This is a simple two part compass for drawing circles, measuring, and navigating the open seas old timey pirate style.
Parts:
2 copies of the compass half
2 thumscrews
2 washers, 1 wingnut and bolt
Instructions
Download
Skeinforge
Print two copies (It should fit diagonally on the makerbot build surface)
Insert 1 thumbscrew in each end of the compass to hold a pencil, pen, dowel extension, etc.
Bolt together the two halves with a small thumbscrew or wingnut for easy adjustment. You may want to put a larger washer on the outside of the two parts if the plastic isn't stiff enough to hold a precise angle.