# Balsa Bridge

This balsa bridge was built by some students of mine for a Science Olympiad competition. It spanned 14 inches, weighed 8.1 grams, and held 29 pounds. That puts its efficiency at 1630.

This photo makes the bridge look a little lopsided. That wasn’t the case, however.

Here is a photo of where the bridge broke. Click the picture to get a really good close-up.

### 27 thoughts on “Balsa Bridge”

1. I have to build a bridge that will be tested with one side elevated 5cm higher than the other. It’s not elevated as part of the bridge but there’s a block that has to elevate it. Also, the lower end of the bridge must be 2.0cm or less in height perpendicular to the test support at the end of the test support. Do you have any advice on designs for this?

• Hi Sam,

This sounds like Science Olympiad. Am I right? If so, Science Olympiad bridges are all about simplicity. Try to envision how to make your top chords (in compression) the shortest they can be.

• Also, if you haven’t already, check out scioly.org .

2. Can you tell me the differance between the span and the length of a bridge?

• The length refers to the measurement from one end of the bridge to the other. The span refers to how much of the length is suspended over air. For instance, my model bridge might be 18 inches long, but 1 inch on each side rests on blocks. Thus, the span is only 16 inches.

3. Any tips for a first time builder Garret?

4. my bridges had a set of x’s on all side it held 60 piunds im in 8th g

5. hey garret do you know what science olympiad is?

• Yep, I spent 7 years competing in SO, and these past few years keeping tabs on what’s been going down in the SO world.

6. i am a 7th grader and i have to build a bridge out of balsa wood and i have 20 ft of sticks to work with. how many feet was used for the 2nd bridge?

7. Garret can u tell me how tall and wide this bridge was

• This bridge was 2 inches wide and 3 inches tall

• how long was it and how long was the top part?

• The bridge was just over 14 inches long, and the top flat part was 2 inches long.

8. Im an 8th grader and we are doing this project what do you think would be the lightest yet strongest bottom. Need to know soon!!!!!! Thanks

9. I’m looking for blueprints for a balsa bridge for my class prj where’d u find yours

10. sorry i haven’t been posting much lately been very busy at school with speech and debate.

• No worries, I appreciate any time you spend here posting and answering questions.

11. The load was placed on top in the center of the bridge.

• I am competing in a truss bridge building contest, and I’m not quite sure I understand where they put the weight. If the top of the bridge is covered, do they just put the weight there, or do they put it inside the bridge?

• Ellie, I’m afraid I cannot answer your question. I have no idea where your bridge will be loaded. I’d ask the host of your contest, or refer to any rules/guidelines you were given.