SCIENCE OF SPORTS: Speed Sailing
Traveling faster than the wind is a sailor's dream. Frontiers goes on location in Australia and California to meet two sailors who are devoting their careers to beating the world's record for a wind-powered craft -- held in recent years by windsurfers. A combination of ingenuity, radical boat design, determination, high-technology and scientific tests gives these sailors the edge they will need to accomplish their goals.
Notes & Discussion
Activity 1: Sailing on Land
Activity 2: Testing Hull Designs
NOTES & DISCUSSION
- Ancient mariners had only ocean currents to power their vessels. Once ship designers harnessed the power of the wind, world travel was revolutionized. Sailing ships raced across the globe for riches and for sport. Innovative sail types and inventive hull designs added a new dimension: the racing sailboat. Today, many racing boat designers keep their plans a guarded secret.
- How does each boat design featured on Frontiers use physics to its advantage? What are the drawbacks and benefits of each design? How does the hydrofoil on Greg Ketterman's craft compare with the wing of an airplane? Research the phenomenon of cavitation. Does a parallel occur in flight?
- Geography Connection: Only a few sites in the world provide optimum conditions for racing sail-powered craft. Criteria include: strong winds, perpendicular to the shore; the wind must blow from land toward the water. Where do these conditions occur? Two sites seen in this episode include waters off the coast of North Africa and Spain.
ACTIVITY 1: SAILING ON LAND
Invent a wind-powered land sailing vessel that will out-race other designs. Your goal is to design a landspeeder that will successfully challenge those created by other groups in your class.
You will race on a 24-foot, wood-lined course. Follow the instructions for the skill level chosen by your instructor. Design the course with your class in a location that lets you test your landspeeder design in secret.
Skill level 1: design a straight course.
Skill level 2: design a course with two 45 degree turns.
Skill level 3: design a course with two 90 degree turns.
Your landspeeder will be powered by a 20-inch, 3-speed box fan set at one end of the course. The fan will remain in a stationary position with its speed constant throughout the race. Two parallel tracks should be built so you can race two landspeeders at once. After all heats, the fastest overall time wins the competition.
Use graph paper to draw a design and label all parts of your landspeeder. Keep your design a secret! Write a detailed description of the intended operation of your landspeeder and submit it to your teacher. If you have access to a computer with a graphics program, you may wish to design your craft on the computer.
Assemble your landspeeder. Be sure to include a body, wheel(s), mast(s) and sail(s).
If you are using skill level 2, you can walk beside your landspeeder to steer it. Remember that both the mast and the wheels must be able to turn.
If you are using skill level 3, you should design radio-controlled operators to steer the craft. You may not walk beside your landspeeder during the race.
Test your landspeeder with the small fan. Modify your design as needed to increase speed and efficiency. When you are satisfied that your design works efficiently, test it with a larger fan.
SKILL LEVELS 1 and 2
- plastic, nylon, cotton or other sheeting
- dowel rods
- craft sticks
- wooden or plastic "boat" forms or plastic bottles
- coat hangers
- wheels or jar lids
- table fan (for testing)
- 3-speed 20-inch box fan
- 9 track liners (1-inch x 3-inches x 8-foot wood furring strips)
- masking tape
- clear tape
- white glue
- graph paper
- stop watch to time the races
SKILL LEVEL 3
- all of the above, plus:
- small electric motor(s)
- small pulleys
- various sized springs
- fishing weights
- radio remote controller and receiver
- battery or solar cells
- "Sailing on Land" is designed as a competition for groups of students. There are three skill levels of increasing difficulty and complexity; choose the level best suited for your students.
- Materials are suggested, not mandatory. Students may add materials not listed on the guide as long as they meet your approval.
- Students should review the principles of sailing before designing their landspeeders. Tacking, for example, is an important skill to learn for skill levels two and three.
- Students are asked to submit drawings and written descriptions of their land-speeders to you. Your input will help to uncover design flaws. Advanced students should study the concept of drag and design different boat hulls from flat and square to hydroplane. Use the Testing Hull Designs activity in this guide to test designs.
ACTIVITY 2: TESTING HULL DESIGNS
- Build a hydro-tank to test different hull designs. A 20-gallon or larger fish tank is ideal, but smaller models can be made.
- First, you will need to design a variable-speed electric motor, drive shaft, gear and propeller system. Worm gearing should include two 908 bend assemblies, one set of which will be submerged in water, so it should be made of plastic. (A pinion gear could be used instead.)
- You will need three drive shafts of varying lengths. The primary drive shaft should be long enough to keep the motor a safe distance from the water. A vertical drive shaft should be mounted securely to the tank. The propeller shaft should be 1 inch long, with supports as needed. Use a propeller from a model boat. During trials, the speed of the motor must be adjusted so that surface disturbance is minimal. It is important that this speed be maintained during all tests.
- Hang a spring scale near the drive shaft, directly above the inside edge of the tank. Before filling, glue a small ring to the glass at the projected water-air interface. Fill the tank so the ring just touches the water.
- Design hollowed boat hulls of varying shapes. The hulls should hold enough ballast to sink them to a depth of half their height in the water. Pass the string through the ring on the glass, then attach it to the spring scale. Measure and compare the drag forces for different designs to determine optimum design characteristics for the least drag.
CREDIT: Science teacher Frank Weisel, who developed this activity, is taking students from Poolesville Junior-Senior High in Poolesville, MD, to Yellowstone Park in June for a week-long field trip, as part of an interdisciplinary science curriculum.
- A knot is a unit of speed equal to one nautical mile or about 1.15 (statute) miles per hour. The Endeavor sets a world record of 46.2 knots; how fast is that in miles?
Scientific American Frontiers
Fall 1990 to Spring 2000
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