Do you need to have a sinew back?

[joachimM]

sinew (sg 1.3) and osage (sg 0.75) have very different moduli of elasticity (low versus high stiffness), and yet if you combine them (without horn) it makes really great bows.
Osage cannot compress the same amount as sinew can stretch, but if you combine them in the right amounts, the forces of compression on the osage will balance the tension on the sinew (plus some tension on the osage's back).

The point is that strain doesn't need to be the same on back and belly (how far it bends, which depends on the position of the neutral plane), only the stress (what force is exerted on each surface).

 I suggest you ask Jaap Koppedrayer if his horn-bamboo bows are rubbish or not 

[Pat B]

James Parker built an Asiatic style bow with boo back and caramelized boo belly. That was one quick little bow and pulled, I believe at least 30".

...but again, this thread is specifically for true Asiatic Horn Bows, not wanna-bes.

[bubby]

Japp's boo backed composites are longer, 55-60" and have 5" more draw length with sinew back

[PatM]

Gemsbok only horn bows shoot....well poorly at best.
Horn is 1.3s.g. so adding it to a bow will simply make it slower if the horn isn't used to it's full potential.
Just because bamboo makes great 'self'bows that is not a reason to add horn into the mix. Bamboo just isn't suited to a bow with a horn belly.
Horn and sinew can both stretch/compress about the same amount and have similar resistances to bending - this is what you look for in a well designed laminated bow. Try mismatching bow woods with different properties and see what happens - broken bows or lots of set depending on which way you do it.
Make some and see! 

As noted Jaap makes them. You're not thinking this through very well.

[joachimM]

...but again, this thread is specifically for true Asiatic Horn Bows, not wanna-bes.

"all composite bows with bone, antler, ribs, baleen, sheep horn, sinew,bamboo , and/or any ethnographically correct /historical materials will be accepted"
First post in this thread. I can't see what's wrong with discussing the properties, pros and cons of a bamboo-horn composite here.
But in any sense, we're not progressing anymore. It's at risk of becoming an unproductive discussion between believers and non-believers...


Joachim

[bubby]

Not saying it can't be done but even with japp's bows they are longer than the norm with a few exceptions, and when he adds sinew hw gets 5" more draw length so there are limits to the boo backed composite

[james parker]

i see this has come full circle again... my opinion, ((just saying))
 their is  no other natural material that can come close to the well established effects or perimeters of sinew  in a glue matrix when applied to a bows back, especially in a composite horn bow,  lesser effects will be had, if replaced with other natural materials, , one material may have a greater stretch property  compared to another , and each different in gain or loss,, in cast,  early draw weight, limb return speed, and set within the most bending part of any bow limb, of any design..
of course  one does not need sinew on a per say horn belly bow, but it is nice if you have the sinew to back with, also, are you building freeform horn composite bows ,,or are you following true historical specimens ,and measurement,,
   composite  bows can be of any design, I was not trying to categorize any one bow as being legit or not.. this forum was and is intended to help ,teach,learn and show what each of us  are capable of..
 historically there is all sorts of composite bows, with sinew , without, with horn ,without, and soforth.
im going to go out on  a limb here,, not intended for any one individual.
 
do your homework, build some bows , have failures and successes, learn from them both, then report back with the end results,
we are all here to learn and share , including myself.


 

[mikekeswick]

PatM - what bit am I not thinking about? Clearly somebody makes them - what i'm saying is that it's not an optimal mix of materials. I could sinew back a bow of pasta and make it shoot arrows...doesn't mean it's optimal...now does it?! I could also use balsawood to back ipe and make it shoot arrows but it may limit my drawlength a little....comprende?!
JoacchimM - Yes indeed you can make sinew backed osage bows but if you made a good self osage bow and added sinew what would happen? Do you see what I'm saying? Did I say that Jaap's bows are rubbish?

IF bamboo worked really well as a horn bellied bows back then there would be reams of them about...because they simply don't get made may suggest something about the design...maybe?
A true composites draw length limits are only reached because of the almost perfect blend of materials and their properties. Sure it's possible to make a bow with some/half/most of the same materials BUT is it going to be as effective....no.

