How do you build a roadway or deck for a balsa bridge?
Some contests require a deck to carry a car or a loading platform. How to make a light deck, support it, and keep it from adding weight or twisting the bridge.
Updated · 1 min read
Short answer: make it as light as the rules allow, support it every few centimetres by cross-beams on the chords, and check what must roll or sit on it.
Find the rules first
Check if the contest requires a deck at all, its width, whether a car or a block must travel along it, whether it counts toward the mass, and how the load is applied to it.
Design
- Use cross-beams across the two chords every few centimetres, so the deck is supported.
- Lay thin strips or sheet across or along the beams. Thin sheet is light but easy to dent, and weak across the grain.
- Keep it flat and clear. A car or pass-through block must not catch on a glue bump.
- Brace it. A deck also stiffens the bridge sideways if it is fixed well, which helps against twisting.
- Mind the load point. If the load sits on the deck, make the deck stiff there.
Weight
A deck is dead weight, so make it just big enough. Weigh materials before you choose. See weighing.
See deck or through truss and designing around the loading block.