[..]
You may not have noticed this before but in the Ship Designer of Galactic Civilizations III you can take the ships you have designed (or downloaded) and export them as a .OBJ file. This can be used by 3D printers but also on a cool site called Sketchfab. It's super easy to set up.
Here are a couple I've already uploaded:
Have fun!
p.s. Bonus one:
https://skfb.ly/6tIOy