General HydroStatics
Ship Stability Software
Command of the Week
(New or interesting aspects of GHS that you may not know about)

Towboat_Criterion Wizard

GHS comes with many wizards, each of which is tailored for a specific task. The Towboat_Criterion wizard deals specifically with 46 CFR 173.095, a US regulation that applies to towing vessels. Part B contains a formula for required GM which is calculated directly from vessel parameters shown below.

The wizard supports calculation of maximum VCG for a series of displacements as well as for the current condition. It can also evaluate a condition without altering the weight center.

Part C of this regulation is a more typical criterion with a residual righting energy requirement and a formula for the towing heeling arm. Calculation of Parts B and C can be performed individually or together. Both the GM in Part B and the heeling arm in Part C depend on the displacement, so the wizard updates these values for each displacement in the MAXVCG series. Some sample MAXVCG results are shown below.

Whenever possible, wizards are developed as two separate files. One file is the "front-end" which address input, output options, and data storage. This file is typically named with a .WIZxx extension where xx is a suffix that sorts the wizards into categories in the Wizard drop-down menu. The *.WIZ files are comprised primarily of template and macro commands.

The second file, a library file (*.LIB), is responsible for all the calculations performed by the wizard. The library file is maintained as a separate file so that it can be called directly from a run file. If the wizard is designed to support run file use, it will leave behind a LibInfo template after it is run. You can execute the LibInfo template to see the variables which allow you to direct the wizard library to perform the tasks you need.

This wizard deals only with the CFR towing criterion. If you would be interested in a wizard for another criterion, please let us know.

Questions, comments, or requests?
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