Sea trial

A sea trial is the testing phase of a watercraft (including boats, ships, and submarines). It is also referred to as a "shakedown cruise" by many naval personnel. It is usually the last phase of construction and takes place on open water, and it can last from a few hours to many days.

Sea trials are conducted to measure a vessel’s performance and general seaworthiness. Testing of a vessel’s speed, maneuverability, equipment and safety features are usually conducted. Usually in attendance are technical representatives from the builder, governing and certification officials, and representatives of the owners. Successful sea trials subsequently lead to a vessel’s certification for commissioning and acceptance by its owner.

Although sea trials are commonly thought to be conducted only on new-built vessels (referred by shipbuilders as 'builders trials'), they are regularly conducted on commissioned vessels as well. In new vessels, they are used to determine conformance to construction specifications. On commissioned vessels, they are generally used to confirm the impact of any modifications.

Sea trials can also refer to a short test trip undertaken by a prospective buyer of a new or used vessel as one determining factor in whether to purchase the vessel.

Sea trials are fairly standardized using technical bulletins published by ITTC, SNAME, BMT, regulatory agencies or the owners. They involve demonstrations and tests of the ship's systems and performance.

In a speed trial the vessel is ballasted or loaded to a predetermined draft and the propulsion machinery is set to the contracted maximum service setting, usually some percentage of the machinery's maximum continuous rating. (ex: 90% MCR) The ship's heading is adjusted to have the wind and tide as close to bow-on as possible. The vessel is allowed to come to speed and the speed is continuously recorded using differential GPS. The trial will be executed with different speeds including service (design) and maximum speed. The ship is then turned through 180° and the procedure is followed again. This reduces the impact of wind and tide. The final "Trials Speed" is determined by averaging all of the measured speeds during each of the runs. This process may be repeated in various sea states.

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