Lysergic,

For me "blueprints" are the actual design/construtionplans in scale as made by the builder/designer of the real "thing"
Buildingplans to me are plans that might be used bij modellbuilders to make a ship that resembles the actual ship but go not very deep into detail. i.a.w. like the plans that go with a plastic kit.

Hope this clarifies your question.

Kind regards

Wiljan Bakers