Primitive Archer
Main Discussion Area => Bows => Topic started by: Mesophilic on March 27, 2020, 07:04:31 pm
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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.
(https://66.media.tumblr.com/678b9145d79e39eae93d6d0747c6c32b/f0d44edc5607e411-04/s2048x3072/81bedd1fee09dfd9d39a85e5f8a544da9d915bb0.jpg)
(https://66.media.tumblr.com/d840cda43243ff1eada41572aa636896/a1f8f66f98babe18-29/s2048x3072/15b84b4a4f155f57271a7010f54fd65f33dadf22.jpg)
(https://66.media.tumblr.com/457dea03d1893e205019e8a5462d5144/42afac265de0c6fc-b5/s2048x3072/c0f225dd05685269e46a80e5c6b6488ba2f47bee.jpg)
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My first guess would be clamps to tight and a starved joint...
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Nope. Plate tectonics. You can't have THAT much grain runout, even on a backed bow.
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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.
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Yeah I was gonna say the grain sheared. Just couldn’t hold the compression.
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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
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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.
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Thanks for all the insight guys, I appreciate it.
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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.
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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?
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All of the above...
Poor glue line, poor grain.
Del
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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~
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The glueline IS also bad but with that grain it was going to crumble at some point.
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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
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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.
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Ipe aint Hedge Apple. Ive made a bunch of boo Ipe, or boo and S American rosewood, boo hedge, boo hickory, boo Waiwi boo, etc , etc . Had my own 70ft tall boo thicket in a gulch at my Ranger Camp. So, i did LOTS of Bamboo work.
Eric is right adhesion was the issue but just ipe on belly can be picky. Just a little to much thickness on boo on ipe will blow it out every time.
HH~
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The boo is .190 to .200 measured across the cross section of the crown and a pair of calipers, and .140 at the edge.
I didn't do the glue up on this stave so I can't answer any questions on the process. Figured I'd help support a younger bowyer and have a project to work on during all this virus shutdown. We'll see how he choses to handle the situation and maybe the info you guys are sharing will help him in the future.
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The bamboo backing appears to be thin enough. How thick is the ipe belly? If it is relatively too thin, it still could have been overpowered by the bamboo backing. If it is all about the glue, the bow can be saved, even if you might have to add a full-length belly overlay strip. Another rather thin bamboo strip on the belly would be a good experiment and exercise in gluing bamboo on ipe. Better sand and clean out the old epoxy real well. You can tiller it on the sides or even the bamboo overlay itself. Good luck, depending on how much you are willing to bother with it.
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Why on Earth would you want to do enough repair work that could be spread over three new bows?
If a belly strip like that is considered OK then Rudder bows was a quality bow source.
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Why on Earth would you want to do enough repair work that could be spread over three new bows?
If a belly strip like that is considered OK then Rudder bows was a quality bow source.
I personally make mostly self-bows. I probably made less than a dozen bamboo backed bows. But it appears that my bamboo backed bows are performing better than self-bows. So I have been gathering up some exotic hardwood, just in case I want to experiment more. If backed bows are acceptable, why not a tri-lam, even though I don't remember making one intentionally. I at most did try such a repair once or twice over the last ten years. I'm considering a bamboo backed bamboo bow for this year.
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EA40 is ok epoxy. You would be much better served with a epoxy that was designed for laminating wood lams.
What would be "better" epoxy? EA40 is very good bow gluing epoxy. I have been using it years and now glue failures. So, are there better bow epoxies?
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Huntsman Epoxy.
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Why on Earth would you want to do enough repair work that could be spread over three new bows?
If a belly strip like that is considered OK then Rudder bows was a quality bow source.
I personally make mostly self-bows. I probably made less than a dozen bamboo backed bows. But it appears that my bamboo backed bows are performing better than self-bows. So I have been gathering up some exotic hardwood, just in case I want to experiment more. If backed bows are acceptable, why not a tri-lam, even though I don't remember making one intentionally. I at most did try such a repair once or twice over the last ten years. I'm considering a bamboo backed bamboo bow for this year.
That has little bearing on it being a good idea to repair an awful mess and then turn that into a tri-lam.
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I have to go with the bad glue job. And, it is Ipe. When I glue anything to Ipe I scrub it down real good with acetone and sometimes oven cleaner.
