Ship Construction & Stability Flashcards

What is the purpose of a ship's bilge keel?

Answer: To reduce rolling motion

Bilge keels are longitudinal fins welded along the turn of the bilge to dampen rolling motion and improve ship stability.

The righting moment of a vessel is equal to:

Answer: Displacement multiplied by GZ

Righting moment equals displacement (W) multiplied by the righting arm (GZ), representing the force tending to return the vessel upright.

A ship's metacentric height (GM) is considered dangerously small when it is less than:

Answer: 0.15 meters

A GM of less than 0.15 m is generally considered dangerously small and indicates the vessel is at risk of capsizing.

Which structural member runs longitudinally along the centerline at the bottom of a ship's hull?

Answer: Keel

The keel is the primary longitudinal structural member along the centerline of the hull bottom, acting as the ship's backbone.

Free surface effect in a partially filled tank reduces a vessel's effective GM because:

Answer: The liquid shifts when the vessel heels, raising the effective center of gravity

When a vessel heels, liquid in a partially filled tank shifts to the low side, effectively raising G and reducing GM, degrading stability.

The term 'reserve buoyancy' refers to:

Answer: The watertight volume of the hull above the waterline

Reserve buoyancy is the intact watertight volume above the waterline that provides additional buoyancy if the vessel takes on water.

A transverse watertight bulkhead on a ship primarily provides:

Answer: Subdivision to limit flooding after damage

Transverse watertight bulkheads divide the ship into compartments, limiting the spread of flooding in the event of hull damage.