CR
Comfort ratio
Ted Brewer's comfort ratio estimates motion harshness from displacement, length, and beam. Higher numbers suggest a softer motion for a given size band. FairHelm judgment: useful when shortlisting Baltic passage boats, weak when comparing radically different hull forms without sailing both.
Formula
CR = Displacement_lb / (0.65 * ((0.7 * LWL_ft) + (0.3 * LOA_ft)) * Beam_ft^1.333)
Displacement in pounds. LWL, LOA, and beam in feet.
History
Yacht designer Ted Brewer published the comfort ratio as a practical motion index for amateurs comparing cruising designs. Magazines and data sites adopted it. It is empirical, not a seakeeping CFD result.
Rule of thumb
Rough guide for monohulls: under about 20 feels lively; 30-40 is a common cruiser comfort band; above about 50 reads as heavy and soft. Size still matters: compare similar LOA first.
Limits
Ignores actual weight distribution, damping from bilge keels, and sea state direction. Overhang-heavy LOA changes the blended length term. Brochure displacement errors dominate. Comfort at the dock is unrelated.
Boat examples
- Hallberg-Rassy 36
Often cited in owner discussions as a motion-friendly Scandic cruiser relative to lighter production hulls.
- Sweden Yachts 390
Performance-cruiser balance: expect a lower CR than a heavy centre-cockpit sistership if displacement is lighter.
- Linjett 40
Use CR to frame owner reports of Baltic chop, then verify with a sea trial in real wind.
FAQ
- Who is Ted Brewer?
- A yacht designer who published practical comparison ratios for cruising sailors. The comfort ratio is associated with his name in popular yacht literature.
- Does a high comfort ratio mean the boat is slow?
- Often correlated with heavier displacement, but speed depends on SA/D, hull shape, and sail inventory. Check SA/D and D/L together.
- Can I use metres in the formula?
- Convert to feet and pounds first, or rewrite every constant carefully. Mixing units is the most common error we see in listing math.