Primitive Archer
Main Discussion Area => Bows => Topic started by: Halfbow on October 14, 2019, 05:50:41 pm
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I was thinking about the glues people use to sinew bows. Hide glue is widely regarded as the best glue for it, and there are two main reasons usually given:
1. It's made of basically the same stuff as sinew, so it combines with it and forms a strong matrix of cohesive material.
2. It shrinks when it dries and pulls the bow in to reflex, pretensioning the back.
But a number of people have tried with something like Titebond III for its waterproof qualities, and most seem to report that it works fine and they get a good bow out of it.
If Titebond III soaks in and adheres well enough, why does the cohesive matrix matter? And if you manually add reflex while you're gluing up, why does the shrinking induced reflex matter?
I hypothesized there is a 3rd reason hide glue is the best. So I decided to do an experiment. I used Knox gelatin glue instead of hide glue, as its easier for me to obtain, but the results should be about the same. It's all fairly unscientific, but I think you guys might find the results interesting.
I got 2 equal lengths of flax string. Soaked them in water, squeezed out the water, soaked one in Titebond III and the other in Knox glue, then squeezed out the excess glue. I hung them up to dry and twisted them up with themselves.
(https://i.imgur.com/kireCmP.jpg)
The dark one is Knox glue, the light one is Titebond III (the color difference is only from the wet glues).
They both took 2 days to dry and to stop losing weight. I waited 5 days just to be sure. They had hardened and stiffened nicely, and were both a lot like long twigs. Before the glue, each string weighed 3g. After the glue dried, the Titebond III string weighed 8g, and the Knox string weighed 11g. So Knox is considerably heavier, which is bad.
However... here are some bend tests. The first bend in the video is the first bend ever. Hide glue is on top.
https://imgur.com/a/JaBN0i5 (https://imgur.com/a/JaBN0i5)
I was just eyeballing the amount of bend, trying to bend them each equally progressively more each time. I hope the difference in spring back comes through in the video, it was quite evident in person. But what you can't see is how much stiffer the Knox string was. It took considerably more force to bend. And note the difference in the set they took. In light of this, I will be using hide glue for any backing with which the glue soaks in and makes up a significant part of its structure (sinew, paper, cloth, cordage, plant fibers). Mechanically, using Titebond III seems rather like using perpetually green wood as a backing.
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interesting experiment halfbow there have been similar experiments in the past (I think).
you are probably correct that a PVA glue could offer much in stiffness in thicker sections. Makes me wonder about weldwood (ureaformaldehyde wood glue) with a plant fiber?
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Wouldn't Weldwood be too brittle...or would it? I've used it on a few backed bows and I really like it but the seasoned glue seems pretty hard and brittle. Just wondering.
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the problem with using titebond for sinew backing is it dries too fast for the sinew to really do its magic... IMO..if I go to the trouble to sinew a bow I'm gonna get all I can out of it and sinew and hide glue do just that... gut
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If this sort of test has been done before I'd be really interested to see, if anyone can dig up a link. My searching was unsuccessful. And yeah I'd like to see this sort of test done with more glues. I've never worked with Weldwood but it seems interesting. A chunk of cured hide glue is super hard too, so maybe it would work well?
Maybe the difference I'm showing matters less with backings, because the backing is only under tension? In my test the strings are feeling both compression and tension, so possibly all I'm showing is that Knox glue is better at compression than Titebond III. And we don't need to care about compressive strength for backings? I'm not sure
But... it still seems to me that this difference in springiness has got to make a difference for bows. The hide glue really impressed me. When bending the strings by hand, the difference in feeling was stark. I wouldn't expect to get that much spring from any stick of wood. It actually has me wondering about a bow made out of just a bunch of string and hide glue... Probably terrible, but maybe an experiment for the future. :p
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the problem with using titebond for sinew backing is it dries too fast for the sinew to really do its magic... IMO..if I go to the trouble to sinew a bow I'm gonna get all I can out of it and sinew and hide glue do just that... gut
+1
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If this sort of test has been done before I'd be really interested to see, if anyone can dig up a link. My searching was unsuccessful. And yeah I'd like to see this sort of test done with more glues. I've never worked with Weldwood but it seems interesting. A chunk of cured hide glue is super hard too, so maybe it would work well?
Maybe the difference I'm showing matters less with backings, because the backing is only under tension? In my test the strings are feeling both compression and tension, so possibly all I'm showing is that Knox glue is better at compression than Titebond III. And we don't need to care about compressive strength for backings? I'm not sure
But... it still seems to me that this difference in springiness has got to make a difference for bows. The hide glue really impressed me. When bending the strings by hand, the difference in feeling was stark. I wouldn't expect to get that much spring from any stick of wood. It actually has me wondering about a bow made out of just a bunch of string and hide glue... Probably terrible, but maybe an experiment for the future. :p
You aren't crazy, and I am going to be doing a very similar thing with my 26 inch long pony tail I just cut off. I will be experimenting first with my 8 inch beard I also recently cut and saved for this purpose.
