Monitor
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.
Ironclad is a noun or used as an adjective and need not be capitalized. As example, the CSS Virginia was a ship that was an ironclad vessel.
Virginia
The first Ironclad ship ever made was by the northern states during the civil war was named the Monitor.
a ship heavily armored in iron
it was a ship made of metal
Ironclad
The Merrimack
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