Dome Sweet Dome

Introduction

A geodesic dome is a structure made of struts that are connected to each other to approximate the shape of a sphere (or part of a sphere). Spaceship Earth at EPCOT in Walt Disney World, Florida, shown in Figure 1, below, is a famous example of a geodesic dome that is a complete sphere shape.

Figure 1. Spaceship Earth at EPCOT in Walt Disney World, Florida, is a famous, complete sphere-shaped geodesic dome. (Image credit: Benjamin E. Esham)

Many geodesic domes are only part of a sphere, such as climbing domes at playgrounds and the Desert Dome at Omaha's Henry Doorly Zoo, Nebraska, shown in Figure 2, below.

Figure 2. The Desert Dome at Omaha's Henry Doorly Zoo, Nebraska, is an example of a geodesic dome that is only part of a sphere in shape. (Image credit: Dual Freq)

Typically, the struts of a geodesic dome are joined together in triangles, with the points of the triangles being approximately on the sphere's surface. The edges of the triangles form great circle-like shapes, or geodesics, over the surface of the dome. The struts form a rigid network that transmits stress forces throughout the structure.

Richard Buckminster "Bucky" Fuller, an American inventor, architect, author, engineer, designer, and futurist, patented the geodesic dome in the 1940s and made it popular. The geodesic dome's design gives it some very interesting properties. Since the structure approximates a sphere, geodesic domes have very lowsurface-area-to-volume ratios (i.e., its volume is relatively large compared to its surface area). In fact, geodesic domes enclose more volume (e.g., cubic centimeters [cm³]) per unit of mass (e.g., grams [g]) of the dome than any other structure made from straight pieces. They are also the only known structure built that increases in strength as the size of the building is increased. As you can see with the geodesic dome, R. Buckminster Fuller was interested in ideas that maximized efficiency in design by "doing more with less."

In this science project, you will build your very own geodesic dome by taping together tubes made from rolled-up newspaper and then investigate your dome'sstrength-to-weight ratio.

Terms and Concepts

• Geodesic dome
• Geodesics
• R. Buckminster Fuller
• Surface-area-to-volume ratio
• Volume
• Mass
• Strength-to-weight ratio

Questions

• What are the basic shapes used in most geodesic domes?
• How much mass do you think your geodesic dome will be able to support?
• Can you think of some examples of geodesic domes that you have seen or used before?
• Geodesic domes are sometimes used as greenhouses. Why do you think they would be useful for this, or other, specific applications?

Bibliography

Take a look at these resources for more information on geodesic domes:

• PBS Online. (2000). Building Big: Dome Basics. WGBH Educational Foundation. Retrieved April 30, 2014, fromhttp://www.pbs.org/wgbh/buildingbig/dome/basics.html
• Wikipedia contributors. (2014, April 23). Geodesic Domes. Wikipedia, The Free Encyclopedia. Retrieved April 30, 2014, fromhttp://en.wikipedia.org/w/index.php?title=Geodesic_dome&oldid=605388206

Materials and Equipment

• Sheets of newspaper (44)
• Measuring tape, metric
• Masking tape or painter's tape (1 roll)
• Scissors
• Markers (2 different colors)
• Optional: Glitter, beads, and glue for decorating.
• Kitchen or bathroom scale. This can be purchased locally or at Amazon.com.
• A large tray that will fit the geodesic dome on it. This is for weighing the dome on the scale. The dome will have a diameter of about 58 cm. Alternatively, you could use a small cardboard box and weigh the dome upside down with the top in the box, placed on the scale.
• Many magazines
• Lab notebook

Figure 3. You will need several newspapers and common household items to build and test your geodesic dome.

Experimental Procedure

Making the Geodesic Dome

1. Stack two flat sheets of newspaper together. Starting on the top (long) edge, roll the sheets up together as tightly as you can to form a tube. When you reach the bottom edge, tape the tube to keep it from unrolling. The tube should be about 58 centimeters (cm) long, or the length of the newspaper sheets, and look similar to the one in Figure 4, below.
   1. Note: Newspaper sheets can vary in size. Your tube does not need to be exactly 58 cm long to work for this science project; as long as the tube isat least 54 cm long, you can use the newspaper sheets in this science project.
      1. If your tube is less than 54 cm long, you could either use more sheets of newspaper (see step 3.a.iii., below, for details) or check out the T. Landry resource in the Bibliography in the Background section to figure out how to make a smaller geodesic dome. (Tip: The type of dome you are building in this science project is called a 2V.)

Figure 4. Make a tube of newspaper by rolling two sheets together, from top to bottom, and taping them in place.

