Cotton-clad

Cottonclads were a classification of steam-powered warships where a wooden ship was protected from enemy fire by bales of cotton lining its sides. Cotton-clads were prevalent during the American Civil War, particularly in the Confederate States Navy for riverine and coastal service such as in the battles of Memphis and Galveston. Confederate tactics generally had cottonclads, which were outgunned by Union warships, steam at full speed towards enemy vessels, relying on the cotton to absorb fire, until they were within firing range, and if possible ram or board the enemy.

...
Wikipedia