How do you repair a broken balsa bridge or stick?
When a stick or joint breaks during building or before a contest, how to fix it: clean break, splint, replace the member, and when to just start over.
Updated · 1 min read
Short answer: for a clean break, glue a small overlapping splice or replace the member. Repairs add weight, so for a contest entry replacing a broken member is usually better than patching it.
Options
- Replace the member. Cut a new stick to the same length and angles, remove the broken one with a knife, and glue the new one in. This gives the cleanest result.
- Splice a clean break. Align the pieces, and glue a thin overlapping strip along the side. A butt joint on end grain alone is weak. See gluing joints.
- Re-glue a joint that opened. Scrape off old glue, check the fit, and glue again with a thin coat.
Tips
- Wick thin super glue into a hairline crack and clamp it.
- Weigh after the repair, since it adds mass. See weighing.
- Don't repair a compression member that snapped. It broke because it was too weak, so replace it with a better one. See preventing buckling.
After a test to failure
A bridge that has been loaded to failure has damage you can't see in every joint. Don't use it as your contest entry. See practice bridges.
Check whether your contest allows repairs on the day. See contest day checklist.