Sea Keeping Calculator
Analyze vessel motion characteristics and comfort predictions
% of displacement as ballast (sailboats: 30-45%)
Sea Keeping Analysis
Comfort Ratio
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Comfort Rating
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Roll Period (estimated)
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Pitch Period (estimated)
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Displacement-Length Ratio
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Beam-Draft Ratio
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Resonant Wave Period
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Capsize Screening Formula
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Motion Comfort Index
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Comfort Ratio Guide
| Ratio | Comfort Level | Typical Vessels |
|---|---|---|
| > 60 | Very Comfortable | Heavy cruisers, trawlers |
| 40-60 | Comfortable | Cruising yachts |
| 20-40 | Moderate | Cruiser-racers |
| < 20 | Lively Motion | Racing yachts, daysailers |
About Sea Keeping Calculations
Comfort Ratio: Developed by Ted Brewer, this ratio predicts motion comfort. CR = Displacement / (0.65 x (0.7 x LWL + 0.3 x LOA) x Beam^1.33). Higher is more comfortable.
Capsize Screening Formula: CSF = Beam / (Displacement/64.2)^(1/3). Values under 2.0 are considered safer for offshore sailing. This is a screening tool, not an absolute measure.
Roll Period: Natural roll period depends on beam and metacentric height (GM). Longer periods (slower rolling) are generally more comfortable but may indicate reduced stability.
Note: These are simplified estimates. Actual sea keeping depends on hull shape, weight distribution, sea conditions, and many other factors.