Navigation:  Quick Start Tutorials > Design Hydrostatics

This tutorial shows you the basics of computing hydrostatics in the "Design" condition in Orca3D. For more detailed instructions and background information  on Orca3D Hydrostatics in general, see the Hydrostatics & Stability section.

Note: Orca3D computes most of the hydrostatics parameters from the surface mesh, not in the traditional manner of integrating stations (stations are used for the sectional area curve, and the prismatic and maximum section coefficients). In general, this leads to more accurate results, and avoids the possibility of missing or mistreating features in the hull surface, such as the end of a hull skeg. The accuracy of the calculations, therefore, depends on the smoothness of the surface mesh (this is true in Rhino for other things; for example the curvature maps depend on the smoothness of the analysis mesh). To adjust the smoothness of the Orca3D mesh, use the OrcaProperties command, or the icon (), and set the values in the Orca Mesh Parameters section.

 

 

Orca3D can compute hydrostatics and stability in various combinations of waterplanes/displacement and center of gravity/heel/trim, with a range of heel angles. However, while you are fairing a hull, you are usually just interested in the hydrostatics at the "design waterline," or at a particular displacement/center of gravity, without needing to go through entering values in a dialog box each time you want to see the calculations.

To simplify the process, Orca3D has a special Hydrostatics and Stability condition called the "Design" condition. The intent is to define the Design condition once, and then as you create and modify the hull, you can compute hydrostatics and stability at that condition with a single button click. This saves having to go through the dialog to define the condition each time you wish to compute the hydrostatics.

To define the Design condition:

1. Select Define Design Condition from the Orca3D > Stability menu.

2. Select the surface(s) to be included in the calculations, and hit Enter. The following dialog will appear:

3. Select which mode you want: Weight/Center, or Flotation Plane.

4. If your model represents just one-half of the vessel, check "Mirror About Centerplane"

5. If you want to see hydrostatic values in real-time as you edit the hull, check the "Real-Time Hydrostatics" box.

 

To compute Design hydrostatics:

1. Be sure that you have defined the Design condition, using the steps above. You only need to do that once, unless you wish to change the surface(s) to be included, or change the Design condition.

2. Select Compute Design Hydrostatics from the Orca3D > Stability menu, click on the () icon on the toolbar (the icon is on a flyout toolbar with the Hydrostatics & Stability icon), or type the command OrcaPlayStabilitySimulation.

3. After a moment, the hydrostatics report will be displayed.

4. If you checked the "Real-Time Hydrostatics" box, the hydrostatics will be displayed in a dockable control, as you modify the surface with the Orca3D control points.

 

 

See also:

Hydrostatics & Stability