Was curious, what kind of output were Union shipyards capable of when they hit their stride? How much did the Navy grow during the war? Were a lot of those ships scrapped or mothballed after the war? Did the Navy return to pre-war levels like the army?
Though when Union shipbuilding tried to produce larger vessels during the war (the Webb frigates, the Dictator, the Puritan) it took quite a while; the steam frigates begun in 1854 took just under two years for the fastest and they weren't all built in parallel.No, actually, the USN had little need for heavy vessels-- since the Confederacy had very few, what the Union needed was many smaller vessels for blockading and riverine/littoral operations. The building of larger vessels (such as the USS Franklin) was mostly put on hold.
But at the same time, if the USN had wanted to build large warships in any kind of numbers then the assets it would be using for that would not be assets useless for small warships (being mostly engine manufacture, men, slips and raw materials, all of which could be used for small warships).I'll reiterate that the USN, for the most part, built the type of ships it needed for the war it was fighting; there was no need for (line of) battleships when the enemy had none, and the blue-water areas where large warships operate was not where the action was. It was most decidedly a gunboat and logistics war, and that's what production and conversion concentrated on.