: The Wooden Boat Magazine sells study plans for very little,
: including several older designs like the Haven 12-1/2 which may
: be suitable for model building.

I was curious - study plan for $0.99 sounded like a bargain! so I just 'bought' the 'study plans' for the Wm Garden 27'9" cutter Capt'n Blackburn.
The digital download produced the equivalent of two very (very!) poorly photocopied pages from WoodenBoat magazine, with all lines and details completely obscured.
Other WB 'study plans' may be better?
YMMV
BTW, I noticed that WB is asking $30 for 'plans' for a half-hull model! It sure puts those kayak plan prices into perspective!

Another place to look is in your public library (if you have one) in the naval architect/yacht design section. Some books have quite nice lines suitable for model building.