Ship Hull Design and Modelling

 

 

 

The model of the hull is based on the ship parameters defined in the early stages of the ship design. Normally, the required parameters may be organized in the following different levels:

  • Ship type (tanker, bulk carrier, container, fishing vessel, motor yatch, sailing boat, etc.)
  • Main characteristics:
    • Length between perpendiculars
    • Breadth
    • Depth
    • Design draught
    • Displacement
    • Block, waterplane, longitudinal and vertical prismatic coefficients
    • Freeboard
    • etc.
  • Form parameters:
    • Longitudinal geometric centre of the hull
    • Longitudinal geometric centre of buoyancy
    • Particular angles and tangents
    • Steam and stern contours
    • Bulbous type
    • Knuckles
    • etc.
  • Midship section configuration:
    • Midship section coefficient
    • Bilge radius
    • etc.
Here are some hull examples I have modelled in Rhinoceros 3D with NURBS surfaces
Dreadnought Frigate
   
LNG Carrier XVI Century Nao
   
Ro-ro Carrier without bulbous Ro-ro Carrier with artificial added bulbous
   
Sloop boat Stern Trawller
   
Tanker modelled with single surface Tanker modelled with multiple surfaces
   
Tug boat Whale boat
 
Reproduction of existing hulls or hull parts

Many ships currently navigating are not provided with 3D surface models of the hull shape. Only lines plans are available to aquire the shape of the hull. These drawings can be used to generate the 3D surface models of the hull or of certain zones of the hull, which can be very useful when an accurate hull form of the existing ship is required. Normally this happens when reppairing work of the hull is reuqired. Thus, surface models of ship hulls can be built based on lines plans.

Surface models can also be generated for ancient ships based on existing drawings that describe the main characteristics of the hull, such as forward and afterward contours, midship section shape, etc.

 

 

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Hydrostatics calculations

The calculations for ship hydrostatics include the following:

  • The displacement table
  • The metacentric diagram
  • The hydrostatic curves:
    • Centre of buoyancy above base line
    • Moulded displacement
    • Extreme displacement
    • Increase displacement per unit increase in draught
    • Moment causing unit trim (MCT)
    • Transverse metacentre above base line (KM)
    • Centre of floatation from amidships
    • Centre of buoyancy from amidships (LCB)
  •  

  • Righting arm GZ curve
  • Cross cruves of stability