wonders of 2k

[simk]

Hey, it was on monday when i initially stringed a d/r on the pegboard, still quite strong...when suddenly the string popped off. Bow hit a corner and broke in the d/r transition. belly lam completely through and backing affected a little. game over, i thought. it was really annoying loosing all that work.
well, nothing to loose putting some resin in the cracked limb and wrapped with rubbertube.
Yesterday I continued tillering where I was stopped. As if nothing had happened 
Today I put some 100 arrows trough it @ 42# " 25" (with saftey goggels)
It's just incredible what 2k can do.
Would you trust it? I might do a psychological wrapping

[DC]

Logic says that it's in compression, should be fine but my gut goes, ehhhhhh?

[simk]

yeah that is what I tought too DC. But the crack goes way above the neutral zone and even affects the backing on one side of the limb. still thankfull for that free play I was given 

[Hamish]

Seriously bad grain at that spot.

I have no idea whether it will stay safe, looks scary as hell though. I'd wrap it, for your own safety.

[PatM]

I would have been nervous with that grain  anyway.

[Rākau]

PatM and Hamish: In what way does grain like that on the belly cause problems?

[simk]

Rakau: It's the grain undulance in this spot due to a little knot in the grain

PatM & Hamish ...that grain is not perfect there, off course. But in this case it had nothing to do with the fail, imho. I'm still a learner and always like to find out myself where the limits are. I have laminated a few with grain like that and even worse and never had any problems with bows up to 60#. I sure will remember your words when the first explodes...and be more careful with grain runoff from then on. I also wouldn't laminate this if it wasn't yew. Still I don't feel perfectly safe now with this one and even don't really trust a wrapping, because yew, if it lets go, shatters in many pieces. 

   


 

[Rākau]

Sorry simk, I realise that the undulation is the subject of conxern, I just thought that it didn't matter if it was on the belly, is this not the case?

[simk]

It can lead to so called plate tectonic fail...when the grain splits along the rings under compression. I personally have not had these problems with yew but will maybe find out in the future and get wiser  In this case my personal concerns mainly were caused by the almost complete break of the limb and the 2k fix... I will probably overdraw it on the tiller wall a few times before shooting it regularly     

[DC]

I will probably overdraw it on the tiller wall a few times before shooting it regularly 

That will just weaken it

[bownarra]

Belly grain like that on woods that split like yew is a bad idea. That 'wave' could easily pop out. When fibers come to the surface at an angle like that they are weaker in compression than if the fibers parallel the belly. If you had to use grain that bad I would only go with an interlocking wood...but then again I've learnt the mistakes of thinking you can use sub par wood on lam bows. You can to a degree but it is a fine line. Belly and back should have very good grain. Core lams can be more tolerant of poor grain but even cores can fail.
If this bow had had a straight grained belly it would likely have survived. The crack has followed the dip in the grain.
If this bow breaks it won't go into a lot of pieces
Your glue is holding for now because you have a fair amount of surface area and good mating surfaces. However it will break at some point.

[simk]

thank you bownarra - I do appreciate your advice. I think the bow broke there regardless of grain - its exactly where the back hit a wooden corner when the string popped off. yes on one side it follows the grain and jumps from ring to ring, but at the beginning (on the back) there is no visible correlation to the grainpattern...imho. But maybe I'm wrong also.
Sometimes you gotta go with what you have and sometimes you just need to check where the "fine line" really is. Up to now I always was too lazy to splice the good pieces and just used the full length slats.
Why do you think it won't break into pieces? Not long ago I had the same model shattering  into  5 pieces - it was subpar glueing in think and the reason to build 2 newe ones 
I now tillered it to 28 and pulled it to 29 a few times and will shoot it 26". I think I'm fine now with a wrapping. 

[PatM]

Yew was well known for breaking on the belly if a string  broke in the past.

  The limbs swinging forward would make the belly fail in "tension".  It looks like that's what happened here.

 

[simk]

yes PatM. and I will have rework that top limb a tad - sometimes a picture helps