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Can I get your take on what are the implications with using flat sawn material for the back material and sides material that is slightly tilted off quarter? It seems that some of the more interesting grain patterns are displayed in flat sawn material. Are there any negative implication using flat sawn material.

That main reason I ask is there seems to more flat sawn hardwoods available. I know I have an bunch more. The other reason is I have some african mahogany the I like but is not quarter sawn. The part I want to use for the sides is straight grained but tilted (sorry I don't know the technical term for this). What's your take?

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Mark Ewing
Columbus Ohio
"Trees are an important and precious thing. We should build good things with them. Building good guitars with heart are the best use for them." K. Yairi.

Generally speaking, quartersawn wood is more stable than flatsawn, and will exhibit less movement with changes in humidity.
Off-quarter wood, is better than perfectly flatsawn wood, again in theory. Some species are more stable than others, and you can get away with more with some than with others. You should do some reading on the subject in the archives here and on the MIMForum, as well as on other wood related sites. Understanding wood is the first thing that an aspiring luthier should learn.

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Only badly."

mark11, Don hit the nail on the head with your question(s).

If you have ever seen any nice birdseye maple guitars these sets are usually flatsawn. A lot of quilted woods are also flat or rift sawn.

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personly i try not to cut my sides flat sawn if i can possably avoid it becouse it tends to cup and bow when you start bending.
but the other day i was looking at taylors factory friday when the cut there "killer Koa" and they say that they look for quatered backs and slab sides from the boards.
i would do this the otherway around.

when i cut boards i will sometimes sacrafice a wide board that would yeild a lovely quarter sawn back in favour of sides.

why?, becouse i think its more important to have quartered sides.

with the back i allways make sure that the jointing edge is quarter sawn even if the rest of the board falls off to slab on the other edge.
this is usualy fine.
and in some species its the only way you can get two peice backs.

i general if you can quarter saw then do it but the fact is that trees dont grow in a way that makes it possable to get every board quarter sawn without alot of wastage and in expensive woods this is unexceptable.

if the grain runs at a slightly off quarter angle (rift sawn) even up to 45 degrees you can get away with it also becouse by the time you cut the board down the angle wont be as accute.
this sometimes will make the board less stiff but this isn't realy a problem with back and sides.

with top woods they need to be smack on quarter or else they wont hold up to the string tension and you will your preciuose stiffness.

so look for quarter sawn side billets but you dont have to be as fussy with backs as long as you have a quarter sawn jointing edge.

Joel.

That's a huge question and there is no easy answer but here are a few more things to think about.

I assume the reason Joel likes quartered sides is that they tend to ripple less after bending. But I've seen flat sawn sides that bend fine and quarter sawn that cup and ripple like crazy. But because of their width, I don't think dimensional changes with humidity is an issue with sides. Or at least it's way less of an issue than with the plates.

As for backs, dimensional changes are not nearly as much of an issue as with tops. First of all, backs tend to be made with species that move much less than top woods. For example, mahagony is more dimensionally stable flatsawn than spruce is when quartered. Also, backs don't have the stress concentrations associated with a fingerboard and bridge glued to them so they are freer to move around without splitting. And when they do move around, it doesn't change the action like top movement does.

Then there's the fact that other issues can have more of an effect on a wood's stability than whether it's quartered or flat. Things like case harderning in a kiln or reaction wood.

Then there are woods like wenge and BRW that, when quartered, will split if you look at them wrong. For those woods, I prefer rift sawn (or a lattice braced back).

So in my book, it's a much bigger picture than just quartered vs. rift or flat.

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What Don said .

