Questions? 1. Low rpi Yew. 2. Yew ring violations

[ionicmuffin]

ok, but in general there are several ways to make it equal right? so wouldnt keeping it wider for the same draw weight be another solution or am i wrong?

[Bryce]

Higher ring count in yew has been proven to be stronger time and time again. Does it make a better bow? Yes! Does low ring count yew make a good bow? Yes!
Low ring count seems IMHO to bbe more brittle.
A yew tree that's had a hard life has to grow slower and grows to be stronger to survive.
That's why we climb mountians to get the good stuff.
Bc it's slow growing and has grown strong.

[Del the cat]

Are we even sure that high ring count is denser?
If you make a multi layer sandwich of bread and cheese 2" thick out of 1/4" slices it will have exactly the same density as if it was made of 1/16" slices.
Or are we saying the size of the individual cells is smaller and thus has more cell wall to empty space an is denser?
But at what point is denser better? Without the cellular structure, absolutely solid compressed wood would be too heavy.
So what is the optimum cell size for Yew?
Do we know or are we spoting received wisdom which hasn't actually been tested over a large enough sample size to be meaningful?
Can I be bothered to go to the garage and cut two cube of Yew and weigh them...? I think not... or maybe I will... watch this space.
Del

[adb]

ok, but in general there are several ways to make it equal right? so wouldnt keeping it wider for the same draw weight be another solution or am i wrong?

I don't think you can make two different pieces of wood 'equal.' For me it's just application... higher ring count = warbow, lower ring count = ELB. I will often dimension them the same, and the higher ring count seems to make better heavier bows.

[adb]

Are we even sure that high ring count is denser?
If you make a multi layer sandwich of bread and cheese 2" thick out of 1/4" slices it will have exactly the same density as if it was made of 1/16" slices.
Or are we saying the size of the individual cells is smaller and thus has more cell wall to empty space an is denser?
But at what point is denser better? Without the cellular structure, absolutely solid compressed wood would be too heavy.
So what is the optimum cell size for Yew?
Do we know or are we spoting received wisdom which hasn't actually been tested over a large enough sample size to be meaningful?
Can I be bothered to go to the garage and cut two cube of Yew and weigh them...? I think not... or maybe I will... watch this space.
Del

You would have to make SURE that both pieces had precisely the same moisture content. I'm not exactly sure how you'd do that, because the two pieces would need to come from two different trees. I'd love to know the results!!

[Del the cat]

Higher ring count in yew has been proven to be stronger time and time again. Does it make a better bow? Yes! Does low ring count yew make a good bow? Yes!
Low ring count seems IMHO to bbe more brittle.
A yew tree that's had a hard life has to grow slower and grows to be stronger to survive.
That's why we climb mountians to get the good stuff.
Bc it's slow growing and has grown strong.

A lot of unsupported assertions there!
I'm playing Devil's advocate here to some extent. I'm not saying high RC isn't better, I'm just saying 'not in my experience'.

Ok it grows slower, but why does that make it necessarilly stronger?
I could argue that a tree growing slowly at high altitude will be shorter and thus need to be less strong than a taller tree of the same age as it will have less wind load and leverage on it!
Del

[Del the cat]

Are we even sure that high ring count is denser?
If you make a multi layer sandwich of bread and cheese 2" thick out of 1/4" slices it will have exactly the same density as if it was made of 1/16" slices.
Or are we saying the size of the individual cells is smaller and thus has more cell wall to empty space an is denser?
But at what point is denser better? Without the cellular structure, absolutely solid compressed wood would be too heavy.
So what is the optimum cell size for Yew?
Do we know or are we spoting received wisdom which hasn't actually been tested over a large enough sample size to be meaningful?
Can I be bothered to go to the garage and cut two cube of Yew and weigh them...? I think not... or maybe I will... watch this space.
Del

You would have to make SURE that both pieces had precisely the same moisture content. I'm not exactly sure how you'd do that, because the two pieces would need to come from two different trees. I'd love to know the results!!