[PatM]

PatM - what bit am I not thinking about? Clearly somebody makes them - what i'm saying is that it's not an optimal mix of materials. I could sinew back a bow of pasta and make it shoot arrows...doesn't mean it's optimal...now does it?! I could also use balsawood to back ipe and make it shoot arrows but it may limit my drawlength a little....comprende?!
JoacchimM - Yes indeed you can make sinew backed osage bows but if you made a good self osage bow and added sinew what would happen? Do you see what I'm saying? Did I say that Jaap's bows are rubbish?

IF bamboo worked really well as a horn bellied bows back then there would be reams of them about...because they simply don't get made may suggest something about the design...maybe?
A true composites draw length limits are only reached because of the almost perfect blend of materials and their properties. Sure it's possible to make a bow with some/half/most of the same materials BUT is it going to be as effective....no.

But those examples are silly when comparing a horn bow backed with bamboo. Horn and bamboo are likely as favourable a mix as any highly regarded mix like bamboo and Ipe. or Osage and hickory.
Your sinew backed Osage in the above example would be capable of more draw length, just as adding sinew adds draw length to Jaap's bows.
PS Nobody is saying the mix would be as effective as the perfect blend at the optimum draw length but most composites don't actually reach that or the core breaks down if they do as noted elsewhere on here.

[joachimM]

PatM - what bit am I not thinking about? Clearly somebody makes them - what i'm saying is that it's not an optimal mix of materials. I could sinew back a bow of pasta and make it shoot arrows...doesn't mean it's optimal...now does it?! I could also use balsawood to back ipe and make it shoot arrows but it may limit my drawlength a little....comprende?!
JoacchimM - Yes indeed you can make sinew backed osage bows but if you made a good self osage bow and added sinew what would happen? Do you see what I'm saying? Did I say that Jaap's bows are rubbish?

IF bamboo worked really well as a horn bellied bows back then there would be reams of them about...because they simply don't get made may suggest something about the design...maybe?
A true composites draw length limits are only reached because of the almost perfect blend of materials and their properties. Sure it's possible to make a bow with some/half/most of the same materials BUT is it going to be as effective....no.

Hi Mikekeswick,

I follow your reasoning. Consider there may have been reasons not to add sinew on those bow, maybe because of relative humidity being very high, or some other reasons. My point is a horn bow without sinew isn't by definition useless (as suggested earlier in this discussion), and it can likely be optimized to be even a rather good bow, by taking design constraints of both bamboo and horn into account. 

A lot of time during the history of mankind, making particular bows was a matter of make do with the materials at hand and the constraints posed by these materials in their environment to adapt the design to fit your needs. The Vikings were perfectly well acquainted with asiatic horn bows, having done conquests and raids through the Mediterranean along North Africa up to Turkey and Syria in their time, as well as through the eastern European steppes. But in Scandinavia, they used wood longbows, because in the cold and wet climate of Norway asiatic composites were utterly useless.

So one answer to the very first question (do you need to have a sinew back on a horn bow) could be:
no, but if you live in a dry enough climate, adding sinew makes more sense if you want the best bow.

I don't think we disagree. In the current situation, where you have hotboxes to dry your bows, where climate hardly influence which bows you shoot and where you can get any materials from anywhere in the world, it doesn't make sense to make a bow that is inferior in performance, unless performance is not your main goal.
But following this reasoning, we should all chuck away our wood bows and move over to compounds with glass fiber, carbon and kevlar.

Why would anyone want to build a sheephorn bow? Not because it's the best possible bow in the world. but because it's part of someone's cultural heritage.  You don't find them around the corner either. Would they shoot better with a wood core? Yes! but you do need access to good bow wood. which the original builders of sheep horn bows didn't have. 
It's the constraints that drive us, not the limitless possibilities.
Comprende?
I'm sure you do 

[Dances with squirrels]

I came to this thread, the whole forum acthally, because my intention was to build a bamboo/osage/horn bow. Thank goodness I checked here first. Now I know not to even bother.



Just kiddin... I'm still doin it.