The purchase of an additional boat did not necessarily require that of sixteen more missiles , nor even for two more crews .
A second construction line at Cammell Laird permitted work on a fifth boat to proceed without impacting schedules for the other for boats .
The purchase of an additional boat did not necessarily require that of sixteen more missiles , nor even for two more crews , and a second construction line at Cammell Laird permitted work on a fifth boat to proceed without impacting schedules for the other for boats .