The technology behind shade sails is often misunderstood and underestimated, and this causes many shade sails to fail long before their normal life expectancy. This was the message from Alan Stewart, vice president of MPanel Software Solutions LLC, and Timothy Akes, software representative, during a highly-detailed classroom education session at Expo 2019 in Orlando, Fla.
When it comes to 3D sails, the basic “hyper” sail demonstrates an “anti-clastic” double-shaped curve. Built-in stiffness resists loads and reduces deflection. From a design perspective, a three-dimensional anchoring system is a good design for a shade sail.
Flat sail designs are not well restrained in a vertical plane. When they get wet, the fabric increases in weight and causes the middle of the sail to sag, which deforms the shade structure.
As a rule, good design requires:
- A double-curved surface
- Height differences
- A range of 20-30 percent of span for a basic “hypar” sail
Stewart and Akes also covered the basics of a catenary, which is the idealized shape of a chain held at two ends. In the industry, the term is used to describe the edge of the sail.
The presentation wrapped up with comparisons between the old process of making 3D sails versus the modern process. During the old process, a site was often only measured in five dimensions, checks for measurement errors were usually overlooked, and a sail was forced into a 3D form by “shear” during installation. These errors resulted in wrinkles (due to low tension), and a shorter lifespan due to high stress and stretching.
Today’s modern process of making 3D sails now measures a site in 10 dimensions (for Hypar), the sail is fabricated into a 3D shape, and there is low shearing stress during the installation. Correctly formed sails result in fewer wrinkles, a longer product life, a better-looking product, increased inherent stiffness and less deflection.