Geometric Analysis

Introduction

In addition to specific marine analysis features like Hydrostatics and Stability, and Resistance and Powering Estimation, PolyCAD features a number of basic geometrical analysis routines as well as Lines Plan Generation, Table of Offsets and Parametric Weight Estimation.

Extents

The Entity Extents calculation presents the minimum, maximum and extents in each coordinate direction. The table may be copied to the Windows Clipboard as text or an HTML table, printed or a formatted HTML report generated for copying or printing.

Compartment Volumes and Centres

The Volume and Centre calculation presents the volume and centroid for Polyline List Elements considered to be Compartments. In addition, the associated permeability is presented with the Net Volume (VNet). This calculation is used to support the preparation of GF, SUS and DAM files used with external calculation software. The table may be copied to the Windows Clipboard as text or an HTML table, printed or a formatted HTML report generated for copying or printing.

Areas and Centres

This Area and Centres Calculation presents the surface area and centroid of any geometric elements with this property, including closed planar polylines. The table may be copied to the Windows Clipboard as text or an HTML table, printed or a formatted HTML report generated for copying or printing.

Lines Plan Generation

The Lines Plan Generator automates the production of this traditional drawing using the selected surface. Sections, Waterlines and Buttocks are presented on separate views with the option of annotating the grid and label text for each curve. Four different layouts are available which place the body plan above, centre, right and overlayed on the buttocks view.

Contour positions are independent of the main definition and can be adjusted for the best presentation. The location of the contour labelling text can be improved by interactively moving the positioning definition. Additional curves can be projected into the views to pick out specific surface boundaries, knuckles and other features that may not be automatically identified in the surface. The drawing configuration persists in the model allowing updates to be produced without any adjustment settings.

The Drawing can be copied to the Windows Clipboard, Printed, Exported to DXF or taken back into the 3D model environment as Polylines.

Table of Offsets

Requested as part of the Cloud Points development, the Table of Offsets Calculation and Report allows the numerical coordinates of surfaces to be documented or checked against existing reports. The calculation generates three tables of coordinate intersections between each group of contours, defined on the first tab of the form. The general contour definitions from the main model or frame positions can be copied in if desired. It should be noted that offset values are generated by numerically analysing the surface to a tolerance of 1e-6 design units. There will be discrepancies between the normal contour curves and offsets since contours are indirectly generated from the surface for speed and do not have the same level of accuracy as the offset values.

The intersections are output on the following three tabs. The columns and rows of these tables can be swapped. The vertical direction of Y (Buttock) and Z (Waterline) rows is reversed by default to present the figures in a similar style to the layout of plan and profile view in a Lines Plan. This can be changed. These tables can be copied to the clipboard or printed.

The final tab prepares a report by converting the tables into an HTML document that can be printed, copied to the clipboard or saved. The style of this report can be customised.

Parametric Weight Estimation

A Parametric Weight Estimation tool has been under development in PolyCAD for some time and it now mature enough to be released. The tool allows a weight estimation to be generated using various properties of geometrical elements in the model. The options are as follows:

Point Weights

The Point Weights table allows you to position an explicit Weight at the centre of elements in the model. You can also add a non-modelled point weight by typing in a name for the definition. The centroid of the weight can be modified by editing the positional coordinate component.

Area Weights

Area based Weights generate the load by multiplying the area of the element by a Weight per Area parameter. The centroid is taken from the centre of area. A Copy Symmetrical option is available to introduce a copy of the weight on the other side of the centre plane, i.e. it doubles the weight and sets the transverse centre of the weight to zero.

Volume Weights

Volume based Weights generate the load by multiplying the Volume of the element by Density. Densities can be typed in or selected from the Materials Definition library. The centroid is taken from the centre of volume. A Copy Symmetrical option is available to introduce a copy of the weight on the other side of the centre plane, i.e. it doubles the weight and sets the transverse centre of the weight to zero.

Structural Weights

Structural Weights extend the approach used by the Area and Volume Weights using the area of surfaces with a thickness and density to produce a structural weight. Additional weight due to stiffeners and brackets can be included as a percentage. Densities can be typed in or be selected from the Materials Definition Library.

Materials Definition

The Materials Definition Library contains the definition of common fluid and solid elements. The default list can be extended and saved by the user if the need to keep common elements. Density is displayed both in the currently selected units and in terms of Specific Gravity. The Specific Gravity of a material is maintained as constant regardless of changes to the default Units.