Author Topic: Wood Strength Chart (Read 20648 times)

bow101 · « **Reply #15 on:** December 19, 2012, 06:06:11 pm »

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...

DavidV · « **Reply #16 on:** December 19, 2012, 06:38:04 pm »

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."

burn em up chuck · « **Reply #17 on:** December 20, 2012, 09:25:02 am »

I have been very grateful for this thread, informative, technical and practical. thanks guys.

chuck

DavidV · « **Reply #18 on:** December 20, 2012, 05:27:52 pm »

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.

Onebowonder · « **Reply #19 on:** December 20, 2012, 07:44:34 pm »

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.

Jim Davis · « **Reply #20 on:** December 21, 2012, 12:35:42 pm »

Quote from: DavidV on December 20, 2012, 05:27:52 pm

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

rossfactor · « **Reply #21 on:** December 21, 2012, 01:34:59 pm »

Quote from: Onebowonder on December 20, 2012, 07:44:34 pm

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

for some first hand testing of course.

Gabe

Carson (CMB) · « **Reply #22 on:** December 21, 2012, 02:33:09 pm »

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?

rossfactor · « **Reply #23 on:** December 21, 2012, 03:09:36 pm »

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

Onebowonder · « **Reply #24 on:** December 21, 2012, 03:12:16 pm »

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

rossfactor · « **Reply #25 on:** December 21, 2012, 03:32:26 pm »

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

Jim Davis · « **Reply #26 on:** December 21, 2012, 07:10:24 pm »

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

DavidV · « **Reply #27 on:** December 21, 2012, 07:44:53 pm »

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)

Hrothgar · « **Reply #28 on:** December 21, 2012, 09:26:40 pm »

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?

Jim Davis · « **Reply #29 on:** December 21, 2012, 11:10:27 pm »

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!

Jim Davis

Primitive Archer