MMC Ship Construction & Stability 2

Question 1

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

Accepted Answer

To reduce rolling motion

Answer

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

Question 2

The righting moment of a vessel is equal to:

Accepted Answer

Displacement multiplied by GZ

Answer

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

Question 3

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

Accepted Answer

0.15 meters

Answer

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

Question 4

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

Accepted Answer

Keel

Answer

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

Question 5

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

Accepted Answer

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

Answer

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

(MMC) Merchant Mariner Credential Practice Test