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Dwight Brown

Grain Width on Spruce Tops

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5 hours ago, JPOWTC said:

In handling  many 1000's of guitar tops (where flexing is practicable), I came to the conclusion that grain spacing does not necessary correlate with  lateral (cross-grain) stiffness.  Longitudinal stiffness isn't so easy to assess, and perhaps there is some correlation - or effect?

I think of each ring as if it is an i-beam. If the top is quartersawn, I'm getting the stiffness that comes from the ring being perpendicular to the face (in the same way the vertical body of an i-beam is perpendicular to the floor it is supporting). More i-beams (or joists) than required = unnecessary weight = mass sucking up energy from string movement. Kind of makes sense to space them out. 

But I'm no engineer. 

Here's a darker variety of spruce we found recently. It has fairly wide grain (6-12 per inch). 

dark spruce 5.jpeg

dark spruce 4.1.jpg

dark spruce 3.1.jpg

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8 hours ago, Scott Moses Murray said:

I think of each ring as if it is an i-beam. If the top is quartersawn, I'm getting the stiffness that comes from the ring being perpendicular to the face (in the same way the vertical body of an i-beam is perpendicular to the floor it is supporting). More i-beams (or joists) than required = unnecessary weight = mass sucking up energy from string movement. Kind of makes sense to space them out. 

But I'm no engineer. 

I AM and engineer, and although that kind of thinking might seem right, the microscopic details of the wood structure go the opposite way.

It turns out that the cell walls don't line up in the direction of the annular rings, so your "i-beams" turn out to not be very stiff.  Perpendicular to the rings, the cell walls DO line up much better, and the wood is stiffer in that direction.  If you look up radial (perpendicular to rings) vs. tangential (parallel to rings) modulus, you can see the difference.  Or measure it, like I have.

Also, the quantity of "i-beams" doesn't matter for density, but the width of the i-beams compared to the space between them is what matters. 

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8 minutes ago, Don Noon said:

I AM and engineer, and although that kind of thinking might seem right, the microscopic details of the wood structure go the opposite way.

It turns out that the cell walls don't line up in the direction of the annular rings, so your "i-beams" turn out to not be very stiff.  Perpendicular to the rings, the cell walls DO line up much better, and the wood is stiffer in that direction.  If you look up radial (perpendicular to rings) vs. tangential (parallel to rings) modulus, you can see the difference.  Or measure it, like I have.

Also, the quantity of "i-beams" doesn't matter for density, but the width of the i-beams compared to the space between them is what matters. 

Thanks for that clarification! I looked up radial and tangential - I think I thought I was describing longitudinal modulus.  If I follow you: quarter-sawn tops are stiffer (eg across the lower bout, in a horizontal direction in the first picture above) because the cell walls between rings are perpendicular to the rings, and my "i-beam" analogy is more true horizontally than vertically (or is just a bad analogy)? What makes the top stiff along the longitudinal axis? Is it the cohesion of fibers one to another due to cell walls lining up?

I attach a sketch. What makes the wood stiff / less flexible in the direction of the black curved line (imagining we're seeing a sound board quarter sawn, as shown by the red vertical lines)? Practically speaking it's stiffest in that direction, which is the one I had in mind with my i-beam analogy. Would love to understand this better but the papers I've found thus far are written for experts.

Been telling our builders the grain is stiffer when quarter sawn just like a ruler is stiffer when held on edge instead of flat (or at an angle, like the grain in the second sketch). Lots to learn...

Screen Shot 2019-11-10 at 11.49.14 AM.png

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11 hours ago, Scott Moses Murray said:

What makes the top stiff along the longitudinal axis? Is it the cohesion of fibers one to another due to cell walls lining up?

That's the main direction of the cellulose fibers.  It doesn't matter if the wood is quartered or flat sawn, the longitudinal bending stiffness remains the same.

It is just the crossgrain stiffness that depends on the cut.  Quartered is stiffest, where the cell walls line up in the plane of the wood.  Flatsawn is significantly worse, and about 45 degrees off-quarter is like a noodle (due to the rectangular cell shape, this gives the most zig-zag cell wall alignment in the plane of the wood).

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22 hours ago, Scott Moses Murray said:

Fascinating. That makes sense. Brings up a question - does quarter sawing matter near as much on hard woods?

Not nearly as much, as the cell geometry isn't as regularly rectangular as in spruce.  But it's still significant.

