Coefficients of Form And Its Significance

         Cofficents of forms are used to understand the shape or configuration of ship and dimensions of the ships.These are dimension less quantity.

Waterplane Coefficient (Cw): It is the water plane area divided by multiplication of length and breadth.
                         Cw =  Aw / B*L

           Aw -Area of water plane
            B  - Breadth
            L  - Length
        > High Cw indicates good stability, good maneuverability in rough conditions and high frictional resistance.
        >Low Cw indicates low frictional resistance and fine ends 

Midship Coefficient (Cm): It is the cross sectional area of under water portion of the midship section to the product of breadth and draught
                                Cm= Am/BT 

                              Am - Midship section cross section area of immersed portion
                               B   - Breadth
                                T  - Draught
          > It gives an idea of shape of the ship at the mid ship
          >Cargo vessels having boxy shape at mid section because of high Cm where as Sail boats having low Cm 

Block Coefficient (Cb): It is the ratio of volume displaced by the ship to the product of length, breadth and draught of the immersed portion of the ship. 
                          Cb= ∇/LBT
                          ∇ - Volume of displacement
                          L -Length of immersed portion
                          B- Breadth of immersed portion
                          T- Draught
         > Under water volume of ships are calculated using block coefficient
         >Tankers having high Cb Passenger vessels having lower block coefficient                   

Prismatic Coefficient (Cp):  It is the underwater area, divided by the area of a midship section and the length of the ship

                          Cp= ∇/AmL

                           ∇         - Volume of displacement
                          Am   -Area of immersed portion of midship section
                          L      -Length of immersed portion

Relation between Cp,Cb and Cm


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