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

[Bryce]

A couple years back in my chem class we did density testing. I chose to do yew. I did 10 low elevation and ten high elevation. Figures there densities and averaged then out. There is no doubt that higher ring count is denser.

DS, seems this discussion comes up every few month :/

[Del the cat]

Here are the blocks (all heartwood). I cut 'em on the bandsaw and then checked the dimensions on each end with the calipers and made a slight correction as the high altitude block was a whisker larger (that's why I scaled up the weight of the low altitude block from 134.6 to 136.5grains) butr not significantly so.
I can post dimensions if someone else wants to mess with the maths and count the rings... my work here is done (swishes cape and dissappears into the dusk)
Del

[Del the cat]

A couple years back in my chem class we did density testing. I chose to do yew. I did 10 low elevation and ten high elevation. Figures there densities and averaged then out. There is no doubt that higher ring count is denser.

DS, seems this discussion comes up every few month :/

Now if only you'd said all that in your first post, I wouldn't have bothered...
Go and sit on the naughty step...
Mind it's always good to calibrate this side of the pond against your side.
maybe we can get someone in the Southern Hemisphere to do the test too?
Del

[Onebowonder]

Done it, <snip>
Del
(BTW cheese sandwich is at about 20%  )

That's some awfully dry ole cheese!

OneBow

[Bryce]

A couple years back in my chem class we did density testing. I chose to do yew. I did 10 low elevation and ten high elevation. Figures there densities and averaged then out. There is no doubt that higher ring count is denser.

DS, seems this discussion comes up every few month :/

Now if only you'd said all that in your first post, I wouldn't have bothered...
Go and sit on the naughty step...
Mind it's always good to calibrate this side of the pond against your side.
maybe we can get someone in the Southern Hemisphere to do the test too?
Del

I used 1"X1" blocks made the math easy.
Yeah but del it's always good to find things out for yourself

[adb]

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.

Having thought about this since last posting, I'd have to agree with the above. Is weight a fair and exclusive measure of density? I think SG would be more accurate.

[Del the cat]

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.

Having thought about this since last posting, I'd have to agree with the above. Is weight a fair and exclusive measure of density? I think SG would be more accurate.

Eh???!!!
Density may be 'more useful' but it can't be 'more accurate' if it's derived from the same measurements.
Density is just weight per unit volume. It doesn't matter a jot what the unit of volume is! It can be a bushell, or a cubic centimeter.
Like I said I'll measure the samples if you like, but would you like it in metric imperial or cubits?
Same as I weighed 'em in grains, could have been grams, or ounces... doesn't matter as long as it's the same units for both.
10% is still 10% regardless of units. I could take 'em to the moon where the gravity is less, but there would still be a 10% difference between 'em.
I adjusted for the slight difference in volume of the two samples, I just didn't bother to calculate the actual volume and divide it into the weight.
grains per cubic centimetre wouldn't be a recognised unit anyway.
C'mon gimme a break, I've done enough arithmetic for one day .
Del

[vinemaplebows]

I have made them from both low ring count, and high ring count. The high ring count is nicer, but not always the best.


VMB

[vinemaplebows]

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'?

People are like broken tape players hearing something from a "expert" never to find out there is truth in expirience. Low yew is yew.

[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.

Having thought about this since last posting, I'd have to agree with the above. Is weight a fair and exclusive measure of density? I think SG would be more accurate.

Eh???!!!
Density may be 'more useful' but it can't be 'more accurate' if it's derived from the same measurements.
Density is just weight per unit volume. It doesn't matter a jot what the unit of volume is! It can be a bushell, or a cubic centimeter.
Like I said I'll measure the samples if you like, but would you like it in metric imperial or cubits?
Same as I weighed 'em in grains, could have been grams, or ounces... doesn't matter as long as it's the same units for both.
10% is still 10% regardless of units. I could take 'em to the moon where the gravity is less, but there would still be a 10% difference between 'em.
I adjusted for the slight difference in volume of the two samples, I just didn't bother to calculate the actual volume and divide it into the weight.
grains per cubic centimetre wouldn't be a recognised unit anyway.
C'mon gimme a break, I've done enough arithmetic for one day .
Del

Del, there is some truth in what adb is saying. You say the weight is 10% difference, which is correct. But then there is the huge assumption that both blocks have to be the same volume.  You say "I adjusted for the slight difference in volume of the two samples" which is very trivial. Did you just eyeball the two blocks so they appeared to be the same size? Sorry, not trying to be a nuisance here! It's just that you are a footstep away from data we can ALL actually use. The specific gravity. You have the squared blocks of wood and the weight. Please take your caliper and measure the size (length*width*thickness) in millimeters. If you can give me those dimensions, for each block, I'm more than willing to calculate the SG at EMC. It's more than likely that the SG will also be in the 10% difference ballpark. But it might as well be 9% or 11%, depending on the difference in volume of the two blocks.

[Del the cat]

High ring count Oregon heartwood.
length 62.77mm
End 1. 15.29 x 14.63mm
End 2. 14.88 x 14.73mm
weight 9.99g

Low ring count English Yew heartwood.
length 62.47mm
End 1. 14.76 x 14.73
End 2. 14.78 x 14.51mm
weight 8.72

I must admit I didn't check the lengths before, I was after a quick look see.
I averaged the area of the two ends for each piece and assumed the lengths were the same.
Having done all this I might as well do the arithmetic myself. You can do it too to check it.
Volume of high ring count =14.055 cc. Density = 0.711 g/cc
volume of low ring count  =13.789 cc   Density = 0.632 g/cc

This still works out about 11%. There's a fair bit of rounding and measurement error. But it's pretty conclusive.
However there is only an 11% increase in density for approximately a doubling of ring count.
To me that says that ring count doesn't make a huge difference (dunno what the varition is between sample of  similar rpi)
Although maybe one could argue that I'm using a medium ring count and a high ring count.
Extremes of high and low rpi might give a bit more variation of density, but I'm certainly not going to be sweating on 'have I got 50 rpi or 70rpi !'
Any how, it's past my bedtime and it's work in the morning.
Del

[adb]

So... there really is a difference. 11% is 11%. Interesting. There is merit to this story. Thanks, Del!

[Japbow]

@Darksoul...

I counted from 5 to 17 rings of sapwood
on the 10 or so staves I have. It seems to
 correlate to rpi. The sapwood is about the
same width regardless of rpi...if you know
what I mean.

[Japbow]

Nice, hearty debate...and we've come to some useful conclusions.
 Way to keep it civil, too. I see that more than any other woods yew
and osage spark the most passionate debate.

Thanks Gentlemen!

[mikekeswick]

I have some pieces of yew that I could test as well.
The way to know they are at the same moisture content is to put them in the oven for a couple of hours on low heat or microwave them for 30 sec blasts until they both lose no more weight.
Personally I don't think ring count is the be all and end all, as Del says all you need to do is adjust the width to thickness ratio proportionately to compensate for density.....IF (big if) the elasticity is the same.....which is unlikely......but that's the principle.
Like designing anything that is going to take some sort of loading
1st - determine the properties of the material to be used.
2nd - determine the stresses/strains/load
3rd - work out how much of said material you need to do said job.
Bows are fairly simple in the scheme of things but it all gets a little confusing when myths fly around unchecked.