Barrow can work on several submarines without completing all in parallel

How many submarine construction lines can Barrow operate at the same time?

A tentative estimate is about three boats in fuller assembly, with blocks for others bringing the total to roughly five or six active builds at different stages. The exact layout would need checking.

Barrow's capacity is estimated cautiously, with the exact yard layout still needing to be checked. Roughly three boats could be in more complete assembly, with additional sections occupying other positions and facilities. Recent space changes suggest that work associated with five or six submarines could be active at different stages. That estimate counts block production as well as fuller assembly, rather than describing five or six identical complete-boat production lines.