Sailboat Righting Moment Calculator
Evaluate your sailboat's statical stability, righting moment ($RM_\theta$), initial stiffness ($RM_1$), and counter-capsizing torque across target heel angles.
Stability & Righting Moment Breakdown
Computed statical restoring torque & arm levers
Statical Righting Moment & $GZ$ Stability Curve
0° to 90° Heel ProfileUnderstanding Sailboat Righting Moment
Righting Moment ($RM$) is the mechanical torque generated by a sailboat to counter capsizing forces exerted by wind pressure on the rig. It is the core metric used by naval architects to assess a vessel's statical stability, sail-carrying ability, and seaworthiness.
Key Principles
- Displacement ($\Delta$): The total weight of seawater displaced by the vessel. Higher displacement with a low Center of Gravity ($G$) increases righting capacity.
- Center of Gravity ($G$) & Buoyancy ($B$): When heeled, the Center of Buoyancy shifts outward toward the leeward side, creating a horizontal lever distance known as the Righting Arm ($GZ$).
- Metacentric Height ($GM$): Indicates initial stiffness at small heel angles ($0^\circ$–$10^\circ$).
- Initial Righting Moment ($RM_1$): The righting moment per single degree of heel, used to gauge how quickly a sailboat stiffens up in light breezes.
Mathematical Formulas
Statical Righting Moment:
$$RM_\theta = \Delta \times GZ_\theta$$
Initial Stiffness per Degree:
$$RM_1 = \Delta \times GM \times \sin(1^\circ)$$
Metric SI Torque Conversion:
$$\text{Torque (N}\cdot\text{m)} = \Delta \text{ (kg)} \times 9.80665 \times GZ_\theta \text{ (m)}$$