When attaching a modular section of a ship's hull to another, the cut may be straight across transversly on the decks and bottom shell, but on the sides it is staggered like looking at a set of stairs from the side. The does not allow a vertical butt to run all the way around the ship in a straight line.
Also, the stiffeners (longitundinals and deck girders) are projected at least one foot beyond the plating cuts so their weld joints do not line up with the shell welds.
LBNSY [Long Beach Naval Shipyard] replaced the bows on 3 Fletcher class destroyers by that method (I worked on two of them). There were a number of unfinished Fletcher hulls sitting in San Francisco, so they were just towed down and their bows cut off to replace the damaged DD's. LBNSY also replaced the bow of a Frigate that rammed a tender. But that bow we had to rebuild from scratch in the shop and then install.
All replacements used the stagger-step method of shell cuts to eliminate a possible weakness of a continuous straight weld.
- 18 December 1998