Sea trial
Overview
 
A sea trial is the testing phase of a watercraft (including boat
Boat
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

s, ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

s, and submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s). 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
Open Water
Open Water is a 2003 horror film loosely based on the true story of an American couple, Tom and Eileen Lonergan, who in 1998 went out with a scuba diving group, Outer Edge Dive Company, on the Great Barrier Reef, and were accidentally left behind because the dive-boat crew failed to take an...

, and 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.
Encyclopedia
A sea trial is the testing phase of a watercraft (including boat
Boat
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

s, ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

s, and submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s). 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
Open Water
Open Water is a 2003 horror film loosely based on the true story of an American couple, Tom and Eileen Lonergan, who in 1998 went out with a scuba diving group, Outer Edge Dive Company, on the Great Barrier Reef, and were accidentally left behind because the dive-boat crew failed to take an...

, and 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
Certification
Certification refers to the confirmation of certain characteristics of an object, person, or organization. This confirmation is often, but not always, provided by some form of external review, education, assessment, or audit...

 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.

Typical trials

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.
  • 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
    Maximum Continuous Rating
    Maximum continuous rating is defined as the maximum output that a generating station is capable of producing continuously under normal conditions over a year. Under ideal conditions, the actual output could be higher than the 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 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.
  • Crash stop: 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. The trial begins once the order to "Execute Crash Stop" is given. At this point the propulsion machinery is set to full-astern and the helm is put hard-over to either port or starboard. The speed, position and heading are continuously recorded using differential GPS
    Differential GPS
    Differential Global Positioning System is an enhancement to Global Positioning System that provides improved location accuracy, from the 15-meter nominal GPS accuracy to about 10 cm in case of the best implementations....

    . The final time to stop (i.e.: ship speed is 0 knots) track line, drift (distance traveled perpendicular to the original course) and advance (distance traveled along the original course line) are all calculated. The trial may be repeated at various starting speeds.
  • Endurance: 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. The fuel flow, exhaust and cooling water temperatures and ship's speed are all recorded. The trial may last from 4 hours for small boats to 24 hours for large ships. The trial may be repeated at various drafts and trims and is often done in conjunction with the Speed Trial.
  • Maneuvering trials: A number of trials to determine the maneuverability and directional stability of the ship may be conducted. These include a direct and reverse spiral manoeuvres, zig-zag, and lateral thruster use.
  • Seakeeping: Was used exclusively for passenger ships but now used in a variety of vessels. Involves measurements of Ship motions
    Ship motions
    Ship motions are defined by the six degrees of freedom that a ship, boat or any other craft can experience.- Translation :HeaveSwaySurge-Vertical axis:Vertical axis, or yaw axis — an axis drawn from top to bottom, and perpendicular to the other two axes...

     in various sea state
    Sea state
    In oceanography, a sea state is the general condition of the free surface on a large body of water—with respect to wind waves and swell—at a certain location and moment. A sea state is characterized by statistics, including the wave height, period, and power spectrum. The sea state varies with...

    s followed by a series of analyses to determine comfort levels, likelihood of sea sickness and hull damage. Trials are usually protracted in nature due to the unpredictability of finding the correct sea state and the need to conduct the trials at various headings and speeds.

Noteworthy sea trials

- While steaming at high speeds, severe vibration was noted at the stern
Stern
The stern is the rear or aft-most part of a ship or boat, technically defined as the area built up over the sternpost, extending upwards from the counter rail to the taffrail. The stern lies opposite of the bow, the foremost part of a ship. Originally, the term only referred to the aft port section...

 during her sea trials. This prompted her builder, John Brown & Company
John Brown & Company
John Brown and Company of Clydebank was a pre-eminent Scottish marine engineering and shipbuilding firm, responsible for building many notable and world-famous ships, such as the , the , the , the , the , and the...

, to reinforce that area before acceptance by Cunard
Cunard Line
Cunard Line is a British-American owned shipping company based at Carnival House in Southampton, England and operated by Carnival UK. It has been a leading operator of passenger ships on the North Atlantic for over a century...

. - During sea trials, vibration was noted at the ship’s stern. The stern was reinforced, accepted by her owners Compagnie Générale Transatlantique
Compagnie Générale Transatlantique
The Compagnie Générale Transatlantique , typically known overseas as the French Line, was a shipping company established during 1861 as an attempt to revive the French merchant marine, the poor state of which was indicated during the Crimean War of 1856...

, and continued onto her maiden voyage
Maiden voyage
The maiden voyage of a ship, aircraft or other craft is the first journey made by the craft after shakedown. A number of traditions and superstitions are associated with it....

. The vibration was severe enough to necessitate relocating Tourist Class passengers and some crew members with cabins
Cabin (ship)
A cabin or berthing is an enclosed space generally on a ship or an aircraft. A cabin which protrudes above the level of a ship's deck may be referred to as a "deckhouse."-Sailing ships:...

 near the affected area. The problem was subsequently resolved by changing her propellers to four-bladed ones from the original three-bladed ones. - Her trials were conducted over two periods, September 25–29, 2003 and November 7–11, 2003, each lasting four days at sea, shuttling between the islands of Belle-Ile and L'ile d'Yeu
Île d'Yeu
Île d'Yeu is an island and commune just off the Vendée coast of western France.The island's two harbours, Port-Joinville in the north and Port de la Meule, located in a rocky inlet of the southern granite coast, are famous for the fishing of tuna and lobster....

 off the French coast. On board for each set of trials were 450 people, including engineers, technicians, owner and insurance company representatives, and crew. - Lost during deep sea diving tests on April 10, 1963.

See also

  • Dock trials, a demonstration of the functionality of ship's equipment. Usually conducted alongside prior to sea trials.
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