Sane looked at the Crown Prince in confusion. "An Iron Shell? What do you plan to use that for?"
Joseph answered without hesitation, "To stop cannonballs, of course."
Sane smiled and shook his head just as readily. "That's impossible, Your Highness. Even to defend against cannonballs fired from a relatively long distance—say, a 24-pounder Cannon from 500 meters away—you would need iron plating at least five centimeters thick."
He rapidly calculated it in his head. "That would add more than 250 tons to a Fourth-rate Battleship. You know that although a Steam Warship has powerful propulsion, such a heavy load would reduce its speed to below nine knots and severely affect the amount of coal and supplies it could carry."
He had put it rather politely. For a Fourth-rate Ship with a displacement of just over a thousand tons, having external armor account for a quarter of its weight would make it nearly impossible to sail.
Joseph nodded regretfully. It seemed an "Ironclad" would not be possible anytime soon.
And five centimeters of armor would not be nearly enough. He remembered that the historical Napoleon had armor ten to twelve centimeters thick, capable of withstanding direct fire from Russian Army 32-pounder Cannons. Only that had real combat value.
The main issue was still that Steam Engines lacked sufficient power. Otherwise, with enough strength, even bricks could be made to fly.
Sane consoled the Crown Prince. "Your Highness, if you wish to improve its protective capabilities, we can thicken the Steam Warship's hull by another four centimeters. I mean the Oak Wood hull."
Joseph sighed. A few extra centimeters of wooden hull would have almost no effect. At most, it could improve protection against cannons below 12-pounders. But when Battleships exchanged broadsides, their main weapons were Cannons of 24 pounds or