Build & Load-Test a Spaghetti Bridge
A classic structural engineering exercise — design a bridge, then find out exactly how much weight it can hold before it fails.
Related field: Civil Engineering
Mission Briefing
Objective
Design and build a bridge out of spaghetti that spans a fixed gap and holds as much weight as possible before it breaks.
Constraints
- The bridge must span the gap you chose without touching the ground in between
- Only spaghetti and glue are allowed as structural materials
- Weight must be added gradually and evenly at the center, not dropped or applied unevenly
Concept You're Testing
Truss design and load paths — why triangles resist collapsing sideways the way squares don't, and how a structure's shape determines where it's strongest and weakest.
What You'll Need
- 1–2 boxes of uncooked spaghetti
- Hot glue gun (with adult supervision) or white glue
- A ruler or tape measure
- Weights for testing — books, canned food, or water bottles work well
- Two sturdy surfaces of equal height (chairs, boxes, or thick books) to span a gap
Ask an adult before using a hot glue gun — it heats up enough to burn skin.
Instructions
- 1Decide on a span length — the gap your bridge needs to cross. Start small, around 20–25 cm (8–10 inches), for a first attempt.
- 2Sketch your design before building. A truss pattern (triangles, not squares) is much stronger than a flat bundle of strands — squares collapse sideways, triangles don't.
- 3Bundle 3–5 strands of spaghetti together and glue them at the ends to make thicker, stronger beams instead of using single strands.
- 4Build the two long side rails of the bridge first, then connect them with triangular cross-supports.
- 5Let all glue joints dry fully before testing — a joint that looks solid but isn't cured is the most common cause of an early failure.
- 6Place your bridge across the gap and add weight gradually and evenly at the center, pausing between additions.
- 7Note the weight at which it starts to bend, then the weight at which it actually breaks — these are two different, both useful, data points.
- 8Look at exactly where it failed. That tells you where the design was weakest, which is the most useful part of the whole exercise.
How to Measure Results
Record the weight at which the bridge first visibly bends, and the weight at which it actually breaks — two different, both useful numbers.
Skills You'll Practice
- Why triangles are structurally stronger than squares (truss design basics)
- The difference between a structure bending (still working) and failing (broken)
- How load travels through a structure, and where forces concentrate
- Reading a failure to understand a design's weak point, instead of just seeing it as a loss
If It Doesn't Work the First Time
That's normal — this challenge follows the same design process real engineers use. A failed test just tells you where to go back and improve.
Figure out what problem you're actually solving, and what would even count as success. Skip this step and jump straight to building, and a lot of bad designs happen right here.