Sub-skill of doc-extraction-naval-architecture: Stability Constants (+4).
Metacentric height and related parameters for intact and damage stability.
Detection heuristics:
Key extraction fields:
- content_type: constants
domain: naval_architecture
sub_type: stability_constant
data:
name: "Transverse metacentric height"
symbol: "GM_t"
value: 1.85
units: m
applicability:
loading_condition: "full load departure"
free_surface_corrected: true
source: "Stability booklet Section 3.2"
GZ curve extraction (from cross-curves or direct calculation):
Ship resistance prediction methods and empirical correlations.
Detection heuristics:
Key extraction fields:
- content_type: equations
domain: naval_architecture
sub_type: resistance_equation
data:
name: "ITTC 1957 friction line"
expression: "C_F = 0.075 / (log10(Re) - 2)^2"
variables:
- {symbol: C_F, name: "frictional resistance coefficient", units: dimensionless}
- {symbol: Re, name: "Reynolds number", units: dimensionless}
source: "ITTC 1957 Model-Ship Correlation Line"
applicability:
method: "ITTC-1957"
flow_regime: "turbulent"
Holtrop-Mennen method — extract these specific parameters:
Dimensionless ratios characterising hull geometry.
Detection heuristics:
Key extraction fields:
- content_type: constants
domain: naval_architecture
sub_type: hull_form_coefficient
data:
name: "Block coefficient"
symbol: "Cb"
value: 0.82
units: dimensionless
applicability:
vessel_type: "tanker"
design_draft: true
source: "Lines plan / hull definition"
Hull form coefficient definitions (screening heuristic ranges):
| Coefficient | Symbol | Definition | Typical range |
|---|---|---|---|
| Block | Cb | Displaced vol / (L × B × T) | 0.35–0.85 |
| Prismatic | Cp | Displaced vol / (A_m × L) | 0.55–0.80 |
| Midship | Cm | A_m / (B × T) | 0.85–0.99 |
| Waterplane | Cwp | A_wp / (L × B) | 0.65–0.90 |
Note: ranges are non-normative screening heuristics for extraction QA only.
Displacement, trim, and stability parameters as functions of draft.
Detection heuristics:
Key extraction fields:
- content_type: curves
domain: naval_architecture
sub_type: hydrostatic_curve
data:
title: "Hydrostatic curves"
x_axis: {label: "Draft", units: m}
columns:
- {name: displacement, units: tonnes}
- {name: KB, units: m}
- {name: BM, units: m}
- {name: KM, units: m}
- {name: TPC, units: "t/cm"}
- {name: MTC, units: "t-m/cm"}
- {name: LCB, units: "m from AP"}
- {name: LCF, units: "m from AP"}
source: "Hydrostatic particulars table"
Mandatory and recommended stability criteria from IMO instruments.
Detection heuristics:
Key extraction fields:
- content_type: requirements
domain: naval_architecture
sub_type: imo_stability_criterion
data:
id: "IS-A-2.2.1"
text: "Area under GZ curve up to 30 deg shall not be less than 0.055 m-rad"
threshold:
parameter: "GZ_area_0_30"
operator: ">="
value: 0.055
units: "m-rad"
standard_ref: "2008 IS Code Part A, Section 2.2.1"
normative_strength: shall
IMO intact stability criteria checklist (2008 IS Code Part A):
| Criterion | Parameter | Threshold |
|---|---|---|
| 2.2.1 | Area under GZ to 30 deg | >= 0.055 m-rad |
| 2.2.2 | Area under GZ to 40 deg (or flood angle) | >= 0.090 m-rad |
| 2.2.3 | Area under GZ between 30 and 40 deg | >= 0.030 m-rad |
| 2.2.4 | GZ at 30 deg or greater | >= 0.200 m |
| 2.2.5 | Angle of maximum GZ | >= 25 deg |
| 2.2.6 | Initial GM | >= 0.150 m |
| 2.3 | Severe wind and rolling (weather criterion) | ratio >= 1.0 |