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Today I tested my final design for invitationals. It held a considerable weight and seemed to be doing well, until it completely broke into dozens of pieces all at once. When checked the pieces, I found that every single one had come apart at a glue seam - not a single piece of wood had actually been snapped. I'm not exactly sure why this happened. I used a good, strong, fast-drying CA glue. Any ideas on what might have happened and how to fix it? Any advice would be greatly appreciated!

tarsavage wrote:Today I tested my final design for invitationals. It held a considerable weight and seemed to be doing well, until it completely broke into dozens of pieces all at once. When checked the pieces, I found that every single one had come apart at a glue seam - not a single piece of wood had actually been snapped. I'm not exactly sure why this happened. I used a good, strong, fast-drying CA glue. Any ideas on what might have happened and how to fix it? Any advice would be greatly appreciated!

Just because that's what you saw in the end doesn't mean the glue seams were the initial cause of failure. I would think it's likely that most of the glue seams were secondary failure from shear stress.

You probably have a bad bottle of glue. I remember seeing comments about one CA that had changed their formula and several serious builders were complaining about it. CA can go "bad" after it has been opened. Humidity is a killer of it.
I would go to another brand and try that.
CA should not fail with sheer alone. Then it begs the question-How well did you glue it? Enough, too much or?? Thin CA should have partially soaked into the wood and when it broke at the joint, it should have torn out some of the wood on some of the parts. The glue is supposed to be stronger that the wood.
Possibly oil on the wood from your handling??

If possible, slow-motion video it and may tell you what happened first.

jinhusong wrote:If possible, slow-motion video it and may tell you what happened first.

Yes, I would advise always slo-moing the break because it helps in many ways that math could not.

You may also want to use a safety cage that confines the damage to only the primary failure and will not allow secondary failures, so you don't need to wonder which came first.