The Ocean 71 Sailboat
Specs & Key Performance Indicators

The Ocean 71, a centre-cockpit staysail ketch, was designed by EG Van de Stadt and built in the UK by Southern Ocean Shipyard Ltd.

'Ocean Joy', an Ocean 71 sailboat regularly sailed by a crew of just two!An Ocean 71

Published Specification for the Ocean 71

  • Underwater Profile: Fin keel & skeg-hung rudder
  • Hull Material: GRP (Fibreglass)
  • Length Overall: 71'0" (21.6m)
  • Waterline Length: 59'4" (18.1m)
  • Beam: 17'5" (5.3m)
  • Draft: 8'3" (2.5m)
  • Rig Type: Staysail ketch
  • Displacement: 75,600lb (34,020kg)
  • Designer: EG Van de Stadt
  • Builder: Southern Ocean Shipyard (UK)
  • Year First Built: 1970
  • Number Built: 20+

Published Design Ratios for the Ocean 71

1. Sail Area/Displacement Ratio: 28.0

  • 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: 27.3

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

3. Displacement/Length Ratio: 161

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

4. Comfort Ratio: 41.4

  • 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: 1.7

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

Read more about these Key Performance Indicators...

Summary Analysis of the Design Ratios for the Ocean 71

1. A Sail Area/Displacement Ratio of 28.0 suggests that, in the right hands, the Ocean 71 will have enough performance to leave most other sailboats of similar waterline length well astern. 

2. A Ballast/Displacement Ratio of 27.3 means that a sailboat like the Ocean 71 (which doesn't have its ballast concentrated in a bulb at the foot of a deep keel), is likely to benefit from being reefed early to keep her sailing upright in a moderate breeze.

3. A Displacement/Length Ratio of 161, tells us the Ocean 71 is clearly a light displacement sailboat. If she's loaded with too much heavy cruising gear her performance will suffer to a degree.

4. Ted Brewer's Comfort Ratio of 41.4 suggests that crew comfort of an Ocean 71 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 1.7 tells us that an Ocean 71 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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