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That has little bearing on it being a good idea to repair an awful mess and then turn that into a tri-lam.
I don't sell or even give away my bows. All my suggestions are for learning and experiment. We learn more from our failures.
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Huntsman Epoxy.
Hard numbers and facts would be nice, and some reasonings too. Comparing for example Araldite 2011 and EA40, pure strength values are quite similar. But EA40 has for example much higher glass transition temperature, which is very good feature.
This case, it was not the glue's fault but user's fault. I have made some gluing mistakes also and good gluing is not always so simple. There are many issue, which are affecting to the quality of gluing. Usually the instructions for use of the glue are valid.
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That has little bearing on it being a good idea to repair an awful mess and then turn that into a tri-lam.
I don't sell or even give away my bows. All my suggestions are for learning and experiment. We learn more from our failures.
This wasn't his failure.
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Pat M hit it on the head.
HH~
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That has little bearing on it being a good idea to repair an awful mess and then turn that into a tri-lam.
I don't sell or even give away my bows. All my suggestions are for learning and experiment. We learn more from our failures.
This wasn't his failure.
Was it the failure of the bow? If you are not interested in investigating the failure further, why do you bother to keep on reading the thread? Not sure what you are trying to achieve here.
I still wanna know how thick was the ipe belly.
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The guy who glued it up is responsible. My purpose is to stop people from trying to rectify mistakes made b.y others.
And to stop noobs from rushing into business before they have even mastered the simple side of things.
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Diagnosis: Broke across the belly first, because of short grain. Glue line not optimal adhesion, is apparent, but the trouble did not start there. 40 grit sanding or toothing plane grooves as have been mentioned earlier, would increase chances of success, as would a pre glue wipe down with acetone.
A poor glue line can delaminate one entire limb, and the underlying belly wood won't break if the grain is reasonably straight. It will also happen early in the tillering process, during floor tiller to low braced string work.
I had a similar break in the past, with an elb with short grain across the belly lam. Deep rounded belly and narrow limbs are the riskiest combination with short grain, but apparently it happens on flat bows too.
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The guy who glued it up is responsible. My purpose is to stop people from trying to rectify mistakes made b.y others.
And to stop noobs from rushing into business before they have even mastered the simple side of things.
I never pretended to be an expert. But for the last ten years on and off I read almost a dozen books on "primitive" bow making and made more than 50 bows. I even made almost a dozen bamboo backed bows without even realizing doing so. And I basically ask questions here and say what I would do as a hobbyist if I am in the position of other posters who are asking questions.
As I review your reply here, first it was tectonics. Then it was the bad glue-up. Then it was not the original poster's fault. Nobody ever accused anyone for the failure. It was either the ipe's grain runoff or the careless glue-up. Someone suggest the glue itself. But more likely the glue has gone bad or the gluing surfaces was not properly prepared or too much pressure was used.
I'm more interested in the question of whether a bamboo backing can overpower a weak belly wood. The wood can be too weak because either it has bad grain run-off or it is relatively too thin. I don't think this issue has been resolved here. There are almost limitless case by case questions to be answered if we sincerely pursue this hobby. Better not presume to know the answer without investigating the details.
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The belly wood suffered from plate tectonics due to the grain running practically diagonally through the limb and the poorly applied backing allowed that movement to pry the bow apart.
You can clearly see that at spots the bamboo was a cable backing relatively.
Someone else glued up the bow, not the OP.
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I have to say I wouldn't try and repair that
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The belly wood suffered from plate tectonics due to the grain running practically diagonally through the limb and the poorly applied backing allowed that movement to pry the bow apart.
You can clearly see that at spots the bamboo was a cable backing relatively.
Someone else glued up the bow, not the OP.
We are not disagreeing much. The bow failed because the glue-up was not good AND/OR the belly grain run-off was terrible. Many people here were satisfied with just one simple answer or answering the question from the perspective of their own expertise in how bamboo backed bows normally fail.
The failure might not have happened if the belly ipe was at least as thick as the bamboo backing, or the glue had not gone bad, or the glue-up was well prepared and done right, or if the bamboo back was thinner, or who knows what else. Way too many variables and that's often what fascinates us in making "primitive" bows. I'm often quite relentless in questioning, probably because of my training.
