Jigging the Rigging

Your sail converts your breath into the forward force that propels your boat. All forces act through the balance point (center of mass). So, if you blow high on the sail, the nose (bow) of the boat dips down. Blowing low causes the bow to pitch up. If you blow on a line passing through the center of mass, the boat is free to determine its own pitch to optimize speed.

Design Your Sail

It is best to place the sail low and as far back as possible.

The sail must "trap" all the air it can. It must not let air escape. Cloth has tiny holes in its weave, unless it has been coated with plastic, but then it is heavy! Foam, thin, painted card stock, transparency film or other plastics work better.

What is the best sail shape? The answer is a rounded "w"-shape. Breath hits the middle divider directing it to the sides and out along the side edges. This type of sail reduces energy lost to turbulence. One must blow very straight into this type of sail. Otherwise, the center divider acts like a rudder and results in turning (if vertical) or tipping (if horizontal)! A non-rounded one can be made just by bending two pieces of cardstock or plastic against eachother or folded in the middle.

For a Parabolic sail, the energy loss due to turbulence is probably not great but it won't cause as much snaking down the raingutter. It can be made by bending a piece of cardstock or plastic to shape.

Simple Sails

• Use the bottom half of a styrofoam cup (or side half)
• Make one like the one on the simple hull. Slanting the top piece reduces air resistance while creating a place for the sail back and sides to be anchored.
• Carve one out of a block of styrofoam or join thin panels of foam to form a roof, wall and floor for a sail.
  

  Here's the idea:

  1. Wall - The main part of the sail. Wrap it around the roof and floor edges. It rises vertically, straight up. A useful variation makes the sail look like a "C" when viewed from the side instead; the roof and floor become sides this works well when placed inside a deck cabin.
  2. Roof - The top part of the sail. Usually flat and down-sloping toward the front. The rear edge is usually straight across, but other shapes, like hearts with the point forward, have been achieved.
  3. Floor - The bottom of the sail. Usually flat and horizontal. It is anchored to the top of the hull. Sail floors built into hulls may assume contours dictated by the hull.

  Join the edges to make a complete sail. When used with card stock or plastic, line the joins on one side with triangular tabs. Bend them up and apply glue.

Put it on the rear of your deck or bury it in the rear of the hull almost to the water line if you can.