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Common mistakes first-time balsa bridge builders make

Ten mistakes that cost points or break bridges: missing a rule, too much glue, loose joints, long compression sticks, no practice and weighing too late.

Updated · 1 min read

Short answer: most lost points come from missed rules, sloppy joints, too much glue and building only once.

  1. Not reading the rules closely. A missed clear-space or size rule can disqualify a good bridge. See reading your rulebook.
  2. Too much glue. It adds weight and weakens joints. See gluing joints.
  3. Gaps in joints. A joint with a gap is much weaker. Sand until no light shows through.
  4. Long, thin compression members. They buckle early. See preventing buckling.
  5. Butting end grain against a side with no overlap. See why joints break.
  6. Using sticks at random. Weigh and sort them. See choosing sticks.
  7. Dull blades. They crush instead of cut. See cutting balsa.
  8. Building only one bridge. Practice teaches what no plan can. See practice bridges.
  9. Weighing too late. Weigh as you build and again before the contest. See weighing.
  10. Skipping cross-bracing. A bridge can twist before anything breaks.

Fix the first three and most beginner bridges improve a lot.