Bow fail diagnosis request

[Mesophilic]

Would like to see what you guys think caused this bow failure.

Bow was 66" long, bamboo backed ipe, laminated with EA40.

Thanks, guys, I appreciate it.

[bushboy]

My first guess would be clamps to tight and a starved joint...

[PatM]

Nope.  Plate tectonics.  You can't have THAT much grain runout, even on a backed bow.

[BowEd]

Yes...What Pat means is grain run out in too short of length span.
The glue side does look too dry too or not sized well enough.

[aznboi3644]

Yeah I was gonna say the grain sheared.  Just couldn’t hold the compression.

[mmattockx]

Nope.  Plate tectonics.  You can't have THAT much grain runout, even on a backed bow.

Yes...What Pat means is grain run out in too short of span length.

Wow. I never would have expected that to be possible, even at that grain angle. Very instructive and a good warning to us rookies that the grain has to be reasonably straight, even on the belly.


Mark

[willie]

if the bright spots on the ipe are spots where there was not good adhesion on the bamboo, then I would say the belly failed where it did because of a glue failure. as for why it failed, I think pat is correct.

[Mesophilic]

Thanks for all the insight guys, I appreciate it.

[scp]

Definitely glue failure. Possibly too thick bamboo backing. How thick is the backing? If it is not too thick but still intact, I would love to see the bow cleaned up and glued back together, at least for experiment.

[bownarra]

Definitely glue failure. Possibly too thick bamboo backing. How thick is the backing? If it is not too thick but still intact, I would love to see the bow cleaned up and glued back together, at least for experiment.

I've been making lam bows glass and wood for 15 years that isn't a 'glue failure'. Shady grain on the belly lam is the cause.
Regarding the glue there are too many variables.
What has the thickness of the backing got to do with anything?
Why on earth would you glue that back together.....it would do the same thing at best. Main thing being that the pores the glues 'ran into' are now filled so good luck gluing again. How would gluing it back together alter the grain run out on the belly?

[Del the cat]

All of the above...
Poor glue line, poor grain.
Del

[HH~]

Did you tooth the boo side of that lam?

Looks like you glue stayed on Ipe but not the boo. Which is sometimes not the case. Looks like you have separation from Bamboo.
EA40 is ok epoxy. You would be much better served with a epoxy that was designed for laminating wood lams. A slim piece of hickory sandwiched in there would have went a long way in saving that ipe or better Ipe inbetwix the the boo and hickory.

Lots of folks think ea40 was made for what bowyers use it for. It was not.

I can tell your glue surfaces were not roughed up enough. Why the glue looks glassy upon failure. You can either tooth the surfaces or sand to 40 or 60 grit. The Ipe would have lasted a bit but prolly would have given up the ghost being as it was on belly and not sandwiched.

HH~

[PatM]

The glueline IS also bad but with that grain it was going to crumble at some point.   

[Marc St Louis]

I've made several bows with that much grain runoff without a failure and some of them were high stress RD bows.  I would say glue

[Eric Krewson]

I don't know about ipe but I have made tons of bamboo backed osage bows with terrible grain runout and never had a failure. I see a bad gluing surface and very little glue adhesion which caused the bamboo to come loose and let the belly wood fail.

I have always made most of my bamboo backed osage bows out osage with tight rings, sometimes even propellor that I cut through instead of straightening first. I would say I have made 40 such bows at least with no runout failures.

Here is a typical example of my normal osage belly for bamboo backed bows.