Do you think this story would work better as an asb.
Oh, it's not ASB by any means. ASB is "why didn't Hitler just drill a tunnel to invade Britain", which I believe is the premise that got me into alternate history. It's just that there are two tendencies with technology-based WI's: the first is to neglect the train of logic behind the development, and the second is to make it work too well. Normally, I don't think you get this many people attempting to inject reality, so don't be disheartened.
I was talking more about the idea of the US embarking on construction of a new, ocean-going ironclad in the mid-1850s. Building an ironclad floating battery, less capable than New Ironsides, is more plausible. What you need is a good reason to complete the Stevens Battery in the 1840s before it's discredited. A big, unsuccessful naval attack on some Mexican coastal fortifications might fit the bill in the same way that the Crimea did historically. However, once the war's over, the navy runs into the problem I highlighted- the ship doesn't fit into their plans and, most likely, ends up in ordinary in the same way that the battleships did. Provided it hasn't been broken up by the Civil War, it will see some limited service bombarding Confederate coastal forts and confronting CSS Virginia. As long as you don't make it set the world alight- which very few ships do- there's a solid TL in there somewhere.
The French resorted to iron plating the Gloire since their iron and shipbuilding industries were not up to producing the quantity of iron needed and they didn't, at the time, have the experience to build an iron hulled ship.
Not the experience, more the capacity- Couronne (ld. 1859) is iron, but they can only really build one at a time.
The was also a question of the quality of iron and the fears, both in Britain and France, that a shell pierced iron hull would send iron shards all over the interior. Wood backing was used in absorb and strength the sides such an occurance.
Based on trials on the Crimea floating batteries- HMS Meteor, made of wood, stood up to shelling far better than HMS Erebus.
Does anyone know if the "iron" being spoke of was cast iron, or wrought iron ?
By nature, it's wrought iron- the plates are invariably hammered out to a specific thickness.
Personally, by "ironclad" I mean a seagoing armoured vessel, either wooden or iron-hulled. Something like the Stevens battery would be a "floating battery"- USS New Ironsides is right on the borderline between the two. A floating battery could be steam powered only because of their limited capacity, but an ironclad would have to have sails. Engines at this point aren't efficient enough to do away with sails but any vessel without steam is at a dramatic disadvantage in any engagement.