Magnetic compass

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The magnetic compass is fitted on the upper bridge exactly center line of the ship   It is referred to as standard compass     1. D ry C ard    2. W et C ard   A compass point north because all magnets have two poles north pole, south pole.   The north pole of the one magnet attracted towards the south pole of another magnet     DRY CARD COMPASS   A light aluminum ring about 254mm in diameter is attached to a brass hub by silk cord which is threaded in and out through holes in the ring.   This tight silk cord is act like bicycle wheels.   There is no other connection or support between the ring and the hub.   Silk cord is used because it doesn’t shrink or stretch due to moisture or change in atmospheric temperature.     Card support: -     The bottom of the hub has small cap fi tt ed with a sapphire bearing surface.   This rests on a pivot tipped with iridium which is hard nonmagnetic metal....
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Basic CARGO WORK definitions

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STOWAGE FACTOR :  it shows the space occupied by a tonne of cargo. 

It is the volume occupied by a unit weight of cargo. Generally it is expressed in:

  • cubic meters/ tonne ( metric)

       ( 1 metric tonne=1000kg)

 

  • cubic feet/ long ton 

         ( 1 long ton=1016 kg)

 

for eg: stowage factor of iron ore=0.40 cubic m /  metric tonne

this means that for storing  one tonne of iron ore 0.40 cubic m is required.  

stowage factor= volume/ mass

( density = mass/volume) 

thus stowage factor is the reciprocal of density. Cargoes with high density have low stowage factor and vice-versa


BROKEN STOWAGE : It is the space between packages which remains unfilled.

This factor varies according to type of cargo and shape of hold. 

Broken stowage will be higher for packages with large size and irregular shape. 

This factor is always expressed as percentage of the volume of cargo. 

broken stowage=(gross volume  - net volume * 100)/ net volume

NOTE:

to obtain correct volume of cargo, broken stowage must always be added to stowage factor.

TOTAL VOLUME = STOWAGE FACTOR+BROKEN STOWAGE 

 

LOAD DENSITY : It is the maximum weight that can be safely loaded on a unit area. It is expressed in tonnes/ sq.m.
The height to which cargo can be stowed on a deck will depend on load density of that deck and stowage factor of the cargo.  


DEADWEIGHT CARGO:  It is the cargo on which freight is charged on its weight.
 
MEASUREMENT CARGO: It is the cargo in which freight is charged on the volume occupied by the cargo.
 
 OPTIONAL CARGO: It is the cargo which is to be discharged at one port or another as decided by the shipper before the ship reaches the discharge ports. such cargo must be stowed as to be available at either of the optional ports.
 
 
BALE CAPACITY:  
It is the cubic capacity of a space when:
 
 breadth is taken from inside of cargo battens
 depth    from tank top to underside of deck beams 
 length   from inside of bulkhead stiffeners or spar ceiling where fitted 




GRAIN CAPACITY:
It is the cubic capacity of a space when length,breadth and depth are taken right to the plating. Allowance is made for volume occupied by frames, beams and stiffeners.
 
Obviously the bale capacity will be less than grain capacity. Inmost cases sometimes they can be equal in certain bulk carriers, ro-ro ships etc. 
 
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