Your vessel is in port. Current KG = 4.20m, displacement = 1800t. You load 120t of cargo at a KG of 6.50m (high deckload). Calculate the new KG.

A. LOADING WEIGHT EFFECT ON KG: New KG = (Old displacement × Old KG + Weight loaded × KG of weight loaded) / New displacement. Calculation: (1) Existing moment: 1800t × 4.20m = 7560 tm; (2) Added moment from cargo: 120t × 6.50m = 780 tm; (3) Total moment: 7560 + 780 = 8340 tm; (4) New displacement: 1800 + 120 = 1920t; (5) New KG = 8340 / 1920 = 4.344m (approximately 4.34m). EFFECT ON STABILITY: KG has INCREASED from 4.20m to 4.34m (the weight was loaded HIGH — above the existing KG). This INCREASES KG and REDUCES GM (since GM = KM − KG, and KM changes relatively little with displacement, the net effect is a reduction in GM). Principle: loading a weight ABOVE the existing KG raises KG; loading BELOW the existing KG lowers KG. For stability, low loading (in tanks, in the bottom of holds) is preferable. The stability booklet must be consulted to verify the new loading condition meets IS Code criteria.

B. New KG = (4.20 + 6.50) / 2 = 5.35m. Loading a weight averages the KG of the new weight with the existing KG.

C. New KG = Old KG × (new displacement / old displacement) = 4.20 × (1920 / 1800) = 4.48m.

D. Loading cargo does not affect KG — KG is fixed by the hull design and only changes when ballast is adjusted. Recalculate KM for the new displacement.

A. ANGLE OF LOLL: this is the classic presentation of negative GM (unstable equilibrium). Cause: the vessel's metacentric height (GM) has become negative — the metacentre (M) is now BELOW the centre of gravity (G). At 0° upright, the vessel has no restoring moment — but as she heels, the waterplane area shifts, moving B outward until a point of neutral equilibrium is found: this is the angle of loll (typically 5°-20°). The vessel "rests" here rather than returning upright. Common causes on a small coastal vessel: (1) Free surface effect from flooded compartments, slack tanks, or water in bilges; (2) Topside icing (raised G); (3) Cargo shift or absorption of water by deck cargo (timber); (4) Consumption of fuel and water from the bottom of tanks without compensating. IDENTIFICATION test: if you push the vessel toward the loll (to starboard) she returns to the loll angle; if you force her past the loll, the GZ curve at higher angles may generate restoring force — she "snaps" back to the loll. EMERGENCY ACTIONS: (1) DO NOT immediately ballast the high side (port) — if she rolls through the loll onto the other side, she may capsize; (2) Check and pump out bilges; (3) Fill double bottom ballast tanks SLOWLY starting with those on the LOW side (starboard) to raise M; (4) Reduce topweight; (5) Call master (if OOW); (6) Alert crew and consider reducing speed.

B. An 8° list to starboard means a weight has shifted to starboard — immediately correct by ballasting the port side to bring her upright, then investigate the cause.

C. A list that stays fixed at 8° is a permanent heel caused by off-centre loading. Correct it by shifting cargo from the starboard side to port before continuing.

D. A vessel that doesn't return from a list has insufficient GM. Calculate a righting lever at 8° using the GZ curve and if positive, the vessel is stable enough to continue.

A. IS CODE 2008 (International Code on Intact Stability) — criteria for cargo ships: the IS Code provides mandatory stability criteria for vessels under the 2008 International Code on Intact Stability (made mandatory under SOLAS II-1 and Load Lines). Minimum criteria: (1) AREA under GZ curve from 0° to 30° must be not less than 0.055 metre-radians; (2) Area from 0° to 40° (or flooding angle, whichever is less) not less than 0.09 metre-radians; (3) Area between 30° and 40° (or flooding angle) not less than 0.03 metre-radians; (4) GZ at 30° or greater must be not less than 0.20m; (5) Maximum GZ must occur at an angle of heel not less than 25°; (6) Initial GM (GM_0) must not be less than 0.15m. In this scenario: GM of 0.22m exceeds the minimum 0.15m — it satisfies this criterion. HOWEVER: GM alone does not determine acceptability — you must check ALL the criteria listed above (particularly the GZ curve at 30° and the area criteria). A vessel can have a positive GM but still fail the area criteria if the GZ curve drops too early. The stability booklet must be consulted to verify the full GZ curve for the proposed loading condition.

B. A GM of 0.22m is inadequate — the minimum for any vessel is 0.30m. Loading in this condition is not permitted under MCA regulations.

C. GM is the only stability criterion — a positive GM of any magnitude above zero is sufficient for a vessel to be considered stable and safe to sail.

D. The 0.22m GM is acceptable for a near-coastal voyage but would not meet the standards for an ocean passage. Near-coastal vessels have lower stability requirements.