Question 61 GLI01 - Master-Unlimited Tonnage

The Correct Answer is A. **Explanation of Option A (Correct):** During a stability test (such as an inclining experiment or a lightweight survey) performed on a vessel, the absolute priority regarding the surrounding environment is to ensure the vessel is free to rotate and settle naturally in the water, without any external constraint. Grounding, or touching the bottom, introduces external forces (vertical reactions) that effectively change the vessel's displacement and its natural center of buoyancy/gravity, thereby invalidating the fundamental measurements required for calculating the true center of gravity ($KG$) and metacentric height ($GM$). Therefore, the water must be deep enough to prevent grounding throughout the entire test, including any expected angles of heel. **Explanation of Incorrect Options:** **B) All dunnage, tools, and extraneous items are secured:** While securing loose items is standard good practice for safety and general accuracy (as moving weights affect stability), it is not a **mandatory condition** that must be met for the validity of the fundamental stability test itself. The mandatory condition is that the vessel's current lightweight condition (including all fixed and movable weights) is accurately recorded, and that the external environment (water depth/mooring) does not interfere with the vessel's hydrostatic response. **C) Each tank must be partially full to show it does not leak:** Tanks are typically kept either completely empty (pressed up and drained) or completely full (pressed up) during a stability test. Partially filled tanks (slack tanks) create "free surface effect," which severely reduces the vessel's stability ($GM$). A stability test requires the $GM$ to be measured accurately; therefore, slack tanks are strictly avoided unless they are essential and their free surface effect is precisely accounted for. Filling tanks to show they don't leak is irrelevant to the validity of the stability calculation. **D) The vessel must be moored snugly:** The vessel must actually be moored **as loosely as possible** or, ideally, not moored at all (if feasible and safe), allowing it to float freely. Snug mooring (tight lines) introduces external forces (horizontal constraints) that prevent the vessel from heeling freely and settling naturally to its equilibrium waterline, which would invalidate the measurements taken during the inclining process.