Capturing the wind

Wind is something we don't really see but only feel. We actually know there is wind when trees and other objects move for the force of it. So, how can wind be captured you may wonder. There are many ways it can be done.

More than 4,000 years ago, people were already capturing the wind in sails to move boats through the water. These boats had 'square rigged' sails which caught the wind. The wind was 'caught' in the sail and the boat was pushed forward. There were oars for roaring when the wind pushed the boat in the wrong direction or when there was no wind and the boat didn't move.

About 1,500 years ago sailors discovered something very important. That is by using a special triangular sail called the 'lateen' they could actually sail against the wind, not just 'with the wind.'

Modern sail boats have now more advanced things such as specially designed tough, nylon sails to catch the wind from any direction.

A windsurfer's single sail swivels around the board to take the craft in any angle.

Sail power

Here's an experiment that would help you to find out how a lateen sail really works.

You need to make a small sail boat to do this experiment. The material you need to make it are very simple. So, first get an empty plastic bottle and then cut a rectangular hole in the side of the bottle. Next, secure a blob of modelling clay inside the bottle because the mast (pole for supporting the sail) has to be held in place with the help of clay. What can be used to make the mast? A drinking straw is ideal. Cut it to the height you think the mast should be and stick it into the clay in the bottle.

Now its time to make the sail. You can use a piece of paper or thin polythene for your sail. Cut a triangular piece and decorate it if you wish. Pierce two holes and pass it through the mast. Your sail boat's ready now but you need to make a keel for your boat and it has to be waterproof.

You can make the keel by cutting a wedge shape from an empty juice carton. Put two chunks of clay on each end and attach it to the bottom of the boat (Just below the sail). Everything's set? Well, then it's time to test how well your boat will sail. Fill the bath tub or a large basin with enough water to float your boat. Use a hair dryer or even a fan at some distance to blow on the boat. Remember, the sail has to capture the wind. You can even blow hard with your mouth. Watch how your boat sails away. Both the rudder and the keel keep the boat moving in a straight line.

How it works

No matter which way the wind blows on it, your little sail boat can be made to go in any direction. When the wind is directly behind the boat, holding the sail at right angles to the wind, channels your boat forward.

You can move at right angles or 'across' the wind by again fixing the sail at right angles to the breeze.

For a 'square rigged boat' the sail is caught in the currents of moving air and pushed along. It's similar to you blowing a ping pong ball across the table. For a triangular sail, the effect is different. The wind blows over the top of the sail and causes low pressure which sucks the sail and the boat forward.Which shape do you think is best for a sail? You can experiment with rectangles, triangles, squares and even circles to check. Once you find the best shape, try it out in different sizes to find out if a big or small sail works better.

You can also fix the sail at the front of the boat or at the rear and see how it works.

When the wind is blown at it in one direction.

Then you can try blowing from different directions to find out how smoothly the boat moves in different wind direction.Have fun with your sail boat.