Tension Cracks in Sinew Backing

[Marin]

Hello,
I've been tillering a sinew backed bow as of recently and it seemed to be going well. Just today, I was bending it once again to a point I have already bent it to last weekend. It bent fine last weekend and this weekend it still seems to be bending evenly (even checked the bend with a block and ruler to measure along the curve and see if it's bending evenly). I heard very quiet snaps and cracks as I pulled it today and noticed the formation of several horizontal cracks on the back today. I was expecting this to happen at some point as I tend to add a bit more glue than most and I read about it in TBBI  being something fairly normal when making backed bows. However, the cracks seem to be concentrated along a short 5" section and there are quite a number. I checked the bend at this area with my gizmo and ruler and it does not appear to be bending any worse than any other part of the bow, plus this bow is only being bent at about 5" in total currently. I don't mind having these cracks, but I am only curious if this is something that is worse than I think it is? Would this lead to performance issues?
I've attached pics of the cracks in question as well as bow tiller at this point from two different angles. I should note that this bow is heavily reflexed with some slight recurved ends, so at this low level of bending, more reflexed portions are going to look stiff and unbending when in reality they are bending. The cracks in question appeared on the back of the portion closest to the handle.

[Marin]

Unstrung profile for reference

[bradsmith2010]

Id say you need to string the bow to see how its bending,, braced it may show that area as week,,
then proceed to even it out and go from there,,

[Marin]

So the cracks themselves aren't anything to worry about? Just as long as the bow is bending evenly

[Marin]

Also, isn't it still to early to brace this style of bow? I thought I should at least get it tillered up to about 10" of bend or so before I try to brace it.

[PEARL DRUMS]

That usually means you just used just a bit too much glue and the glue itself cracked a tad. Nothing to worry about in my experience.

[bradsmith2010]

looks pretty even to me,, it will probably shift when you string it,,  you need some weight to even it,,
I would string it,,

[superdav95]

looks pretty even to me,, it will probably shift when you string it,,  you need some weight to even it,,
I would string it,,

I agree.  Low brace it at least and then look at your bend from low brace.  It makes a difference on how the bend will look.   You will have a clearer idea on the potential weak spots if any.  Also you will have the confidence to continue also from low brace.  Best of luck.  So far it looks good.

[Marin]

Thanks, I guess I can try to low brace. I'm a little worried though as the last time I braced one of these bows too early, one of the inner limbs ended up getting too much strain and chrysalling really bad. I chopped this up to being poor wood (made this narrow style bow from a piece or low ensity ERC with bad Hair-pin grain), but wasn't entirely sure if this had to do with bracing one of these bows too early on in the tillering process.
Any tips on how to string this type of bow at low brace? I've strung one of these before with help, but admit I am still learning, and with these types of heavily reflexed bows, I find trying to do low brace increases the likelihood of it flipping back around on me.

[bradsmith2010]

Tie some temporary nocks below your nocks,,put long string on those pull the bow using your foot on long string,,
string the bow,, if it looks really uneven,,unstring and even it,,try again,,till the braced bow looks good,,

you can cut the long string off if needed,, after you get it evened out,, you can probably step through and get it strung,,

[superdav95]

Those cracks are just excess glue.  I would be very surprised if your sinew failed here.  My experience is that the wood will fail first.  The sinew may lift off or pull away or delaminate from the wood due to a sizing issue or something but the sinew is crazy strong.  If the sinew was of good quality and not pounded to death or over heated it will be fine.  I would consider also making yourself a stringer if you don’t already have one.  Here’s a few pics of one I made last year.  I got the idea to make my own like this from bowEd on here.  At the time I was neck deep into a highly reflexed bow and needed a specific stringer for this bow.  Here’s a couple pics.  Hope this helps ya.  Good luck. 

[Marin]

Well I was able to figure out a way to string it at low brace. These reflexed-recurved bows are pretty hard to string at low brace without them flipping on you, so I first put it on the long string, then tied the shorter string before taking it off of the long string and having it partially pulled back with this shorter string. It's thus quasi-low braced, as otherwise it would flip on me.
Tiller still seems good, though would like second opinion if you guys think the recurves should be bending more at this point or not. I wouldn't be surprised if they are too stiff. What do you guys think?
Also, in pulling it yesterday on the long string to get these photos, I saw that more cracks on the glue formed on top of the cracks that were there. Don't think this indicates that its bending more in this area, especially since these form in the area around the handle only on the long string, and I keep checking with my gizmo but the bend in this area is not more than the bend on the other limb in the same respective area.

[superdav95]

Looks good to me.  Bend looks good too.  Ya those cracks are scary looking but sinew just doesn’t break that way that I’ve ever seen if that helps ya. 

[Marin]

Thanks, I'll just assume I must've put too much glue in these spots where its cracking
As to the tiller, so you think the recurves are bending enough for this amount of bend? I don't think I mentioned it, but this bow will not be a contact recurve but a working, non-contact recurve.

[superdav95]

Ya Ed I made that assumption too.  It looks good so far to my eye.  We won’t know what this thing will do till you bend it a little more.  The first few bending pics it’s almost to brace height and from the pic it’s pretty close to being contactless on the recurves.  It’s hard to always tell from pics.  I’d be hesitant to remove any material till you bend a little more past where you’ve already gone.  I suspect you’ll see those tips working a little then.  Best of luck.