Documenting Your Work

*Documenting Your Work

Most think that being able to build a great structure is the key to doing well in the structure challenge. While this is definitely important there is one thing that is much more important than being able to build a great structure. And that is being able to build a great structure twice. The best design in the world does you no good if you can’t repeat it.

While building your structure document every step of the construction process. What is your design? What wood are you using? What glues are you using? How much does it weigh? Keeping good records allows you to build the same structure again.

Record keeping

  • Keep a notebook to record your designs and make notes.
  • Label your structures and design so you can refer back to them. Record how much weight a particular structure held.
  • Take digital photos of your structures and put with your design

Part of your record keeping should be to analyze the broken structure to determine what failed and what might be changed to improve the structure.

Analyzing the structure

  • Watch the structure while it is being tested and make notes. It is best to leave the safety shields in place while doing this. If your tester does not have safety shields make sure you wear safety goggles although I recommend that you wear them even if safety shields are in place.
  • Video tape the testing and then watch the video tapes to see if you can determine what caused the failure. The failure of structures is faster than most video cameras can record but you may be able to get an idea what happened. Something I have always wanted to do is to find someone who has a sports camera like those used to film golf swings. These cameras are fast enough to record the actual collapse of the structure.
  • Keep your old structures to review while contemplating new designs. Study them to see if you can determine what caused the failure. I keep structures in a baggie with a label and the results so that I can refer back to them while thinking about design changes. In the photo on the right you can see that we labeled structures with the initial of the person who built them with a running count number of the structure. Thus “J5” in the photo indicates that this was the fifth structure built by Jeff. These tests were of structures that were scored on a ratio and so we also recorded the structure weight and weight held on each of the label sheets we put into the baggies with the structures.

One reason it is difficult to analyze a broken structure is that the failure is often catastrophic with lots of pieces flying all over the place. One way to control this is to adapt the structure tester. After the structure is set and the pressure board is in place (but before any weights are placed) add shims made from hardboard and sheet metal to the top of every safety corner post so that the maximum the pressure board will fall when the structure fails is 1/8″ to 1/16″ or less. The shims should be cut to approximately the same size as the safety posts (3-1/2″ x 3-1/2″). If the pressure board only falls 1/16″ when the structure fails it may be easier to isolate the initial failure.

As you modify the design of your structure to improve its performance don’t change too many variables at once. If you change too many things you may not be able to determine which design changes worked and which didn’t. Consider changing only one variable at a time. This may require you to build more structures initially but it will pay off in being able to isolate the changes that improve the structures performance and those that do not.

* Copied from: “Diary of a Balsa Goddess” http://structure.txdi.org/node/30  ©2009 Heather Compton

Diary of a Balsa Goddess by Heather Compton is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License.

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