yew longbow broken

[costa_ct]

Hi guys!
I need some help to understand why this longbow (72#, 55 lbs @ 29#) decided to die after about 100 arrows shot. The wood is English yew cut down in september. No dry shot, no drawn over 29#, no knot in the break's area.

 

 

Any opinion welcome!

[Shifting Shadow]

Excuse me for my ignorance, but could the wood be too dry?

[Pat B]

That was my first thought too, too dry.   Also, the way the piece popped out on the belly it almost looks like there was a grain swirl there. Will you post a pic of the back at the break?
 If the back gave out first(tension failure)it would have to either be too dry of the sapwood was rotten, possibly from not being cared for correctly after it was cut.

[rmorris]

Constantin, I think I can help you a little bit. That looks like what is call in material engineering as a "block failure" which means that it failed in shear. That is the worst and most catastrophic failure because there is no warning or signs before failure but thankfully is very rare. More than likely there was some kind of defect in the limb. My guess is there was some material defect running perpendicular from the knot and parallel with the limb. In roughly the center line of the limb (depending on the cross sectional shape of your limb)there should be no tension or compression forces on the limb but in this area, but shear stress is the greatest here. In this zone any defects will greatly increase the chance of shear. Thankfully this is the rarest failure and I would bet that you made a great bow and you should not change anything about your bows.

[costa_ct]

Thank you very much guys!
@rmorris, you've brought some peace in my heart     No, unfortunately I cannot make bows at this level yet, being at the very beginning of the traditional archery. But the man who made it is a professional and this is why the failure was a surprise to me.
I've been making a bow from the same kind of wood, from the same place and I was afraid it could be something wrong with the quality of the yew here. But you say this happens very rarely, so I'll go on with it even if my stave was not straight enough for a beginner like me.
 

And it seems to have very few rings per inch compared to what I've read here about yew   :(  
 

If I make it I will post pictures.

Thanks again!

[Art B]

Cut in September, then had to be quick dried. Wood was probably brash/brittle/dry IMO....Art

[gringol]

I'm new at this, but I've read that the number of rings per inch is not a factor on its own, thin rings just make it hard to follow a growth-ring without accidentally damaging it...

[fujimo]

looks like that stave was sawn, were those bends sawn in, or did it bend as it was drying?

[Shaun]

The bow failure looks like it happened in an irregular grain swirl area. Some imperfection in the middle of the limb looks to be the starting point, not a belly or back failure. Most yew bows are at almost failure at full draw - the tiniest imperfection can be the seed for such explosions.

[ONE SHOT]

As a old saying goes a wooden Bow is 98% broken from the start. Be it one piece or laminate. You are working with wood, and
against Nature. They have broken in the past and will continue to do so in the Futher, just the Nature of all wood. ONESHOT

[Pat B]

The saying is...a bow fully drawn ia 9/10th broken...meaning if a wood bow is drawn beyond it's tillered draw length it is likely to break. Otherwise a wood bow can be shot many thousands of times and not break.

[Flem]

Thats a massive knot just above the break. You must have had excessive runout grain adjacent to that. Looks like a wood cowlick.