I like to chime in and state that the DNC put the following estimates for the building programme all numbers are the cumulative years to First Study, Approval, and 1st ship complete:
Battleship 1, 3, 7
Carrier 1, 3.5, 7.5
Cruiser 1, 2, 5
Destroyer 1, 1.5, 3.5
so as you can see on a pre war...