Primitive Archer
Main Discussion Area => Bows => Topic started by: Japbow on April 29, 2013, 03:04:29 am
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Ok. If you want a 150# warbow you're gonna need some high rpi yew...of course.
What I have access to is more in the 5-20 rpi range. I assume that this is sufficient
for bows with draw weights of 40-60# while still getting the excellent tension
and compression attributes of yew, right?...or perhaps I'm wrong!?
I've made one shorty elb style (out of a branch) which started out 65# at 22",
49" ntn which shoots fine. (I later re-tillered down to 55# because it was killing
my shoulder)
Also, I always silk back my bows just for a little added insurance!
Would I be goofy to try to get a decent flatbow or elb bow from yew with the
below stats at around 10 rpi???
60" ntn, 55# at 26"
One more yew question...
I've kinda gotten the vague idea from various sources that yew will tolerate
minor ring violations in the sapwood when thinning it down. Is this true?
I hope it's true b/c I dread the idea of chasing one yew sapwood ring.
This is why I previously made a bow out of a branch; it already had a good
sapwood-heartwood ratio.
I appreciate any insight...
Thanks,
Japbow.
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You can make a 150lb'er from low rpi yew.
Low rpi yew really , really benefits from a good heat treating (make sure it'sdry first).
No need to back it with silk.
Yes it will handle a few violations but you should strive for perfection!
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+1
IMO This ring count thing is largely nonsense. But a high ring count and dark heartwood looks pretty :-*
I've ocasionally had a 'soft' bit of Yew which as Mike says benefits from heat treatment.
My Yew has varied in ring count and colour but I've found no consistent correllation between either of these factors and performance.
You can get two bits of Yew growing 100yards apart which look entirely different yet behave the same, or look the same but behave different.
'Violations' implies a brutal dissregard for the rings. Sometimes you may need to go across rings, for a variety of reasons (see below) but it should always be done reluctantly, with caution and trying to keep any violations running along or diagonally across the bow if possible. Try to keep an even smooth sapwood layer. The ideal bow has a nothing done to the back other than taking off the bark and cambium layer.
Common reasons for going through rings.
1. Heartwood suddenly swirls or dips (or you just don't have much of it! Following a ring would leave the stave with too much sapwood (I wouldn't want more than 50% sapwood)
The pic shows an extreme example (not recomended) on a 40 year old bow, where I had to step down through about 8 rings else I'd have had no heartwood left! Bottom line, is you can only use the wood that's there.
You'll waste your life if you wait for the prefect stave.
2. The heart/sap boundary doesn't parallel to the rings. You can make the back back follow a ring or follow the heart sap boundary, but you can't do both.
I suggest you ignore the opinions of anyone who starts by saying "I read..." or "I heard..."
If they've actually made some Yew ELBs then listen, but always try to become your own expert.
After all when a bow breaks on you, people who were all too keen to give advice, won't be queueing up to take the blame.
Your suggestion of a 60" ELB is a contradiction in terms. You want at least 70". Trying to make a bow too short for it's drawlength, weight and style is a recipe for disaster. If you only have 60" then go wide and flat, you'll potentially end up with a superb bow.
If 60# hurts your shoulder.. I dread to think what 150# will do to it >:D
Del
(sorry if this sounds like I'm in 'grumpy mode' )
PS Google bowyers Diary if you want to see all my build alongs including the failures. Plenty of ELBs there with twists bumps bends and tricky sapwood... search for 'ridgeback' on the blog, that's an interesting one.
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First of all, Thanks Del for the well-thought out and detailed reply!
I think you've managed to dispel a few a few yew myths, there.
(at least in my mind!)
You seem to be the man with the experience so I'm not gonna
argue with you!
Secondly, I have NO plans or desire to make OR shoot a 150# elb!!
I was just using the example that high rpi equaled performance.
I guess that's not the case...but, I also agree that it does look pretty!
I misused the term "elb". What I meant was a "D" shaped cross-section.
I have a bunch of yew staves just waiting for some action but I wasn't
sure how to deal with the excess sapwood without possibly ruining them.
You've given me some peace of mind and confidence to proceed, for sure.
Thank you!
Oh, BTW, I check your Bowyer's Diary blog regularly. It's a great source
for inspiration (and a few laughs!).
Japbow.
P.S. Ever gotten your hands on some quality Japanese Yew?
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Thanks Mike!
I'm a realist with less than excellent draw knife skills!
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Since you're from Japan, I'm guessing you will be using your local species of yew, Taxus cuspidata? I can imagine there will be little, if any, experience with that particular species on this message board. You could run a search here; I seem to remember someone used some ornamental yew in the past... It's probably not too different from the other species, but it could still vary quite a bit. I personally think the European species of yew is generally a bit stronger than the north American species of pacific yew. I don't know where the Japanese yew would fit it, but I'm sure it'll make a good bow in the 50 pound range.