If you are crazy, at least youn arent alone....
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You aren't crazy, and I am going to be doing a very similar thing with my 26 inch long pony tail I just cut off. I will be experimenting first with my 8 inch beard I also recently cut and saved for this purpose.
If you are crazy, at least youn arent alone....
Haha well it's good to be crazy with company, I look forward to hearing more about that. Maybe your hair will become the most sought after bow material in the land.
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Interesting, Halfbow. Thanks for sharing.
T
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Would the weight of the dry hide glue,.,depend on how u mix it,,....thick or thin
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The hide glue does a much better job of allowing the inner parts of the sinew to day out. The tightbond may be sealing some of the moisture inside of it.
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Dick Baugh did some testing on this. Interesting read. You can Google "Secrets of Sinew Revealed" with his name.
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Would the weight of the dry hide glue,.,depend on how u mix it,,....thick or thin
Yep, as well as how wet the fibers were when you put them in the glue, and how well you squeeze out the excess glue. Many variables here. I think most of them can be basically boiled down to, how many solids are are you leaving to dry. I had the Knox glue at about as thick as maple syrup at 130f. From there I tried to keep it the same between the Knox and the Titebond. Same damp fibers, same level of squeezing out the excess glue. My goal was a typical use scenario, and I did what felt right to me for a bow backing.
The hide glue does a much better job of allowing the inner parts of the sinew to day out. The tightbond may be sealing some of the moisture inside of it.
Would the same be true for my wet flax fibers here? Perhaps that's part of the reason the Titebond had so much less spring. However, with the Titebond ending up weighing so much less, I imagine the effect can't have been too pronounced.
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Tight bond is a plastic, is known to flex with what's called glue creep. It's part of the features of the glue. Hide glue hardens up much more and doesn't have the flex that tight bond does. These lies the difference.
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ok you guys knew this was coming,, which one is gonna shoot faster,, I mean more effeciently (lol)
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ok you guys knew this was coming,, which one is gonna shoot faster,, I mean more effeciently (lol)
Probably a tie. consider how light the tight blond is.
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Dick Baugh did some testing on this. Interesting read. You can Google "Secrets of Sinew Revealed" with his name.
Thanks, an interesting read indeed. But his main conclusion seems to be to use hide glue because it shrinks and pulls the bow in to reflex. I don't see why you couldn't get all the benefits of that by just manually inducing reflex during glue-up with a different glue. I don't see anything special about getting reflex from shrinking glue vs getting it from a backwards braced bow. Just different ways of getting the same reflex.
What I'm talking about has much more to do with the hardness and springiness of the cured glue. (Like you were saying Sleek)
ok you guys knew this was coming,, which one is gonna shoot faster,, I mean more effeciently (lol)
In the context of a bow backing, I'm not sure. But I will say this. If I took my two flax twigs and strung them up, making tiny bows with terrible tillers, I'm certain the hide glue bow would've made a decent toy. It would've confidently shot a tiny arrow across the room. The Titebond one.. I imagine that when I released, the arrow would just fall to my feet. So though the hide glue is heavier, it seems much more able to carry its own weight than the Titebond.
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http://www.primitivearcher.com/smf/index.php/topic,63182.0.html
has some discussions about hide glue. related to this thread, I dried some strands of sinew with out glue, and they did not shrink much when mildly restrained. If glue/sinew matrix shrinks, but the sinew by itself, not so much, then I am not sure that having a stave pulled into reflex by drying is all that beneficial. This is not to say that having reflex does not help a design, but only to support your Idea that how you obtain the reflex may not matter much.
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I believe that shrinkage is the main benefit. If you use a PVA glue the sinew still shrinks, but the glue does not. That means some of the sinews potential is used up pulling on the glue. With hide glue it is pulling the bow into reflex along with the sinew. That, coupled with the sinews ability to stretch without breaking is the “secret” so far as I am concerned.
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Slim,
are you saying you have tried the titebond/sinew combo and the bow was pulled into reflex by the matrix(or possibly the sinew acting alone)?
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No, I never have. I simply know a lot of people who have done it with PVA glue and none have said the results were as good as hide glue. When you question why, and look at the available research, what little there is, that appears to me to be the most reasonable conclusion.
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reported results cannot be argued with Slim, Thanks
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Not sure I follow...
