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burl stability (Read 268 times)
 
Ralph Fahringer
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burl stability
Aug 12th, 2017 at 11:15am
 
Here's a question for you...

We all know that a bowl will dry/shrink/warp based on the grain and.. said grain being fairly uniform (non swirly) from outer log to inner log.

That being said, has anyone ever had a bowl from a burl have the same drying properties or is it way more stable due to the random swirliness of the grain in burl?

So far, i have once-turned 2 pieces from a birch root burl and one from a maple burl and had all be quite stable.  Is this typical with burl wood or just luck on my part?

My main reason is that I have a ton of burls that i'd love to get into and some are fresh cherry burls that i'm dying to throw on onto the lathe!!

I'm heading out Sunday for another log that has the burl right in the crotch... (sounds painfull, I know!!... Shocked)
and am imagining  this piece not only having the burl swirls but the flame of the crotch wood as well.

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Ed Weber
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Re: burl stability
Reply #1 - Aug 12th, 2017 at 11:51am
 
"in general"
With a straight grained piece of wood (aligned grain) you can easily see and measure the percentage of shrinkage due to drying.
With a piece of burl, there is no clear grain direction so there is no way to tell.

Without being able to tell the difference between the radial, tangential and longitudinal grain direction there is no way to really know how the wood will react to drying. Some say that the interlocking (confused) direction of the grain helps to make the piece more stable. When there is a force (shrinkage) in one direction, is counteracted by a similar force in another direction. This internal struggle helps to keep the piece in equilibrium or more stable.

I haven't work with enough burl to confirm this for myself.
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Ralph Fahringer
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Ellsworth, Maine, USA
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Re: burl stability
Reply #2 - Aug 12th, 2017 at 11:57am
 
Thanks, Ed.

That is what I was thinking as well but sort of needed to hear it come from someone else than the little guy in my head who tells me all sorts of crazy stuff!! Shocked

I might  have to send you a hunk to play with.. errr.. do scientific testing on. Thumbs Up
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Don Stephan
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Re: burl stability
Reply #3 - Aug 12th, 2017 at 6:36pm
 
Havn't turned many burls, but a cherry I turned a few months ago had numerous areas of included bark, and became all canty-whompered as it dried.  Don't have a picture with me.
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Rick Caron
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Re: burl stability
Reply #4 - Aug 13th, 2017 at 7:55pm
 
I've only turned 2 burls.  As they dried  they had little cracks going in all directions  so  it was safe to turn.  They also didn't need as many coats of finish.
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Tom Coghill
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Re: burl stability
Reply #5 - Aug 14th, 2017 at 10:55am
 
I have had the opportunity to core a few burls.  What I have learned is that because they don't move like a normal section from a tree, I can core with less than the normal 10% account for movement. I am specifically talking about Birch Burls, I don't have experience with other burls, so I don't know if this transfers directly to other species.

Summary - less movement and less cracking - still dry slowly as you would with any wood.
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