Stability

Question 1

What is free surface effect?

Answer 1

• Loss of ships stability caused by liquid/grain moving freely and sloshing side to side.
As the liquid moves, its centre of gravity shifts towards the low side and raises the ships overall centre of gravity, decreasing the GM and reducing the stability.

• Caused by partially filled tanks, especially in wider tanks (DB, Ballast)
• Try to keep tanks full or empty not half full and also use longitudinal/swash bulkheads.

Question 2

What is list and trim?

Answer 2

List - Port & Stbd (transversal)
Trim - Fwd & Aft (longitudinal)

Question 3

What is a bilge keel and a duct keel?

Answer 3

Bilge keels are welded fine on the bilge section of the hull to reduce rolling & improve stability

Duct keel is a tunnel for cables and piping from the FWD ER BH to the Collision BH

Question 4

Types of watertight doors

Answer 4

• A - Left open & only closed during emergencies
• B - Kept closed and only to be opened when working in the adjacent compartment
• C - Closed all the time and only opened for passing through
• D - Not SOLAS compliant, closed before departure and remained closed during
navigation and cannot be upgraded to another class