give a go or not?

[Frodolf]

So the worst happened. A fumed elm flat bow with a sinew backing, 63" ttt. I aimed at 45# at 26,5". Straight, easy stave, backing looked solid, 3" of reflex. I tillered it carefully and pulled to full draw about 50 times when I heard the dreaded "tick". My heart stopped for a second. Elm should be able to handle this kind of strain even without sinew so I figured it must have been my tiller tree or the wall (it was windy that day) that cracked, not the bow. I pulled it again, it showed no hinge, no loss of draw weight. I took it to full draw again. Another 20-30 times and there it was again, another distinct "tick".

I stopped. I've had it happen to me once before, the wood under the sinew cracking. That time I pulled the bow 3" farther than full draw and it showed a very obvious hinge and loss of weight afterwards. This time, nothing like that. The bow still looked good. But since I've already spent a so much time making the bow I figured better safe than sorry. I removed the backing, expecting to find a pristine back underneath, that it had just been the tiller tree or whatever. But, lo, there it was – an obvious crack running straight across the upper limb. 

The limb is about 2" wide and the crack little over half of that. It seems to only run through the outermost ring. It opens slightly when I carefully flex the bow. Had I not already tillered the bow, I'd remove the outermost ring, but If I do that now I'l end up with a far lower weight than I want. Unless I compensate with a massive backing, which I don't really want.

So, do you think I can just do the old superglue trick? I'm thinking, flexing the crack open just a little bit and cram in superglue and let dry, and then add a thicker backing than last time (2,5 layers instead of 1,5). Will that work, you think, or am I just spending another X hours on an already lost bow?

[osage outlaw]

If that was my bow I would not trust it.  Even with a sinew backing. 

[SLIMBOB]

+1 Outlaw.  Transverse crack across the back....that's an ender for me.

[PatM]

If it can't even hold itself together when starting out as one piece it certainly won't as a patch job.

[bubby]

Agree with all above, ye ol' superglue fix only apply's to cracks running with the grain

[Frodolf]

That was what I was afraid of. I think I'll remove the outermost ring just to see what happens. If the crack is just one ring, it might still turn into a bow eventually – just not the one I wanted. We'll see.

I think I know the reason why it happened. I think I was too eager to introduce reflex when I backed it. I strung it backwards about 6" when it had a draw weight of about 50# to 24". Must have been a compression fracture which then developed into a crack when bent the other way. Elm just don't crack like that for no reason. Even less so when covered with sinew.

How far do you reverse-brace when you back with sinew?

[bradsmith2010]

if you are going to string a bow backward,, its a good idea to heat it and gently pull it a little at a time,,while heating it,,
also once you have the bow tillered that far,, it might not be a good idea to string it backwards,, maybe just tiller it to brace,, and then slowly ,, brace it to backwards a little at a time,,

[BowEd]

I'm a fan of making reversed braced sinewed bows.Done 8 or 10 I guess that way.Different type woods too.It works good.I'd think elm is a very good wood to do it with.
If you were wanting 45#'s @ 26.5" finished.Tillering it to 20" in good tiller @  30# to 35 #'s could of easily got you your draw weight.Probably still a 65# bow yet for sure.6" was not asking too much for a 63" bow.I would of been more afraid of the belly crushing unless the belly was heat treated before sinewing.I sinew bows most times in 3  sessions a week apart.Reverse bracing it a bit more every time I sinew it.Some do it all in one session but reverse brace it just after sinewing it not before.Usually somewhere between 900 to 1200 grains of sinew altogether on a bow like yours would give a bow at least 20#'s if not more.