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The primary formula used to calculate the displacement of a ship is based on its physical dimensions and block coefficient. The block coefficient is a dimensionless number that describes how closely the shape of a ship resembles a rectangular block. Displacement = Length × Breadth × Draft × Block Coefficient. Where:
HULL FORM AND GEOMETRY. Be familiar with ship classifications. Explain the difference between aerostatic, hydrostatic, and hydrodynamic support. Be familiar with the following types of marine vehicles: displacement ships, catamarans, planing vessels, hydrofoil, hovercraft, SWATH, and submarines.
The displacement or displacement tonnage of a ship is its weight. As the term indicates, it is measured indirectly, using Archimedes' principle, by first calculating the volume of water displaced by the ship, then converting that value into weight.
displaced volume: it doesn’t matter what is inside the outer skin, or how it is arranged. Calculating trim of a flooded vehicle: Use in-water weights of the components, including the water (whose weight is then zero and can be ignored). The calculation gives the center of in-water weight.
• For a displacement boat, the volume of tank is approx. 5 l/kW, in which case you can cruise over a day. • For a planing boat approx. 1 l/kW, in which case you can cruise over two hours by a 2-stroke and over three hours by a 4-stroke engine. • Rules of thumb (1 hp = 0,746 kW): –An old 2-stroke engine burns approx. 1/2 l/hp/h
The prismatic coefficient is the ratio of actual underbody volume to the volume of a prism having a length equal to the DWL, and a section equal to the boat's maximum sectional area. The prismatic coefficient provides an indication of the distribution of displacement.
C. Schneekluth’s Formulae : This formulae is based on statistics of optimization results according to economic criteria, or length for lowest production cost. LPP =∆∗V ∗C 0.3 0.3 Lpp in metres, ∆is displacement in tonnes and V is speed in knots C = 3.2, if the block coefficient has approximate value of CB = Fn
