Bamboo backed hickory delaminated

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Bamboo backed hickory delaminated

jtester
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jtester
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Joined: 26 Dec 2014, 17:15

27 Dec 2017, 18:12 #1

I was building my first bamboo backed bow, a hickory board with a planed bamboo backing.  It delaminated at the junction of the bamboo and the tip overlay when I first put it on my tillering board.  I had rasped the bamboo off the hickory at the overlay so I would have a overlay/hickory joint and that's where the failure started.  Right at the joint, the glue let go of the bamboo, but an inch or so towards the handle, the glue held and the hickory split.  I used Unibond 800 epoxy.  Should I have done the overlays differently, or maybe left them off entirely?  I'm pretty disappointed, I had a lot of hope for this bow.
Any ideas or suggestions would be appreciated.
Thanks
Jim
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jtester
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jtester
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Joined: 26 Dec 2014, 17:15

29 Dec 2017, 12:53 #2

I've studied this thing for two days.  At first I thought my mistake was removing all the bamboo where I applied the tip overlay.  Now I'm not so sure.  I watched a couple you tube videos and they indicate that the glue joint should be stronger than the wood itself.  If that's true, butting the overlay up to the bamboo instead of gluing it over the bamboo wasn't the problem, or at least not all of it.  As I mentioned, the bamboo separated from the glue and hickory right at the tip overlay.  It looks like the glue joint was faulty.  I'm going to try another backed bow and see if my theory is correct.  If I could post pictures I would, but so far I haven't had any luck.
Jim
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Quest for fire
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Quest for fire
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Joined: 22 Mar 2007, 06:19

29 Dec 2017, 20:45 #3

I admire your aplomb.
If I were to break such a bow when almost finished there would be a lot of unmentionable words in my thread.😣
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jtester
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jtester
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Joined: 26 Dec 2014, 17:15

30 Dec 2017, 00:31 #4

It's not my first bow blow up, but I was disappointed.  
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burnbarrel
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burnbarrel
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Joined: 11 Sep 2008, 19:02

30 Dec 2017, 15:37 #5

Following. Thanks for posting. I'm getting ready to start my first bamboo backed bow.
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jtester
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jtester
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Joined: 26 Dec 2014, 17:15

14 Jan 2018, 14:32 #6

Sorry for the delay in posting, a friends daughter wanted to learn to build a bow so I took two weekends helping her.  I'm sure my problem with the first bow was a bad glue joint.  When I use wood glue, I apply it to both surfaces being glued, but when using epoxy, I heard I only needed to apply it to one surface.  That was the cause of the first blow up.  The glue didn't adhere to the bamboo completely.  This time I put glue on both surfaces and it was apparent that the bamboo resisted the glue a bit.  I put lots of glue on and things came out perfect.  The bow pulls about 45# at 27".  I shot about 50 arrows yesterday and it's sweet.  I'll try to figure out how to post pics again and post some when I get the finish on.
Jim
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