My vessel model has a sunken poop deck on the aft sections while a sponson
that wraps the hull remains at the original deck height.  How can I specify
the margin line to follow the deck edge and not the sponson?


If you want to lower the margin line in way of the sunken poop, you could put
deck-edge markings on the shape of hull.c starting at 129.57.  Then you could
leave your sponson marked and use a uniform 3" margin for both.

You can do this with Model Converter as follows:

 MC (hull\hull.c) fixup /deckedge: 129.57, 141.98 /margin:0.25
 MC (hull\sponson.c) fixup /margin: 0.25

Then to get a full report on the freeboards and margins in any condition, try


This will show freeboards to deck edge as well as the margin values.  It
includes every deck-edge point, listing them component-by-component.  So you
will first see the hull freeboards in way of the poop, then the sponson

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