Sinew - Layers Versus "Pile It On"?

The only real advantage of 'installments' is thorough drying of the inside layer. I suspect that the disadvantage of 'one massive layer' may only appear after a few years.

Also, the addition of sinew is the only tillering option for a sinew-backed bow. You can't tiller by sanding down.

I can also see where you would get more uniform orientation of the strands with thin layers. I've been able to get thicker layers to dry evenly, but you have to let it dry slowly or the surface will crack open. In the futre I will apply in several thin layers.

That sound interesting (and a little strange?) for me.
If you can tiller the bow by adding sinew why does sanding the dried sinew layer does not work?

Btw, I think (but can not prove) that applying the sinew layer by layer with an appropriate drying periode in between helps to build up the stress more uniform between the layers.

And, not at least, to work layer by layer helps a lot to avoid the separation between sinew and wood. The outmost layer drys faster, shrinks and peels the inner layers, which are not bound so tightly, off the wood.
I found this behaviour when I forced the drying by applying a moderate temperature when the sinew was not dried to a translucend layer :o

But I'm open for any prove that my failure was something different :shock:

Edit: Tom, you've been faster :-).

One more reason for a layer by layer technique: it is easier to avoid to have too mutch glue which makes this nasty cracking sound when strung first. :shock: :twisted:

Axel I think you are right about the outer layer pulling the moist inner layer loose. I've had that happen a time or two. And I do think that several thin layers may build up a bit more tension. Although, when I have tried to apply a second layer, I've found that it causes the first layer to relax a bit as it absorbs soem of the moisture of the new application. I suppose I should focus on getting as much excess moisture squeezed out of the new layer prior to application.

As for sanding, it would be somewhat like violating a ring on a wooden bow back. Although, these strands do not extend the length of the bow to begin with. But they are cemented together well enough, but not so much to the layer of sinew below a given level. Come to think of it, I added another layer of sinew to the inner limbs and handle of my bow, it seemed those areas were a bit thinner than midlimb. Now I think I should add another even layer over the whole bow to re-create the "single ring" effect.

Guys; Once again someone else may have other experience but here is what works for me. Prepare leg sinew until it is soft, removing all "crunchy ends". Preparation is so important. Size the bow several times. My thinking is that it would be difficult to overdo the glue because glue shrinks to nothing! My read on squeezing out glue would be more like removing air bubbles. Glue is more easily kept warm in a double boiler, but as others have warned, do not overheat the glue, it is not necessary.

Lay out the bundles by size and put them on the easiest way possible, but not all at once.

Here is where others may disagree. After sinewing one limb, I cover the backing with short sections of plastic wrap, pull it down on the edges. Sinew the other limb and wrap. After finishing sinewing, the sinew can be worked through the plastic. remove the plastic after 12 hours, let dry for an hour and reapply but more lightly. Too much time under plastic will cause fungus. In this manner, the drying time can be regulated exactly for an incredibly smooth surface.

of course sinew can be added or subtracted at will without harm, this is the beauty of sinewing. But old, cured sinew is stronger than freshly dried sinew. Consider how much moisture is being held in the bow, how quickly it is leaving, and how much remains. -j-

If you can tiller the bow by adding sinew why does sanding the dried sinew layer does not work?

The sinew only works when the strands are intact. If you sand them down, you will be sawing through the outer strands, causing them to split.

Most people have told me that in a hornbows, tillering is not usually a big problem because of the adjustments that you can make by warming the limbs and bending them. You can also thin the horn for minor adjustments.

Jack you give good advice. Your experiences mirror my own. I just let my hornbow sinew job air dry, it was cool and the drying was controlled. I do think the plastic wrap would help to provide a smoother surface though. I've used it, but back before I appreciated how inportant it is to adequately process the sinew. Now I take it past the wiry stage, and then comb it as well to get rid of rats and get all fibers lined up. I can see the difference when I dip in water, I can see the strands lining up so much better now.

I'm getting there!

There's one other aspect of processing sinew, that does bear mentioning. With leg tendon, the finrer I strip the strands, the more broken those strands seem to become. There's a certain amount of crossing over and winding going on in the tendon, and you cannot avoid breaking some of these each time you pull things in half. I suppose it is just a matter of having to break a few eggs to make and omellette, but is it possible to over-process sinew and, in the process, weaken it?

Doesn't seem to be near the problem with back sinew, that stuff seems to grow much more linearly. I suppose that is why it is preferred by Asian bowyers.

Stephen, i do not mean to disagree but offer another method.

Lennie; leg sinews do not make continuous fibers but look more like netting or a mesh. Would be hard or impossible to comb. When dipped in glue and spread out there is some inevitable crossing of strands. But with practice in dunking, can be made fairly smooth and straight.

The short bundles of sinews-3inches or so- are much more easily placed than the really long ones. They are laid on like feathers or shingles contacting the wood and overlapping onto the just sinewed area, finally meeting and overlapping somehow at the grip. So in my method, there are no continuous strands. Sand if you want. glue more on later. whatever.

It is always the other parts of my bows which give up first. Not the sinew.

please others chime in. i am still a student. -j-

Jack, I've had luck in combing leg sinew bundles, at least enough to get them straightened and get rid of large lumps of material. It also feathers out the ends a bit which helps in blending the ends of bundles and you don't get a hump where the overlap is. But I agree with your assessment that leg sinew is something of a mesh as compared to back sinew.

I've never heard of anyone intentionally shortening their sinew bundles. I do think the ideal situation is one where your sinew is as long as the working limb. That would be most like a growth ring on a selfbow. But I don't doubt that the cementing of shorter strands, allows the whole piece to behave similarly to one long strand. I've popped a few sinew backings off and they never shear they just come loose in one long strip.