Q7 (10 Marks) Ship Stability
SC&S • Written Exam

(a) Why is an inclining experiment carried out? Write a short account of the method adopted. (6)

(b) An inclining experiment was carried out on a ship of 8000 tonne displacement. The inclining ballast was moved transversely through 12 m and the deflections of a pendulum 5.5 m long, measured from the centreline, were as follows:

3 tonne port to starboard 64 mm S

3 tonne port to starboard 116 mm S

Ballast restored 3 mm S

3 tonne starboard to port 54 mm P

3 tonne starboard to port 113 mm P

Calculate the metacentric height of the vessel. (10)

Appeared In: Aug 2022

Verified Model Answer (Text Solution)

Structured for DG Shipping MEO Class II examination scoring criteria.

Exam Ready
Part (a)

An inclining experiment

is conducted to determine a ship's metacentric height (GM) and, consequently, the location of its centre of gravity (CG). Knowing the CG of an empty vessel allows for calculations of its position under various loading conditions.

The inclining experiment is performed on:

  • Newly built ships.
  • After major alterations to the vessel.
  • As required by the classification society.

Conducting the inclining experiment:

  • The ship should be in a sheltered location (like a dry dock) with mooring ropes slack, only essential personnel on board, all tanks either empty or full, and any loose weights removed or secured.
  • At least two pendulums (one forward, one aft) are used, ideally as long as possible and suspended from convenient points (e.g., under a hatch). A hood filled with water or oil is placed beneath each pendulum bob to dampen its swing for accuracy.
  • Four masses are positioned on the deck, two on each side of the midships, their centres as far from the centerline as possible. These masses are moved systematically: all four to one side, then all four to the other, and finally two on each side.
  • The pendulum deflection is recorded for each mass movement.
  • The average of these deflections is used to calculate the metacentric height (GM).
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