I also happened across an old test where I had a Sitka board with widely varying grain widths.  So I cut it up in strips to see how the properties varied, and shown below with density and speed of sound.

IMG_4191.jpg.0dfd68795677a5784b09390736eda435.jpg

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1 hour ago, Don Noon said:

Not nearly as much, as the cell geometry isn't as regularly rectangular as in spruce.  But it's still significant.

I also happened across an old test where I had a Sitka board with widely varying grain widths.  So I cut it up in strips to see how the properties varied, and shown below with density and speed of sound.

 

That's weird. What's going on there? Why the hugely different speed of sound from strips of the same board?

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1 hour ago, sospiri said:

That's weird. What's going on there? Why the hugely different speed of sound from strips of the same board?

 

1 hour ago, sospiri said:

That's weird. What's going on there? Why the hugely different speed of sound from strips of the same board?

wood is not a homogeneous monolithic structure, the cell density/packing ,the cell wall dimensions, how those things effect bound water storage, the delineation lines,where saps will reside in higher or lower quantity all will effect what the final actual "figures" are for "that" particular piece of wood ,which may be similar to "that"piece of wood but rarely identical 

IMO it is the cell density and bound fluids, sugars,saps,water,acids and other fluid chemical compounds that have the greatest impact on radiation and damping as well as other important properties that really matter once things get dimensional, such as elasticity and recoil 

Recoil IMO is something not talked about much but is extremely important. Once dimensional thin material that has been flexed and held for an arbitrary amount of time,say 30 seconds, once released,how quickly will it want to return to it's un-flexed state? Some snaps right back, some slowly returns and some likes to take on the new twisted dimension and will resist re-conforming to it's original state. I look for stuff that like to snap back to where it was, this somewhat corresponds to radiation and stiffness, but torsion resistance and recoil is a different type of "stiffness" 

If we were to think about having a handful of spaghetti and tried to break it in half,this is the type of 'stiffness' that is often thought of,as it does relate to the downforces of the bridge island and arch strength.

however if we took the same noodles and then twisted them like were wringing them out like a rag, and then stop twisting, how quickly do they return to the untwisted state.

These forces interact with the dynamic modal states and in my opinion are directly related to play'abilty and response time feel. I feel "saggy" "soggy bottom" wood has a tendency to impart deconstructive wave patterns that make for a unresponsive feel "wet blanket" type of sound.

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Within reason, I am not too concerned by grain width.
There is a width I prefer, but that is more for optical reasons. Above a certain number per inch, spruce can look very bland when the grains are very fine. What I really do pay attention to is the proportion of winter grain, and would avoid anything where this is wide.

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2 minutes ago, sospiri said:

Number 4 is anomalous. Maybe the machine got it wrong. Maybe you did?

I double and triple checked it, since it was so deviant.  That's what it is.

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1 minute ago, Don Noon said:

I double and triple checked it, since it was so deviant.  That's what it is.

But why? It's neither sapwood nor heartwood.  Enquiring minds need to know.

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On November 9, 31 Heisei at 4:58 AM, David Beard said:

While Cremona makers certainly did sometimes use fine grained spruce, I think you can fairly claim that they mostly steered toward medium wide and very straight grained spruce.

This also seems like a contrast to some other traditions.  

I found it interesting that Late Strads have wider grain. In any case dendrochronlogy could pin down that Strad worked from whole trunks so once he got one he had to use it. In this sense I believe it was not always a completely free choice of the makers in the past. They bought a trunk (or an part of a trunk) and we can speculate if they would have had a chance to see the yearring width before they bought it. 

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20 hours ago, jezzupe said:

 

wood is not a homogeneous monolithic structure, the cell density/packing ,the cell wall dimensions, how those things effect bound water storage, the delineation lines,where saps will reside in higher or lower quantity all will effect what the final actual "figures" are for "that" particular piece of wood ,which may be similar to "that"piece of wood but rarely identical 

IMO it is the cell density and bound fluids, sugars,saps,water,acids and other fluid chemical compounds that have the greatest impact on radiation and damping as well as other important properties that really matter once things get dimensional, such as elasticity and recoil 

Recoil IMO is something not talked about much but is extremely important. Once dimensional thin material that has been flexed and held for an arbitrary amount of time,say 30 seconds, once released,how quickly will it want to return to it's un-flexed state? Some snaps right back, some slowly returns and some likes to take on the new twisted dimension and will resist re-conforming to it's original state. I look for stuff that like to snap back to where it was, this somewhat corresponds to radiation and stiffness, but torsion resistance and recoil is a different type of "stiffness" 

If we were to think about having a handful of spaghetti and tried to break it in half,this is the type of 'stiffness' that is often thought of,as it does relate to the downforces of the bridge island and arch strength.

however if we took the same noodles and then twisted them like were wringing them out like a rag, and then stop twisting, how quickly do they return to the untwisted state.

