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## World's Largest Icosahedron

### A Student Project at Lexington High School, Lexington, Massachusetts

#### by Jason Rosenfeld

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We were taking a new class at our school, Modern Geometry. Our teacher, Mr.Kelly, had read on the Net about the icosahedron mentioned in a newsgroup thread in the Math Forum's archives. He gave two groups the assignment to build a larger one. Due to the rivalry between the two groups, our group decided to build a massive 15-foot icosahedron, and set to work.

Our group of eight people decided to build the structure out of PVC tubing with vinyl tubing as connector elbows. We would cover the edges with blue tarps to make it a solid. We got the materials, did the construction, and started to put it up, but the tubing bent and it fell down. We tried again, but the wind knocked it around.

We then decided to try building a wooden structure to help support it from the inside. We did this, but when we put the icosahedron on the structure, the wind again blew it down.

We were now very frustrated and in debt, and our group had shrunk to four. We decided to try the structure once more and put it up again.

It stayed up for about 12 hours, but then we got about 8 inches of really heavy snow and most of the tubes and wood bent and were shattered.

Despite already having gotten credit for the project, having the maintenance crew hate us, and being in debt over \$300, we decided to rebuild it in the spring using a different approach. Now down to three people, we bought aluminum electrical conduit piping and 480 lb. test shark fishing leader. We drilled holes in the ends of the pipes and put the wire through. We laid the icosahedron out flat on the ground and planned how we were going to put it up.

We gathered two more people and went back to work. After a number of weekends of work we had our icosahedron built--but the wind came back and snapped the fishing line we had used to hold the vertices together.

We got more materials and tried again, this time trying to make the vertices better, and making slits in the tarps. It fell down again. Persistently, we put it up again. This time we used crimping tubes between pipes so the wire couldn't come undone, and we cut off the remaining tarps. This time when we put it up again it only took about five hours. This was in mid-July, and it has been standing 15 feet tall ever since.

We estimate that the whole project took 750 hours.

Now we have moved on to trying to get publicity and documentation for The Guinness Book of World Records. We have raised over \$500 selling candy to pay for it. We have also enlarged our group and have decided to complete the rest of the regular platonic solids in similar sizes. We have already built the tetrahedron and octahedron, and the cube and dodecahedron should be going up in fall of 1996. We have made this a hobby and now do it not for school credit but only pride. We are still selling candy to pay for the new solids and the project has become a complete obsession.

The group members on the project, all currently juniors, are: Raphael Bras, Saro Geotzyen, Stephen Hayden, Josh Magri, Nick Varrgelis, David Rosner, and me, Jason Rosenfeld.

The original Lexington High School largest icosahedron Web pages are also available. (Warning: large pictures!)