preventing sinew drying cracks

[sonny]

speaking of ERC by the way..........

...so when I rough out a bow that I plan on sinew backing I will generally round the back before applying sinew,, mostly as I don't care for the look of a flat back (though I may have to get over it). unfortunately the last one I did cracked so severely along the edges of the limbs that I'm worried about proceeding. I went so far as to squeeze some Gorilla glue in the cracks but the foaming action of the glue left voids,, when I hoped for a good "filler".
so I think I'm going to soak the sinew off of that bow as well as another that I broke some time ago. my concern is that the next one may crack.
looking for suggestions on how to keep the limbs edges as well as belly cracks from forming.
if I think about it I'll post a pic or two tonight to show how wide these cracks are.....

[episaacs]

I don't know for sure, but it seems intuitive that laying only one layer at a time and letting it dry before laying another might help.  Less force from shrinking at any one time.

[Pat B]

Persimmon , Lots of Jay Massey's sinew backed bows checked in the belly due to moisture being added to dry wood and the sinew pulled the checks open as it dried. He mentioned that it happened particularly when he used well seasoned wood. My friend Alan has a Jay Massey bow and the belly is checked all to hell. He doesn't shoot it and probably never will because it doesn't want it to break. It probably wouldn't anyway.
   Maybe like Ed said, do a layer of sinew at a time and let it cure before adding the next. Also, you might try using unseasoned(green) wood and let the sinew and wood dry together.   Pat

[Hillbilly]

Reginald Laubin said in his book that glueing a layer of rawhide (or even tape) on the belly and then scraping it off after the sinew cures will keep the belly checks from happening.

[tom sawyer]

I've had it happen a time or two, nothing extensive though.  I've had mroe problems with the sinew poppiing off, so at least you know you're doing good on prepping your surface.

You might need to pretiller your bow more before applying the sinew.    If the blank is so stiff that the sinew can't pull it into some reflex as it shrinks, then it might pull the wood apart instead.  That, and you might let it dry more slowly so the wood has time to adapt to the increasing reflex.  Sometimes reverse-stringing the wood just a bit prior to sinewing, gets the reflex going in the right direction.

[sonny]

I took a couple of pics but don't think they'd show very well.

the sinew was applied one course at a time.
It seems Tom Sawyer is likely on the right track in that the blank should have been pre-tillered a bit more,, but then there's the problem of inducing too much reflex (making a very unstable bow blank,, been there, done that) as the sinew dries. I guess there's a happy medium in there somewhere that I need to find.

I think now I have at least made up my mind that I won't continue on this bow but will soak the sinew off (however much I dislike that chore) for use on another project..



 

[tom sawyer]

For less reflex, use a thinner layer of sinew.  ERC is pretty light stuff, a thin layer of sinew should work on it.  Maybe even put it down the middle, and taper off to nearly nothing towards the edges.

I've never been able to make myself recycle sinew.  As tough as processing tendons is, sokaing it and resorting it by length is even worse.  More power to ya, do you have any tips for recycling sinew?

[sonny]

....only tip I can come up with is "grin and bear it"
 

[Hillbilly]

I remember a pic of a bow in Jim Hamm's book, I believe it was a sinew-backed yew, that had huge scary-looking sinew-induced checks on the belly, but he said that it shot great.

[Marc St Louis]

Can't say I've ever had splits develop when sinewing and I have sinewed a number of bows. I apply sinew a bit differently than many though. I mound the sinew down the center of the limb and only put down a couple courses on the edges.