luthery lumber questions

[Aviacs]

I build/have built a lot of things, but stringed instruments, not.
Hopefully my questions are not too naive:

1.) is tonewood for backs always QS/vertical grain? Within what degree of perfectly vertical? For instance, with Tasmanian myrtle, what kind of slope would be acceptable? In Wenge?

2.)Are sides vertical grain as well?

3.) is old growth vertical grain redwood considered a good tonewood?

Thank you.

[runamuck]

Originally Posted by Aviacs

I build/have built a lot of things, but stringed instruments, not.
Hopefully my questions are not too naive:

1.) is tonewood for backs always QS/vertical grain? Within what degree of perfectly vertical? For instance, with Tasmanian myrtle, what kind of slope would be acceptable? In Wenge?

2.)Are sides vertical grain as well?

3.) is old growth vertical grain redwood considered a good tonewood?

Thank you.

With humidity changes, flat sawn wood expands and contracts more than vertical grain and expansion and contraction is usually what causes the wood to crack. So vertical grain - quarter sawn wood - is always preferable for tops, backs and sides..

In spite of this I have seen an increasing number of people use flat sawn because they either don't know better, it's cheaper or they are enamored of the look. But look at the guitars made by the most respected luthiers and you'll see that it's quarter sawn wood that is almost always used.

Old growth, quarter sawn redwood is used quite a bit these days for tops.

PS - if the wood is cut off vertical so there's a slant to the grain, at some point it's referred to as rift sawn. Rift sawn wood is structurally weaker across the grain and with a brittle wood such as Wenge should be avoided. I can't say anything about Myrtle having never used it.

[Aviacs]

So grain like this, 30 deg to 45+ deg off vertical would not be a good choice?

[ProfChris]

Originally Posted by Aviacs

So grain like this, 30 deg to 45+ deg off vertical would not be a good choice?

It's not the best choice, but you can make it work for a back.

You need to allow for the extra,movement across the grain. Thus your design needs to have anough dome in the back that it can reduce as the wood shrinks, and rise as it expands. Second, you want to ensure you close the body in low humidity - it's shrinking against the rigid sides which causes cracks.

[hubcapsc]

They can make a good guitar out of all kinds of stuff...



My simplified perception of why you'd want quartersawn comes
from thinking about floors... a flat-sawn floor will try to get wider
and narrower with the change in humidity, possibly buckling or
having wide spaces between the boards. A quartersawn floor
would merely get a tiny bit thicker or thinner with changes and
would be more stable...

-Mike

[Aviacs]

simplified perception of why you'd want quartersawn comes
from thinking about floors...

Someone is reading my mind!
This is my dilemma exactly.
A couple decades ago i replicated the borders and restored a floor using original methods and materials in a public building that had inadvertently been destroyed. While buying out his 5/4 & 6/4 ebony shorts inventory for the floor, the lumber dealer asked if i would also be interested to buy the remains of a pile of 6/4 & 8/4 pinkish colored lumber that had not sold very well/make an offer.

FF, I'm now old, never used the pinkish stuff, decided to use it instead of mahogany and replicate that same border in my wife's new billiard room.
Then some spoil-sport said it was good for instruments.

So realistically, your note is good news.
I'm going to go back to sawing this material up today, but will save some 35" lengths of the true vertical grain with the black lines in it for friends or in case i need another hobby. What is really great is that the material like in the first picture, is the most dense and spectacular in terms of small shiny features (curl, blister, etc) so ideal for flooring accents. The boards that are true vertical have a lot of defects (that cause the black lines in the good wood on either ends of the defect) & make sense to cut out. They are also wider. (10"+) In a floor, the black would just look like a stain or dirt.

I am relieved, and it seems like a win-win.
Thank you!

smt

[printer2]

I have built guitars with flat sawed and quartered wood. Some split in the dry winter, some not (was an experiment, yeah I am different). About equal split (I did not even see that pun coming) between the two. So you never know if the wood will be susceptible or not. Have not built with skew cut though, need to try it.

[Fathand]

Originally Posted by Aviacs

So grain like this, 30 deg to 45+ deg off vertical would not be a good choice?

I'd use it. Is it mahogany of some sort?

[Aviacs]

Is it mahogany of some sort?

Pretty sure it is Tasmanian myrtle.
Only competing wood AFAI have analyzed it is Pyinma.
There is known 8/4 curly Pyinma here and the end grain is not really a good match though somewhat ambiguous.
However, Pyinma is exceedingly rare in wide boards esp long length so not realistic.

Per yesterday's discussion, I've cut anything that is not dead vertical grain up for a flooring border parquet. That does leave several wide boards with various defects for when i have opportunity to deal with breaking them down. One thing discovered while resawing the 8/4 & 6/4 for 1/2" thick parquets, the wood eats (steel) bandsaw blades. It has no perceptible odor, but the minute i started even cross-cutting for bust-up and end grain determination, my nose and eyes started running like a waterfall. That is rare for me even with woods known to be sensitizers. Needless to say, all further machining was done with a full respirator. The effect does not seem to linger in the air, and wife is burning the chunks and off-cuts in the kitchen stove this morning to cook, with no effect on either of us.

smt

[redir]

I would use it. I've built several reclaimed barnwood guitars with less than quartered Whit Oak and pine and as long as you build in proper conditions it will be okay. It's not ideal but totally doable.

