This module calculates the gross and net tonnage from seagoing vessels, according to “The 1969 International Convention on Tonnage Measurement of Ships”.

Attention: When using this module it is of paramount importance that compartments for cargo are selected. See description of Select cargo compartments for more information.

Tonnage calculations

1	Definition of superstructures not included in the hullform
2	Definition general data for net tonnage
3	Select cargo compartments
4	Print sideview hull plus superstructures
5	Calculate and print tonnage calculation (GT and NT)

Definition of superstructures not included in the hullform

At this stage superstructures are defined (primarily deckhouse layers) which are not included in the hull form. For example, a poop already included in the hullform (with a hull shape definition module Hulldef of Fairway) does not have to be defined in this module, while a bridge which is not already included in the hull form, should be defined in this module. For each superstructure, which is assumed to be rectangular, the location of the limiting bulkheads has to be specified by the user. Is the superstructure not of a rectangular shape, the mean values have to be specified. For each superstructure is specified :

Location of aft and forward bulkhead.
Location of low and high deck.
Half the breadth.

Definition general data for net tonnage

For the calculation of the Net Tonnage several specific particulars, as defined in the Tonnage Convention, have to be specified here.

Select cargo compartments

With this option the cargo compartments selected for the calculation of the net tonnage are being defined and previewed. By entering in this option, the names of the compartments which are already selected for the calculation are listed. The user is able to adjust this list by adding or removing compartments. Adding new compartment(s) can be done by clicking the List of compartments button, which opens the full list of available compartments, indicating which of those are already in use. Then, the user can select the compartments to be calculated, and exit the list. The selected compartments list will now be updated. Removing a selected compartment can be done by selecting the compartment to be removed from the list and then pressing the Remove button. This compartment will no longer be included in the calculation of Calculate and print tonnage calculation (GT and NT).

Print sideview hull plus superstructures

For checking purposes with this option the hull and the superstructure are drawn schematically in plan view.

Calculate and print tonnage calculation (GT and NT)

This option calculates and prints the tonnage calculation. For the calculation of Net Tonnage, the volume of the cargo spaces has to be determined (reg. 4 from Annex I from the Tonnage Convention). To enable this module to recognize the appropriate compartments as cargo spaces, those compartments have to be selected in the compartment list of option Select cargo compartments. All compartments not being part of the cargo space are not allowed to be selected. According to the regulations, the volumes of the cargo spaces are being calculated without deduction for construction (permeability = 1).

See underneath for an example of the output of tonnage calculations.

Example of the output, first page

Example of the output second page