What Is an Inclining Test?

An inclining test is an assessment of a ship's stability and center of gravity, performed on ships over 79 feet (24 meters) in length before they go into service. This test is part of a series of assessments usually required by law before a ship can be approved by a regulatory authority for sailing. Shipbuilders must make arrangements to make these tests and record the data. The information can be made available by request from concerned parties, including the owners of the ship. It is also used as the base for technical specifications on top speed, laden weight, and other parameters.

In the inclining test, personnel perform a series of movements with weights while the ship is in calm, inland waters. The weights force the ship to heel, tipping to the side. This provides information about the stability of the ship while underway, and about the center of gravity. Technicians can note of ship performance in optimal inland conditions so this information will be available in the technical specifications.

The inclining test also provides an opportunity to check on the draft of the ship, and to determine the lightship weight. In a lightship survey, personnel measure the weight of a ship when it is unladen, without passengers, gear, cargo, and any nonessential supplies. Fluids like fuels and lubricants are left on board, but everything else is stripped. While it is possible to track and roughly estimate weight during construction by monitoring what is installed, the lightship weight provides a definitive number.

Some shipbuilders have the supplies and personnel to conduct an inclining test. Others contract it out to third parties with experience in this area. Third party specialists can also conduct other tests and sea trials to generate a detailed profile of a ship's characteristics and prepare documents for regulatory authorities who need to review the ship before authorizing it for use. The fees for inclining test procedures and other services vary, depending on the nature of testing required.

In sea trials and other tests, a ship must match a set standard for other ships of that class, based on length, intended use, and other parameters. If it does not, it may not be deemed seaworthy. The shipbuilder will have to make modifications to address the issue before repeating the tests to confirm that the ship is ready. Naval architects and engineers work carefully on the designs of craft before they enter the construction phase to avoid costly failures in the testing phase.