If I didn't have a specific piece in from of me and I was just looking at general properties of that type of wood(this is where it all gets theoretical, because we are only speaking in generalities). There are a couple things you can look at. If the piece has grain going from flat to quarter, it is a good idea to consider the difference in the radial to tangential as the shrinkage and expansion will vary across the piece with those ratios. Most woods have close to a 1 to 2 ratio(Quarter to Flat), some wood have closer ratios like Mahogany with a 1 to 1.25, then there are some wood like Beech that are more like 1 to 2.25. Closer ratios will generically be less likely to ripple or turn to that potato chip looking thing. Of course you are only considering radial and tangential differences, if you have twisting or turning long grain it can be a whole lot more significant, as long grain moves very little in relation to either the radial or tangential. The other thing you can look at it how much change will likely occur with say a 3% change in moisture at the width of the piece. Smaller widths will move less obviously so significance will vary with that, and how much impact a change in the dimension of that part. If you looked at a back set with a width we will call 15.5" and a full 3% change in moisture. Most woods that are quartersawn would have a change of about 1/16" across the back, Flatsawn would change about 1/8". There are some that will change a little less some can change more. A wood like Beech is an example of a wood that although it would change close to 1/16" in a quarter sawn piece, a flasawn piece will change closer to 1/4"(a very significant difference). Again close attension to how the long grain is oriented because it will have a slight dimensional change in relation to the radial or tangential. These changes are easy to see in action if you want to do a little hands on testing. You can also see how differences in moisture will make the board react with a spray bottle(this will be more radical than typical changes if water is applied directly).

Since we subject sides to rapid changes in moisture during bending, we get to see some radical movement(more than what we would ever expect in service). How much of a problem that becomes is going to depend on the piece. Much like with the back though you can't go wrong with quartersawn, clear, straight grain wood. It gives you the best stability relative to the dimensions of the piece of wood every time.

Rich

i think this question is so dificult awnser really as everyone will give you a diferent answer.
i know that as a dealer its much easier to quarter sawn sets in most woods.
and as such i will allways try to quarter saw where i can.

but the fact is with some species you can not get fully quartered backs at all becouse the logs are too small.
for example alot of the nicer rosewoods such as mad rose, kingwood, tulipwood,even alot of honduras will not yeild quarter sawn backs period.
in these species it is standard practice to "boule cut" this means to cut accross the face of the half log so the grain often runs quarter-flat-quarter.
in alot of species this will cause cupping off the saw but with good stable wood like mad rose you can get away with it.
if you tried it with ovangkol you would never get away with it.
the only way to get a fully quarter sawn mad rose back is to do a four peice back like lmi do.
this can also maximise the pigment figure becouse the black line/spiderwebbing is on the outside of the log.

of course there are some woods that are not stable even when quarter sawn and will cup as soon as you look at them.
euro maple is bad culprit of this.
but in these cases by the time you have the back braced up it will be fine in service as long as take humidity in account as with any guitar.

every luthier you speak to will have there own opinion on what they like to work with but the fact is its not as important with back and sides as it is with tops or necks.

Joel.

I should have put up these pictures earlier. Here are some pictures of the wood I am talking about. The back and the side materiel are from the same board. It was 14+" wide.

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Mark Ewing
Columbus Ohio
"Trees are an important and precious thing. We should build good things with them. Building good guitars with heart are the best use for them." K. Yairi.

I find the most important thing is that the guitar with a flat sawn back be kept in the same humidity as it was assembled in.
This will help it to stay stable .

On my web site on the woods page you'll see a slab Brazilian back that has been perfect for many years.
I made it in a 40% invironment and it never sees less than that-it does see high humidity but as long as you do not let it get wet it's fine.

Mike

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Mike Collins

Please, somebody define for me "flat sawed", "quarter sawed", etc.

Mike

This is a pretty good image showing the difference between quarter, rift and flat sawn.
Warren

the bottom one looks ok but with mahogany,s they do tend to cup if not quater sawn.

i would avoid the top one becouse the there is pretty big transition from rift to flat.
in fact i would class that as a flat sawn board.

i must stress that i will only use non quartered wood in species where quarter sawing is not possable.

with african mahogany quarter sawn boards are readily available so if you can use boards that are as close to quarter as poss.

i have some cusomers that dont like fully quartered mahogany becouse of the ray flecking you get but this is a personal preferance and i like to see it as it shows that the wood is well quartered.

a mike says keeping the wood at contant rh is more important with flat sawn wood.

Joel.

