Is it a requirement, to be able to copy a design without tracing? Blueprints seem to have been the main way of storing designs for quite a while. Maybe the drawings are just as good as it gets until you have computers that really want numbers.
Think about buying a ship for example — I guess the person buying it would just specify a type of hull (or for high end stuff, go to a shipwright they specializes in a type of hull), and a couple dimensions.
As to actually doing the design, must be their experience plus conventions built on outcomes from the field — this part of the hull has to be convex, etc etc. So, trial an error, but built up over generations.
Think about buying a ship for example — I guess the person buying it would just specify a type of hull (or for high end stuff, go to a shipwright they specializes in a type of hull), and a couple dimensions.
As to actually doing the design, must be their experience plus conventions built on outcomes from the field — this part of the hull has to be convex, etc etc. So, trial an error, but built up over generations.