Compression Woods?

[willie]

Greg,

There is a good thread about the mass theory in the archive library, and  a search of badgers posts should return something.

A google search similar to         mass theory site:http://www.primitivearcher.com             may also return good results.

[joachimM]

You should want to care about the stiffness and elasticity, and mass:
if elasticity is the only thing you care for, try making a bow out of cooked spaghetti. very flexible, doesn't take set!

Second, mass: you mention if it doesnt draw enough, just add more material (more spaghetti?). But I bet you wouldn't be satisfied with a bow weighing as much as a 60# normal bow, but drawing only 30#. Mass (and mass placement) is critical to bow performance.

As for the bone information: the information I gave was on the yield point, not the failure. The load-displacement graph: check it out here
http://dx.doi.org.sci-hub.cc/10.1016/0021-9290(74)90018-9, look for figure 7b and the text just under "results" on the next page.

And for the database update: you can find it on my google drive: https://drive.google.com/open?id=0B3YYA3Sr_3gqMm9oWkExTjdiOTg

Joachim

[Limbit]

I have no idea about the technicalities of using the bone as a belly material apart from seeing it being used by horn bow makers from time to time as a belly material. I've never made a horn bow or a bone bow, but am wanting to try bone at some point out of curiosity. Most horn bows are made with a wood core to stabilize the horn and as I am guessing, also to reduce the overall weight of the bow since horn is also very heavy. I would do the same with a bone bow if I were to make one. I would make the belly lam as thin as I could get away with to reduce weight and have a wooden core. The thinner the material, the more likely it will bend, so I am guessing this would take care of any bend issues with the bone. Like I said, my information is very incomplete on bone, I am just throwing the possibility out there since others have used it and you seem interested. Biggest problem would be getting long enough bone and reducing it to size. Doesn't exactly split well of cut easily!

[Del the cat]

Regarding bone:-
It does flex a bit and it isn't all that brittle, I s'pose it's a matter of degree.
I remember playing footbal (soccer) and sliding into a tackle. I got the ball but the other guys legs caught me and I felt the whole leg bend sideways, just like floor tillering a bow. Fortunately it didn't go bang.
Del

[joachimM]

Bone is a composite material, consisting of a matrix of collagen (which gives the flexibility) surrounded by calcified tissue (hydroxyapatite; which gives rigidity). Remove the calcium and you get a floppy, porous rubber-like core. Remove the collagen, and you have a brittle stick.

Bone is three times as heavy as most bow woods, but also about three times stronger (according to the paper I discussed). So per unit of mass, you get about the same compression strength as wood. You can compress it a bit further than wood, in theory, according to these lab results, that may not represent actual conditions in which we shoot bows.

Antler is also bone, by the way. Ask people making antler bones how they perform.
Many people will talk about "elk horn" (including the bowyer in the video below), but antler is bone, not horn. 
http://www.primitivearcher.com/smf/index.php?topic=49910.0
https://www.youtube.com/watch?v=STP-n-s_Ji4

Check this one out, especially
https://www.youtube.com/watch?v=JmfYJBha7SU
and https://www.youtube.com/watch?v=LpkLs_3jpI4 (shooting at 5:39): wood handle, working limbs of caribou antler and a sinew cable (see 7:45 for details)

And also see this thread from 2010: http://www.primitivearcher.com/smf/index.php?topic=20199.0
quoting KenH: "I would guess that if bone were a reasonable substitute for horn, this whole conversation wouldn't be taking place, because we'd have seen lots of examples"

[Selfbowman]

My recommendation is to quit researching spend the time making money to buy a good Osage stave say 100 plus shipping and build a bow dude. You have the cart before the horse. I don't know you and your skill level with working wood . Working wood is the only way to learn it though. Arvin

[PatM]

Yep. Unless there is some as yet undiscovered super wood out there we're just juggling the known woods with design factors.

[Limbit]

Bone is a composite material, consisting of a matrix of collagen (which gives the flexibility) surrounded by calcified tissue (hydroxyapatite; which gives rigidity). Remove the calcium and you get a floppy, porous rubber-like core. Remove the collagen, and you have a brittle stick.

