Compression Woods?

[PEARL DRUMS]

Weird doesn't even start to describe your ramblings. 

[BowEd]

Butt joints are fine with kerotine or horn on the belly as long as the joints are not in the apex bending portion of the limb.Mostly on shorter limbs.Longer ones not quite so dangerous.Otherwise they are doomed to fail in time and I won't try it that's for sure.Too much time gets put into it I don't care to see it blow apart so quickly any more....lol.

[Tom Dulaney]

Weird doesn't even start to describe your ramblings.

Ramblings? What gives? It's an honest question, not a rambling. Gross, but honest. I'm surprised nobody has tried this yet. I found another thread where a guy wanted to use deer hoves for the belly, why not toenails? Remember the old saying, "if you don't have anything nice to say, don't say anything at all?"

[Tom Dulaney]

Butt joints are fine with kerotine or horn on the belly as long as the joints are not in the apex bending portion of the limb.Otherwise they are doomed to fail in time and I won't try it that's for sure.Too much time gets put into it I don't care to see it blow apart so quickly any more....lol.

Thanks, I'll keep that in mind.

[Pat B]

Tom, you are describing a bow with 3 backings. Once you add another backing the previous backing it becomes a core. Hickory or sinew would make a good backing for a juniper bow. A bamboo lam would not make a good backing but would be a good core in a multi-lam bow. Even a sinew cable would make a good backing for a juniper bow.
 If you are serious about making a bow, we are here to help. If you are just blowing smoke then you will get back what you serve up.

[Tom Dulaney]

Tom, you are describing a bow with 3 backings. Once you add another backing the previous backing it becomes a core. Hickory or sinew would make a good backing for a juniper bow. A bamboo lam would not make a good backing but would be a good core in a multi-lam bow. Even a sinew cable would make a good backing for a juniper bow.
 If you are serious about making a bow, we are here to help. If you are just blowing smoke then you will get back what you serve up.

Thanks for your help. I swear I am not here to blow smoke, I just want answers for the questions that never get asked. I would like to know what you think of the reptile-scale form of gluing a material to a bow's belly? Let's assume we did it with pieces of horn that had been cut in to hundreds of very small, thin plates, and layered them over the bow's belly like scales, 2 or three times over. Has anyone ever tried this before? Seems labor intensive, but I don't know, it might produce a superior bow. It's easier to find small horns than horn that is big and clean enough to make slats for a bow belly.

[BowEd]

I have not seen that overlapping scales type of use on the belly a bow with horn.The butt joint is the only way to join horn that I know of.You don't want it to move though.Forces want to compress.One thing that does work like said earlier is to put the butt joint in the stiffer area of the design of the bow.Not in the apex bending portion.Horn bow makers that make a lots of horn bows have lots of shorter pieces left over.Longer bending limbs are more forgiving to get this done.Say a bendy handle bow for instance.An arch.I would keep that in mind.

[PatM]

I can obtain unicorn horns more readily than a sufficient supply of finger and toenails and they are easier to work and apply.

[joachimM]

Some time ago, I did an attempt at deducing bow wood properties (tension and compression) from the wood database. See this post (and especially the graphs added) http://www.primitivearcher.com/smf/index.php/topic,50571.msg692147.html#msg692147

Meanwhile, I expanded the list (and figures) to some 100 wood species, and also compiled data for other materials such as bamboo, silk, horn, sinew, flax, jute, sisal, cotton, dacron, steel, ... even fibergl*ss)

Do take this with a good grain of salt (as the primary data may be a bit iffy at times with very limited tests per species, or strongly depending on test conditions such as wood MC), and remember (otherwise Jim Davis will correct me on this): the test on osage was done on green specimens and extrapolated to seasoned wood. So it likely represents an underestimation of its true properties.

But I fully concur with Springbuck: any wood can give good bows, but design (not osage) is king. I once made a shooter out of a board of scots pine at 0.35 SG...

Joachim

[willie]

do you mean one of these, Pat?

ht    tps://polarfurtraders.com/product-category/narwhal-tusks-%c2%ad-ivory/

[gfugal]

I'm going to relist the woods suggested earlier:
Yew, Osage, Ipe, Black Locust, Plum, Juniper/ERC, Incense Ceder, Black Cherry, Padauk, Mulberry.
(Sorry SpringBuck, I didn't include your long list of exotic woods. I also didn't include very hard to come by, unfamiliar exotic woods in the following list either).
 
I also am going to propose some potential candidates for good compression woods based off my research from the wood database. They are:
Wenge, Olive, Lemonwood, Hickory, Dogwood, Indian Rosewood, Turkey Oak, Chinaberry, Muninga, Hophornbeam/European Hornbeam, Black Walnut/English Walnut, Blue Ash, American Beech, Yellow Birch, and Slash Pine.

Do any of you have it on good wisdom that any of these woods would make a bad compression wood for bows?

