What is a gusset and do I need one on a balsa bridge?
A gusset is a small plate across a joint. What it does, when it helps, its cost in weight, and why many contests allow or ban it.
Updated · 1 min read
Short answer: a gusset is a small flat piece, usually thin balsa sheet, glued across a joint where sticks meet. It adds glued area and holds the joint together, but it adds weight and some contests ban it. You don't need one for every joint.
What it does
Where several sticks meet, the glue area between them may be small. A gusset glued across the faces adds a larger glued patch to carry the force, and stops sticks from pulling apart or twisting.
When it helps
- At a joint where sticks meet at an angle, especially one that ends on end grain. End grain is the weakest place to glue. See gluing balsa joints.
- At the busiest joints, near the middle of the span, where forces are greatest.
The cost
Every gusset adds balsa and glue. Use them only where a joint would otherwise fail, and make them as small as will do the job.
Check the rules
Rules differ. Some contests allow gussets of a stated thickness and size, some limit how many, and some ban them. If they're banned, build joints from overlapping sticks instead. See reading your rulebook.