Bone is three times as heavy as most bow woods, but also about three times stronger (according to the paper I discussed). So per unit of mass, you get about the same compression strength as wood. You can compress it a bit further than wood, in theory, according to these lab results, that may not represent actual conditions in which we shoot bows.

Antler is also bone, by the way. Ask people making antler bones how they perform.
Many people will talk about "elk horn" (including the bowyer in the video below), but antler is bone, not horn. 
http://www.primitivearcher.com/smf/index.php?topic=49910.0
https://www.youtube.com/watch?v=STP-n-s_Ji4

Check this one out, especially
https://www.youtube.com/watch?v=JmfYJBha7SU
and https://www.youtube.com/watch?v=LpkLs_3jpI4 (shooting at 5:39): wood handle, working limbs of caribou antler and a sinew cable (see 7:45 for details)

And also see this thread from 2010: http://www.primitivearcher.com/smf/index.php?topic=20199.0
quoting KenH: "I would guess that if bone were a reasonable substitute for horn, this whole conversation wouldn't be taking place, because we'd have seen lots of examples"

I agree, antler bows are essentially bone bows and prove that bone is a usable belly material, but they also highlight the issues of using bone as a material. For one, it is far more time consuming to prepare than either wood or horn. Second, it has more complications due to the difficulty of getting appropriate material. Third, and most importantly, it does not perform as well as horn. I think this all sums up why we don't normally see it used in bows. Thanks for the detailed info by the way!

[Tom Dulaney]

How do you know which side of a bone has the collagen material and which side is hard? I know antler is easy because it has a spongey core that makes up the back of the bow, so you scrape the horn on the outside which is the belly. What part of the bone should I scrape?


I disagree that bone is more difficult to work. It is hollow so all you have to do is find a piece that is near to the dimensions you want your bow to be (ribs?) and engrave or saw it longitudinally. Bone is also very easy to work by abrasion as compared with wood (try using rocks to abrade wood that hasn't been dried for 30 years). Wood on the other hand is a treacherous, spiteful, sick, unforgiving, hatefuuuuulllllllllllll material

[PatM]

Sounds like you have a firm opinion of something you've never worked with.

[Tom Dulaney]

Sounds like you have a firm opinion of something you've never worked with.

I have worked with bone before. Made all kinds of stuff from it, with nothing but a flint burin and a few river stones. What're you talkin bout, Bertha?

[Tom Dulaney]

Why are there so many people named Patrick on this website?

[PatM]

Sounds like you have a firm opinion of something you've never worked with.

I have worked with bone before. Made all kinds of stuff from it, with nothing but a flint burin and a few river stones. What're you talkin bout, Bertha?

 Well you don't know which side is porous and don't realize that the collagen is dispersed throughout.    Are you a vegetarian?  Most people could glance at a T-bone or a dog bone and figure that out.

[Tom Dulaney]

Sounds like you have a firm opinion of something you've never worked with.

I have worked with bone before. Made all kinds of stuff from it, with nothing but a flint burin and a few river stones. What're you talkin bout, Bertha?

 Well you don't know which side is porous and don't realize that the collagen is dispersed throughout.    Are you a vegetarian?  Most people could glance at a T-bone or a dog bone and figure that out.

Well, that was my concusion, but bat-boy Joachim M over here said that if you scrape off too much collagen you'll get something stiff, and that if you scrape off too much of the stiff stuff, you get something wobbly. If the collagen is dispersed throughout, that should be impossible. No matter where you scrape you're going to have a piece of bone with roughly equal parts collagen and equal parts hydroxyapatite. It's not like antler where you have a visible sponge layer (in the core). So, which know-nothing am I supposed to lend faith to here? Wil it be JoachimM, or PatM? Why are there so many people here with a surname that starts wifh the letter "M?"

[PatM]

I don't believe he used the word scrape. You need to soak a bone in vinegar to remove all but the collagen since it is dispersed throughout. That's what makes it a natural composite.