California ASNE Reviews Automatic Position Control

The members who attended the regular monthly meeting of the Long-Beach-Greater Los Angeles Chapter of The American Society of Naval Engineers in March were rewarded by an evening of good fellowship, fine food, and an excellent technical paper by Dr. Maxwell C. Cheung and Nathan Friedland.

Following the social hour and the usual fine fare at the Ports O'Call Restaurant, the speakers were introduced by program chairman Joe Lovett. Nat Friedland and Max Cheung, co-authored the paper for the evening, titled "Automatic Position Control—An Advanced Mooring Concept." Their paper presented a new development in the ancient art of mooring — automatic positioning. By means of a computer, either onboard or by radio link, the master of a deeply moored ship or platform receives instant and simple information as to the optimum deployment of his mooring lines to suit changing weather and sea conditions. The computer print-out lists the modifications to be made to the lengths of each mooring line to maintain the prescribed limits of excursion within the allowable tensions of the mooring lines catenaries.

They described the requirements for deep mooring, pointing out the effects of platform size and configuration, water depth, bottom characteristics, sea and weather conditions, permissible excursion limits, and hardware limitations. Current spread mooring systems are also described, especially those of a composite configuration using both chain and wire rope mooring lines.

Their paper discusses the design procedures and automatic positioning program in considerable detail, together with examples of the computer program. They also describe the required hardware for both manual and automated systems. The computer output is shown to be used directly to adjust the mooring lines automatically in the fully automated system.

The paper was enjoyed by all and elicited much discussion. Copies may be obtained by request, addressed to Comdr. E.L. Jones Jr., Eleventh Coast Guard District, 400 Oceangate, Long Beach, Calif. 90822.

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