what sinew can do to a bow...

[sonny]

Just thought y'all might like to see what sinew is capable of,,though I'm sure some already know.

The bow in the pics below is a short sinew backed ERC sapwood bow similar (where dimensions are concerned, fairly close I suppose where profile is concerned) to the Ishi bow also posted below. As far as I know Ishi's bow isn't sinew backed, mine is for safety's sake.
The first couple of courses of sinew was applied, some minor floor tillering was done, then another course of sinew was applied which is when the belly split.
I talked it over with a buddy who suggested that I fill the crack in the belly with glue and sinew, a thought that had crossed my mind as well.....
unless one of y'all has a better suggestion ??.......

     
 

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[sonny]

trying to post the pic of Ishi's bow....

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[radius]

harsh

[FlintWalker]

As long as none of the split runs off the side, I'd try to tiller it out.  If you succeed at that, you could put some sinew wraps along the limbs.

[ricktrojanowski]

I've read about that happening.  I also read somewhere that you can tape the belly of the bow to try to prevent the drying from doing that.  But I've never seen it.  I would just try to tiller it anyway,  you have nothing to lose now.  If it survives it will be one wild looking bow.

[Pat B]

This is a sinew backed bow that Jay Massey made. It was given to me by a friend. You can see how the sinew has pulled the belly apart just like on your bow.  Jay said this would happen with wood that was well seasoned(at least with osage) when backed with sinew. He may have also mentioned about putting tape on the belly to prevent the moisture from escaping there and causing the checks.
  I think I'd do as others have mentioned and add sinew and glue into the check and maybe add a wrap or two also along each limb.

[M-P]

Hi,  I haven't had this happen yet, but it is a fairly well known possibility.  Jim Hamm mentioned it in his book from the 80's and suggested that it might be due to moisture from the glue, etc... etc.  The same thing occasionally happens when building horn belly bows!  (That last from A. Karpowicz' book on Turkish bows.)  I don't think moisture loss from the belly is likely on a horn bow!  Remember that glue and sinew shrink in all directions while drying.   Side to side shrinkage on the back of the bow will place the belly under side to side tension and can cause cracks.  Jim Hamm  and Karpowicz both report no deleterious effects from shallow cracks.   Just keep shooting.  For deeper cracks you may want to take some of the advice about wrapping with sinew.  Cracks that run off the edge probably are fatal to the bow.
Taping the belly while the sinew is drying is supposed to reduce the chances of cracking.  Karpowicz suggests gluing  a strip of cloth on the belly and then removing the cloth once the sinew is fully cured. 
 Ron