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.
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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