KER 11.5 Sail Configuration Guide

Overview

The KER 11.5, designed by Jason Ker and built by Waterline Systems, is a high-performance racing yacht optimized for IRC and offshore competition. This design focuses on technical efficiency and speed, targeting the competitive racing market.

Rig Specifications & Performance Analysis

Analysis of the KER 11.5 dimensions reveals a modern, high-efficiency power plan:

• Mainsail Configuration: A P/E ratio of 2.83 indicates a tall, high-aspect rig designed for maximum lift and reduced drag.
• Foretriangle Design: The I/J ratio of 3.48 is specifically suited for high-aspect, non-overlapping jibs that provide superior upwind pointing.
• Sail Area: 78m² total upwind area provides an aggressive power-to-weight ratio.
• Performance: The configuration is strictly racing-oriented, prioritizing weatherly performance and speed in light-to-moderate conditions.

Popular Sail Configurations

Due to the technical nature of the KER 11.5 fleet, configurations are tailored to specific rating rules:

• Mainsail: Typically high-roach or square-top designs to maximize the 15.5m luff.
• Headsail: Optimized as a series of non-overlapping jibs (J1, J2, J3) to suit the 3.48 I/J ratio.

Key Characteristics

• High-aspect rig (P/E 2.83) optimizes aerodynamic lift for superior upwind speed.
• Tall foretriangle (I/J 3.48) allows for efficient, high-tension headsail trim.
• Deep 2.46m draft ensures a stiff, stable platform for the 78m² sail plan.
• Reactive hull design provides exceptional acceleration and close-winded performance.

Sailing Considerations

• Requires an active, experienced crew to manage the high-aspect sail plan effectively.
• The boat is exceptionally weatherly, capable of sailing very tight angles upwind.
• Performance expectations include rapid plane initiation off the wind in moderate breezes.
• Strategic sail changes are required to maintain the narrow optimal trim window.

Sailmaking Recommendations

For the KER 11.5, we recommend SurgeX membrane sails as the optimal choice for competitive sailors. SurgeX utilizes continuous fiber construction where high-modulus fibers are laid precisely along calculated load paths and embedded in a thin, durable membrane. This provides superior shape retention compared to traditional laminates while remaining a cost-effective alternative to premium grand-prix products. The continuous fiber structure ensures that the 15.5m mainsail luff remains stable under high backstay tension, maintaining the designed aerodynamic profile for multiple seasons.

For racing applications, specify a lightweight SurgeX configuration with a film-on-film finish to minimize aloft weight and maximize responsiveness. If the vessel is used for fast passage making or performance cruising, add a lightweight taffeta protective layer to both sides to increase UV resistance and chafe protection. Based on the 2.83 P/E ratio, a load-path membrane layout is essential to prevent horizontal stretch in the tall mainsail. A typical inventory includes a high-roach mainsail, a versatile J2 jib, and an A2 asymmetric spinnaker. Given the 78m² of upwind sail area, most crews should plan to take the first reef as true wind speeds exceed 16-18 knots.

Conclusion

The KER 11.5 is a precision racing tool that demands high-modulus sails to reach its full potential. Utilizing SurgeX membrane technology ensures the rig's high-aspect geometry is fully exploited. Explore sail options for the KER 11.5 to enhance your racing performance.