BONIN 31 Sail Configuration Guide

Overview

The BONIN 31 is a performance-oriented cruiser-racer designed by Cossutti, engineered for agility and speed in competitive club racing. With a small fleet of only 4 boats, it remains an exclusive choice for sailors seeking a refined balance between racing performance and functional cruising.

Rig Specifications & Performance Analysis

• Mainsail Configuration: A P/E ratio of 2.93 indicates a high-aspect ratio mainsail, providing excellent aerodynamic efficiency and lift.
• Foretriangle Design: The I/J ratio of 3.51 is optimized for high-aspect jibs, facilitating efficient windward performance and easy handling.
• Sail Area: 46m² total upwind area provides a strong power-to-displacement feel for a 9.39m hull.
• Performance: The design is heavily weighted toward racing and performance cruising, favoring weatherly performance in light to moderate air.

Popular Sail Configurations

• Mainsail: Configurations typically feature a high-roach design to maximize the efficiency of the tall 11.85m luff.
• Headsail: The rig most commonly utilizes non-overlapping or slightly overlapping jibs to maintain balance with the mainsail.

Key Characteristics

• High-aspect P/E ratio (2.93) delivers superior lift-to-drag ratios upwind.
• Tall foretriangle (I/J 3.51) allows for precise headsail trim and efficient tacking.
• LOA of 9.39m combined with a 3.34m beam offers a stable yet responsive platform.
• Cossutti design lineage ensures a stiff, weatherly boat with predictable handling.

Sailing Considerations

• The BONIN 31 is sensitive to mainsail trim and rewards active backstay and traveler adjustments.
• Crew requirements typically range from 4 to 6 for competitive racing, though it remains manageable for couples when cruising.
• Performance peaks in light to medium airs where the high-aspect rig can fully energize the hull.

Sailmaking Recommendations

For the BONIN 31, we recommend SurgeX membrane sails as the optimal choice for most sailors. SurgeX uses continuous fiber construction where fibers are laid along load paths and embedded in a thin membrane, providing superior shape retention compared to traditional Dacron while being more affordable than premium laminates. The continuous fiber structure means less stretch over time, maintaining the designed sail shape for years.

For racing applications, specify a lightweight SurgeX configuration with minimal base weight to maximize performance. For cruising or club racing, add a taffeta protective layer on both sides to enhance UV resistance and abrasion protection. Based on the 2.93 P/E ratio, a radial load path fiber layout works best to manage the high vertical tensions of this rig. A typical inventory includes a performance-cut mainsail and a high-aspect J2 jib. With 46m² of sail area, plan to reef around 18-20 knots to maintain helm balance.

Conclusion

The BONIN 31 is a sophisticated racing platform that excels when paired with high-performance, low-stretch sail materials. Explore sail options for the BONIN 31 to maximize your competitive edge.