How do I run a balsa bridge contest?

Short answer: write clear rules, build a rig that matches them, rehearse the day, and decide in advance how you will settle ties and disputes. Most arguments come from rules that can be read two ways.

Write the rules so they can't be misread

State, with numbers and a drawing where possible:

• The span, and whether it is measured between inner or outer support edges.
• The size limits and the clear space, and how they are measured.
• The load, where it attaches and what counts toward it.
• The mass limit, and what is weighed (glue, hooks, loading pieces).
• Materials and glue, and whether lamination or gussets are allowed.
• The scoring formula, any cap and the tie-break.
• What counts as failure.
• Rules on outside help, including AI tools, and whether students will be asked to explain their design.

Answer questions in writing, and share each answer with every team.

Build the rig

Make a test rig that matches the rules, and test it with sample bridges before the day. See how contests load a bridge.

Plan the day

1. Check-in: measure, weigh and tag every bridge.
2. Loading: add weight gradually, and record the final load and any failure.
3. Scoring: calculate and double-check, and post results.
4. Disputes: have a clear way to ask for a re-check.

Safety

Eye protection for everyone near the rig, a clear floor and a bucket that can't swing. See testing safely.

Our contest pages show how common rulebooks read, and where we found an unclear rule.