Bow of the USS Constitution#

Licensed under PD
The latter is particularly dense, heavy, and difficult to work, but very strong. Because her hull was built 53 cm (21 in) thick in an era when 47 cm (18 in) was common, she was able to withstand cannonades, thus earning the nickname of "Old Ironsides."
The copper sheathing along the keel prevents the attachment of shipworms.