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Rules and specifications for the Bridge Builder competition


The objective of this competition is to see who can design and construct the most efficient bridge within the specifications.


Only one bridge may be entered per 2-student team.  Read the specifications carefully.  Any bridge that does not meet these specifications will not qualify for the competition.


  • The bridge must be constructed from only 3/32” x 3/32” square cross section balsa wood. The wood may be cut, notched, sanded, or laminated, but must still be easily identifiable as the original wood species.
  • Joints may be made with wood joinery and/or common adhesive. “Common adhesive” means art glue, wood glue, super glue, construction adhesive, or any other liquid adhesive found at a building supply store. 
  • No other materials may be used. The bridge may not be taped, stained, painted, or coated in any way.


The total bridge weight may be no greater than 1.80 ounces. 

As a guide to budgeting how much material 1.80 ounces is: (qty) Twelve balsa wood sticks, each 3/32”x3/32”x36”, without any glue, weigh approximately 1.35 ounces.

See Figure 1. 

Sketch of an elevation bridge

  • The bridge shall span a clear distance of 24”. The total bridge length shall be no greater than 30”.  The width shall be no greater than 5”.  The bridge height shall be no greater than 6”.  The bridge height may extend above or below the horizontal support plane, but must be no greater than 6” total.
  • The bridge must be constructed to accommodate the loading plate and load chain (see section 5)


See Figure 2.

Loading plan for the elevation bridge

  • The load will be applied by means of a square loading plate set on the top of the bridge, with a hook and chain hanging down through the bridge and connected to a bucket where sand will be added.
  • The loading plate will be a 5” x 5” square plate. It will be located only on the center of the span on the bridge top chords.  It will not be moved along the bridge.


  • The stand-alone bridge will be weighed.
  • The bridge will be centered on the supports.
  • The loading plate will be applied and sand will be added to the bucket.
  • The bridge will be loaded until failure. “Failure” means the bridge is no longer able to carry load or it has deflected more than 3”. 
  • The loading mechanism and sand will then be weighed.
  • The ratio of: (Supported weight) / (Bridge self-weight)   will be determined for each bridge.  The bridge with the highest ratio will win.


All construction and material requirements will be checked prior to testing.  Any bridge that does not meet these specifications will not qualify for the competition. 

If, during testing of a bridge, it becomes apparent that materials not meeting the specifications have been used, the bridge will be disqualified.

If a disqualified bridge is testable (will fit on test platform and accommodated load plate) it may still be tested as an exhibition, but it will not qualify in the standings.

For questions about these specifications:

Damon Feuerborn 
(913) 469-8500 ext 4909

Matt Andring
(913) 469-8500 ext 3901