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Sail trim question
Here''s the question: at what point does a sail cease acting as a foil, thereby deriving it''s drive from high and low pressure on either side of the sail, to acting as a parachute, deriving its drive from the force of the wind pushing against its windward side? I know that point happens somewhere between a beam reach and a broad reach. I guess the point is, when on a beam reach....I mean a dead beam reach, with the wind coming directly from the side, is it better to let the main sheet out so the sail acts as a foil or keep the line drawn from the foot to the clew of the sail perpendicular to the wind and use the sail as a parachute?
I''m not asking so much about sail shape as how to position the boom. Should it be perpendicular to the wind on a beam reach or let out to act as a foil. Seems to me like letting it out would just spill wind and de-power the sail, but a longtime sailor says otherwise, and becasue I know sails get power as a foil when pointing, there may be something to his claim. His point is, on all points of sail, the sheets should allow a straight line drawn from the foot to the clew the most obtuse angle possible without luffing. Is this right?
My instinct is to keep the boom perpendicular.
End our debate!