I purchased the stl files from a designer on the Wargaming 3D marketplace called East Coast Ironclads. He has a large range of ACW ships to choose from and of the two I've purchased I have been very impressed.
The spars on the masts can be a bit delicate so I plan on reinforcing them with some green stuff sculpted to look like furled sails. Off course if they break due to gameplay one can always just print off a new one!
I've got some pretty large gaps in my ACW ironclad collection and these models are a great way to fill them without spending a ton of money.