Sail Shape Tracking: Assess How Your Sails Are Performing

Sailmakers have been using photographs to analyze upwind sail shape for years. By taking pictures of a sail and extracting the numerical sectional shape data, a sailmaker can compare the photographed sail with the target sail shape for that boat. This data can be used to assess how materials and construction techniques perform. It is also valuable information when considering re-cutting, repairs or replacement. Sail owners can benefit from this process by getting to know their sail inventory better.

Sail shapes change because all sail materials stretch. When a sail stretches it can become wrinkled, the leech can flutter excessively, the battens might not fit as tightly as they used to and the sail can also become too long in the foot or luff. No matter how stretch manifests itself, it is a sign that the sail material is loosing its ability to handle the sail loads associated with the boat. As the sail cloth becomes fatigued, the sail loses durability, performance and value. Two characteristic that are consistent among upwind sails as they stretch are that the sectional shape of the sail becomes deeper and the position of maximum depth moves aft. Recording these changes in sectional shape is what sail shape tracking is all about.

The sail shape tracking process involves taking pictures of your upwind sails and analyzing those pictures to determine the condition of your sail. As the sail ages you can develop and accurate history of how your sail has performed and make informed decisions regarding sail repairs and re-cutting. You can also gauge the performance of the material your sail is made from and can make a more informed material choice when buying a new sail. You may decide your new sail should incorporate a stronger fabric because the data for your current sail shows it has lost its shape quickly.

For the racing sailor, the sails sectional shape is a critical factor in boat performance. Draft depth and position determine how much lift and power the sail can generate. Being able to tell when a sail is beginning lose performance can help you decide when to recut and replace sails. This can help you get more mileage from your existing sails, better race performance and can save some money.

Maine Sailing Partners
www.mesailing.com
1-888-788-SAIL