First sinew job....little gaps?

[Prarie Bowyer]

Yew.
heart wood.

[PatM]

The sinew is just shrinking and pulling the wood apart. Pretty common for yew bellies to do this when sinewed. Osage as well.

[Prarie Bowyer]

Pics of one layer of Sinew.

[JW_Halverson]

Oh no!  I do NOT like the look of that!

[Prarie Bowyer]

Dang it!   I was working so slowly and methodically!  What a craptacilar result!

[Del the cat]

Yeah, but on the plus side, the crack is longitudinal and right down the middle.
Keep Calm and Carry On !
Sinewing isn't my thing, so I may be talking nonsense, but Yew is tough stuff.
I'm just finishing up a boo backed Yew and noticed a couple of "scratches" except they are some sort of very fine crack, can't feel 'em with a fingernail and CA doesn't even soak in... bow shoots fine... sometimes you just have to press on... it's how we learn.
There is a difference between pressing on knowingly to see what happens and being in denial.
If they were chrysals I'd say you were dead in the water... but they ain't so... who knows.
Good luck
Del

[mikekeswick]

As I said before you dried your sinew too fast.
Sinew doesn't just shrink in length it shrinks in thickness and width also. This puts tensile stress on the belly of the bow.
Was the yew 8 - 10% dry before you started?
Use a comb to straight the sinew out when laying it down.
You definitely should have added a few inches of reflex BEFORE glue up then added more once you had the sinew applied and the glue had gelled. Sinew bows with no reflex don't shoot particularly well.

[Prarie Bowyer]

So. How to fix these cracks?   So far they seem to be getting worse.  Eventually it will stop. 
I'm going to try clamping and gluing them out.   

What kind of glue.  Knox?   Tb3?

I'm inclined to do the tb3 thn use thin superglue in the tiny ends parts.

[Comancheria]

Wondering if this might be an instance where you would squirt super thin crazy glue into the crack and hit it with a heat gun??

[Prarie Bowyer]

I decided on tight bond 3.

The cracks are kinda like laminations and tb3 can be used for that.  I think it was the Knox more than the sinew.  My leftovers were cut into pieces and allowed to dry.   They shrank from the jelly cubes that were cut by almost 75%!

The sizing coat was my problem.  Other hide glues have "stuff" in them preventing such shrinkage I think?

[Prarie Bowyer]

So far clamping with TB3 seems to be working. 

[Blaflair2]

I've only sinewed two bows, but I've never had a problem like that. One was juniper and on was osage. The juniper came out nice, light but nice, and my dog ate the osage :0/  what ratio did u use for the glue? I got a bow I'm getting ready to sinew. Then it's gonna sit till I bring it to the classic to get some help not messing it up. Lol.

[bubby]

What do you mean other hide gluse have "stuff"  in them, ?

[Blaflair2]

They're all the same. Knox is what most people use from my understanding, I mixed mine until it was a polyurethane consistantcy. The second would have been better. The one I'm planning on now has been awhile in the works. I may try pats wrapping technique. We'll see. Hopefully urs can be helped

[Prarie Bowyer]

I think and this is just my speculation here, that the knox stuff is highly refined and "pure" (hence it's clarity inthe useable form). 

I'm not certain that the consistancy matters that much since it is water and the "stuff".  The water evaporates out but I mixed it to the consistancy of warm syrup.  It coudl be that as teperatures dropped right after I did it the humidiy in my house dropped also.  BUT my basement was cooler so thta should have slowed evaporation and I had no fans or anything like that running.

By "stuff" I mean organic material.  if you grind fish bladders or odd bits of sinew and hide you get that hide glue that is opaque... which is opaque bercasue there are particles that are suspended in the colagen.  These particles may nor may not have the same capacity to shrink as much as the knox...

I could be way off base also.