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Well Deck Securing System for Landing Craft Utility

Description:

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR)

 

TECHNOLOGY AREA(S): Ground / Sea Vehicles

 

OBJECTIVE: Develop a maintenance-free securing system that can reliably secure Landing Craft Utility (LCU) vessels in the well deck of Navy Amphibious Class Ships in extreme sea conditions.

 

DESCRIPTION: Overview: L-Ships embark, transport, deploy, command, and fully support all elements of a marine expeditionary unit (MEU) of 2,000 marines, inserting forces ashore via helicopters and landing craft such as LCUs. This capability enables the Navy and Marine Corps team to accomplish a seamless transition from the sea to land to support ground forces on enemy territory by an amphibious assault.

 

Operation: LCUs weigh approximate 256 Long Tons when empty and 428 Long Tons when fully loaded and are transported to designated operating areas in the well decks of amphibious ships (L-ships). L-ships are capable of lowering the aft end of the ship to a depth of up to 10 ft at the stern ramp to float craft into and out of the well deck. The well deck is then pumped dry and then timber shoring and chain lashing is installed to secure the craft. The desired craft stabilization system must be able to secure the craft in robust sea state conditions. Excessive flexing of the ship can result in the legacy shoring falling loose with possible catastrophic results.

 

Current state: The legacy shoring system for the LCUs consists of high maintenance timber supports installed between the hull of the craft and the L-ship’s well deck bulkheads and metal lashings. Each support is comprised of lengths of fire retardant timbers which are cut in place and assembled in various configurations. There are five 6” x 6” shores per side for a total of 10 per craft, or three 8” x 8” shores per side for a total of six per craft. A 8”x8” timber 15 feet long weighs approximately 215 to 250 lbs. There are then 11 lashings per side for a total of 22 per craft. The length of the timbers is determined by the location of the LCU in the well deck and must be one piece. With the difficulty to position the LCU in the exact same location every time, timbers are eventually trimmed to the extent that they become too short for most installations and need to be discarded. Cutting and installing the timbers and installing the lashings is cumbersome, a personnel hazard, and very time consuming.

 

Requirements: An alternate securing system that can quickly secure the craft is needed. The securing system will need to be able to secure a 482 LT LCU in a well deck in sea states up to Sea State 8. The securing system will need to be easily adjustable, simple to operate, and can stow the LCU in less than 3 hours. Concepts previously looked at include metal “timbers”, air bags, tie rods, and friction mats. These concepts have been proposed but none have been prototyped on a ship.

 

PHASE I: Define and develop a concept for securing an LCU in the well deck that meets the requirements as stated above. Demonstrate the feasibility of the concept in meeting the Navy needs and establish that it can be developed into a useful product for the Navy. Feasibility that the LCU Securing System concept can be readily manufactured will be established by material testing and analytical modeling.

 

The Phase I Option, if exercised, will include the initial design specifications and a capabilities description to build a prototype solution in Phase II.

 

PHASE II: Based on the results of Phase I effort and the Phase II Statement of Work (SOW), develop and deliver a prototype LCU Securing System. The prototype will be evaluated to determine its capability in meeting the performance goals defined in the Phase II SOW and the Navy requirements for adjustability, simplicity, weight, and maneuverability. System performance will be demonstrated through prototype evaluation including shipboard testing and modeling or analytical methods over the required range of parameters. Evaluation results will be used to refine the prototype into a design that will meet Navy requirements. Prepare a Phase III development plan to transition the technology to Navy use.

 

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the system to the amphibious ships with well decks. Transition opportunities for this technology include commercial ship and offshore systems that must secure heavy cargo in extreme conditions.

 

REFERENCES:

  1. United States Navy, COMNAVSURFLANT/ COMNAVSURFPAC Instruction 3340.3D “The Wet Well Operations Manual”, 28 Aug 17. https://theboatswainsmatestore.com/collections/comnavsurfpac-lant-comusfltforcom-inst/wet-well-operations-manual.
  2. United States Navy, NSTM Chapter 584, “Landing Craft and Amphibious Assault Vehicle Handling Stowage and Support Systems, S9086-TY-STM-010/CH-584R1”, 15 Mar 19. https://theboatswainsmatestore.com/products/s9086-ty-stm-010-nstm-584-landing-craft-and-amphibious-assault-vehicle-handling-stowage-and-support-systems-rev-4-15-mar-2019.
  3. Forest Products Laboratory 1999. Wood handbook : wood as an engineering material. General technical report FPL ; GTR-113. Madison, WI : U.S. Department of Agriculture, Forest Service, Forest Products Laboratory: xi, [463] pages : ill. ; 28 cm. https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.pdf.
  4. Northam, Jackie, Cargo Overboard, Intense Rolling: The Risks Of Fully Loaded Mega-Container Ships, NPR, International Affairs Correspondent https://www.npr.org/2021/04/01/983017153/cargo-overboard-intense-rolling-the-risks-of-fully-loaded-mega-container-ships.

 

KEYWORDS: Shoring; Landing Craft Utility; Well Deck; Amphibious Ships; Legacy shoring system; Lashing

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