Section-Based Aftship

MaritimeThis functionality requires the Maritime add-on to be enabled. 5.3.0This functionality requires CAESES version 5.3.0 or later.

The section-based aftship is a component used in the Ship Modeling Workflow which is accessible via the Maritime-Tab (CAESES add-on). It is part of the modeling workflow for the ship type Component-Based, a component-based ship type. As the name already suggests, the base curve for the generation of the main surface of this model is a section running from the flat of bottom (FOB) and the centerplan curve (CPC) to the flat of side (FOS).

Model Structure

This model follows the same structure as all other models of the Ship Modeling Workflow. It is split into three main scopes:

• 01_geometryCurves: contains all curves that have a real physical meaning, e.g. stem
• 02_surfaces: contains all surfaces and functions for meta-surfaces
• 03_brep: contains the final BRep and prior processing steps, i.e. trimming, if necessary

All design variables are located in the scope where they are first used. Their names are chosen to be descriptive of their functionality and the bounds are tested for robustness of the model. The Ship Modeling Workflow allows to change any values, object types or the overall model structure for maximum flexibility.

Inputs taken from Ship Modeling Workflow

Ship dimensions provided by the hullParameters component:

Main Dimensions

• beam
• depth

Additional Dimensions

• xTransom
  • absolute x-position of the transom (usually a negative value)
• bilgeRadius
• tFlatbar_half
  • absolute value for the thickness of a flatbar at the centerplane of a ship
• flare

Derived Dimensions

• xStartMidship
  • absolute x-position of the end of the aftship/start of the midship
  • derived from the relative design variable relStartMidship which is the relative position with respect to the maximum x-value of the ship xPeak
• xStartFob
  • absolute x-position of the Start of the flat of bottom
  • derived from the relative design variable relStartFob which is the relative position with respect to the maximum x-value of the ship xPeak

Geometry Curves

Midship Section

The midship section is built from three parts. The flat bottom, the flat side and circular fillet between bottom and side. The midship section can be varied via two design variables:

• bilgeRadius
  • absolute value in project units (usually meters)
  • radius of the quadrant that is connecting FOB and FOS
• flare
  • absolute value in degrees
  • angle of the flat of side

Flat of Bottom

The flat of bottom (FOB) is an F-Spline with control over the x-coordinate of the start position and the angle at the start position:

• relStartFob
  • relative position with respect to the maximum x-value of the ship xPeak
• angleStart (shown in animation below)
  • absolute value in degrees

Deck

• relYStart
  • relative value with respect to half the beam
  • y-position of the start point of the deck at the transom

Flat of Side (FOS)

• relZStart
  • relative value with respect to the depth
  • z-position of the start point of the FOS at the transom
• angleStart
  • absolute value in degrees
  • angle of the FOS at the transom

Center Plane Curve (CPC)

• relZStart
  • relative value with respect to the depth
  • z-position of the start point of the CPC at the transom
• angleStart
  • absolute value in degrees
  • angle of the CPC at the transom

Transom Section

• weight
• deadriseTransom

Surfaces

Main Surface

Curve Engine

The Base Curve is a section which is a NURBS curve. The NURBS curve is built from three points:

• the start point lays on the FOB curve or CPC
• the end point lays on the FOS
• the mid point has the same z-coordinate as the start point and the same y-coordinate as the end point

The section is quite restricted and can only be varied by the weight of the NURBS curve at the mid point.

Functions

Functions	Sections

Flat of Bottom

The FOB surface is generated (in scope 02_fob) with the faces from planar curves BRep operation which takes a closed loop as input.

Flat of Side

For the FOS surface (in scope 03_fos), a ruled surface is used between the FOS and deck curves.

Transom Surface

As the FOB surface, the transom surface (in scope 04_transom) is also generated with the faces from planar curves BRep operation.

Final Aftship

The final section-based aftship can be found in the scope 04_brep.