USING AND READING MARGIN, FREEBOARDS, AND DECK EDGES IN GHS
When using the MARGIN statement, Part Maker automatically ensures that the
deck edge is marked on any component for which a margin is specified. See the
Margin section below for more instructions.
Defining deck edge using Section Editor:
When in Section Editor, deck edge can only be applied to the current selected
component. While the deck edge is visible with both the isonometric or body
views as a brown longitudinal line, it is typically easier to see and
manipulate using the isonometric view.
Tab to isonometric view, and press CONTROL-D.
You may see other longitudinal lines represented by different colors present,
but they are unimportant. Please ignore them.
GHS defines a component's deck edge by marking the first point after the hull
deviates past a 45 degree angle inward from the vertical plane with a suffix
of DK in every station. You can manipulate the deck edge by removing or adding
this suffix to different points.
CONTROL-Z will deconstruct any deck edge for the selected component, while
CONTROL-K will toggle the display of the deck edge lines.
Defining deck edge using Model Converter:
You can establish the deck edge in Model Converter using the regular mode:
MC Infile (ComponentSpec) Outfile (ComponentSpec) /DECKEDGE:l1,l2
or you can use the Fixup Mode:
MC InOutFile (ComponentSpec) FIXUP /DECKEDGE:l1,l2
Notice you can use longitudinal references to define where the deck edge
begins and ends on a specified component. This is useful for restricting
areas that extend outside your deck that are still part of your selected
component, such as reversed transoms, bulbs, pontoons, ramps, or even just
irregular deck geometries.
To remove the deck edge, simply use the /NOCODES statement:
MC Infile (ComponentSpec) Outfile (ComponentSpec) /NOCODES
or you can use the Fixup Mode:
MC InOutFile (ComponentSpec) FIXUP /NOCODES
Freeboard is the shortest distance between the deck edge and the waterplane.
You can view the current freeboard in GHS by using the STATUS command with the
This specifies that the minimum freeboard to deck edge and to the defined
margin line be shown. It may also be used with the ALL subparameter to
display freeboards, required freeboard (margin) if defined, and extra
freeboard at all station locations.
The line formed by applying the margin distance from the deck edge downward is
often called the "margin line". GHS treats this not as a fixed line but truly
as a margin on the freeboard; i.e. the freeboard from deck edge to the
waterplane is reduced by the margin distance. Margin is assigned to a
geometry file using Part Maker or Model Converter.
Both programs use the MARGIN m1,m2,m3 statement, where m1,m2,m3 are margin
distances relative to the deck edge of the present component. For example,
using the statement
specifies a constant margin of 0.25 throughout the length of the selected
component. If m1 and m2 are given, the former is taken to be the margin at
the forward end of the deck edge and the latter at the aft end (in between the
margin is a linear interpolation between m1 and m2). If three margin values
are given, m2 is taken to be the margin at the mid point, and m3 is the margin
at the aft end (the margin in this case is a parabola).
Defining margin using Part Maker:
Part Maker automatically ensures that the deck edge is marked on any component
for which a margin is specified. This statement can be used with the MODIFY
or CREATE commands within Part Maker. Example:
Defining margin using Model Converter
You need to establish your deck edge before or when you establish the margin.
Efficiently, these two can be defined in the same command using the regular MC
MC Infile (ComponentSpec) OutFile (ComponentSpec) /DECKEDGE:l1,l2 /MARGINS:m1,m2,m3
or in Fixup Mode:
MC InOutFile (ComponentSpec) FIXUP /DECKEDGE:l1,l2 /MARGINS:m1,m2,m3]
Last, if you are interested in documenting the initial input for the margin,
you can insert a comment in the geometry file using Part Maker, as seen in
this run file below:
FIXUP /DECKEDGE /MARGIN: .08
COMMENT The freeboard margin distance has been set to 0.08 m
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Creative Systems, Inc.