When I understand it correctly, it was for additional stiffening of the frames, against torsion of the hull, like the thick stuff planks......very interesting detail - thanks for the explanationThis is seen in the last photographs, it is not the ballast. It is a filling of the clear between the frames. This procedure is regulated in the Ordinances of the 17th century and continued to be used until the 18th century. It is a classic method of Spanish galleons. The ballast, properly speaking, goes on top of this platform that is called "el soler"