Sail Shape and Controls
BOOM VANG: The boom vang, or vang, affects sail shape by altering leech tension and mast bend. The vang is the secondary means of controlling leech tension, after the mainsheet.
Tightening the boom vang puts more tension on the leech of the sail. When you tension the leech you close the leech, causing it to curl more to windward and reducing twist.
Upwind sailors tighten the boom vang so the battens are parallel with the boom. The way to sight this is to position yourself underneath the boom while you are sailing and look up at the windward side of the boom and the sail. If the outer edge of the battens point to windward, the boom vang is too tight and needs to be loosened; battens that are parallel to the boom allow the boat to point higher on a close hauled course.
Open leech
When you are going upwind in heavy air conditions, pull the boom vang on hard. This will help flatten the sail by reducing draft and minimizing power to make the boat more stable and controllable. This is referred to as vang sheeting. Vang sheeting allows you to ease the mainsheet without losing leech tension; in effect, you are spilling excess pressure without losing the ability to point.
If the boat is being overpowered in very heavy air, consider increasing twist a lot by loosening the boom vang or tightening the backstay to depower the sail.
In light air, the boom vang may be left cleated without tension because the weight of the boom will likely eliminate all twist. Just a little twist in the leech allows the wind to flow smoothly along the sail and creates more power for upwind sailing.
TRAVELERS AND BRIDLES: Travelers and bridles are used to control the location of the boom relative to the centerline of the boat and the angle of the mainsheet to the wind. A traveler uses a car on a track that is adjusted using control lines to move it from side to side and change the position of the boom. A bridle (as on a 420) is a fixed piece of line that when shortened or lengthened affects the boom position relative to the boat’s centerline.
Pulling the traveler to windward of centerline, or lengthening the bridle, enables the sailor to center the boom to achieve an efficient and powerful close hauled course. Easing the traveler car to leeward, or tightening the bridle, depowers the mainsail when you are sailing on a close hauled course and on close reaches.
Table of Contents 19 Closed leech
TIP
EA looser boom vang that opens the leech slightly will provide speed but sacrifice pointing ability.
EA tight boom vang will be slower, but it could benefit pointing ability (until the sail stalls and wind doesn’t flow over the sail).
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