Mike,
The pictures give you a great example. You will find there is confusion on this subject if you are talking to a woodworker or lumber dealer that does not deal with instrument wood. You will find out that there is no clear distinction between "rift" and "quartersawn" in regular lumber grading. Basically 45 or less off perpendicular to the face is rift or quarter, otherwise it is called flat or plain sawn. There are other terms where there is something lost in the translation. You need to keep that in mind when you are buying wood, especially if it is not from someone who deals with instrument wood.

Even in the instrument wood world you have some confusion. What is the exact number of degrees allowable deviation to still call the wood quartersawn? Some will tell you 15 degrees off perpendicular, some may say 25 degrees. Then from there to 45 degrees becomes rift sawn. You will also hear quarter to rift, rift to flat and so forth, but there is not difinition of how much of the board is closer to one orientaion or the other. That is really confusing because boards that are truely flat across the board are rare, but they are often called flat. It all becomes very confusing when trying to figure out what is happening. A picture does tell the story though, and often that is a good way to make sure there is no confusion(when you can see the woods growth rings are forming up nice circles on the face and the person you are dealing with says it is quartersawn, you can be assured they don't have a clue This much I can say for sure ).

You will have more expansion and shrinkage with flatsawn wood, and this will lead to higher stress with changes in moisture content. Effetively most woods change half as much in dimension when they are quartersawn, but if you allow any wood to constantly be subjected to large swings in moisture it will be tuff on the wood. If you allow your quarter sawn wood to be subjected to 4% or greater changes in moisture, yet you limit your flatsawn backs to less than 2% changes, the flat will move no more than the quarter. It is certainly a good idea to pay more attension to moisture levels with flatsawn backs.

Trick to flatsawn wood is that trees are round and you will not often see truely flat grain across the board, this leads to a difference in shrinkage and this may lead to cupping(flat in the middle rolling closer quarter on the outer edges). When you have quarter rolling to flat you will have a similar effect, but it is less likely to cup as much. It seems like this would be pretty straight forward, but the trick is the grain you see is only one part of the picture. You also have to consider the direction of the fibers between the grain lines(can be real tricky to read in quartersawn wood), you can also have twisting, reaction wood(harder and softer areas), and so forth. Grain can get really crazy all the way to burl which is all over the place.

If you are not sure about this stuff, you are always best off going for straight, clear, grain in well quartered wood. As Joel pointed out, many woods that we like to use simply do not grow very large(rosewoods and the likes). These types of wood are good candidates for 4 piece backs. You can select good grain orientation, and actually you will likely have better back sets than if you paid a premium for flat or rift to flat two piece.

Rich

For example, mahagony is more dimensionally stable flatsawn than spruce is when quartered.

I beg to differ. Mahagony flatsawn = 5.1% Sitka Spruce quartered = 4.3%

Not related to the above but worth noting is that all things being equal hardwoods have more pull or strength when moving. Soft woods will give a bit but a hardwood with equal movement %s will be able to exert more force on joints or stuctures of objects made of wood.
Link

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Cut to size.....Beat to fit.....Paint to match.

Are those numbers for humidity induced movement or shrinkage during drying?

According to the "Wood Movement Calculator" (download from here http://wood-movement-calculator.software.informer.com/) at 70 degrees F, a 16" wide piece of quartersawn Sitka will shrink .142" if it goes from 45% RH to 10% RH. Flatsawn Honduras Mahogany will shrink .135".

Here are the credits for the program...

"Wood shrinkage data and EMC formulas used
in this program were adapted from "Wood
Handbook - Wood as an Engineering
Material", USDA Forest Products Laboratory,
1999.

Some shrinkage data was also adapted from
"Understanding Wood - A craftsman's guide to
wood technology", R. Bruce Hoadley, The
Taunton Press, 1980."

