Stability and Buoyancy

What are the reference points for the keel, center of gravity, center of buoyancy, and metacenter? How is each reference point defined and changed?

• Keel - Baseline reference point from which all other measurements are compared

• Center of Gravity - that point through which the weight of the entire ship’s structure and contained load is acting vertically downward.

• Center of Buoyancy - point through which all the force of buoyancy may ne considered to act in a vertically upward direction.

• Metacenter

What is initial stability, including its reference point, and which reference points affect it?

What types of information does a ship’s stability curve provide?

What are the types of draft marks? Include a description of or purpose for each.

What stability and buoyancy diagrams are available in the ship’s Damage Control (DC) book?

What types of information does the ship’s draft diagram provide?

What are righting arms and freeboard, and what happens to them when the ship’s draft is increased?

How do vertical weight additions affect the Center of Gravity (G), Center of Buoyancy (B), Metacenter (M), and ship stability?

How do vertical weight removals affect the Center of Gravity (G), Center of Buoyancy (B), Metacenter (M), and ship stability?

For which types of weight movement are the sine and cosine correction curves used to correct the stability curve, and how are they calculated?

What is a permanent list? What are three basic conditions that can cause a ship to take on a permanent list?

List the possible causes of negative metacentric height. What measures can be taken to correct for a list caused by negative metacentric height?

What are the Longitudinal Center of Flotation (LCF) and Change in Trim (CT)?

• LCF - Geometric center of the waterline plane

• CT - Defined as the change in the difference between the forward draft and the aft draft

How are LCF and CT related in terms of shifting, adding, and removing weights longitudinally?

A shift of weight forward, or addition of a weight forward of the LCF, increases the forward draft and causes a change in trim by the bow.

What is trim, and how does it factor into ship design?

The difference between the forward draft and aft draft.

How does too much trim by the bow or stern affect a ship’s operation?

• Maximum speed is reduced

• More horsepower and fuel oil are required to maintain a given speed.

What will happen to the ship’s stability if the trimming moment becomes greater than the maximum longitudinal righting moment?

The ship will plunge

What is Free Surface Effect (FSE) and how does it affect stability? What factors determine the effect of free surface on initial stability?

What methods are used to reduce FSE? Include a brief description of each.

What is Free Communication Effect (FCE) and how does it affect stability? What three conditions must exits for FCE?

Explain the compartment color coding on the flooding effect diagram.

What are the initial damage control actions following a grounding?

Who is responsible for developing the docking plan, and what items are included in it?

What are soft caps, and how thick should they be?

What must be done to the ship’s propellers, rudders, and projecting devices before entering dry dock?

During docking and undocking, when does responsibility of ship transfer?

For what are divers used in docking?

What hull board inspections occur during docking?

When is the leakage report submitted?

What hull board inspections occur before undocking?

What are the actions to be accomplished if a leak is reported during flooding of the dry dock?

What spaces are manned during undocking?

What windows might be included in the Commanding Officer (CO) summary for surface ships?

What type of stability analysis does FCCS provide?

What type of load groups can be managed through FCCS?

What two input methods are used for icing predictions?

What three ways can flooding be managed through the Flooding Specification window?

What is the first step when specifying grounding?

What is the function of the Draft Adjustment tool? What steps must be performed before entering data in the Draft Adjustment tool?

What are the possible recommended operations that could be generated by the Intelligent Decision Aid (IDA)?