Build a Strong Balsa Wood Bridge: Tips, Tricks, and Requirements

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SUMMARY

The discussion focuses on constructing a balsa wood bridge for a competition with specific requirements. The bridge must use no more than 30 linear feet of 3/32” x 3/32” balsa wood, be freestanding, and span a 12-inch gap without supports in the water. Key construction tips include laminating the balsa wood, ensuring the roadbed is solid and level, and potentially baking the wood to enhance strength. The design should resemble an arch bridge to maximize weight-bearing capacity.

PREREQUISITES
  • Understanding of balsa wood properties and characteristics
  • Familiarity with basic woodworking tools and techniques
  • Knowledge of bridge design principles, particularly arch structures
  • Experience with adhesives suitable for wood bonding
NEXT STEPS
  • Research techniques for laminating balsa wood for added strength
  • Learn about the structural advantages of arch bridge designs
  • Explore methods for drying and strengthening balsa wood, including baking
  • Investigate weight distribution principles in bridge construction
USEFUL FOR

Students participating in engineering competitions, hobbyists interested in model bridge building, and educators teaching principles of structural design and materials science.

bababooey
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Hi,

I am not sure if this belongs here and I apologize in advance if this has been placed incorrectly. Please move it to the appropriate forum.

I have a Balsa bridge due in about 2 weeks. I have picked up the supplies but I am not sure how to start the process and I want to do it correctly. I have the Balsa wood, cutting tools and glue.

The requirements for the bridge are as follows:

The bridge must be freestanding, constructed of no more than 30 linear feet of 3/32” x 3/32” balsa wood (NOT BASS WOOD) cemented with the glue of your choice. The roadbed must be constructed of a single balsa sheet of the same 3/32” thickness. No balsa sheeting may be used below the roadbed. Laminating of the 3/32” x 3/32” stock is allowed.
The bridge must be able to span a 12-inch river with no supports in the water.
The bridge roadbed must be a minimum of 5 inches above the water and level all the way across. No balsa structures may be above the roadbed.
The roadbed must be a minimum of 2 inches wide. The roadbed must be solid from end to end. No holes are permitted in the roadbed.
The maximum allowable height is 10 inches and the length may be anywhere from 12 to 20 inches.
A clear channel of 3 x 4 inches must be provided under the center of the bridge.
The bridge may not be painted or cemented so that the balsa wood grain is hidden.
Your name and period must be clearly marked on the bridge.

Anybody have any tips on where to start? I am lost. If anyone can provide a good, reliable design I would appreciate it. Any other information that would be helpful is also appreciated.
Thanks
 
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Start here:

http://www.google.com/search?hl=en&q=balsa+wood+bridge&aq=0&oq=balsa+wood+

I helped my son build one for a 9th grade class. He won. It may have helped that we baked the bridge in the oven to the point where the wood darkened a bit. This dried out any moisture and may have strengthened the bridge. The rules for his competition were a bridge of fixed size and then the ratio of the breaking weight divided by the bridge weight was to be maximized.
 
Make it an "Arch" bridge.

Roman bridges are still standing after 2,000+ years. :wink:
 

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