The Mariner 40 Sailboat

The Mariner 40, a long-keeled ketch, was designed by Clair Oberly and built in Japan by Far East Yachts.

A Mariner 40, a traditional cruising ketch from the 1970'sA Mariner 40 ketch at anchor off Sandy Island, Carriacou.

Published Specification for the Mariner 40

Underwater Profile: Long keel

Hull Material: GRP (Fiberglass)

Length Overall: 40'4" (12.3m)

Waterline Length: 30' 2" (9.2m)

Beam: 11'5" (3.5m)

Draft: 5'8" (1.7m)

Rig Type: Masthead Ketch

Displacement: 26,500lb (12,020kg)

Designer: Clair Oberly

Builder: Far East Yachts


Published Design Ratios for the Mariner 40

1. Sail Area/Displacement Ratio: 15.8

  • Less than 16 would be considered under-powered;
  • 16 to 20 would indicate reasonably good performance;
  • Over 20 suggests relatively high performance.

2. Ballast/Displacement Ratio: 34.0

  • Under 40: less stiff, less powerful
  • Over 40: stiffer, more powerful

3. Displacement/Length Ratio: 430

  • Under 100: Ultralight
  • 100 to 200: Light
  • 200 to 275: Moderate
  • 275 to 350: Heavy
  • Over 350: Ultraheavy

4. Comfort Ratio: 47.2

  • Under 20 indicates a lightweight racing boat
  • 20 to 30 indicates a coastal cruiser
  • 30 to 40 indicates a moderate offshore cruising boat
  • 40 to 50 indicates a heavy offshore boat
  • Over 50 indicates an extremely heavy offshore boat

5. Capsize Screening Formula: 1.5

  • Under 2.0 (the lower the better): Better suited for ocean passages
  • Over 2.0: Less suited for ocean passages

read more about these all-revealing numbers...


Summary Analysis of the Design Ratios for the Mariner 40

1. A Sail Area/Displacement Ratio of 15.8 suggests that the Mariner 40 will need a stiff breeze to get her going. In light conditions, unless you've got plenty of time on your hands, motor-sailing may be the way to go.

2. A Ballast/Displacement Ratio of 34.0 means that unless the bulk of the ballast is concentrated in a bulb at the foot of her keel, the Mariner 40 will have a tendency to heel excessively in a gust, and she'll need to be reefed early to keep her sailing upright in a moderate breeze. 

3. A Displacement/Length Ratio of 430, tells us the Mariner 40 is firmly in the ultra-heavy displacement category. Load her up as much as you like and her performance will be hardly affected, not that it was ever startling. Few if any sailboats are built to this displacement category these days - but they remain popular with some long-distance sailors.

4. Ted Brewer's Comfort Ratio of 47.2 suggests that crew comfort of a Mariner 40 in a seaway is similar to what you would associate with the motion of a heavy bluewater cruising boat. Pitching and rolling will be well damped - your cup of coffee on the salon table stands a reasonable chance of staying there in most conditions.

5. The Capsize Screening Formula (CSF) of 1.5 tells us that a Mariner 40 would be a safer choice of sailboat for an ocean passage than one with a CSF of more than 2.0. 


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