Both limbs broke simultaneously

[simk]

How ist that possible?
What went wrong?

The bow was 62" long, pyramidal from 1 6/8" to 5/8", yew - left about 5 or 6 sap rings.
Heat treated in the morning, took it to brace in the afternoon first time - after some short draw exercises...bäm!
Tiller was good, no hinge at all, no knot, and I properly chased a ring.

Was it the design and layout? (I got away with this design with rowan so i thought, there shouldn't be a problem with yew)
Was it the heat treating in the morning?
Was it because the wood was seasoned only since february?
Does yew not like the heat treating?
Does it need more sap wood?
Was it the back or the belly that broke first?

I don't know.

Let's go for a new stave, cheers

[simk]

more

[bjrogg]

Sorry for your bad fortune smik. I've never tried yew so take my word with a grain of salt. I'm just guessing the heat treat in morning and then bending in afternoon. I always wait three days for wood to reclimatize after a good heat treatment till bending. Some may feel this is over cautious but it's what I've been told and what I do. I like to build two bows at a time so while I'm waiting for one I can work on another.
Hope you find you answer. It always helps to know why.
Bjrogg

[BowEd]

Sorry to see that nice piece of yew broken.You can get away with that quick turn around from heat treating to bracing and bending with woods that are more tension strong than compression strong.If that's the reason assuming tiller was good like you said.
Personally I have a 10 day rule I live by when heat treating no matter what the species.

[DC]

I have heat treated Yew successfully but I kind of suspect it may be a bit iffy. Yew quite often breaks in many pieces. I've had five a couple of times . I would suspect the short waiting time. Sometimes Yew just blows up.

[Bob W.]

It happens, I have had a nice seasoned 69" yew explode violently into a dozen pieces on the pulley when I thought I was  about done tillering, both limbs mirrored each other on the breaks. Don't know why and probably has nothing to do with your break.

[simk]

Thanx for your sincere sympathy and thoughts. Me myself and I also really do suspect the heat treating short before - but there will be no clear evidence in the end. Sure I will wait longer after heat treating next time.

For further projects still maybe anyone can anwswer, if 6 thin rings of sap wood basicly is enough with yew?

Thanx a lot!

[Badger]

  I never heat treat yew, I very often use heat the bend it a little bit but never heat treat it.

[Del the cat]

Did you stop heat leaking round to the back? Any sign of rot in the sapwood, did it feel smooth and creamy or a bit crumbly? (any blue colour?)
At least the tiller was symmetrical if both broke simultaneously 
I've had similar when I felt the sapwood was suspect. The logs had been left outside to "season" with a tarp' over 'em (not my doing) and that's a recipe for rot to get in.
Del

[simk]

Badger: Why not heat treating yew?
Del: The sapwood was good, no signs of rot or fungus.
You do heat treat yew? I did it to correct a little deflex in the stave and to improve the string alignement...is this generally ok with yew in your opinion? 
You also already mentioned lately here in the forum, that you do some kind of protection whilst heat treating to prevent the heat leaking to the back...i didnt. How exactly do you do this? Are 6 sap rings enough with yew?
Thanx

[DC]

I don't touch the sapwood unless it's more than 3/8"(1cm) thick, roughly. Six rings could be anywhere from 1/8" to more than 1/2"

[simk]

DC - I mean very thin rings...like in the pics above...1/8" maybe...is that enough?

[DC]

Warbow guys use very little sapwood. I don't think there is a minimum but there's no sense in messing up a good back unless you have to. I just use what's there, mostly.

[JNystrom]

I once had maple with some hidden fungus. The bows exploded just like this, both limbs simultaneously. That's all i know...
About heat treating, I feel like there just isn't enough evidence to prove you need to wait 24h or more. One could of course weight the bow before heat treating and after to see the difference in moisture if there is any.

[FilipT]

Dry rot?