crappy yew?

[simk]

So.....I made a bow. The wood seemed to be high quality yew, dark color, thin rings...
After shooting the first few arrows it quickly developped deep chrysals for no obvious reason. Tiller seemed ok and there where no real  knots or strange grain where it chrysaled. It simultaneoulsy chrysaled at several spots.
This never occurred to me with yew - in fact - up to now - I never occurred any compression problem with clean yew.
For me it looks like a century event.
Thoughts?
Thank you

[Eric Krewson]

Are those tiny knots or powder post beetle holes?

[Dances with squirrels]

I've found some yew can be more delicate even though it may look like grade A #1.

I wouldn't say yours did it for no apparent reason whatsoever though. The frets in the pictures run right through pin knots that appear to neighbor humps and potential stiff areas... hard to tell without studying it in person and actually measuring the taper rates in those areas and watching the limbs in action. But if the way the growth rings are fading out/feathering are any indication... at least those frets there, seem potentially logical. Still should have held, but it's yew, so.... all bets are off.

I've had yew where I've drilled out and plugged or epoxied numerous punky knots, left other hard ones in the same limb alone, and a fret never occurred.... then the next piece of yew, perfectly quatersawn, absolutely clear and straight without a single visible flaw to be found, frets in the middle of the limb for some mysterious reason. I don't 'fret' over it none... just burn it and start another.

[Del the cat]

What's the draw weight?
Del

[Hamish]

I've seen plenty of guys on this site get away with ignoring pins on yew in both tension, and in compression. My guess is your bow isn't overbuilt, in length or width  so the weakness of the pins came into play.

Regardless of the type of wood, I've learnt to always leave swellings around these types of pins. It makes tillering more complicated, but I never get frets, at pins. Without doing that, you win sometimes and lose other times.

[simk]

Thank you!
Sorry Eric, I forgot to mention, it's tiny pin knots.
Dances with squirrels: the growth rings on this one don't necessary correspond with taper rates because it's a sapling like stave that I backed with hazel due to damage in the sapwood. It was not my first bow and not my first yew either... I have seen frets on yew with knots or grain undulation. I haven't seen frets on clean yew, also tiny pin knots never caused problems. Also there are more frets far away from any pin knot. Usually I find yew quite forgiving for little tillering mistakes...worst case is a little set. If it gets catastrophic it usually is the back....never a compression issue.
Of course I will make a new one  but this one really hurts because it was some kind of special with the hazel backing.
Del: It was around 45# @ 27" ....the bow is rather short, around 60"ntn or a bit less ... yes it was meant to run on the edge, almost a flight bow... still: frets like these on yew are a first time experience for me.
Hamish: Could be. Another quite experienced bowyer not long ago told me, he wouldn't care about pins because they would act similar to armoring in concrete...
Cheers

After all: It's probably my fault - I made the bow - layout maybe was a little on the risky side - tillering maybe was not careful enough for the delicate design and shortness. Hopefully learned something.

[Del the cat]

Just comparing it with my go-to yew primitive 45# @27" (but it has pulled to 28"when I first made it... I've lost 1" of draw ), that's 64" long and doesn't have flipped tips.
So I s'pose you are working it quite hard, but I'm surprised it's done that.
I've always fancied doing a Hazel backed Yew, not got round to it yet
Del

[simson]

...... Another quite experienced bowyer not long ago told me, he wouldn't care about pins because they would act similar to armoring in concrete...
Cheers

/quote]

That's absolutely nonsens!
Every pin weakens the wood.

It irritates that the chrysal appeared only on one pin. Was the stave/bow wet there?
I cannot see a mistake looking at the tiller.
It looked very good!

[simk]

thanx for clarification Simson! And NO, the stave wasn't wet at all - it has been laying in my workshop for about 4 years now and felt very dry.

I have a suspicion:

Hazel is just too strong for yew  

Maybe the backing was too thick? I have heard (!) that a too thick boo-backing can easily crush yew and osage (Anyone?)...maybe it's the same here... the hazel tapers from +3/8" at the grip to less than 2/8" at the tips. In the main bending zone there is about a 1:1 hazel/yew ratio.
On the other hand: I have sucessfully put thin yew facings on selfbows without problems...

[bownarra]

If pin knots don't weaken wood....I want some of that stuff
Hazel has pretty low stretch resistance it should have been a good candidate for yew. Hickory doesn't 'overpower' it so I highly doubt its the hazels fault. Also thickness of backing has very little to do with it. It is the outermost fiber that do the majority of the tension work....so how does making the backing thicker alter that....? What matters more is it the backing is full width or trapped and or crowned.
The first chrysal is explainable. There appears to be the remains of a knot/weird grain section on the handle-side of the chrysal and the rings step through a bit, it also appears to be thinner on that side. The weird grain will act stiffer than the clean wood thus causing a mini hinge/stress riser (sort of!).
In all fairness it is probably just a junk stave....

[Yooper Bowyer]

concrete doesn't have grain.

[bownarra]

concrete doesn't have grain.

what does that mean?

[Yooper Bowyer]

I don't think the analogy of pin knots as armoring in concrete works because the grain runs at weird angles out of the wood on the belly around a knot, so it does not have the same strength as straight grained wood.

[bownarra]

I don't think the analogy of pin knots as armoring in concrete works because the grain runs at weird angles out of the wood on the belly around a knot, so it does not have the same strength as straight grained wood.

Aye that's the trouble with comparing apples with oranges