Osage recurve selfbow-Crack in the back!

[VanceMan]

I have been working on a 55" osage recurve ,with limbs 1 1/2" average width, for awhile now and I have just finished the early tillering stage and I braced the bow for the first time at full brace height.  After a few seconds braced I heard a low cracking sound and I carefully unbraced it and checked the back and found a small crack running across the grain.  I was always planning on adding 1 or 2 courses of sinew to the back, will the sinew save this bow? It will only pull about 40# right now. I think the main reason for the crack is that the growth ring I chose for the back was too thin (but I did so because I planned on using sinew). Any help is appreciated, thanks!

[Eric Krewson]

I have only seen these type of cracks in one bows back, mine. I didn't get them right away, it took years and thousands of arrows. I loved the bow but didn't trust the cracks so I bamboo backed the bow.

[VanceMan]

hmm. Maybe they don't go all the way through the ring? Idk.  Worse case scenario say that they do, you think sinew backing would fix it?

[huisme]

I'd try chasing the next ring, especially if it's thin.

[huisme]

I'll admit I've only worked a few pieces of osage, it seems to my locust-trained intuitions that almost half an inch is still really thick for forty pounds. If it is an issue the sinew, heat treating, and additional reflex can all up the poundage. Seems like a sound last resort

[VanceMan]

Okay so I just remeasured with the calipers, and I forgot that I hit it with the course sanding already and its at 4/16" right where the crack is at.  The crack is at midlimb and the bow tapers from a little less than a half inch at the fades all the way to 3/16" at the nocks. Im not sure I can still tiller it to 40# if I chase the next ring can I?  I have recurved the last 8" and the bow already has some reflex...how much poundage would a layer a sinew do me? thanks for all the input!

[mikekeswick]

You won't get much draw weight from one sinew layer. Maybe upto 5 lbs.

[VanceMan]

will the sinew layer keep the bow from breaking at that crack?

[huisme]

I really don't know about sinew's back-saving properties, haven't backed a bow with it myself and I'm pretty careful with my backs. Still thinking about the last resort here

Can you guess about how much removing the ring will cost you? Going from a flat profile to ~3" starting reflex can really up the potential poundage and force-draw curve, plus the heat treating itself has added as many as seven pounds for me, and then you've got the sinew which like Mike said would need to be more than one course for anything over five-ish pounds.

How thin is this ring? Pic?

[VanceMan]

Here are pics of both tips. As you can see the rings are pretty thin : /

Also here is a side profile of the bow.

[bubby]

According to your measurements your taper is all fubar, nearly a 1/2" at fades and mid limb on a 55" bow its 1/4" and from there only tapers 1/6" you should have a smooth taper from fade to tips any pics of it braced

[VanceMan]

sorry no pics of it braced  .  I don't wanna risk that again yet.  What should it taper to? When on the tillering stick it looked decent to me. The recurves are not as wide as the midlimb so I thought it best not to taper thickness too much for fear of the recurves being under too much stress.   What thickness should they be at? and also will a sinew backing take care of that crack problem? Thanks!

[wizardgoat]

I would not waste the time and sinew on a bow that will maybe survive.
Its very hard to see in the photo, but any crack across the grain is never a good thing.

[VanceMan]

Okay so I had a hunch so I grabbed my knife and carefully excavated the damage, a appears that just a small flake was all that lifted off. The damage was very shallow. What do ya think? Is it worth it to continue?

[Del the cat]

Maybe that was just a bit of the previous ring that hadn't been completely scraped away... like a small island?
From what I've seen it's an all or nothing thing. Just shoot it, it'll either explode or it won't .
If you really want to do something... maybe a rawhide backing will give some reassurance with minimum effort?
Del