Primitive Archer
Main Discussion Area => Bows => Topic started by: DavidV on December 18, 2012, 11:10:57 pm
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I've been using a neat site for my wood properties information but comparing multiple woods was difficult. I made this excel spreadsheet with all the necessary information I need of the common (and uncommon) bow woods. These are just American domestics but I have plans for exotics for backed bows and such.
Oh and sorry if the type is too loud, it's meant for print.
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No particular order although I tried to match related species.
and here's the origional website. http://www.wood-database.com/
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David, that is a very useful chart. I have been using the Forest Products Laboratory data for years and have made a few charts similar to yours in Word, but yours is far easier to use.
I tried to sort the data according to the elasticity and got a message that the operation could only be done if the "merged cells are of exactly the same size." So, I tried to sort for specific gravity, because it looked like those cells were of the same size, but got the same message.
Can you sort your original by elasticity, or s.p.?
Jim Davis
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I like the chart and I use the wood database a s a reference sometimes also. I do have some serious doubts about some of the data here.
It seems like crazy and wrong to me that woods like mountain ash, yellow birch and red oak are rated at a higher elastic strength than Osage, Yew and Hop Hornbeam. I have no data to back this up, but it feels wrong. I wonder if elasticity is measured based in green or kiln dried wood.
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Could someone perhaps give a brief breakdown of this data, the subgroups the data is in, and its correlation to the wood and performance? Not looking for an in depth analysis by any means, just something to make the data a little more understandable to a guy like me! ;)
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I agree with Rossfactor. Some of this data seems a little suspect.
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DavidV, I think your chart is a good idea, I've visited that website several times. Anymore I tend to regard it with a grain of salt. I don't so much doubt the info as I doubt my ability to understand or implement the info. For example, Persimmion is rated denser and more elastic than osage (or about any other wood) but rarely do you see guys making bows with it. Also, sweet gum is rated similiar to the elms, yet I know when my grand kids attempt to climb the one in my front yard the limbs bend and snap without much resistance, much like a cherry tree. Most bowyers will tell you that shagbark hickory is the top choice of the hickories, yet in the chart two other hickories are supposed to be more elastic. An another important factor for good bow wood is how quickly the limbs will recover after the arrow is released. I'm not sure this factor can be predicted using the wood chart. Nonetheless, this is still good information to have charted.
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Have any of us ever asked to people over at Wood-Database for an explanation of the numbers they have posted or our confusion over some of the things that appear odd to us? What kind of responses have you gotten?
OneBow
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DavidV, I think your chart is a good idea, I've visited that website several times. Anymore I tend to regard it with a grain of salt. ... For example, Persimmion is rated denser and more elastic than osage (or about any other wood) but rarely do you see guys making bows with it. ... Most bowyers will tell you that shagbark hickory is the top choice of the hickories, yet in the chart two other hickories are supposed to be more elastic....
The information in the chart appears to have been copied from the data presented long ago by the Forest Products Laboratories. It is good data. The one exception I have found is that FPL never recorded data for DRY Osage. The website that is the source of David's chart notes that its data for dry Osage is an estimate (because no test data is known).
For the hickories, however, pignut is the strongest in every measure I have ever seen on any chart. All the hickories are good, but pignut is the best. Those bowyers who say shag bark is the best are demonstrating how experience is compiled from anecdotes, and 1,000 anecdotes do not constitute either a statistic or a proof.
Yellow birch is always way up in the charts, as are black locust. persimmon, and serviceberry. Persimmon had quite a following in the middle of the last century. Hornbeam and white ash have similar numbers.
<a href = "http://www.fpl.fs.fed.us/research/centers/woodanatomy/techsheets_display.php?geo_category_id=2&genus_commonname_criteria=c&sorting_rule=1a">forest products laboratories</a>
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Jim,
Elastic strength is a measurement of the ratio of stress placed upon the wood compared to the deformation (lets call it set :)) that the wood exhibits along its length.
I will take a piece of yew and apiece of red oak, of the same dimensions, dried to the same moisture content and submit them to the same stress, and I'll eat my hat if the red oak takes less set (or is deformed less).
Gabe
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Jim,
Elastic strength is a measurement of the ratio of stress placed upon the wood compared to the deformation (lets call it set :)) that the wood exhibits along its length.
I will take a piece of yew and apiece of red oak, of the same dimensions, dried to the same moisture content and submit them to the same stress, and I'll eat my hat if the red oak takes less set (or is deformed less).
