13. Ship Stability and Construction for Applicants to the Fourth-Class Engineer Certificate

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Annex C

13.1 Introduction

This annex was developed in response to Table A-III/1 of the STCW Code, Maintain seaworthiness of the ship. It will enable the applicants who can not get the basic training on this subject to reach the level of competence required in order to obtain an STCW-endorsed certificate.

Applicants who intend to complete this annex in lieu of the approved training need to have on hand good manuals on ship stability and naval architecture.

One should expect that with proper documentation in hand, approximately 40 hours will be required to complete this annex; upon completion, it must presented to a Marine Safety examiner for assessment.

13.2 Objective

The objective of this annex is three fold, namely:

1. to ensure basic working knowledge and application of stability, trim and stress tables;
2. understanding of the fundamentals of watertight integrity and actions to be taken in the event of partial loss of intact buoyancy; and
3. general knowledge of the principal structure members of a ship and the proper names for the various parts.

13.3 Ship Stability

(1) Basic knowledge and definitions

What is the Centre of Gravity of a ship?
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What is the Centre of Buoyancy?
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What is the transversal Metacentre?
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What is the longitudinal Metacentre?
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What do the acronyms TPC and TPI stand for? What do they mean?
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What do the acronyms MCTC and MCTI stand for? What do they mean?
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For a specific ship, where can we find the information on the above?
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Define briefly the following terms:

What is Free Surface Effect? Generally speaking, how does this affect the stability of a ship?
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What is meant by the trim of a ship? What makes it change?
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With regard to a ship's hull, what do Hogging and Sagging mean? How are they measured?
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How do we find the stress in a ship's hull? How can one find the maximum allowable stress?
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Define the propeller pitch. What is meant by Propeller slip?
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State and explain Archimedes's law.
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How is the draft of a ship affected by the density of the water in which it floats? What is meant by Fresh Water Allowance?
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Explain what happens to the ship's centre of gravity when cargo is added or removed. In which direction does it move? What is the effect of a weight suspended from a crane boom?
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What is the Righting Arm? How is it calculated?
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What is meant by Intact Stability?
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What is the purpose of watertight bulkheads? Where are they installed on a ship?
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Describe the fitting of a watertight bulkhead valve. What arrangement is provided to control this valve from outside the compartment?
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What is the function of the watertight doors on board a ship? Where are they located? When are they used?
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Describe an arrangement provided to close a watertight door from outside the compartments it isolates. Why does it have an alarm? Where and when does it sound?
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Explain how you would make a temporary repair to stop the water entering the engine room through a corroded spool between a sea water inlet valve and the ship's bottom.
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(2) Exercises

What is the weight of a steel block 1m x 1m x 0.5m having a density of 7500 kg/m3 ?
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According to Archimedes's law, what is the weight of this same block when it is immersed in water having a density of 1000 kg/m3 ?
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Calculate the TPC of a box shaped barge 20m long by 5m large floating in water of 1000 t/m3.
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What will be the change in the mean draft of this barge when 500t of cargo are discharged?
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Draw a diagram of the midship cross section of a general cargo vessel and show the relative positions of the Centre of gravity (G), Centre of buoyancy (B) and Metacentre (M). Give the typical values in meters relative to the keel (K).

 

 

Draw the same diagram at an angle of 10° and show the righting arm. Give the value relative to the ship's displacement.

 

 

13.4 Ship Construction

(1) Basic knowledge and definitions

Define the following terms relating to a ship's structure:

(2) Exercises

Explain the purpose of double bottoms
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Draw and label a transverse framed double bottom

 

 

Define Pounding and Panting. How are these stresses compensated for?
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Draw and label the midship cross section of the vessel you are presently working on, or one that you are familiar with.

 

 

Sketch and describe the construction of the bow section of the vessel you are presently working on, or one that you are familiar with. Name all the members.

 

 

Sketch the steering gear arrangement of the vessel you are presently working on, or one that you are familiar with, and explain its operation. Explain also the operation of the emergency gear.

 

 

Sketch and describe the rudder of the vessel you are presently working on, or one that you are familiar with. Show in detail one pintle bearing.

 

 

Draw the shafting arrangement of the vessel you are presently working on, or one that you are familiar with, showing also the thrust bearing and how it is attached to the structure.

 

 

Sketch and describe an oil-lubricated stern tube, showing how it is fitted in the ship's structure.

 

 

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