Submitted on August 14, 2005 by Brian C.

Question: I have a cunningham question.

Over the past year I have been trying to understand how the boat sails. Since I started sailing in college I knew how I was supposed to trim the boat under different conditions but recently I have tried to come to a deeper understanding of sailing, rather than knowing what to do I am trying to understand why I should do that.

One big question I have is the cunningham. I understand and can visualize how to tighten the leech with the main sheet and vang, I can understand and visualize how flatten the draft in the main with the outhaul. And I accept through experience that the cunningham moves the draft forward but I cannot visualize how this is done. I know that the mainsail is a right triangle and the cunningham pulls from the head
more than the clew and wouldn't this flatten the luff? I am missing somewhere how this control moves draft forward. Is there a way to describe the cunningham to help me visualize how it works?

Thank-you.
- Brian C

Answer: Hi Brian,

The easiest way to visualize how the Cunningham works is to pull on your shirt. Sit up straight, put your shoulders back and puff out your chest or belly- which ever is more prominent. You shirt should be drawn tightly. Now grab the fabric in two places and stretch it apart. If you watch closely you can see the fabric moving towards the line between your two hands and forming a deep crease. The Cunningham does the same thing to your sail. When you tighten the Cunningham it pulls fabric out of the body of the sail forward into a fold along the mast. The pressure from the wind smoothes the fold out so it becomes a more evenly distributed pocket of fabric in the front of the sail. That extra fabric has to come from somewhere so when the fabric is pulled into the front of the sail, there is less fabric in the back of the sail. The front (luff) gets deeper and back (leech) gets flatter.

Regards,
Dan Neri

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