Ever had sinew rip your bow apart?

[NorthHeart]

There's nothing like a humbling experience to show you what a bowyer noob you really are(me).  I do things in phases, sometimes for better and sometimes for worse.  I have used extensively TB3 for sinew jobs.  Thinking id like to get back to the original way and benefits of natural glue(reflex from shrinkage, a good thing in this context yes ) I did 8 bows in my normal method...minus changing from TB3 to hide glue. No biggie i thought.  I worked the stave to bow dimensions but left it thick as i normally do(as in NOT floor tillered). I put tape on the side and belly to protect from overspill of the glue. Added a couple layers of sinew then a week later added a few more sinew layers to the middle and low "valleys". Boy did i have a surprise a few weeks later when i removed the tape to find checks all down the side of my bow, some literally all the way through.

I took the bows to my buddy James Rempp, and fearing the worst i assumed they were goners, as this is what i had always been taught regarding what i will refer to as laminar cracks or side checks.  We CA glued the checks and wrapped them with sinew. A couple of the bows we finished together and they turned out to be great shooters!  However, a few i'm afraid might not make more than wall hangers at best.  Some of these are Yew and some are Osage....all with the same results(side checks).  He told me that i may have used too much sinew...but most importantly that i should have worked the bow down to brace height and then tillered them all the way out to partial draw...and only then afterwards added the sinew, so that the bow could draw into reflex without pulling the wood apart.  I learn more from doing (my mistakes) than reading from a book. These lessons really stick, no pun intended. But i also learn from the experts on here. I was self-convinced that the wood with the added moisture of the sinew was not drying correctly.  But he informed me its because i left the wood way too thick. I do not mind sharing my mistakes here as you can clearly see.  So...have any of you ever seen or experienced this phenomenon, side checking/tears from the tension that the sinew put on the wood?

[maitus]

Never happened to me. And there is no reason to protect bow from hide glue. Even more.... its good to put sinew bands over the edge to avoid lifting of sinew on corners while sinew shrinks. You will sand it down anyway. I suppose the tape holded moisture in the bow wood and weakened the bond between growth rings.

[Limbit]

Yes, I have had that happen once. I had a member contact me with some info. Wood cracks due to uneven drying. So, if your hideglue is too wet, it is causing the wood to soak up a bunch of moisture. Adding tape on it probably made the situation worse if it wasn't allowing it to breathe enough. Also, if it dries too quickly the same problem might happen. Sinewing can be tricky I've come to find out.

[Eric Krewson]

I have posted this picture before, my wood was very dry but had side checks in the stave that I worked past, I blame the lousy wood.

[Pat B]

I've heard of it happening but it hasn't happened to me...yet!   

[bradsmith2010]

What was the temp and moisture content of the room where the bows cured?

[JW_Halverson]

The one time I had this happen was when I sinewed early as you described.  I have always finish tillered a bow, then added sinew, waited months, and corrected for the new tiller, waited another month whilst shooting in and making more adjustments to tiller.  I thought sinewing early would allow me to just take it slowly down to tiller and finish it out in one job. 

If you think that sinew cannot rip that wood apart, remember that the first "frosted glass" was made by laying hide glue over sheets of glass and allowing it to dry and contract, ripping the surface right off the glass!  If your wood is not flexible enough to bend as that sinew and hide glue contracts, it will shear. 

Check out how they chip finish patterns into glass using nothing but masking and hide glue:  https://youtu.be/WjddrwkJPvE

[NorthHeart]

You all make some good points, which i have considered.

What gets me is that it literally happened on all 8 bows, from completely different pieces of wood.  That's why i have a hard time just blaming it on bad wood, though i'm still open to it.  Seems that i'm consistently doing something wrong in my methodology.  I even remember removing the tape on one yew bow(the one with sapwood left on), sighed in relief that it hadn't checked, then watched as it started to check in the following few days.  So the blue painters tape i wonder about.  Do any of you use similar tape to reduce cleanup on your sinew bows?  If no one else is using the painters tape on the belly and sides then ill need to remove that variable on future builds.  I just get the darn glue everywhere no matter how clean i try to be.

Forgot to mention, i tempered and heat corrected most if not all of these pieces of wood.  I know that can affect the moisture content of the wood, but IIRC i waited 2-4 weeks before sinewing.  Regarding moisture in the room, i believe my hygrometer said 20%, its hard to recall, temp 55-65 throughout the day.  Bows kept on my bow rack with 2 pegs so hopefully air could circulate around it.  Is 20% reasonable?

JW- interesting about that one bow that you sinewed early in the build process like mine.  After we filled the checks with CA glue i was told to go and reduce the belly wood so that the bow could continue to reflex as the sinew dried.  Almost immediately the bows pulled into more reflex!  So i'm still thinking this is most likely the issue.

[Mesophilic]

I've delt with this problem alot myself.  Based on humidity, in my case I think it dried way too fast.  We'll get in to the single digits for long stretches of time.

I can't remember the book, but I found one author who had this problem as well.  His solution was to glue rawhide to the belly and up over the sides.  When the sinew  dried he sanded it off.  Haven't tried it yet myself.

[bradsmith2010]

I think 20% seems low, but I am not expert on that,,
I live in the high destert Santa Fe,, and my moisture meter inside does not go that low,, unless it is heated in winter,  I am just guessing now, but maybe let the bow cure in a cool place not heated, I have read that before,, and maybe thats whey they suggested it,,???

[High-Desert]

This has happened to me, but only after moving to the high desert. So I assumed it was drying too fast. I try to keep my curing sinew bows somewhere the humidity is around 50%. This helped a bit, but the last bow sinewed, I removed it from the room after 3 months, and BAM, a small laminar crack formed at the upper mid limb, but it was only about an 1-1/2” long, i filled it with a touch of CA, and no problems. That’s was the modoc style bow I posted last month.
I had three previous other bows do the same thing, but I just kept them in the house at about 25-30% humidity, and they had sever cracks form on all limbs. Neither bow has given way and both shoot fine

[TimBo]

I think Reginald Laubin talks about putting rawhide on the belly in his book American Indian Archery.  I will have to go reread that part to see if he gets the stave to floor tiller first.  Maybe he also started with thicker staves.

[bradsmith2010]

I think he tillers the bow out a bit before sinew

[TimBo]

Yep, I found it - he tillers to half draw, then sinews.  I think he is talking about avoiding belly cracks though, not side cracks/delams.

[bradsmith2010]

yes but I think it would help the side cracking also,,??