutch model builders organization (Nederlandse Vereniging van Modelbouwers) a go, they have an extensive archive of all kinds of model plans which they print on demand. They are paid plans, though.
I found a plan for a "Groninger Tjalk" there already, page three for sailing ships: http://www.modelbouwtekeningen.nl/epages/64899739.sf/nl_NL/?ViewAction=View&ObjectID=7017874&PageSize=36&Page=3
Do browse a bit there. I think you might find at least inspiration.
Edited By Diede van Abs on 16/12/2015 09:23:17