Project Number: S2890

Project Title: Inner Bottom Transformation

Period of Performance: DEC21 – NOV26

Hundreds of structural support assemblies are used throughout a typical Navy ship. These are often large and complex structures, such as support tanks and stairwells, and many other common ship structures that require stiffening. The support assemblies are typically a lattice-grid box, sometimes called “egg crates” or “box girders,” which consist of a matrix of longitudinal and transverse members that run perpendicular to one another creating a grid framework.
The objective of this Center for Naval Metalworking (CNM) project is to transform the requirements and processes for construction of U.S. Navy surface ship inner bottom assemblies at Huntington Ingalls Industries – Ingalls Shipbuilding (Ingalls). Two major construction processes are being evaluated for improvement. The first improvement involves the elimination of reinforcing rings around openings inside the inner-bottom structure. The second improvement involves defining a slotted construction process for the grid framework of the assemblies. Technically, proving unreinforced openings and slotted construction meet the performance requirements will facilitate a change in construction requirements. If successful, this will lead directly to major construction process changes and enable future robotic process applications.
This effort will be accomplished in two phases: Phase I has down selected vendors and developed test plans, and Phase II will execute the testing and analyze the results.

By eliminating the handling, fitting and welding of reinforcing ring parts and implementing a new slotted construction method, the initial estimate for cost-savings is $5.7M for DDG and $15.4M across all platforms built at Ingalls over five years.

The results of this project will be implemented across all ship classes at Ingalls. Training for inner bottom opening-reinforcement construction processes, inner bottom slotted- construction processes and other project recommendations is included in the transition plan. The new construction parameters will be implemented on in-process construction, including DDG 131, LPD 30 and future LHA ships not yet awarded. A schedule for implementation across ship classes and specific applications will be based on the project execution timeline. Process implementation will be phased into production.