Stability of submersible vehicles is dependent on the relationship between the center of gravity and center of buoyancy locations on the object. Improper relationships between the two can reduce performance and adversely affect the mission goals of the vehicle. Measuring these values can reveal variations from the designed values that may have been introduced during the manufacturing or assembly process. These values can also change in modular submersible vehicles which allow swapping or modifying components based on the needs of their mission. Errors associated with an improper relationship may not arise until sea testing, which may lead to the need for vehicle disassembly in order to shift or change ballast weights of the submersible.

This paper examines a measurement system designed to measure the center of gravity and the center of buoyancy of a submersible object using a hanging weight and center of gravity instrument. The method demonstrated is applicable for vehicles ranging from a few pounds to upwards of 15 tons. With proper fixturing, the machine is capable of measuring center of buoyancy and center of gravity in all 3 axes, which can help determine lateral, longitudinal, and directional stability of a part. This paper outlines a process for measuring submersible vehicles (with negative or slightly positive buoyancy) to determine weight, buoyant force, center of gravity, and center of buoyancy.

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