FreeCAD Ship Workbench

Welcome to FreeCAD-Ship!

Introduction

FreeCAD-Ship is a free module for FreeCAD oriented to aid naval ship design by providing several tools commonly used in naval architecture, seakeeping and ship resistance.

Contents

• Features
  • Areas curve
  • Hydrostatics
  • Load conditions definition
  • Tank capacity curve
  • Static sink and trim
  • GZ curve
  • RAOs
• Install
• Usage
• Tutorials
• Roadmap
• Discussion/Feedback
• Bugs/Enhancements
• Authors

Features

It currently offers the following tools:

Areas curve

This tool computes the area of each transversal section of the ship, plotting it and providing a spreadsheet with the very same results. The transversal areas curve offers really valuable information in the first stages of a ship's design, as it gives an idea of the shape and volume distribution of the ship.

Hydrostatics

The most common hydrostatics can be easily computed with this tool. The hydrostatics are divided in 3 main groups:

• Volume
  • Wetted area (WSA), heavily related with the ship dynamics.
  • Moment to trim the ship 1 cm (MTC), of critical relevance at the time of planning load conditions.
  • Longitudinal position of the bouyance center (XCB).
• Stability
  • Floating Area/Waterplane Area (WP), related with the ship waves generation, and thus with the ship resistance.
  • Distance between the keel and bouyance center (KBt), which is related with the transversal stability.
  • Distance between the bouyance center and the metacenter (BMt), which is related with the transversal stability.
• Coefficients
  • Block coefficient (Cb), heavily related with the ship resistance.
  • Floating Coefficient (Cf), heavily related with the ship resistance due to the waves generation.
  • Main section Coefficient (Cm), related with the ship transversal stability, as well as the ship dynamics.

On top of that, the Displacement-Draft curve is depicted in all the plots. The tool is also providing you a spreadsheet for further computations.

Load conditions definition

In FreeCAD-Ship you can define as many weights and tanks as required. Then you can combine them all together in a load condition. At the time of defining weights, you can define:

• Punctual masses, providing their masses.
• Line elements, providing their linear densities (i.e. the area of the transversal section multiplied by the material density).
• Surface elements, providing their surface densities (i.e. the width of the element multiplied by the material density).
• Solid elements, providing their densities.

Tank capacity curve

In FreeCAD-Ship you can easily plot the Filling volume-level ratio of any tank. Of course the tool is providing you a spreadsheet with the information about filling level percentage, filling level height and resulting volume.

Static sink and trim

Get a visual hint on the equilibrium draft and trim angle for a certain load condition. You can choose between the representation in the upright ship position, or setting the free-surface as the z=0 plane.

GZ curve

The main transversal stability indicator, it is unsurprisingly required by the vast majority of the classification societies to certify a ship. This tool is computing that for you, providing a plot and the associated spreadsheet.

RAOs

With FreeCAD you can easily compute the Response Amplitude Operators (RAOs), considering the widely validated frequency domain code Nemoh, and more specifially its Python wrapper Capytaine.

Install

This workbench is available for download via the FreeCAD Addon Manager

Usage

Documentation for this workbench is available on the Ship Workbench wiki page

Tutorials

• Official Ship Workbench Tutorial Part 1
• Official Ship Workbench Tutorial Part 2

Roadmap

There are many tools and features which will be implemented in this module:

• Wiki documentation
• Tutorials
• Seakeeping
  • Added masses
  • Time domain solver
• Deterministic damaged stability
• Probabilistic damaged stability
• Ship resistance

Discussion/Feedback

Discuss bugs, feedback, thoughts etc.. on the official FreeCAD forum thread

Bugs/Enhancements

Please open tickets in the issue queue

Authors

• Jose Luis Cercós Pita [email protected]
• Juan Manuel Muñoz-Godin (Ship resistance Holtrop and Amadeo tools)
• Antonio Souto-Iglesias (Advisor of Juan Manuel Muñoz-Godin)