Does thickness ratio affect chrysalling?

[PlanB]

I know there are a lot of variables that can tend toward chrysalling; species, individual trees, individual wood, the bow workmanship, etc.

But I was also wondering if in general, say a thinner wider bow section tends to fail by chrysalling more readily than a thicker narrower one? I mean if you could do longbow style and a broadbow style with the same wood and you overstressed both would the longbow tend to develop more set before chrysalling than the flatbow, or tend toward a tension break first compared to the flatbow (depending on the wood)?

I ask this because it seems like for example, a planed shaving from a piece of pine, bends to a crease (a fret ie. chrysalling massively) without breaking, while a thicker test piece will snap in tension. It seems to me that chrysalling may be at least partially related to the relative thickness of a piece.

And the reason that might be interesting is with a wood that tends toward chrysalling easily, would it be an advantage to consider a deeper section to get the best use out of it? Or is the opposite true?

[stuckinthemud]

Thicker chrysals faster than thinner.  Round belly chrysals faster than flat

[willie]

would the longbow tend to develop more set before chrysalling than the flatbow,

not really, chrysaling and set are both failure modes of compression.  For a particular wood, a wider bow will of course be of higher poundage than a narrower bow at the same level of strain. Different woods may take more or less set before chrysals occur.

tension strength is a proportion of compression strength, ie,  some woods will survive massive chrysals before tension failures. others will fail across the back before much set becomes evident.
one factor to consider with tension weak woods is any imperfection on the back can become the point at which failure is initiated, so a 1mm pin knot can kill you if your back is only 10 mm wide, as with a crowned back. a 1mm pin knot is a much smaller percentage of a back that is 50 mm wide, so I would go for wide and flat back when using brash wood.

[Morgan]

I believe it does. This is why certain bow woods need to be wider than others for a given length and desired draw weight. A narrow bow is thicker, and as bend radius increases you can only go so far before the wood crushes. The thicker the wood is the more material there is to cram in that bend radius and the higher the chance it will crush. Take a pool noodle and bend it, you will see wrinkles on the belly. Cut a thin strip of the noodle and bend it the same way there are no wrinkles. Same concept in my mind, different material.

[mmattockx]

But I was also wondering if in general, say a thinner wider bow section tends to fail by chrysalling more readily than a thicker narrower one? I mean if you could do longbow style and a broadbow style with the same wood and you overstressed both would the longbow tend to develop more set before chrysalling than the flatbow, or tend toward a tension break first compared to the flatbow (depending on the wood)?

While there is a lot about wood behaviour that we don't know, from a stress point of view the ratio doesn't mean anything but the maximum stress level does. In your example assuming both bows see the same maximum stress then I doubt one will chrysal or fail in tension before the other. It is much easier to overstress the wood in a narrow, thick bow, though and that may lead to the perception that narrow designs fail easier.


Mark

[bradsmith2010]

im sure it does in some ways,, but am not expert on that,,
I mostly use osage and it is pretty crysalling resistant,, but very interesting topic,, thanks for posting

[Jim Davis]

A thicker section will bend less before failing in compression. It's the amount of curve away from the straight position that limits. Of course, it will also be stiffer before it fails.

To avoid failure, a thicker section needs to be longer, so that the curve is less for a given draw length.

[bownarra]

Thicker will chrysal first BUT and it is a big BUT a small deviation from perfect taper on a narrow deep longbow isn't that much of a big deal (obviously you want to avoid like the plague but....) whereas on a wide flatbow that same deviation is a much bigger proportion of the total limb thickness and as such the same sized deviation will give a much greater discrepancy to the tiller....so go very careful on your wide thin bows! Same reason a thin childs bow can be tricky to tiller.