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ERC as a core?

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DarkSoul:
If you ain't breaking them....

The bow seems a bit narrow for a projected draw weight of roughly 100#. How wide is it exactly? And how far was it bending at what draw weight when it blew? A picture of the break might also help in getting an autopsy. But as Mike explained, a break can start in the backing, taking the core with it. As long as the belly is still in one piece, the break must have started in the back(ing). It could have been something as pathetic as a sharp corner at that drawweight...
Personally, I'm not liking anything over 1½" of reflex. I always get problems with lateral stability. My dream bow would have 2" of reflex glued in, ending up with 1½" after tillering. Especially with such a narrow ELB, the chance of getting stability issues with the reflex is very real. Although this most likely did not kill the bow, it might still be better to reduce some of that initial 3-4" of reflex in your future attempts. But it could also just be my own inability to deal with some reflex!
Another word of advice would be to taper that ERC core a little bit. Although I do think 1/4" thickness is adequate for this design and estimated draw weight, it is evident you were running out of hickory on the belly near the tips. I would taper the core, starting at midlimb, from the initial 1/4" to 1/8" at the tips. Again, this did not kill your bow, but it might still be an improvement for your next bow.

toomanyknots:
I feel you on the instability thing. That is where I feel a mirror is unmatched for tillering reflexed bows, unless you have a clamp on your tiller tree. Because with a mirror you can firmly hold the bow while you pull it, where with a tiller tree, it will just flip. It was pretty narrow, but that was what I ended up with after floor tillering. And that is considering the extra weight a reflexed bow will feel like, I thought anyhow. I wanted 80# or 90# @ 32" to start with, I just kept running low on wood at the tips, like you mentioned, so I went with it. And although I glued up 3" to 4", it only kept about 2" right after I unwrapped it. I feel this prestressed the backing, which is kinda cool, or would of been, if it didn't blow. I know the bow did not give up any of the 2" reflex, but, after it blew, and I pulled the laminates apart, the belly took a bunch of string follow, that it never had before it blew.

mikekeswick:
That erc has some pretty serious grain violations. I've neverused it so can't comment more about it in particular but if you are using a light 'risky' core material the grain should be perfect, especially if your core is so thick.
I have a feeling the core may have sheered along the fibers which started the break.
Some tips on these sort of bows.
Make a form for your glue-ups. Use a sheet of ply cut into strips then laminated together to give enough width. You need to be able to control where the reflex is. Hanging a weight off the middle will give you too much in the handle area and not enough in the mid to outer limbs - this is important!
Either taper your cores or make them 1/4 inch thick max.
Also you should definately NOT be able to 'pull apart the laminates'. If they came apart at all without being cut on a bandsaw or something then your glue-up was not good enough. What method do you use?
I'm not trying to critise  :) just pass on some of the things i've learnt about elb's. :)

toomanyknots:

--- Quote from: mikekeswick on March 11, 2013, 08:45:39 pm ---That erc has some pretty serious grain violations. I've neverused it so can't comment more about it in particular but if you are using a light 'risky' core material the grain should be perfect, especially if your core is so thick.
I have a feeling the core may have sheered along the fibers which started the break.
Some tips on these sort of bows.
Make a form for your glue-ups. Use a sheet of ply cut into strips then laminated together to give enough width. You need to be able to control where the reflex is. Hanging a weight off the middle will give you too much in the handle area and not enough in the mid to outer limbs - this is important!
Either taper your cores or make them 1/4 inch thick max.
Also you should definately NOT be able to 'pull apart the laminates'. If they came apart at all without being cut on a bandsaw or something then your glue-up was not good enough. What method do you use?
I'm not trying to critise  :) just pass on some of the things i've learnt about elb's. :)

--- End quote ---

Critise all you want, as long as you don't criticize,  >:D. Naw, just kidding around, please always feel free to criticize all you want, I am surprised anyone would take on the huge task of pointing out any of the hundreds of things I am always doing wrong anyway,  :). Yes, I don't think the glue up went too well either. I blame the cedar honestly, although everyone else gets good glue ups with it. When I pulled the laminates apart, the cedar left like a veneer of cedar on each piece of hickory. Some pieces broke off, but most of the cedar delaminated from the pieces of hickory. It is very light, brittle, dusty wood, if you know what I mean,... it sands to very fine dust. I tried to clean off the surfaces as good as I could before glue up. The bond was definitely not "stronger than wood". (I used TB3) I wonder if I squeezed too much glue out? And I tapered the belly lam to get an even reflex, most of the reflex was in the outer limbs actually. Seeing as the hickory backing was an eighth of an inch, and the core was about a 1/4", to get a good 1/2" at the tips I tapered the belly hickory lam to 1/8" thick at the tip before glue up. It worked pretty good to get a nice even perry reflex.

ionicmuffin:
so maybe it wasnt perfectly smooth? not sure, by your description it seems like the wood was weak. so not sure if there was some major factor there that caused that. could be the glue up.

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