Yourbestsailvideo
Sail twist and apparent wind
November 16, 2025 · 6 min · 2K views
What this video covers
Sail trim requires twist—the variation in the angle of the sail chord relative to the boat's centerline—to maintain aerodynamic efficiency across the entire height of the sail.▶ 0:07 This configuration accounts for the vertical gradient of apparent wind, which changes as wind speed increases with height due to reduced surface friction near the water.▶ 3:25 At a constant boat speed of 7 knots, the apparent wind vector at the top of the mast is stronger and more open than at the boom.▶ 3:25 Consequently, the upper sections of the mainsail must be set at a wider angle than the lower sections to align with the varying apparent wind direction.▶ 4:12 The required amount of twist fluctuates based on atmospheric conditions; stable, laminar airflow necessitates more twist, while stronger winds or turbulent conditions reduce the required angle differential.▶ 5:17 Proper sail trim balances these forces to ensure consistent lift and flow along the full span of the sail.
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