Ship Stability

This section should explain the basic
elements of the different stability matters and enable the user to know the
different abbreviations terms and their meanings know and understand a
transverse section of a ship know and understand a longitudinal section of a
ship stability is the vessels ability to return to an upright position after
being healed by an external force for a ship to float it must displace a mass of
water equal to its own mass deadweight is a measurement of the ships total
carrying capacity it is a total weight of cargo fewer oils
provisions crew fresh water stores and so on TPC tens per centimeter immersion
is a measurement of how many tens is required to change the ship’s Draft by
one centimeter the TPC may very different drafts and trim conditions k
is the abbreviation of the keel and is always at the same place this is on the
constructed line going through the center of the ship called the centerline
G is the center of gravity and its vertical placement is dependent on the
placement of masses on board heavy cargo placed me at the bottom of the ship
gives a low G while cargo placed high in the ship gives a higher G the
gravitational forces work downwards as if they work in one point the forces of
buoyancy work all over the underwater health
these forces of buoyancy work upwards as in one point called the center of
buoyancy B n is the meter center of the ship one heeling at small angles the
ship will pivot around this point its importance and placement will be
explained in the next chapter perpendiculars are constructed vertical
lines forward and aft use for measurement purposes the forward
perpendicular goes through the forward end point of the constructed waterline
the aft perpendicular goes through the rudder shaft in calculations the length
between the perpendiculars is often used and referred to as LPP in the middle of
the perpendiculars we have the so-called mid length of the ship this is found by
dividing the distance L P P into L CG is a sense of longitudinal gravity and
displacement is dependent on the longitudinal placement of masses on
board normally LCG is measured in meters from
the aft perpendicular LCB are forces of buoyancy working all over the hull as
described earlier these forces work upwards as in one point normally LCB is
measured in meters from the aft perpendicular x’ when changing trim a
ship will rotate but a transverse axis that passes of the sent to the actual
waterline this center is called longitude in the center of location LCS
LCS is read out from the hydrostatic data of the ship at the given conditions
this is an example of a ship rotating about LCS
the block coefficient is a measurement of how much an underwater hell fills at
a box with the same extreme dimensions

Norman Bunn


  1. Quite informative. The subtitles could be edited to make them clearer. Thanks

  2. Does not go far enough and it is dated, but it is good for a basic knowledge and understanding so people can get the basic concept of ship stability

  3. I want to make a floating boat from concrete
    Do you know any chemical material that can make the weight of concrete light ?

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