Gabe
I don't think it should be called set. My understanding of this is simply how much it bends under a load, just like when you spine your arrows, not how much deformation it retains when the load is removed. Just sayin ;)
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Oh, maybe I'm confusing elastic strength with the tendency of a material to be deformed plastically e.g. retain its deformation, under stress. For some reason I thought that was elastic strength. My bad then. Been outta school too long already ;)
Gabe
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The data seems a bit sketchy.....
They must not be bow makers over at the lab :P
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No offense...but to me these data charts are pretty useless to me...in my opinion other bowyers experiences is waaaaay more trustworthy than some lab test not aimed for bowyering. When I go to use a species of wood I've never used before I research and find out who's used it before and what worked and didn't worked for those folks,and go from there. I have used woods that no one else had ever documented using before as well,and I gauge the wood by its mass as a bow using the mass principle. Sometimes "experiences" are a better teacher,than some classroom/lab numbers.
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No offense...but to me these data charts are pretty useless to me...in my opinion other bowyers experiences is waaaaay more trustworthy than some lab test not aimed for bowyering. When I go to use a species of wood I've never used before I research and find out who's used it before and what worked and didn't worked for those folks,and go from there. I have used woods that no one else had ever documented using before as well,and I gauge the wood by its mass as a bow using the mass principle. Sometimes "experiences" are a better teacher,than some classroom/lab numbers.
All engineering tables of mechanical strength are to be used as indications of what can be expected from a material under certain conditions. Wood is not a uniform material, even within one tree. But the FPL tested hundreds of samples of each wood to come up with an average of the data.
Every stave any bowyer uses may deliver entirely different results than the next stave of the same wood. FPL's data might never prove to be an accurate predicter for any stave we ever use. But the data does display the average relative strengths of woods.
The opinions of bowyers will change over the years of their work, but the average strength of varieties of woods does not change. The data tables are a quick way to get an idea of what to expect.
Jim
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I guess by now we know what makes a good bow wood. I have that chart somewhere, and the way I look at it is even if you are using the "best material" hence best as been in quality, dryness, grain texture, dimension, design characteristics etc.......etc.....if she's gonna break she's gona break no matter what the woods density is. I only think that chart is a guide line. It is not a end all solution to perfect Bow Building... :)
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This chart is by no means meant to tell you what will make a good bow or not. I mainly use it to see what kind of design it could take, wide and flat, narrow and deep ect. . I think the biggest problem with comparing the data is understanding WHAT is being compared. Elastic strength isn't the same as tensile strength which is why osage and yew fall behind. I really wish there was information on tensile strength so I could compare it to compression, THEN the information would be more useful. Specific Gravity is density, weight is weight. Compression is just like the force placed on the belly of a bow.
These numbers are only meant to give general ideas. Like others have said, the tests were not done by bowyers... I doubt anyone was chasing rings. This was the comment for Pacific Yew on the site:
"Yet perhaps Yew’s greatest claim to fame is that of its mechanical properties: despite its strength and density, Yew has an incredibly low and disproportionate modulus of elasticity at only 1,320,000 lbf/in2 (9,100 MPa). What this means is that the wood is extremely flexible, yet strong, making it ideally suited for use in archery bows. In fact, Yew was the wood of choice for English longbows in medieval warfare."
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I have been very grateful for this thread, informative, technical and practical. thanks guys.
chuck
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Jim, I may be able to sort it by elasticity manually... but it takes a long time because I'm using Office 2003 and my computer isn't that great.
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So, I contacted Eric Meier at the Wood-Database site and after some discussion, he directed me to the following article on his site: http://www.wood-database.com/wood-articles/bow-woods/ It's an explanation to his way of thinking anyway, of what woods make good bow woods. Basically, the formula he has espoused is (MOR/MOE)X1000 = B where B is a number that he means to represent an indication of the quality of a wood as a bow making material. This formula achieves results that seem to track somewhat with the experiences of the folks on this site.
If you Osage and Yew bigots read the above article, take some tissues with you. If all things Bow Wood are to be judged by the prescribed ratio, then neither Osage nor Yew will wear the crown. ...they both do VERY well mind you, but neither is the BESTEST.
Unfortunately, the MOR number, is not one of the ones collected in the spreadsheet that was attached to the opening post of this thread. MOE is there, ...but not MOR. the MOR stats are on the DB for most of the wood species on the site however and could be collected and added to the spreadsheet. From there it would be trivial to add the formula into the spreadsheet. One could even tweek the formula to give weight to other factors for each wood type.
