SAIL POWER

When you launch your model sailing boat, you can get an idea of how it is propelled by the wind. To sail in the direction they want to go, sailors must be aware of wind direction, so that they can adjust the position of the sails to make best use of it. If sailing boats face straight into the wind, the sails flap uselessly, and the boat is in a "no-go zone." They can, however, sail into oncoming wind by taking a zigzag course. This is called tacking. The wind blows against one side of the sail to propel the boat diagonally upwind. When the boat changes tack, the wind blows against the other side of the sail, and the boat goes forward on the opposite diagonal. If the wind is blowing from behind the boat, the sail is set at right angles to the boat like an open wing, so that it is filled by the wind.

MAKE A SAILBOAT

Pencil, ruler, thick card, scissors, tape, plastic sheet, stapler, bradawl, nonhardening modeling material, thin garden canes, colored paper, plastic straw, small plastic bottle, string, paper clip, sheet of paper.

Template

STEP 1
Cut out your hull shape from thick card, using the template above as a guide. Score along the dotted lines with the scissors. Use tape to fasten the sides together.

STEP 2
Lay the hull on a plastic sheet. Cut the plastic around the hull, allowing enough to cover the sides and overlap them at the top by 2in. Fold the sheet over the hull and staple it in place.

STEP 3
Pierce a hole in the middle of a strip of card a little wider than the hull. Staple in place. Put modeling material under the hole, and push a 12in cane through the hole into it.

STEP 4
Cut a sail from colored paper with a base of about 8in. Attach the straw along the side and a garden cane along the bottom with tape. Slip the straw over the mast.

STEP 5
Cut an L-shape from the small plastic bottle. Cut the base of the L in half to make two slanted tabs, as shown.

STEP 6
Fold back the two tabs of the L-shaped plastic in opposite directions, as shown, and staple them to the stern (back) of the boat. This is the boat’s rudder.

STEP 7
Cut a piece of string about 8in long. Tape one end to the back of the boom, and feed the other end through a paper clip attached to the back of the boat.

STEP 8
To test out how your sail boat works, make a breeze by waving a large sheet of paper near to the boat. Adjust the string to move the sail into the right position.

When you test your boat, set the sail in these different positions. Alter the position of the sail by using the string taped to the boom (cane). Follow the arrows shown here to see which way the wind should be blowing from in each case. Try blowing from other directions to see if this makes a difference to your boat.