Hello;
For those of you who wish to build Civil War Ironclads. Years ago we had a series of things built as dioramas in our history class in High-School. One of the things needed was a large ironclad that looked like the C.S.S.Virginia/Merrimack. I had an old hull of the Flying Cloud. I cut it down and modified it to be a steam powered Ironclad.
This proved to the class that a hull could be modified by shipyards for this reason. Secondly, the Power-Plants(Steam) were fairly crude and could accommodate modifying a sail ship built for this purpose.The hull would be darned near submerged below any Armor plate anyway.
The small deck running around the sides were beefed up with heavy laminated wood under iron sheathing. Then there was the fore and aft decks that One, in the aft section protected the prop and rudder and forward to create space for a breakwater(A structure on the deck to force water over the side if thay hit waves or wakes.) Then the Ram was attached to penetrate hulls whilst beating the heck out of them with the Parrot rifles or whatever they had while locked together, Then pulling back and leting the opposition sink.
So the structures were by needs simple. Slanted deckhouse sides with armored shutters over the gunports and a wood frame covered with iron plate, wood and then Train Rails if Iron Plates were unavailable. Many times it was just heavy layers of wood that together(Each layer) acted as as erzats armor. Many didn't work out well. They were Slow and Hard to maneuver.Some drew to much and constsntly fought running aground as well. The Cheeseboxes, on a raft, were more practical that way, but they had their shortcomings too.
So building a model from scratch wouldn't be hard. Just an exercise in a form of inventiveness. There were many that couldn't even be called "Ironclads" and were just as hard to operate and use as fighting craft. So in closing, if it resembles the Monitor or Virginia/Merrimack or even and armored version of a cut down Steamer,or just an Armored steamer it would be correct. Very few records were correct. The Davids, mere cigar shaped Steam powered craft that looked like submersibles but really werent(Hard to hit and shells glanced off their spindle shaped hulls.)and many others even some similar to the Hunley.
Remember this too, the Hunley killed two crews in testing, including her inventor in failed dives. Spar Torpedoes were even used in cut down single mast sailboats and modified for the purpose. It was for that reason an interesting time in Maritime History, Especially the results that still reverberate today Only now they're true Submersibles and are dangerous. Oh! if John Ericson or Hunley could see what they started!! Those that were non Semi-Submerged( Like The Davids) Were the start of Littoral Combat ships when they worked.