So I looked at freeware options. FreeCAD is powerful but the documentation lags behind the code too much for me to get anywhere with it. I'm too old and cranky to spend hours fiddling with each option to see how it works. Some cheaper commercial 3D graphics software tempted me but I'd get a little bit in and snarl "Powerpoint handles that better!" before closing it forever.
Then I found Blender. Powerful software. There's great tutorials out there. Katsbits were the best I found (much better than a tutorial linked from the main site which had me telling celticdragonfly "This is not a tutorial, this is a final exam"). An evening of going through parts of two tutorials let me make a rough model of my ship in action. "Action" defined as hauling up a cargo container with the crane--it's a freighter.