Hobbies And Interests
Bow Shape and Water Resistance
Water resistance slows a boat. Explore how the shape of the bow affects resistance. Buy or build three wooden boats with three different bow shapes: v-shaped, half-cylinder and cube-shaped. Hypothesize which will experience the most resistance. Add a water pump to a water tank or aquarium. Affix a spring balance to one side of the tank. Add a 300-gram weight to the first boat to balance it. Attach the boat to the other end of the spring balance, turn on the water pump and record the measurement on the spring balance. Repeat this process with the other boats. Graph differences in resistance measured by the spring scale. Compare these results to your hypothesis.
Surface Tension Experiment
Explore the properties of surface tension and how they aid a boat. Cut a raft from transparency film. Cut a small square in the middle of one end of the raft. Cut several pieces of sponge, smaller than the opening in the raft. Put a toothpick through each sponge. Tape one of the toothpicks across the opening in the raft so the sponge touches the water but not the raft. Fill a sink with water and place the raft inside. Using a small dropper, add a drop of dish detergent to the sponge and observe changes. Continue adding drops of detergent; you will notice the detergent breaks the surface tension of the water. Repeat the process with fresh water, different sponges and various substances such as toothpaste, salt and vegetable oil. Compare the differences in the number of drops of each that are added before a change takes place. Graph the differences.
Keel Design
Explore how keel design affects a boat's rocking. Make two boats out of 2-liter bottles, one with a bilge keel and one without. A bilge keel on a real boat is a piece of metal on the bottom of the boat that reduces rocking.
For each boat, cut a rectangular hole in one side of the bottle and lay it on its side. To create a bilge keel for one, cut the top and bottom off another 2-liter bottle, then cut the remaining central portion in half, lengthwise, leaving two half cylinders. Attach each of these pieces to a boat, one on the right and one on the left of the bottom/side. The pieces should extend below the bottom/side. Bend the pieces until they form 90-degree angles with the bottom/side of the boat.
Attach a dowel rod to the top of each boat and use identical marbles to weigh down both boats. Put the boats in a bathtub full of clean water. Pull the dowel rods down until they almost touch the water and observe which boat rocks more when the rods are released. Record the results.
Floating Metal Boats
Metal boats float while smaller pieces of metal sink. Explore this phenomena with aluminum foil. You will need two squares of foil, about three inches square. Fill a large bowl with water. Crumple the first piece of foil into a ball. Fold the second piece of foil into the shape of a small rowboat. Place both pieces of foil into the bowl of water. Observe the results and brainstorm the reasons for the results. Research water surface tension and its effects on a boat's buoyancy to discover the answer.