300 GHS Output Control
2021-Jul-01
000 Introduction to GHS
2021-Jun-30

210 GHS Tools

This tutorial reviews the different tools you can use to create geometry files.

The first step of any GHS analysis requires you to create a GHS geomery model. There are several tools for model generation, and an efficient GHS user must master all of them. The best method for creating a GHS model is a combination of all the available tools.

Homework 211


Explores how to use deadweight, which is a free add-on for GHS. Shows the various skills needed for working with deadweight.

220 GHS Model Organization

This tutorial focuses on the model organization.  This is the logical structure of how GHS organizes the various pieces of the vessel model.  This is important to understand the reference terms and language used to describe model organization.  The help files use these same terms.  It is also important to understand the organization so that you can efficiently plan your modeling efforts.

Homework 221


Covers how to create GHS models using Rhino. Rhino is a paid third-party program. Very useful for modeling with GHS. Beyond just creating geometry, this tutorial examines how to use Rhino to attach GHS data. This creates the structure and organization of a GHS model, but utilizes the extensive 3D modeling tools in Rhino to create the actual geometry.

230 GHS Part Types

There are three different types of parts in GHS:  hull, tank, and sail.  We cover what makes each part type special, and how to use these different types together in combination.

 

Homework 231


Focuses on creating hull type parts in Rhino. Attaching the proper structure. And how to create negative displacement hull parts in Rhino.

Edit 1: Negative displacement parts are very temperamental in Rhino. Rhino accomplishes this by changing the permeability or effectiveness. Sometimes GHS will not allow this. Try it in Rhino, but if GHS gives trouble, it is better to just define the part using GHS Part Maker (see tutorial 240).

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Homework 232


Expands on homework 231. Now adds tank parts to the Rhino GHS model. Includes adding nested parts. And how to use the same shape objects to create symmetrical tank parts.

Edit 1: For the most consistent use of Rhino, no centerline geometry parts should be modeled across the vessel centerline. This applies to all center tanks. The best way to model these in Rhino: Define the tank as a centerline part, and then manually edit the Rhino limits for that shape so that the transverse limits stop at centerline (Y=0).

Edit 2: For any parts that cross centerline, but are not symmetric about centerline: Do not name these parts with the .C extension. GHS will try to mirror them and get confused. Instead, simply name them with the dominant part side (.P or .S).

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Homework 233


Expands on homework 232. Focuses on adjusting permeabilities and tank contents, using Rhino. Also covers how to define sounding tubes in Rhino.

Edit 1: For the most consistent use of Rhino, no centerline geometry parts should be modeled across the vessel centerline. This applies to all center tanks. The best way to model these in Rhino: Define the tank as a centerline part, and then manually edit the Rhino limits for that shape so that the transverse limits stop at centerline (Y=0).

Edit 2: For any parts that cross centerline, but are not symmetric about centerline: Do not name these parts with the .C extension. GHS will try to mirror them and get confused. Instead, simply name them with the dominant part side (.P or .S).

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Homework 234


Completes the set of Rhino modeling skills for GHS. Now adds sail type parts to the GHS model built in Rhino. Also shows how to create non-displacement skegs in Rhino.

Edit 1: Non-displacement skegs are not really useful. Unfortunately, reducing the effectiveness of the part also reduces its effective wind area. The easier way to model a free-flooding skeg is to model the skeg as buoyant and then add in the weight of the skeg water as a fixed weight item.

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240 GHS Part Maker

Part Maker is the native GHS tool for editing the geometry of your ship.  It includes several features to take advantage of common ship properties like port / stbd symmetry.  Use Part Maker for advanced editing of your GHS geometry files.

Homework 241


Simple exercise to just open Part Maker and save a new file.

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Homework 242


Create a simple canoe hull, using only LOCUS commands.

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Homework 243


Full exercise to create the entire barge model using part maker only.

  • Engine room has contents of AIR (Spgr = 0.0001).
  • LNG Tanks have contents of LNG (Spgr = 0.544).
  • Stern notch is modeled with a negative displacement.
  • Include permeability for all tanks, contents of all tanks
  • Engine room tunnel defined as a component of the main engine room. NOT a separate part.
  • LO and HO tanks deducted from the engine room part.
  • Extra credit: Include the sounding tubes for each tank as well.

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250 GHS Geometry Properties

We review a few of the finer points for geometry file properties.  This includes creating comments, defining critical points, and a few other general properties.  These are non-critical but very useful geometry file features.

Homework 251


Enhances the vessel created in part maker last time. Expands to show a few advanced features that part maker can incorporate for vessel properties. Items such as margin lines and critical points get included in this homework.

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