Stability#

Classes for stability analysis and GZ curve calculations.

StabilityCalculator#

class StabilityCalculator(vessel, water_density=1025.0)#

Calculator for stability analysis (GZ curves).

Parameters:

  • vessel – The vessel to calculate stability for

  • water_density – Water density in kg/m³

calculate_gz_curve(displacement_mass, cog, heels)#

Calculates the GZ curve for a given loading condition.

Parameters:

  • displacement_mass – Base vessel displacement (excluding dynamic tanks) in kg

  • cog – Base center of gravity (LCG, TCG, VCG) excluding dynamic tanks

  • heels – List of heel angles in degrees

Returns:

StabilityCurve object with corrected GZ values

calculate_complete_stability(displacement_mass, cog, heels)#

Calculates complete stability analysis combining hydrostatics, GZ curve, and wind data.

Parameters:

  • displacement_mass – Target displacement in kg

  • cog – Center of gravity (LCG, TCG, VCG) tuple

  • heels – List of heel angles for GZ curve in degrees

Returns:

CompleteStabilityResult with hydrostatics, GZ curve, and wind data

CompleteStabilityResult#

class CompleteStabilityResult#

Complete stability calculation result combining hydrostatics, GZ curve, and wind data.

hydrostatics: HydrostaticState#

Hydrostatic state at equilibrium (draft, trim, GM0, etc.).

gz_curve: StabilityCurve#

GZ stability curve for the loading condition.

wind_data: WindHeelingData or None#

Wind heeling data (if silhouettes are defined).

displacement: float#

Displacement mass in kg.

cog: tuple[float, float, float]#

Center of gravity (LCG, TCG, VCG).

gm0: float or None#

Initial transverse metacentric height (GM0) with free surface correction.

gm0_dry: float or None#

Initial transverse metacentric height without free surface correction.

max_gz: float or None#

Maximum GZ value on the curve.

heel_at_max_gz: float or None#

Heel angle at maximum GZ.

has_wind_data()#

Returns True if wind heeling data is available.

Return type:

bool

StabilityCurve#

class StabilityCurve#

A complete GZ stability curve.

heels()#

Returns the heel angles.

Return type:

list[float]

values()#

Returns the GZ values.

Return type:

list[float]

points()#

Returns a list of StabilityPoint with (heel, draft, trim, gz, is_flooding, flooded_openings).

Each point has:

  • heel: Heel angle in degrees

  • draft: Draft at equilibrium (m)

  • trim: Trim angle in degrees

  • gz: GZ value (m)

  • is_flooding: True if any opening is submerged

  • flooded_openings: List of flooded opening names

displacement: float#

Displacement in kg.

WindHeelingData#

class WindHeelingData#

Wind heeling data from silhouette calculations.

Used for wind heeling moment calculations per IMO 2008 IS Code (MSC.267).

emerged_area: float#

Total emerged lateral area above waterline (m²).

emerged_centroid: tuple[float, float]#

Centroid of emerged area (x, z) in meters.

wind_lever_arm: float#

Lever arm from waterline to centroid z coordinate (m).

waterline_z: float#

Waterline Z at which calculations were performed.