OneBow
BTW - I'm well aware that there a myriad other factors involved in what makes a suitable bow wood.
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Jim, I may be able to sort it by elasticity manually... but it takes a long time because I'm using Office 2003 and my computer isn't that great.
David, sorry I missed your reply when you posted it. Just now saw it. I would not ask you to sort your chart manually. I was just hoping that maybe your version of the spread sheet was sortable automatically. Excel should be able to do that, but my version won't.
I appreciate the work you did to compile the chart.
Jim
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So, I contacted Eric Meier at the Wood-Database site and after some discussion, he directed me to the following article on his site: http://www.wood-database.com/wood-articles/bow-woods/ It's an explanation to his way of thinking anyway, of what woods make good bow woods. Basically, the formula he has espoused is (MOR/MOE)X1000 = B where B is a number that he means to represent an indication of the quality of a wood as a bow making material. This formula achieves results that seem to track somewhat with the experiences of the folks on this site.
If you Osage and Yew bigots read the above article, take some tissues with you. If all things Bow Wood are to be judged by the prescribed ratio, then neither Osage nor Yew will wear the crown. ...they both do VERY well mind you, but neither is the BESTEST.
This is an interesting article, and I think there is some credibility to his approach. Of course lots of the non-numeric values of bow wood are considered; however, when you consider that the only woods that rank higher than Osage and Yew are two relatively obscure varieties of rose wood, I'd say his formula supports the popular opinion on what woods make a good bow. And it also makes me want to get my hands on some Madagascar rosewood >:D >:D for some first hand testing of course.
Gabe
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I doubt yews dynamic nature (sapwood/heartwood) was taken into account during the testing. More likely it was a piece of yew heartwood lumber (or even many samples of yew lumber) that were low-elevation wide grain...not the best yew. Same with osage, I doubt the samples were hand selected for the best early to late wood ratios. I like the idea of a bow wood index, bt i would like to see MOR and MOE numbers collected from yew and osage samples that would be considered prime, grade A yew and osage.
That said, where (outside of Madagascar) do I find Madagascar rosewood? ;)
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Yeah CBM, I thought the same thing. I can see why they would use pieces of heartwood lumber. It's impossible to keep dimensions exactly the same, when you leave the back of a stave intact, or a single growth ring established, which would negate the reproducible of their tests. Although I guess if you were looking at these stats "per unit mass" than you wouldn't need to keep them the same. Hmm.
Gabe
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I just called my local exotic lumber place to check on Muninga's availability. Looks like it would be a special order type of thing.
I understand that Madagascar Rosewood could get you arrested. ...but then again, ...who around here is gonna know what the heck it is???
OneBow
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Yeah, I guess Madagascar's forests have been pretty devastated. Guess I'll stick with Yew and Plum :). Also, there are so many varieties of rosewood the chances of getting one that has all the properties implied in the paper are really really slim.
Gabe
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I like charts and numbers, but when the above article says "the best bow woods tend to be those that will bend easily, and not break.,' I think he has half of the concept exactly backwards. We need a wood that is HARD to bend, not easy. That way, it takes less wood to do the job.
He did say he is not a bowyer. His statement proves it. Willow is easy to bend without breaking, and makes one of the worst bows.
Jim Davis
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I added the modulus of rupture to the chart as well a the "bow number" just to see if there was any credibility. But I'm like Jim on this and I think a better formula could be worked out. I mean Scarlet oak has a higher number than pignut hickory.
First one is the origional list with data added. Second is sorted with highest bow number on top. (Plum excluded)
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After following this thread I'm again wondering why some of the woods that are favored for self bows are never used as core wood or limb laminations by some of the major bow companies; such as ash, mulberry, hackberry, or hickory.
I wonder if this might make for a topic for discussion?
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Hrothgar, woods used for cores are chosen for appearance. The middle of a bow does almost nothing for energy storage. At the center, there is neither compression nor tension--only shear and not much energy stored that way.
The power of a bow is concentrated at the back and belly surfaces.
No doubt this would make a lively discussion because there are those who know nothing of the physics involved and have a favorite magic component such as "Actionwood," that they are sure is improving performance in bows.
That the core does not contribute much to energy storage can be seen in the "foam core" bows. All the core does is separate the back and belly laminations.
There you go. That spark ought to ignite a few bits of tinder! >:D
Jim Davis
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Thanks Jim, this time of the year ignited tinder is welcome.