Historically, sails were constructed with woven cloth panels running at 90 degrees to the leech, this aligned the strong weft threads with loads running between the clew and head.  This traditional panel layout is known as Cross-Cut.  Stress analysis has shown that the primary loads radiate from the clew through the body of the sail to meet the secondary lesser loads running up the Luff.  This analysis lead to the Tri-Radial panel layout.

Sails constructed with the traditional Cross-Cut panel layout are easier to produce. There is less cutting, less sewing and less material wastage than in Tri-Radial construction, so Cross-Cut sails cost less initially.  However, Cross-Cut sails will stretch more on the bias where the fibres are not aligned with the loads in the sail.  This occurs throughout the lower centre of the sail and along the luff. As wind speeds increase the sailcloth stretches, the camber increases and moves aft, the boat heels more, weather helm increases, the keel works less well, the boat slips to leeward and loses upwind speed.

Tri-Radial sails will keep their design shape in strong winds to provide greater upwind speed and more comfort.

Tri-Radial sails will also maintain their shape for a greater number of years, so they depreciate more slowly and cost less over the medium term.  For these reasons we recommend a Tri-Radial panel layout over old style Cross-Cut construction.