The Ullman Sails F18 AP mainsail design offers competitors a design that will carry them through the wind range. The mainsail is built in a tri-radial design using Pen fibers. The cloth Ullman Sails utilizes for our F18 sails features a ZigZag fiber layout that ensures efficient support and distribution of the loads over the sail. The result is a reduced load on the Mylar film, helping with shape retention.