[Aviacs]

More lumber Q's.
at 70, i'm semi-retired from a niche/(miniscule) custom millwork business; except for winters as a near full time ski instructor. I'm starting to pare down a small lumber stash saved for my own uses, or as overage/surplus from small projects over the years. Using a lot of it for long delayed house projects for my ever patient wife.

Then a friend who builds banjos (& had/has a large portion of "the tree") began informing me that some few boards here are actually tonewoods. So i'm happy to save them out & try to understand how to process them. These are OG redwood from deck projects over the years. Only perhaps 3-ish are near perfect vertical grain. My business included resawing veneer, there's a well tuned widebelt sander here, and all the other typical raw lumber processing tools and machines are available. Any advice appreciated. Boards are 14 to 20 ft long.

FWIW, for the moment, this is mostly about managing my shop consolidation & not "wasting" lumber than might be useful in another trade. If the mods feel i need to upgrade my subscription, please send me note.

smt

[Alan Carruth]

Rift sawn ('skew cut') wood, with the annual ring lines at 45 degrees to the surface, actually has higher splitting resistance than quartered wood, in the sense that you can bend it further across the grain before it will crack. It's less prone to shrinkage cracks, too.

In softwoods the grain angle can make a very big difference in the relative cross grain stiffness. If you look at the end grain in a softwood under a microscope you'll see that the cells are rectangular. If the straight edges of the cell walls run parallel to the surface if the wood (perfectly 'quartered' or 'flat' cut) they will have to be stretched or compressed in order to bend the wood across the grain. If the wood is 'skew' cut the cell walls are at 45 degree angles to the surface, and bending wood converts the boxes from rectangles to parallelograms, which takes very little force. A good piece of spruce that is perfectly quartered will have a cross grain stiffness that's about 1/10 of the long0grain stiffness. A flat cut piece with have slightly lower cross stiffness because it loses the benefit of having the medullary rays running along the surface: the flat cut piece will be about 1/12 as stiff crosswise. A skew cut piece of the same spruce, with the ring lines at 45 degrees, can be only 1/100 as stiff across the grain as along. Even a small deviation from 'perfect' quarter, 2 degrees or so, will make a palpable difference in the cross stiffness. This has acoustic consequences, even when it doesn't hurt much structurally.

Changes in the slope of the ring lines across the piece, and especially curved grain lines, as seen on the end grain, can produce cross grain cupping in thin stock It's hard to avoid that sort of deviation in flat cut wood, which is another reason to go with quartered stock.

[Robin, Wales]

As a heathan, I actually quite like the grain pattern of rotary cut plywood veneers. And, as a "tonewood" I like what the northern hardwoods (birch, cherry, maple etc) create when made into plywood. The plywood b/s guitars I have played have a dryness and clarity that I like. I don't think that many luthiers would risk building with plywood though, as having "solid wood" has become the "better" option in the minds of buyers.

I like my D-18, but I also gig with my A&L Legacy (cherry/maple/cherry plywood b/s) because it has great projection and clarity when just mic'd on stage at gigs.

And some of the nicest sounding vintage Gibsons I have heard have been those with maple plywood b/s.

And you are unlikely to get any cracking issues with plywood. Its humidity movement is around 1/10th of solid wood.

So if you do have some nice wood that isn't quarter sawn, perhaps you could veneer slice it and make your own plywood from it?

[printer2]

Originally Posted by Robin, Wales

As a heathan, I actually quite like the grain pattern of rotary cut plywood veneers. And, as a "tonewood" I like what the northern hardwoods (birch, cherry, maple etc) create when made into plywood. The plywood b/s guitars I have played have a dryness and clarity that I like. I don't think that many luthiers would risk building with plywood though, as having "solid wood" has become the "better" option in the minds of buyers.

I like my D-18, but I also gig with my A&L Legacy (cherry/maple/cherry plywood b/s) because it has great projection and clarity when just mic'd on stage at gigs.

And some of the nicest sounding vintage Gibsons I have heard have been those with maple plywood b/s.

And you are unlikely to get any cracking issues with plywood. Its humidity movement is around 1/10th of solid wood.

So if you do have some nice wood that isn't quarter sawn, perhaps you could veneer slice it and make your own plywood from it?

There are a few luthiers that do 'plywood' their B&S's. Veneer slice? That sounds like knife work, more like resaw and then sand down to thickness. Which is what I have done to some maple, hope to build it this winter. Most likely going to do the same for the top, three sets of solid wood to make one guitar, neck excluded. Just had a thought. A laminated neck would be in order I would think.

[Robin, Wales]

Fred, another of my whacky theories is that the neck is as important as the body; in terms of vibration transfer. I'm surprised more luthiers don't fit maple necks rather than mahogany. Mahogany was popular "back in the day" because it was bloody cheap, available and easy to work with. But it is a bit of a tone sponge. Dare I say it, but even nato is probably better at transferring energy. Strings have two ends, and getting the vibrations from the nut or a fret back to the body is just as important as how your bracing allows the top to move..... But folks focus on "the bracing" (or sound ports ) and forgot about the neck that's doing just as much work in shaping the timbre.