260-Foot SEACON Is New Navy Offshore Construction Vessel

The Navy's first and only platform specifically designed for offshore construction has been acquired by the Chesapeake Division of the Naval Facilities Engineering Command (CHESNAVFACENGCOM) as part of its offshore construction equipment inventory. Designated the SEACON (an acronym for "sea construction"), the selfpropelled vessel is a converted YFNB barge hull previously used by the National Aeronautics and Space Administration to carry Saturn rocket components.

The vessel is 260 feet long, has a 48-foot beam, and displaces 2,300 tons when loaded. SEACON's 6,240 square feet of open deck area aft is designed to withstand heavy loading, and configured to accommodate roll-on/roll-off construction equipment as well as permanent deck machinery. She has a 13 by 20-foot centerwell for minimum motion overboarding operations, and a 50-ton gantry crane will soon be installed to complete the outfitting. The vessel can be easily rigged for a wide variety of offshore construction tasks such as cable-laying, diving support, or handling heavy loads.

Although SEACON has a propulsion capability, it is towed to construction sites by a Navy tug. Once on site, the platform's surface and subsurface navigation systems provide inputs to a dynamic positioning control system, and thrust requirements are transmitted to the propulsion units. Both positioning and local transit power is provided by three (one forward—two aft) cycloidal propulsion units capable of producing 1,050 horsepower. This system allows SEACON to maintain fixed position for precise placement and recovery of ocean structures and underwater instrumentation in conditions up to sea state four.

SEACON is jointly manned by Navy military and civilian personnel and is designed to be placed in an unmanned caretaker status when not deployed. The platform has accommodations for 50 persons and an endurance of approximately four weeks.

Conversion of the barge was done at Norfolk Shipbuilding and Drydock Corporation's Berkley Plant under the cognizance of the supervisor of shipbuilding in Portsmouth, Va„ and CHESNAVFACENGCOM.

The vessel was accepted in July of 1976 and immediately deployed to the Virgin Islands, where she was used to support the repair and expansion of the underwater test range at the Atlantic Fleet Weapons Training Facility. This project was the largest offshore repair effort ever undertaken by the Navy, and its successful completion was directly related to the outstanding performance and characteristics of the SEACON.

The vessel is presently being used for cablelaying off Florida.

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