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I believe that shrinkage is the main benefit. If you use a PVA glue the sinew still shrinks, but the glue does not. That means some of the sinews potential is used up pulling on the glue. With hide glue it is pulling the bow into reflex along with the sinew. That, coupled with the sinews ability to stretch without breaking is the “secret” so far as I am concerned.
If you reverse brace a bow, you are compressing the wood on the back of the bow, shortening the back. Then you glue your backing on to this shortened back. Then when you remove the string that was bracing it, the wood tries to return to its original position, tries to lengthen the back. But the new backing stops it from going far, reflex is held. The backing (sinew and glue alike) gets tensioned by the wood trying to return, no shrinkage necessary. If, while drying, the sinew does shrink without the glue, the only potential that gets "used up" is potential to pull the bow in to reflex. Which you don't need because you've done it with muscles and a string. As long as everything adheres and dries properly, the end result seems very similar to getting reflex by shrinkage. In both, you end up with a backing that in some sense is too short for the bow. If do this with both methods on clone bows and you make the amount of held reflex identical, then the amount of pre-tension on the back must be identical. You can tell because it's pulling the wood in the same way.
I'm genuinely curious, did the people you know who tried it with PVA manually induce the same amount of reflex that hide glue would've pulled the bow in to?
If there is a performance difference even with the same amount of reflex, I feel like the difference that my test here highlights is probably the real consequential difference between glues.
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This is just as I understand and interpret things...if the sinew shrinks upon drying, and will pull the bow into reflex of some degree, and the hide glue shrinks at the same rate further pulling the bow into reflex. And we see that the PVA glue does not shrink significantly upon drying, then the shrinking sinew is pulling on the non shrinking glue. This will be true regardless of how much reflex you bend in, so some of the sinews potential is being lost unlike when using hide glue. Again this is just as I have come to understand it.
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If u made two bows,,,used same amount of sinew,..put same reflex,..one bow might hold the reflex better,.depending on the glue...giving it better performance
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I've used TBIII over a sinew backing for waterproofing but never used it as the glue for a sinew backed bow. I know folks that have and are happy with the results but for me it hide glue for sinew. :OK
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If u made two bows,,,used same amount of sinew,..put same reflex,..one bow might hold the reflex better,.depending on the glue...giving it better performance
Definitely. I figure it's usually possible to get the same reflex to hold initially with the necessary know-how, but if one glue loses it faster over time/use I want to know about that. I suspect that might indeed be the case.
Hide glue for me too. But not just for sinew. My test has me thinking it's better for plant fiber and such too.
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Slim,I am just saying that test results are more substantial than speculations.
Two thoughts come to mind Halfbow.
when experimenting, consider that the amount of shrinkage of most things that dry is directly related to how much water is evaporated,
and plant fibers typically have very little stretch compared to sinew/glue. there are exceptions and yarns (twisted fiber) have more stretch than straight fiber
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Gotcha. So much of this is by feel for me. Almost all of it really. I appreciate the the testing that others have done and rely on it, if it matches up with what I have experienced. My rule is that if a test or pole or data tends to defy common sense, I cast it aside. The hide glue vs PVA glue...common sense leads me to accept that hide glue is preferable with sinew. I am open to another possibility.
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Two thoughts come to mind Halfbow.
when experimenting, consider that the amount of shrinkage of most things that dry is directly related to how much water is evaporated,
and plant fibers typically have very little stretch compared to sinew/glue. there are exceptions and yarns (twisted fiber) have more stretch than straight fiber
Yep, I mean, Titebond shrinks a lot in volume when it dries too. A dry glob of it is much smaller than it was when it was wet. It just doesn't shrink in a forceful way that pulls things anywhere, so it doesn't really matter in this context.
And yes I agree about plant fibers. They're a totally different beast from sinew. I wasn't suggesting plant fibers are a straightforward replacement for sinew, or trying to get to a sinew vs plant fiber debate. I certainly wasn't saying plant fibers are a better backing than sinew.
But a lot of people do use plant fibers/cloth/etc as backing, and many use pva glues to saturate them. My point here is merely to suggest that these people might get eek out a little more performance if they switch to hide glue. My test showed me pretty clearly how much more springy hide glue + plant fiber is.
Gotcha. So much of this is by feel for me. Almost all of it really. I appreciate the the testing that others have done and rely on it, if it matches up with what I have experienced. My rule is that if a test or pole or data tends to defy common sense, I cast it aside. The hide glue vs PVA glue...common sense leads me to accept that hide glue is preferable with sinew. I am open to another possibility.
I don't think anyone in this thread has stated a preference for pva, so no worries about other possibilities here. :p My personal feeling is that hide glue might be even more useful in more situations than is usually thought.