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Re: [SCA-Archery] Sinew coatings on traditional bows -- how to evaluate?

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  • Carolus
    Based on what you tell us about the bowyer s statements I would question his knowledge or motivations in recommending a backing. While a fibrous backing may
    Message 1 of 3 , Jun 29, 2013
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      Based on what you tell us about the bowyer's statements I would question his knowledge or motivations in recommending a backing.  While a fibrous backing may help restrain the pieces of a bow in the event of breakage, much depends on the power in the bow at the time of failure, the quality of the fibre, and the nature of the glue.  If the bow is fast and over about 35# don't expect any fibrous backing to significantly restrain the pieces, there is just too much energy in the bow (it might, but don't count on it).

      To understand the reason for backing a bow it is necessary to understand the dynamics of it.  The bow works by then differential between non-conpressibility of the belly and the elasticity of the back.  Sinew is applied not to hold the bow together but to increase that elasticity and improve the cast of the bow.  As Taillear states, no two strands should be applied so has to end in the same location or a weak spot will be created.  While this will not make the bow any less safe, if the performance of the bow is not affected there is no purpose for the backing.
      Carolus


      On 6/29/2013 10:11 AM, Guy Taylor wrote:
       

      Generally speaking, sinew backing is added to a bow to raise the draw
      weight and/or to give support to the wood to enable a longer draw
      length. Many American Indian bows were very short but a sinew backing
      gave them great power and a needed draw length.
      If your bowyer says the sinew did not change the bow in any way then
      it must be a very thin layer indeed.
      I don't see any advantage to adding sinew to a longbow that is fine in
      every other way. Especially hickory, which makes a pretty sturdy bow.
      If the bowyer is that worried the bow will break then he shouldn't
      have used that piece of wood.
      When sinew is applied the ends are staggered so the wood is supported
      with sinew along its whole length. If the gaps you speak of are
      between the ends of strands then that could be an unsupported area. If
      the gaps are between the lengths of sinew then it's not a very well
      done application but it's safe.
      If this bow were to break it's likely that the sinew will hold the
      pieces together and there won't be wood flying abut the countryside
      looking for noggins to bop. It sounds as if that is the bowyer's goal,
      but I suspect his confidence in his work.

      Disclosure:
      I am not an SCA archery marshal or captain. In fact, I have not shot
      at an SCA archery event in some years. I sell custom wood arrows at
      them and am too busy to actually shoot what I make. I am not a
      professional bowyer although I do make bows, am frequently around
      professional bowyers, and have considerable exposure to wood bows in
      many different forms.

      Taillear

      On 6/29/13, childcareguy47 <childcareguy47@...> wrote:
      > Dear SCA Archers;
      >
      > I am a newbie to this list. I hope to open a discussion of Sinew Coated
      > on Bows, Why It Is Applied, and How It Is to be Evaluated.
      >
      > First, please allow me to clarify, I am not an archery expert. I am a
      > low level 40+ year lover of archery. I am not a safety expert, I defer
      > 100%, without reservation, to the SCA marshals and Archery Captains.
      >
      > In brief, asking a marshal questions is OK, but questioning a marshal,
      > in the field, is not OK. Does that make sense?
      >
      > Having said that, I feel that we have before us a possible
      > misunderstanding of the use of a Sinew coating -- final layer -- on a
      > longbow. When we ordered a hickory longbow, the bowyer suggested we add
      > Sinew, for a slight additional fee. He said that it would not change the
      > bow in any way, but it would make it safer, especially if it was ever used
      > in combat.
      >
      > The sinew would not make the bow tougher, stronger or weaker, pull any
      > harder or less, not make it smoother to draw. The sinew would only hold the
      > bow together a bit longer if it were to fail.
      >
      > The purpose of the sinew was exactly the same as the layer of plastic
      > embedded in some safety glass -- hold the broken pieces together in the
      > event of a catastrophic failure. A defect in the sinew may not make the bow
      > any more likely to fail, or any less safe, if I understand the situation.
      >
      > That is the question I hope to raise. I am hoping that actual archery
      > experts will discuss this and come to a consensus.
      >
      > I offer this thought experiment. We have an English long bow, hickory,
      > custom made by our local SCA bowyer. The bow is beautiful, strong, free of
      > defects. The bowyer adds a layer of Sinew, for the reasons described above.
      >
      >
      > Complication: sinew is a composite material, stringy, fibrous, gooey,
      > and difficult to work. The "net" of sinew adheres nicely to the bow, but it
      > appears to be slightly uneven, with small gaps in the coating.
      >
      > *** Does that make the bow less safe? *** If the bow was safe before
      > the sinew coating, may the addition of a good, but not perfect, sinew
      > coating make the bow less safe?
      >
      > Is the sinew coating merely cosmetic, of no importance, unless the bow
      > breaks? Can a chip in the paint job of a car make the car less strong or
      > less safe? Is that a fair analogy?
      >
      > I am hoping that the archery marshals and archery captains may arrive
      > at a consensus agreement. Perhaps the sinew coating adds to the safety of a
      > bow even if the coating is not perfect. Perhaps.
      >
      > Much like a window screen with a tiny hole. A screen with a tiny hole
      > is better than no screen at all. An old pair of work jeans with a small
      > hole provides more protection than no jeans at all.
      >
      > And a long bow with a good but not perfect sinew coating is better than
      > the same bow with no coating at all.
      >
      > Yes? No? Needs more discussion? Please get back to me. I support
      > SCA archery safety and marshal authority 100%, without reservation.
      >
      > Thank you for your time.
      >
      > Thomas Starremon
      >
      > aka Michael Kauper
      >
      > 612-827-3481 home
      >
      > 612-483-0298 cell
      >
      >
      >
      >

      --
      The Greenman Archery <http://www.greenmanarchery.com/index.html> Website
      Fine custom wood arrows for traditional archers.


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