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Old 04-28-2003
JimOppy JimOppy is offline
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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!

Jim
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