UK Sailmakers Tri-RadialThe fully articulated panel layout of a tri-radial mainsail rotates the cloth's thread line to match the primary load paths between the three corners of the sail. To accomplish this, tri-radial sails are constructed from many narrow panels, where the thread line of the cloth is parallel to the longest edge of the panel. Laminates with more structural yarns are used in the highly loaded sections of the sail like the leech. To keep the sail as light as possible, laminates with few structural yarns are used in the lower load areas like the luff and the foot.