I've been reading a couple of books recently on the ACW at sea and the improvisations they used to fit out vessels. The Confederates were so short of iron they wrapped railway tracks onto woodensided vessels to "armour" them and basically bolted anything they could to the ship sides to protect the crew.

The cotton bales are a throw back in concept to similar earth filled bundles used for protection on land for centuries. I'm not sure what a cotton bale weighed but the cotton fibres would have formed a lattice network spreading in different directions in the bale allowing the capture of splinters and disspitation of force of projecticles hitting them. Very inventive.