Over the years, I've tried to reduce the number of 3D printed parts in the OpenCTD to just the bare essentials. Currently, there is only the baseplate, which guides the sensors into position before potting in epoxy, and a 2-part chassis that goes around the control unit, isolates the battery, and provides a bit of protection from incidental leaks. It keeps the electronics away from the walls of the housing so that drips and condensations don't contact the electronics. 

Note: You can absolutely build an OpenCTD without any 3D printed parts, it just won't look quite as nice and may be a more vulnerable to flooding damage. 

Also Note: this was a really ugly print. I'll have to clean my printer and redo it. Let us never speak of it again.