Could Japan have built the Number 13 battleship design?

Japan's machinery, gunmaking and armour capacity make Number 13 technically plausible in this assessment; its fleet role depended on maintaining ships through repair and readiness cycles.

Question

Was Japan's Number 13 battleship design actually buildable?

Short answer

The design is considered technically feasible: Japan had the relevant gunmaking machinery, could produce its armour, and may have needed fewer boilers than the proposal allowed.

Notes

Japan's Number 13 design is judged technically plausible because its designers were conservative about promising capabilities they could deliver. The proposed boiler count may even have been conservative for the pressures available when construction would have taken place. Japan already had gunmaking machinery, and the proposed armour was less demanding than Yamato's. The design also belonged to an Eight-Eight Fleet intended to keep a usable force available through maintenance cycles. The argument supports technical feasibility without establishing that the whole programme would actually have been completed.