Why does Koa have strips of white in it?

Felly

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Hey just wondering, why does some full solid koa have strips of white in it?
Attached is a sample picture
Uke_white.jpg
 

robinboyd

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The white is sapwood and the dark is heartwood. Sapwood grows on the outside of the tree and heartwood grows in the middle. Most woods have this distinction with more or less contrast depending on the type of wood.
 
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Felly

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The white is sapwood and the dark is hardwood. Sapwood grows on the outside of the tree and heartwood grows in the middle. Most woods have this distinction with more or less contrast depending on the type of wood.

thanks!! so if the tree was big enough we would get an entire ukulele made in white? woah.
 

robinboyd

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thanks!! so if the tree was big enough we would get an entire ukulele made in white? woah.

Maybe, but it seems to me that the band of sapwood doesn't really get any wider as the trunk gets thicker. It's just the heartwood that gets thicker. I could be wrong about that, though.

By the way, here is a good example from one of my ukuleles. It's not koa, but I cut down the tree myself!

View attachment 134746
 
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Bluesy

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I don't always love the look of sapwood in Koa, but this one looks great.

I love sapwood in cocobolo.

Bluesy.
 

Contrails

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Does the density of the wood differ between the 2? If it does would it affect the sound?
 

Contrails

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Ok this is what I read online :

This sapwood-heartwood distinction has important implications for woodworkers beyond the obvious implications of color. Because sapwood contains the sap-conducting cells of the tree, it tends to have a relatively high moisture content. This is good for the living tree but it is not so good for the woodworker, because sapwood tends to shrink and move considerably when dried, and it is much more susceptible to decay and staining by fungi.

And this
https://www.fpl.fs.fed.us/documnts/fplrn/fplrn147.pdf
 
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Contrails

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Does the density of the wood differ between the 2? If it does would it affect the sound?

From my googling it seems like heartwood should have a higher density since sapwood has more moisture content and these would dry out over time. This to some extend might affect the tonal properties of the instrument? I am just wondering if over time the shrinking of the sapwood would make it more susceptible to cracks on the uke since the under side of the body is not ‘sealed’ with any coating as it continues to loose moisture. I have to say I have no experience whatsoever with wood and my knowledge is all from what I read. Would be interesting to hear from guys with experience with wood making on their views. But then again it seems like sapwood is not used as much in wood making due to this reason.
 

anthonyg

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Ok this is what I read online :

This sapwood-heartwood distinction has important implications for woodworkers beyond the obvious implications of color. Because sapwood contains the sap-conducting cells of the tree, it tends to have a relatively high moisture content. This is good for the living tree but it is not so good for the woodworker, because sapwood tends to shrink and move considerably when dried, and it is much more susceptible to decay and staining by fungi.

And this
https://www.fpl.fs.fed.us/documnts/fplrn/fplrn147.pdf

Meh, here's the rub. If your going to get hung up on such details, then EVERY wood other than plain, straight grain, quarter sawn wood is weak (EDIT: AND unstable) and should not be used.
Figured and flamed wood? No, chuck it in the bin!
Spalted Maple? Hell no, are you insane!

Are people going to chuck all figured wood in the bin and only use perfect straight grained wood?

Hell no.

Do straight grain instruments sound better? Well actually, maybe they do, but no one is going to stop building and buying figured wood instruments anytime soon.
 
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Contrails

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Meh, here's the rub. If your going to get hung up on such details, then EVERY wood other than plain, straight grain, quarter sawn wood is weak and should not be used.
Figured and flamed wood? No, chuck it in the bin!
Spalted Maple? Hell no, are you insane!

Are people going to chuck all figured wood in the bin and only use perfect straight grained wood?

Hell no.

Do straight grain instruments sound better? Well actually, maybe they do, but no one is going to stop building and buying figured wood instruments anytime soon.

I am not concern with what you described as weak wood. My concern is if the wood isn’t dried well enough sapwood might shrink more than heartwood and so might have a higher chance of a crack? Anyway my knowledge is too limited. Those who have worked on wood would know better.
 
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Ed1

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Ok this is what I read online :

This sapwood-heartwood distinction has important implications for woodworkers beyond the obvious implications of color. Because sapwood contains the sap-conducting cells of the tree, it tends to have a relatively high moisture content. This is good for the living tree but it is not so good for the woodworker, because sapwood tends to shrink and move considerably when dried, and it is much more susceptible to decay and staining by fungi.

And this
https://www.fpl.fs.fed.us/documnts/fplrn/fplrn147.pdf

Thanks for the info. I've never been a fan of sapwood ... but that Koaloha tenor looks great.
 

cyber3d

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I wonder how sapwood affects sound? In any case, I love the look it gives my Soprano of Koa.
20210721_184022.jpg
 

Bluesy

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My guess is that it doesn't have much impact on the sound. Over the years I've never heard the anyone on The Ukulele Site's videos mention sap wood as it relates to tone. It's only mentioned in reference to the uke's appearance.

Bluesy.
 

Kenn2018

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The sap wood does change thickness depending upon weather and soil conditions. That's why the rings on a tree vary in thickness. The better the conditions the thicker the rings. One ring is made every year.

People who study these things can use the thickness of the rings to tell when there were droughts and very wet years. The variation pattern can be used to tell precisely when a log was cut if there is a data base for wood rings in the area where the tree grew.