Do I need a sail with horizontal or radial cut?
This depends on the cloth. During weaving, the warp yarns, the yarns running along the cloth roll, are bent around the weft yarns, which run across the cloth roll. Thus, weft yarns have less crimp than warp yarns. A woven cloth therefore stretches less in width, but more in length. Woven cloth should therefore be used in horizontal cut sails where the greatest stress is across the cloth. Some sailmakers offer radial cut sails and use cloth with correspondingly strong warp yarns. This works well for smaller sails. Laminates should therefore always be used in radial cut sails where the load is along the length of the cloth.
What material is my spinnaker made of?
Most spinnakers are made of nylon fabric because it has a high tensile strength. With nylon, there are various generic terms ranging from 2.2 oz to 0.4 oz. However, these numbers do not denote the weight of the cloth. Nylon is also coated, impregnated, and warp or weft oriented. The important thing here is the relationship between stretch, tensile strength and weight. Heavier nylon does not always have less stretch and better tear strength. A high quality, lightweight fabric can be much better than a heavy product from conventional production.