...vertical uniformity. Most skippers look at their sail shape and check draft position and depth. But how many look at the uniformity of the sail shape along the vertical? The verticle uniformity is even more important to performance than horizontal shape. A sail that is full in the middle yet flat on the bottom is even less efficient than an over trimmed or over twisted sail. Many racing sails have horizontal draft stripes to aid in adjustment but few have vertical stripes that would be of significant help to the uniformity of the sail shape. Rarely have I heard anyone talk about the need for proper sail shape in the vertical although it is the most important performance factor.