Closing mesh without filling

[micah_whitsel]

So, I'm trying to 3D print a part for a coworker's personal project. I don't have any experience working with meshes, so I don't know how to best repair this mesh. The parts are meant to be hollow, but Fusion fills the hollow in the middle whenever I try to use any repair type. Does anybody have any recommendations on how to repair this mesh while maintaining the internal geometry?

[etfrench]

Section Analysis shows most of the model is just a single surface.  You may have better luck modifying this in Blender.

[micah_whitsel]

Ok, thanks. I'll give that a try