"SS OhNo" is a whimsical nautical themed study of balance and center of mass. Balanced on an Octopus base, the SS OhNo, it's captain, a hungry shark, tattered sail and a bird oscillate fore and aft with a gentle push on the boat's anchor.
https://www.youtube.com/watch?v=aF7Sgw4L8pI
Among the many Autodesk Fusion 360 advanced features I've stumbled across, one is center of mass. It works quite simply as follows; select "Center of Mass" from the "Inspect" menu, then select all of the components that you wish to include in the center of mass calculation. Fusion 360 will then display a center of mass icon at the center of mass point for the components you selected; brilliantly simple. For this model to balance, I knew the center of mass must be at or slightly below the keel cylinders, yet as indicated by Fusion 360 the center of mass was slightly above this point. I could easily have lowered the center of mass through the use of a taller tower design and lowering of the anchor (thus lowering the center of mass), but I desired a shorter tower. So to compensate, I designed the anchor such that it includes a container for additional mass (heavier than PLA) in the form of BBs, fine modeling sand, or similar heavy material.
As usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make mistakes in plenty.
Designed using Autodesk Fusion 360, sliced using Cura 2.5, and printed in PLA on an Ultimaker 2+ Extended and an Ultimaker 3 Extended.