First, avoid the continental European companies (Mamoli, Artisania Latina, Corel, Sergal, etc.). Their kits make nice decorations, but almost without exception are lousy scale models, with lousy plans and inferior materials.
I can recommend two American companies: Bluejacket (www.bluejacketinc.com) and Model Shipways (www.modelexpo-online.) Go to either of those websites and take a look at what they offer. Be sure to take a look at the Model Expo/Model Shipways sale items. The company always has quite a few nice kits on sale for a fraction of the normal retail prices.
Another fine company is a British firm, Calder Craft. Its kits represent British sailing warships, and are quite expensive (as much as $1,000).
By the way, there are very few actual plank-on-frame kits on the market. I suspect your father would be equally happy with a plank-on-bulkhead kit. The two construction methods are slightly different; both are highly challenging. The pof method involves constructing all the actual ship's frames (more then fifty in a good-sized ship) and planking over them. The pob method simplifies the real ship's construction somewhat by reducing the scale number of frames to a series of wood bulkheads, which are planked over in the same manner. In most circumstances the difference is invisible on the finished model.
All the Calder kits, and virtually all the continental European ones, are plank-on-bulkhead. Model Shipways and Bluejacket make a few genuine plank-on-frame kits; so far as I know they're the only ones on the market. The websites make it clear which is which.
Hope that helps a little. Good luck.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.