CHAPTER 3 SAIL SHAPE AND CONTROLS
E General Rules for Sail Controls E Assessing Sail Shape E Using Sail Controls for Upwind Sailing E Using Sail Controls for Downwind Sailing
The shape of a sail directly impacts how well the sail works and how fast the boat will move. Sail controls are used to adjust a sail’s shape by powering and depowering a sail. There are several types of sail controls that can change the shape of a sail and improve a boat’s performance. With an infinite number of sail shape possibilities, optimizing your sails for the immediate conditions is the benchmark of a good sailor.
GENERAL RULES FOR SAIL CONTROLS • When it comes to sail shape and power, deeper (fuller) sails have more power; flatter sails have less power.
• Sail controls are set looser in medium wind and tighter in very light and also in heavy wind.
• Generally, adjustments are made in small amounts or incrementally—not maximum on or all off.
•Watch the adjustment being made for the correct setting, not your hands pulling the controls.
ASSESSING SAIL SHAPE
The ability to make informed decisions about sail shape is one of the most important aspects of controlling a sailboat. Two key elements go into defining sail shape: draft and twist.
Power
DRAFT: Draft describes the depth and location of the curvature in a sail. The draft is controlled by the outhaul, Cunningham/ downhaul, backstay, sprit or main halyard. More tension on any of these controls reduces depth and moves the curvature forward. Easing these sail controls increases depth and moves the curvature aft.
TWIST: Twist describes the curvature of the leech, most noticeably near the top batten. Twist is most commonly controlled by the boom vang, traveler, mainsheet, Cunningham/ downhaul or backstay. More tension on all of these controls, except the backstay, causes the leech to curl to windward and decreases twist; more tension on the backstay increases twist. The optimal setting on most boats is when the top batten is parallel with the boom. Wind pressure on the sail changes upwind and downwind, so the boom vang in particular will need adjustment if a boat changes course relative to the wind.
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