Ship stability is the fundamental guarantee of safe navigation, directly affecting the vessel’s resistance to capsizing in waves and the flexibility of cargo loading. The inclining test is a mandatory verification task that must be completed after newbuilding construction and before delivery. Its purpose is to determine the actual position of the vessel’s centre of gravity, providing accurate data for the loading manual and stability booklet. Jiangsu Haizhongzhou Shipping Industry Co., Ltd. has developed standardised and refined procedures for organising inclining tests and analysing the resulting data.
The basic principle of the inclining test is to induce a small angle of heel, and by measuring the relationship between the heel angle and the heeling moment generated by moving weights, to back‑calculate the lightship vertical centre of gravity (KG) and longitudinal centre of gravity (LCG). Before the test, the team at Jiangsu Haizhongzhou Shipping Industry Co., Ltd. carries out a series of preparations: checking the vessel’s condition to ensure all unfastened equipment is securely lashed, movable items are properly stowed, and tanks are either empty or full with recorded actual liquid levels; selecting a suitable test area with sufficient water depth, minimal waves, and low or no current – typically inside a dock or sheltered waters; and arranging the test equipment, including at least two pendulum or electronic clinometers, and four sets of transversely movable weights (usually iron blocks or water tanks), each weighing about 1%–2% of the vessel’s light displacement.
During the test, the weights are moved sequentially according to a predetermined plan. After each move, once the vessel has stabilised, the clinometer readings are recorded, along with environmental parameters such as wind direction, current speed, and water temperature. The heel angle induced by each move is normally controlled between 1° and 4°, with a maximum of 6°. A complete test cycle includes no fewer than six effective moves, with forward and reverse movements used to eliminate systematic errors. Practice at Jiangsu Haizhongzhou Shipping Industry Co., Ltd. shows that using high‑precision electronic clinometers (accuracy ±0.05°) together with a wireless data acquisition system reduces the single measurement time from 5 minutes (manual reading) to less than 1 minute, while also minimising human reading errors.
In the calculation phase, the test data are imported into dedicated stability software. A linear regression analysis using the least‑squares method is performed to remove outliers and calculate the lightship KG and LCG. Taking an 85,000 DWT bulk carrier as an example, the inclining test gave a lightship KG of 12.35 m, deviating by only 0.07 m from the design value of 12.28 m, indicating good weight control during construction. After the test, Jiangsu Haizhongzhou Shipping Industry Co., Ltd. prepares a detailed inclining test report, which is reviewed and signed by the classification society’s surveyor, and serves as the basis for the vessel’s stability calculations.
For sister vessels built in series, Jiangsu Haizhongzhou Shipping Industry Co., Ltd. has also established an inclining test database. By comparing data from multiple vessels, the company identifies weight deviation trends during construction, which in turn guides block weight control and equipment selection optimisation. Currently, the company has achieved digital recording and full traceability of the entire inclining test process, reducing the report generation time from three days to less than one day. Accurate stability data are the first line of defence for safe vessel operation, and a technical commitment that Jiangsu Haizhongzhou Shipping Industry Co., Ltd. makes to its owners.
