Initial stability is described as reflecting the size of the ship's righting arms at small angles. What is the typical heel angle range for these small angles?

• A. 3 to 5 degrees
• B. 7 to 10 degrees
• C. 12 to 15 degrees
• D. 20 to 25 degrees

Answer: (B)

Initial stability is about how the righting lever behaves when the ship heels only a little. In this small-heel region, the restoring moment grows in a simple, nearly linear way because the geometry of buoyancy and the metacenter makes the righting arm proportional to the angle of heel. That linear relationship is why this range is described as the small-angle domain—the math (GZ ≈ GM × sin(phi)) behaves almost linearly, and sin(phi) is nearly proportional to phi for tiny angles.

As the heel increases beyond that narrow band, the centers of buoyancy and gravity shift in ways that make the righting lever curve non-linear, so the initial-stability assumption no longer applies. The option that reflects this shallow, early range is the one that matches how initial stability is defined.