These forces interact with the dynamic modal states and in my opinion are directly related to play'abilty and response time feel. I feel "saggy" "soggy bottom" wood has a tendency to impart deconstructive wave patterns that make for a unresponsive feel "wet blanket" type of sound.

Really interesting. 

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On 11/10/2019 at 12:52 AM, Scott Moses Murray said:

also, if anyone has seen spruce this color before please tell me about it

I've seen lots of it on Washington state beaches, I have cut a lot of it after it has floated in the ocean for who knows how long. Density is about 41 to 48 or higher, very stiff and splintery, tough on tools.. One particular log about 45 inches in diameter had a metal spiked tag driven into the end with numbers on it, I figured that it had gotten loose from a Tug during a storm. Probably came from Alaska. Cut it with a two man saw and split it with wooden wedges, as all I had with me was a saw a hammer and a hatchet, the pieces lacked about an inch of making cellos, another one of my memorable moments! Went back a couple of years later and the winter storms had moved it about a half mile further south and buried most of it in the beach.

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On 11/14/2019 at 12:27 PM, Don Noon said:

Trees are organic things, not machines.

Amen to that, Brother Noon! 

And trees don't recognize political borders or call each other by the names we call them.  That is why good wood is where you find it.   

Trees are wise, positive, easy-going creations, but they don't like nitpickers, know-it-alls, and naysayers.  Try to pigeonhole an Elm tree and it might drop a limb on your head.  

How is your flat-sawn violin belly experiment coming along?  I have for you a viola sized well-seasoned board of flatsawn Transcontinental Spruce that is right from the tree - no laminations.  The fee is a donation to your local food bank.  Give me your shipping address and I'll send it off.

Yours truly,

Randy O'Malley, tree-hugger extraordinaire

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On 11/15/2019 at 10:12 AM, Andreas Preuss said:

I found it interesting that Late Strads have wider grain. In any case dendrochronlogy could pin down that Strad worked from whole trunks so once he got one he had to use it. In this sense I believe it was not always a completely free choice of the makers in the past. They bought a trunk (or an part of a trunk) and we can speculate if they would have had a chance to see the yearring width before they bought it. 

He must also have traded lumber or bought it from estate and going out of business sales  -  just like so many of us do.  Some things never change.

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On 11/15/2019 at 9:11 AM, sospiri said:

But why? It's neither sapwood nor heartwood.  Enquiring minds need to know.

Perhaps some isolated effect on extractives due to natural phenomenon or human activity.  I once lived near a large old Elm tree (resistant to Dutch disease) that was poisoned by zinc and/or chlorine from the galvanized water pipe draining a nearby swimming pool.  When the tree was later milled into boards I could see in the grain evidence of the 'poisoned' years.  Don't quote me - I studied human physiology.

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1 hour ago, Randall The Restorer said:

How is your flat-sawn violin belly experiment coming along?  I have for you a viola sized well-seasoned board of flatsawn Transcontinental Spruce that is right from the tree - no laminations.  The fee is a donation to your local food bank.  Give me your shipping address and I'll send it off.

Yours truly,

Randy O'Malley, tree-hugger extraordinaire

The flat-sawn experiment was a long time ago... that VSO has had 5 other experimental tops on it since then.  And it was also back when I didn't have a waiting list.  So, thanks for the offer, but my situation has evolved, and I don't foresee doing another flat-sawn top experiment any time soon, if ever.  I'm more focused on making stuff for clients now.

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By far the most dense part of traditional European spruce tonewood is the darker annual rings. And usually the wider the rings are spaced the heavier and thicker they are. Other types of spruce which have much closer ring spacing have relatively thin dark wood. So wide ring spacing doesn't necessarily mean lighter or weaker wood. Probably the opposite is true.

 

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