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ERC as a core?

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toomanyknots:
I have been hyped up lately over using erc as a core. It is beautiful and light weight. I have some of it. Everything seems to be falling into place,  ;D. I have recently made a hick, erc, hick trilam. It was really nice, and wasn't wanting to give up a tiny bit of the 2" of perry reflex. I had it bending pretty good on the long string, the bend was looking good. And BAM explosion. Now, it was feeling like a bow would feel, that would eventually end up at 90# to 100# @ 32" if tillering went smooth, maybe a bit less. It did have a good 2" reflex. The back did break, but so did the core. I don't know which one went first! I mean, I have no idea how the core could go first, but I don't trust erc.  :) The lamination didn't seem great either, but it seems the erc is just brittle and hard to get a good lamination. The joints were perfect, I don't think it was glue starved. But it might of been. It did have a good amount of reflex, which would of been hard on the back. But if was freaking straight grain riftsawn hickory! The core was 1/4", the backing was 1/8". I have read of erc being used as a core in elbs, and making record breakingly fast bows. I just don't like big heavy dense longbows either. They are not my cup of tea. I would love a lightweight core to use, that is also as beautiful as erc. But I am starting to hate erc.  :) Btw, it was a completely clean knotless piece. I thought, with the erc being samwiched, there wouldn't be nothing to fear except set, which clearly was not happening either. AHHHH! >:(

ionicmuffin:
I would think it would make a nice backing, or even a belly because the ERC bow i had been working on failed in tension not compression. I dont see how the core could go first, as far as i understand, the core does very little work in comparison to the back and belly, so if you can make a backed ERC normally, then this should be no different. Did you see what caused the back to go? bad grain in that area? knot? ect?

mikekeswick:
Without having it in my hands it's impossible to tell how/why it broke.
Cores are not in tension or compression however they do feel shear forces.
Light weight cores are not really the way to make the fastest bows perfect tillering, weigth distribution along the limbs, thickness to width ratios, bend tests to check the elasticity of the particular wood you are using etc are the way to go.
If the back broke then the core would break too unless the glueline was terrible.
If you don't trust erc then the way to find out wether that lack of trust is justified is to do some bend tests with it and then make some miniture bows. Make the widths/lengths to scale and it will act exactly the same as a bigger bow.
If a wood survives being a mini bow it will survive as a big un.

toomanyknots:
I am guessing (hoping I guess) that the back failed from being over tensioned, it did have a steady 2" perry reflex. But I am thinking the erc has something to do with it... whenever a bow blows up, and erc is in the area, I am a little suspicious,...  ;D. Maybe the belly and the core came unlaminated, and this caused the back and core to break at once, as the belly was in one piece. Like I said,it blew up pretty much, the core was broken here and still intact here and there, etc. The backing was straight grain rift sawn hickory, almost perfect with very little run out, and the bend was perfect at the time. Just made a heavier bow with an identical piece from the same board. No clue. It doesn't seem the easiest thing to get a good glue up with erc, yet I see everyone else do it fine. I am guessing I am the failing factor here,  :). I will try it again, but without the reflex, and maybe come down a bit in weight, and hopefully it will work out. I was surprised to see it was taking no set at the time, and there was very little hickory towards the outer limbs. It was nice and light in the hand, and didn't wanna give up a smudge of reflex, man it was coming along nice before it blew. Has anyone else on here tried erc as a core in a heavier bow?

toomanyknots:
Here are a couple pictures I took before it blew:



It's about 3" (maybe 4"?) perry reflexed, the belly was tapered to give an even reflex profile. When I took it off it had about 2" stay in:











 

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