If yhey've been in my offcuts box next to eachother for 2 years would that be ok? 
Del

[adb]

I don't know. If you're looking to make this scientific, with meaningful results, probably not.

[coaster500]

Never tried yew with low ring count but I have built quiet a few with high ring count and I always seem to get staves with so much sapwood they must be worked down. I have never had one break from that process. Here are a couple of pictures that show the back and the violations. I stained this one (I know that is distasteful to some but I'm not crazy about white in a hunting bow)........  This one is 55#s and drawn to 29"s and still shootin



My tradgang bow swap victum Ralph shooting it......  Looooong arms...  Yew is some bendy stuff!!!!

[Bryce]

Are we even sure that high ring count is denser?

Yes.

[Del the cat]

I don't know. If you're looking to make this scientific, with meaningful results, probably not.

I'll agree it's not going to be an exhaustive scientific test, but it'll be better than unsubstantiated opinion won't it?
If the result isn't going to be considered as meaningful, I won't bother with the effort... or will it only be considered meaningful if it supports the high RP is denser theory.
Lets have some ground rules before I waste my time!
Del
BTW, do you wnt me to measure the MC of my cheese sandwich

Gotta make dinner... I'll do it after. Gimme an hour or so.
One bit will be Oregon Yew grown at high altitude, one bit English Yew. Ooooh this is exciting.

[adb]

It would be interesting to know. Certainly wood suppliers charge more for higher density yew. Is there any truth to higher ring count yew being 'better'?

[adb]

I don't know. If you're looking to make this scientific, with meaningful results, probably not.

I'll agree it's not going to be an exhaustive scientific test, but it'll be better than unsubstantiated opinion won't it?
If the result isn't going to be considered as meaningful, I won't bother with the effort... or will it only be considered meaningful if it supports the high RP is denser theory.
Lets have some ground rules before I waste my time!
Del
BTW, do you wnt me to measure the MC of my cheese sandwich

Gotta make dinner... I'll do it after. Gimme an hour or so.
One bit will be Oregon Yew grown at high altitude, one bit English Yew. Ooooh this is exciting.

I think two different species would probably make the results less valuable?? The less variables, the better, I'd say. Also, the bigger the piece the better, I think. Don't let me stop you though! This could be interesting.

[Del the cat]

Done it, I ran 'em through the bandsaw against a fence but I measured 'em at either end and averaged each piece. This gave a very small correction factor which didn't change the result.
Low altitude 134.6 grains (136.5 after correction for slightly smaller dimensions)
High altitude 154.2 grains
(that's about 10% denser in round figures)

So that test agrees with the received wisdom that high ring count is denser. I'll post a pic of the two samples later if you want.
The point of this is now I believe it 'cos I've measured it.

So, presumably to get the same stiffness we'd need to inrease the cross sectional area by 10%.
Mind with stiffness being proportional to cube of thickness the thickness need only increase by approx 2.3% (the cube root of 10)
Which isn't a huge amount. so On a warbow 30mm thick with high ring count it needs to be increased to about  30.7mm thick for low ring count?
Del
(BTW cheese sandwich is at about 20%  )

[DarkSoul]

Interesting debate. I'm quite sure we had a somewhat similar rpi debate a while ago (one year? two years?).

Del, if you can spare any more of those off cuts, I would love to see your results. In this instance you compare the variability of ringcount, but also the variability of species (English yew versus Pacific yew). Probably not totally fair. I'd also like to know how much heartwood and sapwood you included. Since the sapwood is probably not as dense as the heartwood. However, we do also use the sapwood in bows, so it is actually interesting to include that as well. I would prefer to determine the SG of yew with one third sapwood and two thirds heartwood, just because that is approximately representative of the ratio in a longbow.
I guess you used the bandsaw to create two blocks of wood with a uniform dimension, right? If so, you can even use a caliper to accurately measure the volume of the blocks. Then you can calculate the specific gravity of each sample, which is more meaningful than the absolute weight.