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Elasticity versus poundage

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gfugal:
So that makes sense that the core stiffness wouldn't matter as much since the outer fibers are the ones that do most of the work. But surely the core is stressed still. If it wasn't then it wouldn't be so important to have a blemish free prime wood core, or we could use a knotty piece of pine. So that tells me it is stressed at least to some degree, and if that's true its stiffness will have some factor. Maybe not as large as I was thinking but still present right? or is there something else I'm missing.

BowEd:
gfugal...Yes of course.With any of these type stressful designs a good flawless core is required though.As are the other components.It does'nt make any sense to make a bow with materials with flaws in them in these type designs.
A less strained one possibly so.To walk that fine line is up to the bow maker.

willie:
greg makes a good point, about the work done in the core. just because work is concentrated at the outer surfaces, a fair percentage of the work is done as you get closer to the center. much of the finessing done getting a bow to it's best potential means that all parts of the limb would be well served to be optimized.

Understanding theory may not be necessary to inherit knowledge, but understanding whats going on sure helps lowering the experimentation curve. I am all for learning both. Sometimes there are factors that we overlook in our theorizing.  Experience or history can often show, that the best is yet to be re-found.

BTW, is the flight record for the Turkish bow that has stood since sometime in antiquity, considered to be fact or myth?

BowEd:
I don't know about the Turkish distance record.I've read some shots were not recorded.So who knows.Understanding their language describing things takes a little time.I'd say Adam has got a handle on that info.In fact he's testing bows right now on the atarn web site.
Core is important for sure.A dense elastic one with good glueing qualities would be my choice.Others may say different.Maple has been a go to core material for quite some time.I would say if you can't make a bow out of the core or it take the bend needed from a flat profile then your taking a chance using it is another way to look at it too.

willie:
one aspect considering stress in the core, is the shear forces that come into play. typically with a self bow, tension and compression limitations at the surfaces demand very good wood selection, and govern the designs and materiel selections. As a point of interest, there was recently a bow posted that had a hidden flaw in the limb that resulted in a unexpected failure. A cursory examination of the accompanying photo, looked to me,  to be non-typical for a tension or compression failure. It would not surprise me if that bow failed in shear, at the central flaw, resulting in a weak spot that ultimately induced the total limb failure.
Shear failures are also often seen when a glued handle "pops off".

what reading I have done on composites, often mentions the need for careful core selection, leading me to believe that shear limitations often dictate in composite designs. this makes sense, as the sinew and horn is selected for their exceptional tension and compression qualities, asking the core to handle more shear stress that attends more radical bend radii.

I have often wondered if the preference for maple is on account of its diffuse porus qualities. It does seem reasonable that a shear force could be easily localized on the spring growth portion of a ring porus wood, especially if it were flat sawn, making it a poor choice.

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