Does the relative thickness of the bamboo backing and the belly wood matter at all? In this case, it probably did not matter at all. But someone here thinks the thickness of bamboo backings does not matter at all. However the consensus is probably that the bamboo backing needs to be rather thinner than thicker relative to the belly wood in most cases. Case by case always?
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I have to say I wouldn't try and repair that
I would rather try to get the bamboo backing off with heat and reuse it. But it appears today I have too much time on my hands to think about all kinds of learning possibilities. Sorry.
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I got a run of bad bamboo one time, it all popped splinters. I replaced the bamboo on several bows before I trashed the rest of the 25 piece bundle of bamboo slats. I would grind the bamboo off with a 36 grit belt to just above the glue line, I didn't take all of the bamboo off, I left about 1/16" and glued my new bamboo to this. I never had one of these repairs fail.
I never replaced the belly wood because I never had any fail, I have replaced a limb on several osage bows just to see if I could save an otherwise good bow, never on a bamboo backed one. I guess one couple salvage the bamboo from the aforementioned bow but bamboo is cheap and readily available, I would trash everything and start over.
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I guess I have been watching too many forensic pathologist movies lately. I still like to organize the possible causes of the failure in the order of plausibility, in the form of simple questions. This is just a guesswork of a hobbyist.
1. How old was the epoxy? Gone bad?
2. Was the bow glued up pre-stressed?
3. Was the Ipe belly bend tested at all? Grain runoff checked?
4. Was the Ipe belly well prepared? Cleaned with acetone and/or sanded just before glue-up?
5. Was the glue line good enough?
6. How was the bow clamped in the glue-up? Too much or too little pressure?
7. What was the temperature of the place?
8. How thick was the belly wood? Too thin compared to the bamboo backing?
Is anyone still interested in answering these questions or any other ones?
Is any of the question, especially #8, irrelevant?
How many negative answers will constitute the sufficient cause?
Just about any one of them? Several of them combined?
I guess it's time to get back to the movies.
Be safe, stay at home as much as possible.
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All of the key points have been addressed and make the others redundant.
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All of the key points have been addressed and make the others redundant.
In what combination? So far, I'm the only one who is asking the questions #1 and #2. Are they irrelevant?
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Yes.
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Yes.
I once tested a several years old epoxy. It mixed well and was tacky enough soon. Don't remember how warm it got. I glued some wood strips to test. It never cured completely. It was just very tacky indefinitely. It was turned into a "sticky note" epoxy. It can be very useful in many ways, but not for bow making.
More questions: How long ago was the bow glued up? Was this question answered? Does the cured epoxy last indefinitely? What if it has been frozen and thawed?
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You do see those clear spots across the bow width, no? Those would be gaps a light would shine through. Glue only matters if it's actually gluing something together.
Those areas are unsupported in shear which this bow is already going to struggle with if glued up perfectly.
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I'm pretty late to the party here but if I could offer my 2 cents, I think grain run out was the biggest factor. If you look closely you can see that the grain not only crosses the belly lam from left to right at about 45 degrees, it also crosses from back to belly at about 45 degrees. It looks like the fibers on that lam are only about 1/2" long. The board must have been cut from a seriously crooked log. Cut a 4x4 post at 45 degrees, move up an inch, and make the same cut again. The thin slat you end up with should have pretty similar grain to this, and will be very fragile.
It looks to me like the glue stuck to the bamboo for the most part. The brown coloration on the glue side of the bamboo is bits of ipe fibers stuck to the bamboo. My guess is that the shiny parts on the ipe are where there were air bubbles in the glue up. This makes me think glue was spread on the ipe but not the bamboo, because I don't see any shine on the bamboo (though that could just be the picture). So, maybe not the best glue job? But with those short fibers on the belly I think the best glue would have still allowed this failure.
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If you look at the pictures you'll see exactly where the failure started, right where there is a void in the glue. This was not a failure due to bad core wood. As I said before, it was due to bad glue-up.
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Marc, I can see getting away with a long diagonal runout of grain across the length of the bow but that runout almost vertically through the depth looks like a killer.
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Marc, I can see getting away with a long diagonal runout of grain across the length of the bow but that runout almost vertically through the depth looks like a killer.
It's not. As long as you have good glue-up a bow like that will survive
P.S. Here is the top limb of a bow I made last year. You can see the grain in the wood is a bit wonky. I've shot this bow quite a bit