Some time ago, I did an attempt at deducing bow wood properties (tension and compression) from the wood database. See this post (and especially the graphs added) http://www.primitivearcher.com/smf/index.php/topic,50571.msg692147.html#msg692147

Meanwhile, I expanded the list (and figures) to some 100 wood species, and also compiled data for other materials such as bamboo, silk, horn, sinew, flax, jute, sisal, cotton, dacron, steel, ... even fibergl*ss)

Do take this with a good grain of salt (as the primary data may be a bit iffy at times with very limited tests per species, or strongly depending on test conditions such as wood MC), and remember (otherwise Jim Davis will correct me on this): the test on osage was done on green specimens and extrapolated to seasoned wood. So it likely represents an underestimation of its true properties.

But I fully concur with Springbuck: any wood can give good bows, but design (not osage) is king. I once made a shooter out of a board of scots pine at 0.35 SG...

Joachim

   

I was literally making a spreadsheet when you posted this haha. Thats cool man I'm going to have to look it over. I noticed that you have a "compression before set" value. How did you get that value, since the wood database doesn't have a measurement for it? Did you use the crushing strength value? When I was coming up with that list above I took into consideration the max crushing value, the ratio of MOR/MOE, as well as a new ratio of crushing strength/MOE. The last value isn't a real value but an arbitrary one I came up with, since the wood database doesn't specify a stress modulus of elasticity, wood would not have the same value like most materials. But I figured it would be somewhat proportional. To be considered the list the wood had to score high in all three areas (CS, MOR/MOE, and CS/MOE).

[gfugal]

Does anybody here want to tell me whether this is a futile idea or not? I have a jar full of toenails and fingernails, enough to glue across a short bow several times over. I was thinking about gluing toenails and fingernails to the belly of a bow, like reptillian scales stacked on top of one another, to give compression strength and elasticity. Reason I ask is because a.) it's the same stuff horn is made of and b.) I've seen people gluing 4-5 buffalo horn slats to the belly of a bow, and I was surprised that worked. So thanks for answering all my weird questions.

I don't think its a good Idea for the following reasons
1) I think that's going to be a lot more work than it's worth. It would be like rescaling a fish one scale at a time. It would take forever, plus it wouldn't be very repeatable. It would be easier to buy horn than waiting several years to stockpile a bunch of toe-nails again.
2) Any aesthetic value would be overweighed by its grossness, and you would find it hard to have other people admire your work as much as you do.
3) I think there would be too much glue to nail ratio that any compression value the nail gives will be lossed in the pliable glue. There's no way you would keep all those nails on without a bunch of glue.  I imagine it being almost more glue than nail and dried glue probably isn't the best compressor.

I do like how your thinking outside the box though.

[willie]

Greg

have you looked at a way to quantify the elasticity component that means so much to bow performance?

Springbuck brought up a good point about it earlier.........

 

Compression elasticity really means simply that it WILL return to shape when squished.

willie

[PatM]

It's almost like you guys are trying to re-invent the wheel or use different words to describe the same thing. 

[gfugal]

Greg

have you looked at a way to quantify the elasticity component that means so much to bow performance?

Springbuck brought up a good point about it earlier.........

 

Compression elasticity really means simply that it WILL return to shape when squished.

willie

Unfortunately, there isn't really a good value out there that's been maticoulsly measured in wood. The wood database offers a crushing strength value which is the closet thing to it. However, that value is the point the wood breaks not the point the wood takes set.

So here's a breakdown on it. Materials have certain stiffness when undergoing tension and compression. Tension is often called Strain aswell. In the first image, you have a material that is strained. The steepness of the slope of the black line is the stiffness (or modulus of elasticity). Once it undergoes a certain strain it will no longer return back to its original shape, this is called the yield point. (imagine stretching a spring to the point where it stays stretched out). After the yield point a material will be less stiff and can likewise only undergo an additional amount of strain before it brakes. the strain or stress after the yield point to the point of rupture is called the nonelastic region. Every material has different sized nonelastic regions. Metal has a large region, that's why it's so malleable. Wood however does not have a large region, at least in strain, so it breaks shortly after the yield point. These same principles can be applied to compression. Most materials, like metal, have a similar stiffness when undergoing compression and tension, thus their modulus of elasticity under compression is the same as under strain. I believe wood, however, has a modulus of elasticity under compression that's different than the modulus of elasticity under strain. I tried to illustrate this in image 2. It also has a larger nonelastic region in compression compared to strain. The nonelastic region under compression is the stifness of wood after it undergoes set. Those specific wood fibers now have a weaker stiffness than before, hence why set is bad.

The wood database doesn't have the yield points for either tension or compression. It has the modulus of elasticity for tension only and the two rupture points for compression and tension. Since It doesn't have the modulus of elasticity for compression I just used the one for tension to create a ratio. This ratio is a best attempt to determine how far a material will stretch or compress before breaking. The wood database guy did this for tension and calls it the bow index. It's basically the modulus of rupture divided by the modulus of elasticity. I basically did the same thing for compression.