Offshore Stability Score

A composite score combining the three key offshore stability indicators.

What is it?

The Offshore Stability Score is a composite metric combining the three most widely-used offshore stability indicators — the Capsize Screen Value, the Comfort Ratio, and the Displacement/Length Ratio — into a single 0–100 score.

No single metric tells the full story of a boat's seakeeping ability. A boat might pass the capsize screen but have terrible motion comfort. Another might have a great comfort ratio but be so light it's prone to violent motion in steep seas. The composite score catches boats that fail in one dimension even while passing others.

The score is primarily useful for quickly comparing boats during research, or for screening a large database of boats against offshore capability requirements.

The Formula

Score = Capsize component (0–35) + Comfort component (0–35) + D/L component (0–30)

Capsize earns max 35 pts at CSV ≤ 1.5; Comfort earns max 35 pts at CR ≥ 40; D/L earns max 30 pts at D/L ≥ 300.

Reference Values

80–100Excellent — confident bluewater capability

65–79Good — offshore capable, suitable for extended passagemaking

50–64Fair — coastal offshore in good conditions, selective about weather windows

< 50Poor — best suited to protected coastal and inland waters

What to Look For

•Classic offshore cruisers (Westsail 32, Valiant 40, Cape Dory 36, Cabo Rico 38) typically score 70–90.
•Modern production cruisers (Bavaria, Jeanneau Sun Odyssey, Beneteau Oceanis) often score 45–65 — capable offshore but require careful route planning and weather selection.
•A score of 65+ suggests the boat design is offshore-capable, though crew experience, equipment, and conditions always matter more than any number.
•Lightweight sportboats and coastal daysailers typically score under 40 — not because they're poorly designed, but because they're optimized for different sailing.

Limitations

This score uses three simplified ratios with fixed weighting. It doesn't incorporate AVS (Angle of Vanishing Stability), the full GZ curve, rig type, hull form details, or designer intent. A boat with a questionable score but a well-documented offshore record (Catalina 42, Beneteau 45) should not be dismissed on the basis of this score alone. Use it as a starting point for research, not a final certification.

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