While sailing is always good for moral, a lack of physical well-being in a cruising boat usually obliterates any sense of physical and psychological well-being.
Therefore, The comfort ratio, created by Ted Brewer, an expert boat designer, builder & author, created a formula to assess a boats “comfort” at sail. More so, a formula that assess how quickly a abruptly a boat’s hull reacts to waves in large seaways.
DISPLACEMENT ÷ [0.65 x (0.7 LWL + 0.3 LOA) x BEAM1.33]
I have used this formula, along with many others, as education tool for my clients to decide amongst multiple boats, and in my opinion, the formula is creditable.
- Below 20 = Lite Racing Boat and tender motion
- 20-30 = Coastal Cruiser with moderate stability
- 30-40 = Moderate Bluewater Cruiser
- 50-60 = Heavy Bluewater Cruiser
Most formulas have small variances that can manipulate the results. And this formula is not any different. For vessels 45ft or higher, the results are skewed higher. And for vessels 25ft and lower, results skewed somewhat lower.
In conclusion, this formula will assist the understanding of a predictable roll or tenderness of a ship. So if you have a green crew with wobbly sealegs, perhaps a little math will go a long way into your next boat decision.
Beyond the Sail 
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