What is the effect of increasing tension on outhaul/downhaul/backstay/main halyard?

• A. Increases depth and moves curvature aft
• B. Reduces depth and moves curvature forward
• C. No change in depth or curvature
• D. Increases sail area

Answer: (B)

Increasing tension on those controls tightens the sail along its edges, which flattens the sail and shifts the deepest part of the curvature forward. When you pull on the outhaul, you tighten the foot, reducing sag in the lower part of the mainsail and making the sail shallower with the draft moving toward the front of the sail. Tightening the downhaul (or Cunningham) increases luff tension, which also reduces depth and moves the draft forward. Increasing backstay tension bends the mast, flattening the mainsail and pushing the draft forward. Tightening the main halyard increases head tension, further contributing to a flatter shape and forward-shifted draft.

In short, cranking these controls makes the sail shallower and the point of maximum curvature move toward the fore part of the sail. This depowers the sail in stronger winds and improves upwind performance by reducing power and drag while maintaining drive.