2. Repeat step 1 until you have 22 tubes.

Figure 5. Make 22 tubes total as described in step 1.

3. Now cut down the tubes to make 35 "longs" and 30 "shorts." You should end up with a pile of newspaper tubes like the one shown in Figure 8, below. Be careful when using the scissors to cut the tubes.
   1. Longs: Cut 12 tubes into three smaller tubes, where each smaller tube is 18 cm long, as shown in Figure 6, below. Add extra tape to the tubes if needed to keep them rolled up tightly. You should end up with 36 long tubes that are each 18 cm long (you only need 35 long tubes so you will have one extra).
      1. Use a marker to color all of the cut tubes in some visible way, such as by making a colored mark at each end, so you can tell them apart from the short tubes.
      2. Decorate the tubes if you like.
      3. Note: If your original newspaper tubes are less than 54 cm long, you could use one tube to make only one or two long tubes. (One long tube is 18 cm long and two long tubes are 36 cm long total.)
      
      Figure 6. To make the long tubes, cut the newspaper tube into three smaller tubes that are 18 cm long each.
   2. Shorts: Cut 10 tubes into three smaller tubes, where each smaller tube is 16 cm long, as shown in Figure 7, below. Add extra tape to the tubes if needed to keep them rolled up tightly. You should end up with 30 short tubes that are each 16 cm long.
      1. Use a marker to color all of these tubes in some visible way that is different from the long tubes, such as by making a different colored mark at each end.
      2. Decorate the tubes if you like.
      3. Note: If your original newspaper tubes are less than 48 cm long, you could use one tube to make only one or two long tubes. (One short tube is 16 cm long and two short tubes are 32 cm long total.)

Figure 7. To make the short tubes, cut the newspaper tube into three smaller tubes that are 16 cm long each.

Figure 8. You should end up with 35 long tubes (left) and 30 short tubes (right).

4. Tape 10 longs together to make the base of the dome, as shown in Figure 9, below.

Figure 9. Tape together 10 long tubes to make a base like this one.

5. Tape a long and a short to each joint. Arrange them so that there are two longs next to each other, followed by two shorts, and so on, as shown in Figure 10 and 11, below.

Figure 10. On the base you just made, attach a long (dark-colored here) and a short (light-colored here) to each joint, arranging it so that two longs are next to each other, then two shorts, etc.

Figure 11. Tape a long and a short tube to each joint, placing two longs next to each other, then two shorts, etc.

6. Tape the tops of two adjacent shorts together to make a triangle. Tape the next two longs together, and so on, all the way around, as shown in Figure 12, below.

Figure 12. Tape the tops of two nearby long tubes together, then the next two short tubes, etc., until you have taped all of the pairs together, making a series of triangles.

7. Connect the tops of these new triangles with a row of shorts, as shown in Figure 13, below. The dome will start curving inward. As you continue to add to the dome, you may want to add additional tape to reinforce the joints.

Figure 13. Connect the tops of the triangles with long tubes (10 total).

8. At each joint where four shorts come together, tape another short sticking straight up. Connect this short to the joints on either side with longs, forming new triangles, as shown in Figure 14, below.

Figure 14.Where four short tubes come together, tape on another short tube, pointing up, and then stabilize it with a long tube taped to a joint on either side of it.

9. Connect the tops of these new triangles with a row of longs, as shown in Figure 15, below.

Figure 15. Connect the triangles with long tubes (5 total).

10. Finally, add the last five shorts so that they meet at a single point in the center of the dome, as shown in Figure 16, below. Your geodesic dome is now complete! Feel free to add additional tape to joints where more support is needed.

Figure 16. Fill in the empty pentagon (five-sided shape) space at the top with five short tubes, meeting at a point in the middle.

Testing the Geodesic Dome

1. Weigh your geodesic dome on the scale. Record its mass (in grams [g]) in your lab notebook.
   1. To weigh the dome, place a large tray on the scale, zero out the scale, and then place the dome on the tray.
   2. Alternatively, you could place a small, open cardboard box on the scale, zero out the scale, and then place the dome upside down with its top in the box.
2. Test how strong your dome is by seeing how many magazines you can load on top. Add magazines, one at a time, on the top of the dome, as shown in Figure 17, below. Observe the dome carefully for signs of impending failure. In your lab notebook, record how many magazines your dome could support before failing.

Figure 17. Test how strong your dome is by adding magazines, one at a time, on the top of it and seeing how many magazines it can support.

3. Weigh the stack of magazines that your dome could support. Record the mass (in g) in your lab notebook.
4. What is the strength-to-weight ratio of the dome? In other words, how much mass can the dome support compared to the mass of the dome itself?
5. Did the results surprise you? Why or why not?