# MT-4241

## Stability and Trim

### Course Description

This course is designed to meet all stability knowledge requirements for Officer in Charge of a Navigation Watch defined by STCW Regulation II/1. Building on the principles of stability, the student will use tables and diagrams of stability and trim data to calculate initial stability, drafts and trim for any given configuration of loading. The student will compute both longitudinal and transverse stability for any condition during the load-out or discharge using both the traditional stability booklet and stability software. The student will interpret stability information and identify factors adversely affecting stability. Finally, the student will become familiar with damage stability assessment and fundamental actions to be taken in the event of partial loss of intact buoyancy.

This course consists of three 1-hour lectures or two 1-1/2-hour lectures a week for a semester with a comprehensive final examination.

### Entrance requirements

A strong foundation in algebra and trigonometry is a pre-requisite for this course.

### Learning Objectives

Demonstrate knowledge and understanding of the following STCW elements:

• OICNW-B1.1 Knowledge of the effect of cargo, including heavy lifts, on the seaworthiness and stability of the ship
• OICNW-C2.1 Working knowledge and application of stability and trim tables and diagrams
• OICNW-C2.2 Understanding of fundamental actions to be taken in the event of partial loss of intact buoyancy
• OICNW-C2.3 Understanding of the fundamentals of watertight integrity

### Topics

• Course Introduction

• Six Motions of a Vessel
• ANDREA DOREA Case Study

• Buoyancy

• Archimedes’ Principle

• Displacement

• Draft, Freeboard
• Purpose of Load Lines and Reserve Buoyancy
• Plimsol Marks

• Initial Stability

• Centers of Gravity and Buoyancy
• The Couple and Righting Moment
• Indicators of Initial Stability and Dynamic Stability
• Transverse Metacenter
• Stable, Neutral and Unstable Equilibrium
• Metacentric Height and Metacentric Radius
• Height of the Metacenter
• Height of the Center of Buoyancy
• Metacentric Radius

• Movement of the Center of Gravity

• Calculations for: Vertical Center of Gravity
• Calculating GG' (Shift of Center of Gravity)

• Movement of the Center of Gravity

• Finding KG when Loading and Discharging

• Containership Bays-Tiers-Rows

• Determining the Height of Metacenter

• Calculating Block Coefficient
• Calculating Height of the Center of Buoyancy, KB
• Calculating Metacentric Radius, BM
• Ship’s Lines, Hydrostatic Data: Tables and Curves
• Relationship of Tons per Inch, TPI, to Area of the
• Waterplane, AWP
• Approximating BM for Curved Water Planes
• Analysis of the Vertical Movement of KM with a Change of Displacement
• Analysis of the Movement of KM with a Transverse Inclination

• Trim and Stability Booklets

• Inspection of Contents
• Introduction to the S.S. American Mariner Booklet

• Calculating GM

• Stability v. Stowage
• The Relationship of GM to Rolling Period
• Proportionate Loss of Stability
• Effects of Negative GM on a Vessel
• Practical Methods of Calculating GM
• Long Form Method of Calculating GM

• The Inclining Experiment

• Required Gear and Data Derivation of Formulae
• Precautions to be Taken During Inclining Experiment
• Conducting a “Model” Inclining Experiment and Determining Lightship KG
• T.V. ENTERPRISE Inclining Experiment

• List and Its Correction

• Practical Applications and Solutions
• Calculating Angle of List Resulting from Loading, Shifting or Discharging a Weight
• Calculating Weight to Load, Shift or Discharge to Remove a Given List

• Effects of Slack Tanks

• Free Surface
• Effects Surface Dimensions
• Effects of Specific Gravity and the Amount of Liquid in a Tank
• Effects of Weight and Vertical Position of Liquids
• Free Surface Corrections and Free Surface Constants
• Operation of Cross-Over-Valves Between Deep Tanks
• Free Surface Effects on Overall Stability
• Tankage Systems for the Deck Officer
• Anti Rolling Devices
• Bilge Keels, Antirolling Tanks, Fins and Gyro Stabilization

• Curves of Statical Stability & Dynamic Stability

• Stability at Large Angles of Inclination
• Effects on GM
• Stability Curves
• Constructing Cross Curves of Stability (GZ)
• Drawing the Statical Stability Curve
• Correction for a Vertical Shift of G
• Correction for a Horizontal Shift of G
• Effect of Hull Form on Righting Arm
• Correcting for a Change in Displacement and a Transverse Shift of G
• Stability Criteria and Statical Stability Curve
• Analysis of Statical Stability Curve
• Summary of Analysis of Overall Stability Characteristics

• Fresh Water Allowance

• Water Density and Displacement
• Use of the Hydrometer
• FWA Calculations
• Trim

• Introduction to Longitudinal Stability
• Preliminary Definitions
• Trimming Moments and MT1
• Calculating MT1
• Change of Draft at One End
• LCF Method of Trim Calculations
• Effects of Trim on Draft
• LCF Method of Trim Calculations - Change of Trim Due to Large Weights
• LCG Method of Trim Calculations - Use of Trim Tables
• Effect of Trim on Draft
• Effects of Trim on Displacement and Transverse Stability
• Effects on Trim when Passing From Salt to Fresh Water

• Angle of Loll

• Inclination Due to Unstable Equilibrium
• Calculating the upsetting moment
• Identifying Angle of Loll on Static Stability Curve
• MV STELLAMARE Casualty
• SS EASTLAND Casualty

• Actions To Be Taken in the Event Of Partial Loss of Intact Stability

• Effects of Flooding on Transverse Stability
• Lost Buoyancy Method
• Added Weight Method

• Remedial Measures to Improve Transverse Stability

• Effect of Grounding on Stability
• Effect of Flooding on Reserve Buoyancy
• Effect of Permeability on Floodable Length
• Ice Accretion and Stability Fundamentals

• Damage Control Fundamentals and Actions

• List & Loll, Flooding, Fire, Grounding, Hull Damage

• Introduction to Computer Based Stability Programs

• Vessel Specific, USCG Approved Computer Based Stability Programs
• Excel Work Sheet Stability Programs With And Without Hydrostatic Micros
• Practical Applications And Limitations Of Computer Based
• Stability Programs And Stability And Trim Considerations

Other objectives

Building on the principles of stability, the student will be able to:

• use tables and diagrams of stability and trim data to calculate initial stability, drafts and trim for any given configuration of loading.
• compute both longitudinal and transverse stability for any condition during the load-out or discharge through the use of the traditional stability booklet and state of the art stability software.
• interpret stability information and to identify factors adversely affecting stability. Finally,
• explain the fundamentals of damage stability assessment and the fundamental actions to be taken in the event of partial loss of intact buoyancy.