top runout

The Achilles' Heel of Luthiery
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Posts: 1497
Joined: Thu May 24, 2012 8:03 am
Location: Chestertown Maryland

top runout

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Explaining runout is pretty easy if you have piece of wood that is perhaps a 2X4, but explaining what happens when light hits the two halves a perfectly book matched thin thin piece like a top is not so easy. Today I was driving through our rural landscape - Kent County MD, called the best agricultural land in the state - and I ran across something.

Thinking of the fibers of wood as straws, the perfect top is one that is both vertical grained AND the straws run full length without poking out of the surface anywhere - harder to do with thin wood

1) Here is last year's corn harvest and the remaining short stalks are tipped the direction the harvester was driving. Think of these as the fibers/straws that are inside the wood

2) Stepping back, we can see light and dark areas where the sun hits the flat side of the corn stalk or the end of each hollow tube

3) In the center you can see the color difference as a line where the harvester was going opposite directions

Just like the top where the light is hitting the face or the ends of the fibers in the top
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Ed M
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Joined: Mon Jul 28, 2014 7:50 am
Location: Chadds Ford, PA

Re: top runout

Post by Danl8 »

Interesting analogy. This would be part of the reason for preferring tops coming from split billets as opposed to sawn billets? Ultimately the angle of fiber orientation & related fiber length would seem to be a critical strength consideration.
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