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Kent,
Those numbers are from Hoadly and the US forest labratory's data and are % from green.
However you raise a very good point about the difference between data from green to oven dry and a more realilistic number for wood in the range it would be used and after it is dryed to a "normal" M/C.
In those ranges you may be right about flat Mahog vs. 1/4 sitka.
A while back I was talking quite a bit with the late Jon Arno about a better way of presenting wood values. A example is of Ebony. It has a huge volumetric shrikage of 20% but is about a 1 to 1 ratio of Tan. to Rad. This could indicate that Ebony , once dried is quite stable and empericaly this is true. The question I have and had asked Jon about is how fast do some of these woods take up water. I wanted to do a series of tests on different woods where you would take same samples at say 5% M/C weight them and then expose them to maybe 100% humidity and weigh them after 1 hour, then 5 hours, then 10 and so on. You could get a better idea of how a wood will behave in service. The best he and I could come up with was the take the T/R ratio and the Volumetric and combine them. It is a very good indicator for wood stability but not absolute as again the Ebony example. It's numbers wouldn't be too good with the 20% but it seems pretty stable once dry.
As a aside check out Granidillo. It is one of the most stable woods out there and for it's density probably the most.
It is more stable than Mahogany by the numbers and my experience with it bears this out as well. Good to know because most dense woods aren't that stable.
Link

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Cut to size.....Beat to fit.....Paint to match.

That graphic was awesome! Thanks. It seems to me that really good quater sawn stuff (and perhaps rift) would be the best part and the least available since it would not take long to enter the "rift transition". Are logs precut in a manner to maximize quater sawn or is it just that... so much is flat, so much is rift, and so much is quarter?

Maybe some end cut patterns would help me visualize this.

Mike

Link,
I think chapter 12 of the Woodworkers handbook has a few values for dimensional change between 14-6%. It is tuff to look too hard at those numbers as much more than a fair ballpark number, when they get very close I don't put much stock in one wood moving more than another. I think you would find flatsawn Mahogany and Quartersawn spruce are close, but I am pretty sure Spruce still has a bit less shrinkage(Khaya and Genuine Mahogany post real even numbers though compaired to most woods). Debating too much about the numbers becomes a bit fruitless to me, because other factors can toss through those numbers off sooooooo.... fast(a bit of a turn in the long grain, a minor twist in the grain, how close to quarter or flat you are dealing with, a bit of reaction wood and so forth). Wood is generally just not that homogenous.

Mike,
Some wood is milled specifically to attain mostly quartersawn wood(note, the tree is still round and you will not get all extreamly well quartered wood), but this type of sawing limits the logs yeild so the wood is more expensive. Plain sawn, slab sawn, flatsawn yeild higher and this is the way most logs are cut. Soundboards are cut from split wood(log is cut to rounds then split, to yeild the truest possible cut), but this method is extreamly wasteful and time consuming(thus the high price of this wood). It is also worth mentioning thicker woodbecomes more expensive because you see higher drying losses(cracking, splits, checks and such). I am not sure what type of end ut patterns you arewanting to look at, but you can visualize what your likely to get from trees by drawing a bunch of circles and imagine that is the end of the log. The widest piece off the log(the middle) is going to yeild quarter/rift/flat/rift/quarter. If the log is large enough you could get mostely quarter on each side of the cut(assuming you are looking for two piece backs), but that requires the tree to be pretty good size.

Rich

Only thing I can add is from my current build, number 1 is that back and sides are flat/slab sawn not book marthed either all from pieces I'd been given and they have warped like mad compared to a quater saw book matched top. I'd hate to disagree with those with more experiance, but my sides were badly cupped when I got them, and on bending they straightened up a treat.

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Formerly JJH

I learn more from my mistakes than my successes

Obviously you can change the shape of sides(or backs, ect...) with heat, this is why we are able to bend wood and have it hold the new shape. Really what we are talking about is dimensional changes relating to changes in moisture content. Even after you heat and bend, or even flatten wood, it will still shrink and expand with these changes. I started a little test about 2 years ago. I had a warped piece of englemann(actually I did the same with a bit of Zircote also, but I used it already) that I figured I could do a little testing on. I heated it and pressed it flat, then joined and surfaced it. I have had it hanging(exposed to average changes in humidity *inside my house) since doing this and it is still nice and flat. The test was really more because I was curious about the effect of heat on a soundboard, but it is also showing me a little about post flattening stability(unique to this particular piece granted). If you have a bit of wood you find unusable because of distortion, and all the usual fixes(weight & sticker and such) do not pan out. It is certainly worth a shot with heat, then sticker it for a spell and see what you get(I hung that soundboard freely mainly because I wanted it to have unrestricted movement, but I don't think it is required).

Rich