Ship Inclining Experiment


William A. Fox, Retired

Class Description: 

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his one-day class will discuss the inclining of a vessel in order to determine its displacement (weight) and centers of gravity. The primary emphasis will be on inclining in water, but inclining in air will also be covered. A classroom session on the theory, procedure, and results of inclining will be held, followed by an actual demonstration of inclining techniques aboard a waterborne vessel.

The objectives of the class are to provide the student with an introduction to the principles of naval architecture and to marine terminology, and to discuss and demonstrate the inclining of a vessel to determine its weight and center of gravity. ASTM F 1321-90, Standard Guide for Conducting a Stability Test, will be used as a text for this class. After a brief introduction to the principles of naval architecture, the theory and purpose of the inclining experiment will be presented. The lightweight survey will be described and then the inclining experiment itself will be discussed. Preparations required aboard the vessel and ashore will be described, and plans and equipment required will be discussed and demonstrated. Inclining procedures, data, and calculations will be reviewed and examples from an actual inclining will be examined in detail. Troubleshooting the results of the inclining, and matters of bias and accuracy, will be covered. Inclining of a small vessel in air will be discussed.

Following the classroom session, the class will travel to and board a vessel for a practical demonstration of an inclining. A brief light ship survey will be completed, drafts and specific gravity of the water will be taken, and inclining weight will be moved to obtain a plot of tangents and inclining moments. The resulting data will be processed and the vessel's light ship displacement and centers of gravity will be determined at the conclusion. After the inclining, the class will have lunch at a local restaurant or on board the vessel, then will return to the hotel for a summary and closing. The class will conclude with a short open-book test and exercise to confirm that the student has gained an understanding of the theory and practice of inclining a vessel. A conference room at the hotel will be provided, as will transportation to and from the inclining site. The R/V GOSPORT, a 200-foot research vessel, should be available for the inclining at the Norfolk Naval Shipyard. The GOSPORT has its own crane, and inclining weights are available in the shipyard. If this vessel is not available, then a commercial tugboat will be used, and the class participants themselves will serve as the inclining weights.

Basic calculators will be needed for examples and exercises. Students should wear casual clothes and rubber-soled shoes, as they will be boarding a vessel.

Class size will be limited to about 20 students.