The Union Ironclad ship was the Monitor. The Confederate ship was the Virginia.
A ship is by itself never a weapon, and that also goes for an ironclad ship. The ironclad could only be called a weapon carrier.
Virginia
Ironclad ship is not required to be capitalized unless it is at the beginning of a sentence or part of a title.
The first Ironclad ship ever made was by the northern states during the civil war was named the Monitor.
Ironclad
a ship heavily armored in iron
it was a ship made of metal
Merrimack
The Merrimack
The Union Ironclad Ship that was built to compete with the Confederate Ironclad was called the U.S.S. Monitor and the Confederate Ironclad was called the Merrimack (more accurately, the CSS Virginia).
John Ericsson