Sail - Sail Construction

Sail Construction

A sail might look flat when lying on the floor but once it is hoisted, it becomes a three-dimensional curved surface, in essence an airfoil. In order for a sail to be "built", it has to be designed in a number of elements (or panels) which are cut and sewn together to form the foil. In older days, this was rightfully considered an art which was later complemented (and arguably overshadowed) by technology. With the advent of computers, sail manufacturers were able to model their sails using special computer-aided design (CAD) programs and directly feed the data to very accurate laser plotters/cutters which cut the panels from rolls of sail cloth, replacing the traditional manual process (scissors).

The key features that distinguish a "fast" from a "slow" sail are its shape related to the particular boat and rig and its ability to consistently maintain that shape. These two features rely mostly on the design of the sail (the way that the panels are placed with one another) and the sail cloth used.

The traditional parallel-panel (cross-cut) gave way to more complex (radial) designs where the panels have different shapes for the top, mid, and lower sections of the sail depending on pressure of the air caused by its flow over the sail surface. Again aided by CAD and special modelling software the sailmakers use cloths of different weight, placing heavier cloth panels where there is more stress and lighter cloth where there is less to make savings in weight.

Older fabrics (especially cotton and low budget synthetic), have the tendency to stretch with wind pressure which results in distorted and consequently inefficient sail shapes. Moreover, the cloth itself is heavy which adds to the inefficiency. Synthetic materials such as Nylon and Dacron were followed by advanced sail cloths made from exotic material yarns such as Aramid (e.g. Twaron, Technora or kevlar), carbon fibre, HMPE (e.g. Spectra/Dyneema), Zylon (PBO) and Vectran (see also Sailcloth). These materials were a breakthrough in sail technology as they provided the raw material in the manufacture of low-stretch, low-weight and long-life sail cloths. Manufacturers were able to use different weights of yarn to weave cloths with exceptional properties.

Once the panels are sewn together (often by triple-stitch method), the sailmakers complete the sail by placing the finishing elements such as the leech and foot lines, protective patches in the areas where the sail will scrape against hardware (stanchions, spreaders), steel rings and straps at the tack and clew, cleats, batten pockets (if required) and sail numbers.