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Teaching Guide
Streamlined Design

In "Superhuman Subs", you observed how teams from around the world competed to produce the fastest human-powered submarine. The quickest submarines relied on a sleek hull shape that effectively parted the water as it moved through the tank. Without "slicing" through the water, a sub can encounter a pileup of fluid in front of the hull, slowing it down. To learn how to overcome this effect, designers must examine how different hull shapes behave as they move through water. Now it's your chance to design an effective hull shape. In this activity you'll observe how streamlining affects a vehicle as it is pulled through a water-filled trough.


 

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This activity page will offer:

  • A hands-on experience in streamline design
  • An opportunity to design, build, test, and improve design ideas
  • A hands-on (and hands-wet) construction activity

MATERIALS

  • Trough (a plastic gardening one will do)
  • Waterproof tape
  • Small toy car or similar toy
  • Straw
  • Scissors
  • Waterproof clay
  • Aluminum foil
  • Weight
  • Fishing line
  • Stopwatch
  • Water

 

PROCEDURE

  1. Obtain a long, plastic trough. If necessary, use waterproof tape to seal up any drainage holes in the container.
  2. Position the trough on a sturdy tabletop so that one end aligns with the edge of the table.
  3. Use a scissors to cut two small segments of straw. These segments will be used as guides for the fishing line.
  4. Place one segment in a small lump of waterproof clay. Set the clay at the bottom of the trough as shown in the diagram.
  5. Place the other segment of the straw in another lump of clay. Position this lump on the edge of the trough as shown in the diagram.
  6. Obtain a one-meter length of fishing line. Thread the line through both straws.
  7. Tie one end of the line to a small weight. Use waterproof tape to attach the other end to a small car or similar toy.
  8. Fill the trough with water so that the car is submerged.
  9. Position the car at the far end of the trough with the weight raised.
  10. Release the weight. Use a stopwatch to determine how long it takes for the car to travel across the trough.
  11. Perform several trials to obtain an average time.
  12. Use a small lump of clay to secure a deflection screen onto the front end of the car as shown here. The screen should be made of a piece aluminum foil.
  13. Perform several trials to obtain an average time. Experiment by using different dimensions of this shield. How does this effect the pull-time?
  14. Use two pieces of aluminum foil to create a plow-like blade that can be added to the front of the vehicle.
  15. Perform several trials to obtain an average time.




  16. Try working a piece of waterproof clay into the shape of a bullet. Add this shape to the front of the car as shown below. Make sure that the clay does not interfere with the spin of the wheels.
  17. Perform several trials to obtain an average time.



Questions

  1. What force powered your underwater vehicle? Explain.
  2. How did the shield you added to the car affect its original speed? How does the attachment point affect the performance?
  3. How did adding a plow-like blade to the vehicle affect its movement? Why?
  4. Did adding the extra weight of the clay improve or reduce the speed of the car? Explain.

Critical Thinking
Do you think that the car, without the plow-like blade, would have moved faster if it was moving through air instead of water? How would streamlining have affected the car in this case? Explain.

EXTENSIONS

Streamlined Shapes
How is streamlining applied to the shape of automobiles? Examine illustrations of different types of cars. Compare and contrast their shapes. More specifically, examine the shape of racecars with the shape of minivans. What are the advantages and disadvantages of each design? What characteristics identify a streamlined shape?

Announcing a Submarine Race
Work with a partner. Create a fictional script about a pair of radio personalities delivering commentary on a human-powered submarine race. Keep the dialog humorous, but integrate actual facts about the submarines.

Art Connection
Imagine designing your own human-powered submarine. What shape would the vehicle be? How would it be powered? Think about it. Then, draw a set of scale blueprints. Identify the parts of your vehicle and the mechanical actions essential to its movement and control.

WEB CONNECTION

Of Boats and Waves
http://members.iinet.net.au/~bluep/wavedrag.html
Information about the physics of hull design for surface ships.

Turtle: A Revolutionary Submarine http://www.geocities.com/Athens/Acropolis/4870/
DrGeorgePCPage9Turtle.html

Learn about the first US human-powered submarine.

Bibliography of Human-Powered Submarines Articles
http://scilib.ucsd.edu/sio/indexes/subbibl.html

Teaching Guide from the FRONTIERS Archive http://www.pbs.org/safarchive/4_class/45_pguides/
pguide_403/4543_sub.html

Check out these activities related to our earlier coverage of the human-powered submarine race.


Answers

The activities in this guide were contributed by Michael DiSpezio, a Massachusetts-based science writer and author of "Critical Thinking Puzzles" and "Awesome Experiments in Light & Sound" (Sterling Publishing Co., NY).

Academic Advisors for this Guide:

Corrine Lowen, Science Department, Wayland Public Schools, Wayland, MA
Suzanne Panico, Science Teacher Mentor, Cambridge Public Schools, Cambridge, MA
Anne E. Jones, Science Department, Wayland Middle School, Wayland, MA

 

 

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