There is a plan for the coble Enterprise (Plan Ref. MM1040), available from the Sarik Hobbies website. The plan dates from the 1960's, although it is a Northumbrian Coble rather than a Yorkshire Coble, (the Northumbrian Coble has slightly finer lines).
The website tradboat2.co.uk has info. and pictures about Yorkshire cobles.
Hope this helps
Mike