Open a new file in Blender Under the File menu, Import the (wavefront) Roma.obj file, make sure when the dialog box pops up for selecting the file location to turn on Split by object and Split by group under the geometry heading. 30 seconds later you have Roma with all the little bits (secondary, AA, main turrets, etc) individually selectable. The main hull is in 7 individual parts, but the hull lines are pretty good. You can select parts of a mesh, split the selection off of one object and join it to a different oblect. For example splitting just the smokestack off the center section of hull, without having to delete parts of the model, is possible, and a good exercise to start with. If you turn on the 3D printing dialogs in blender you can export .obj files of whatever sub part of the Roma you are working on, they seem to work just as well as stl files in most printer software. I measure the LOA of the ship in blender, then under the scene properties tab in the scene window change the unit system from metric to imperial, the length to inches and by trial and error the unit scale to 0.010475 to set the model to the correct length in 1/144 scale. Scale doesnt seem to export correctly so you will probably have to measure whatever you are trying to print in the model and then rescale it in the printer software to get it to print the right size.
