Can't seem to separate Ribs from the rest of the model to make separate parts.

I need this to be able to make the ribs independantly from the rest of the mould, as the mould is to cast the hull (for a model boat-mould is for fibreglass and carbon fibre), and the ribs will be 3d printed for strengthening.
I tried the split tool but I cannot seem to make it work the way I need it too (I need all of them to be separate parts so I can print them independantly and be able to modify them each independantly).