Bridge Building Tip Sheet

Use a small balsa wood saw (about $3) instead of an exacto knife to make cuts
Cut small notches to connect bridge components
Use a basic carpenter's glue
Yellow glues contain aliphatic resin, used in the majority of winning bridges
Fewer pieces mean fewer problems
Keep pedestals (feet) simple
Clamp glued pieces for about half an hour (use protective strips to avoid damaging the balsa). If you don't have any clamps you can use clothes pegs. C-type clamps are available quite inexpensively at Canadian Tire
Design for strength at the load application point
Construct roadway of thin, narrow strips of balsa
Don't glue down ends of road ways…they usually bend upwards under load
Use minimal support under roadway, except at load application points
Roadway must support a small Hot Wheels-type car
Most bridges bend inwards (as viewed from one end); consequently they require horizontal bracing
Write your team number prominently on a main horizontal beam of your bridge and on both sides of the bridge
Double check that a 40 cm-long board will fit between the pedestals (feet) of your bridge
Double check that a 5 cm cube will fit underneath your bridge and along your roadway. You can make a nearly perfect 5 cm cube from Lego bricks
Do not cover your bridge with any material. Glue should be used only to join components
Use light sandpaper (number 150 or higher) to gently clean your bridge and remove excess glue

Some common mistakes:

Using a single sheet of balsa for roadway (solution: cut into strips)

Making outside width 5.0 cm instead of inside dimension
Making overall length 40 cm instead of span (between pedestals)
Forgetting 2.0 cm height requirement at 40 cm width
Not allowing room for bolt(s) on test frame

Buying balsa wood? Check out our list of local (Vancouver-Burnaby) suppliers.


Copyright 1980-
Peter L. Vogel