ERC sinew trust

[Kidder]

So I’ve been working a sinew backed ERC bow for months now and am having some potential catastrophic failure issues popping up. There was a hinge and at that spot the ERC has cracked on the side and through the back under the sinew in 3 places now. It’s 65 inches TTT. I’m at 27 going for 30. I’ve filled the cracks and unbraced it and the reflex has clamped it and each time those appear to be holding but a new crack pops up. Can I trust it? If it fails will the sinew prevent explosion?

[Bob Barnes]

I'm watching your progress, but I have never had any luck using the heartwood of ERC.  I know several people that make very nice ERC /sinew bows, but they only use stave sapwood.  Good luck.

[Kidder]

I'm watching your progress, but I have never had any luck using the heartwood of ERC.  I know several people that make very nice ERC /sinew bows, but they only use stave sapwood.  Good luck.

That’s interesting. I’ve made a number of good heartwood ERC/boo bows.

[superdav95]

Kidder.  The sinew will prevent an explosion but not necessarily a failure of the wood.  How much sinew did you put on the back.?  You may be crushing the heartwood under the sinew.  Just curious.  Did you have the erc bow at brace prior to sinew or partial tiller or full tiller?

[bradsmith2010]

wrap that area heavily,, and only draw to 27

[Kidder]

Kidder.  The sinew will prevent an explosion but not necessarily a failure of the wood.  How much sinew did you put on the back.?  You may be crushing the heartwood under the sinew.  Just curious.  Did you have the erc bow at brace prior to sinew or partial tiller or full tiller?

I doubt it’s crushing the ERC as the failures seem to be in tension under the sinew. I did 3 courses of sinew with at most 3 total oz. I floor tillered it good before sinew. Maybe I rounded a back a little too much before sinew?

[superdav95]

Ya it’s hard to say really.  I don’t thing a rounded back would be a problem with sinew.  I find with sinew on these types of bows they crown a bit anyway.  I think is just the wood then that’s found a weak spot.  I think I’d be putting some ca glue to it and moving forward to see.  The reflex isn’t that extreme either so should be fine.  You had it bending good before sinew so any issues with the wood would have popped up prior most likley.