I personally do think the ringcount in yew is important. I've worked with 50 rpi and 10 rpi English yew, and noticed a lot of difference in how the wood worked. Both will make a fine bow around the 50 pound range, but the denser (=higher ring count) wood will yield a dimensionally smaller bow and is much better for heavy warbows. That being said, even 20 rpi (English) yew is good enough for a 120# warbow. Yew with a ring count of 5 rpi is probably a LOT softer than 20 or even 10 rpi. The softer wood gets damaged more easily when you use the bow for instance in the bush. I'd use the stuff with less than 10 rings per inch only for bows below 40#.
On a side note, yew with this low of a ring count is easy to chase a sapwood ring on. Get close to the ring with a drawknife, and then get the scraper to get to the right ring. It's OK if you violate one or two rings a bit, but ringchasing 20 rpi yew is really not difficult. I've also used a course rasp in the past, since this seems to take off the lighter colored earlywood from the dark latewood of the ring below it. Try it out on some scrap wood and see what tool you like best for ring chasing. Good lighting is important here.
As Del explained, the limiting factor in a yew stave is often the amount of heartwood. Especially on low rpi yew wood, the sapwood might take up half of the volume of the stave. It is your task to figure out how much sapwood to maintain. Even an all sapwood bow CAN be made, but I'd recommend to keep at least ½ of the thickness of the bow heartwood. Locate any defects and knots in the heartwood, and see how much good heartwood you're left with, so how much sapwood you'll need. I often establish the width layout first, before I reduce the sapwood.
Would you mind counting the number of annual growth rings of sapwood on your staves? I've found a consistent number between 11 and 17 rings of sapwood for English yew, regardless of the ring count (rpi). I'd like to know hoe much sapwood rings you have in that Japanese yew. Not that it matters for the production of a bow, but 15 rings of 40 rpi will of course result in thinner sapwood than 15 rings of 10 rpi wood.
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Nope... never seen any Japanese Yew.
Del
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The only bow which had the sapwood chased to 1 ring was my 90# warbow. All the rest of the ELBs or flatbows I've made from yew, I ignored that, and just made the sapwood a consistent thickness. No problems. I've never broken a yew bow. Yew is amazing bow wood. It just begs to be bent, and is so amazingly elastic. I usually leave any knots on the back a bit proud.
Also, I haven't honestly noticed much difference regarding ring count. I've made bows with 20 rpi, and bows with 60 rpi, and I can't tell a difference.
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I've never paid attention to RPI I don't see the significance
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How many yew bows have you tackled Joe?
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How many yew bows have you tackled Joe?
Bit antagonistic n'est ce pas?
Del
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Not me Del, just curious.
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I've never paid attention to RPI I don't see the significance
Higher ring count yew is more dense. It should make better heavier bows, all else being equal.
Not to be antagonistic either, but how many bows have you made from yew? Is this like the one board bow opinion? ;) ::)
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so what your saying alb, is that if you use a low rpi piece you need it to be a bit wider to compensate for low density?
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No, I just make the lower rpi staves into lighter draw weight bows.
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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?
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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.
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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
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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.
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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!!
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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
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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
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I don't know. If you're looking to make this scientific, with meaningful results, probably not.
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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 :)
(http://i28.photobucket.com/albums/c210/coaster500/Bow%20trade%202012%20TG%20and%20PA/P2212321.jpg) (http://s28.photobucket.com/user/coaster500/media/Bow%20trade%202012%20TG%20and%20PA/P2212321.jpg.html)
My tradgang bow swap victum Ralph shooting it...... Looooong arms... Yew is some bendy stuff!!!!
(http://i28.photobucket.com/albums/c210/coaster500/Bow%20trade%202012%20TG%20and%20PA/P2212337.jpg) (http://s28.photobucket.com/user/coaster500/media/Bow%20trade%202012%20TG%20and%20PA/P2212337.jpg.html)
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Are we even sure that high ring count is denser?
Yes.
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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.
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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'?
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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.
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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% ;) )
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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.
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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 :/
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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
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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? O:)
Del
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Done it, <snip>
Del
(BTW cheese sandwich is at about 20% ;) )
That's some awfully dry ole cheese!
OneBow
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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? O:)
Del
I used 1"X1" blocks made the math easy.
Yeah but del it's always good to find things out for yourself :P :D
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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.
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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
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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
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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.
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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.
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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
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So... there really is a difference. 11% is 11%. Interesting. There is merit to this story. Thanks, Del!
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@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.
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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!
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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. ;)