The model boat in this project is fitted with two basic devices for controlling water craft. Both operate underwater. The propeller is driven by the engine of a motor- or steam-powered boat. It rotates very fast and pushes the craft through the water. In the project, the engine power comes from the energy stored in a wound-up rubber band. As in real life propellers, the blades are set at different angles, and push the water backward, so thrusting the vessel forward, as it spins. You could try making different propeller designs- with more blades set at different angles, for example – and testing them to see which works best.
A rudder is used to steer both sail- and motor-powered boats. It is controlled by a handle called a tiller, or a wheel, on the boat. As in your model boat, the rudder can be moved to different positions to make the boat turn left or right, but will only work when the boat is actually moving. In addition to making the boat turn left and right, the rudder also keeps the boat going in a straight line when it is set straight.
MAKE A POWERED BOAT
YOU WILL NEED
Cork, bradawl, scissors, small plastic bottle, large paper clip, pliers, ruler, bead, long rubber bands, small pencil, pool, thin garden cane.
Make a hole through the middle of the cork using a bradawl. Cut a diagonal slot in either side of the cork. Push two strips of plastic cut from a small bottle into the slots.
Cut an oblong strip from one side of the large plastic bottle. This slot is the top of your boat. With the bradawl, make a small hole at the back of your bottle in the bottom.
Straighten a large paper clip. Bend the last ½in of wire at right angles. Push the wire through the cork, and thread it through the bead and small hole.
Bend the end of the wire inside the bottle. Hook a rubber band over the wire, and stretch it up through the neck of the bottle. Secure it in place with a pencil.
To wind up the band, turn the pencil as you hold on to the propeller. Keep holding the propeller until you put the boat into the water and release it. What happens?
Now make a rudder for your boat. Cut a piece of plastic about 1½ x 1½in and pierce two holes near one edge. Push a piece of thin cane through the two holes.
Use the strip of plastic cut from the large bottle to support your rudder. Pierce two holes about ¾ apart in the center of the strip, and push the cane through them.
Fix the rudder support to the bottle with a rubber band, so that the rudder is clear of the propeller. Wind up the pencil, and put your boat back in the water.
Like a real boat builder, you will want to test the controls of your boat. To do this, start with the rudder centered to make the boat go straight. Next, try turning the rudder from side to side. What happens? How tight a circle can you make your boat turn in?
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