sitka vs adirondack

[charles Tauber]

Originally Posted by murrmac123

Charles, try dropping a cannon ball and a feather out of a top story window and see which one hits the ground first ...

Is the feather still attached to the bird when I drop it?

[dekutree64]

Originally Posted by Dan of SC

You guys seem to know a lot more about this than me. Not surprising, but if all I see here is correct, why do folks make such a big deal about quartersawn?

1. Humidity. Wood expands and contracts much less in the radial direction than in the tangential direction (usually tangential is about 1.5-2x radial, wood-database.com has numbers for many woods). Cutting slices from the center outward minimizes humidity movement, so the guitar will tolerate a wider range without cracking or swelling excessively.

2. Softwoods have square cells. If you cut it so the endgrain lines are at a 45 degree angle, then the cells are oriented as diamonds, and can deform much more easily when flexed across the grain (long grain stiffness doesn't seem to be affected much). In other words, cross grain stiffness is maximum when perfectly quartersawn, minimum at 45 degrees, and then back to maximum when perfectly flatsawn. If you ever run across a slice with 45 degree grain, give it a try... it's quite remarkable how flexible it is across the grain. Any inherent differences from tree to tree are completely drowned out by the difference caused by how it's cut.

Hardwoods are still subject to the humidity expansion difference, but they have round cells, so no appreciable difference in cross grain stiffness when cut off quarter.

But is cross grain stiffness actually important? I'm not so sure. Two of my best sounding instruments to date (parlor guitar and harp ukulele) are built with 45 degree wood, and two others (00 and small classical guitar) are perfectly quartersawn. Maybe it only matters for large and wide things like dreads and jumbos. I have one in progress with a 45 degree top, so I can at least add one more data point to the set.

[redir]

To simplify just a bit on what dekutree64 said and using some of the same analogies in this conversation, it's all about stability. Braces you don't have to worry so much about, even necks as they are only 2 inches wide, but a 16 inch top and back plate is a different story. If you want to think of the annular rings as floor joists in cross section then in QS wood the expansion between those joists, left to right, is the lowest. The expansion top to bottom is much greater. So if you did the opposite of QS and had those annular rings stacked like a hamburger then the burger and bun would expand greatly left to right but not up and down.

That becomes a problem where the top and back meets the sides and the bridge too. On a flat sawn top the expansion would be so great it would crush up to the stiff sides. As for braces it's more a matter of ease of carving. When you think about a brace that is only like 5/16th inch thick expansion is not much of an issue.

[Alan Carruth]

To add another point:
The differential between radial and tangential shrinkage also causes wood to cup across the grain if there is any curvature in the annual rig lines as seen on the end of the piece. A flat cut piece of wood can only have flat grain lines that will not cause it to cup if it came from the tree on infinite diameter. Sadly, there's only one of those in the universe, and it would take forever to cut it down (at which point you could get an infinite number of tops from it, of course...). Quartered wood has little or no tendency to cup across the grain.

[John Arnold]

You can also get flat grain if the wood is rotary cut like veneer.

Having cut thousands of red spruce guitar tops from logs, I have a good feel over where compression wood forms. It is not that prevalent near the stump. Interlocked grain does tend to occur near the stump, but it is not compresson wood. True compression wood tends to occur on one side of curved logs, and underneath large limbs. It is common in second growth red spruce because of the abundance of limbs, and because trees tend to lean when they are young, and correct their growth by curving back to vertical.
Just to clarify, the terms 'reaction wood' and 'compression wood' are synonyms when the subject is coniferous softwoods. 'Reaction wood' is the more general term that also includes tension wood, which only occurs in hardwoods.

Maybe it only matters for large and wide things like dreads and jumbos. I have one in progress with a 45 degree top, so I can at least add one more data point to the set.

My 1937 D-28 has 45 degree grain in the center, but is near vertical on the outer edges. The grain is fairly wide in the center (~ 10 per inch), and gets tighter toward the edges. It is one of the best rosewood dreads I have ever played, and the top has only the slightest belly. My definition of a good sounding dreadnought is one that is balanced, not bass-heavy. I want loud, clear trebles, and the '37 has that in spades.

All this proves is that you cannot judge the stiffness of a top by looking at the grain spacing or the degree of quartersawn.

[Ned Milburn]

Originally Posted by 6L6

Welp... I'm no expert on the various species of woods. However, I know what sound I like and it goes like this:

* Unplugged I like a dread with Adi top best.

* Plugged in I definitely prefer a Sitka top (all of my guitars sport a K&K Pure Mini pup).

Of my eight acoustics, only one has an Adi top (Collings D2HA).

I play mostly finger style and use a plastic thumbpic and two metal fingerpics. Otherwise I play with a Medium plastic flatpic.

Again, reading Alan's post above is informative. Nothing to add but for this...

Of the guitars that YOU have, the preferred tops are of the above listed species. From this, it is not logical to extrapolate that if a dreadnought style guitar has an Adirondack red spruce top, that it will sound like your Collings Adi-dread. From this, it is not logical to assume that if a guitar has an Adirondack or a Sitka spruce top, that it will sound within your preferences.

This is just another facet of what Alan states. This is the misunderstanding/fallacy under which many guitarists (and guitar builders) believe.

Sure, it is great for marketing to be able to say, "Hey, I'll charge you $500 more for Adirondack spruce top, because the guitar will SOUND BETTER", even though the cost differential is not nearly that much. It makes for good "money making" sense. But it is a fallacy to think that if a guitar is made with rarer or more expensive woods, that it will sound better.

[murrmac123]

Originally Posted by John Arnold

My 1937 D-28 has 45 degree grain in the center, but is near vertical on the outer edges. The grain is fairly wide in the center (~ 10 per inch), and gets tighter toward the edges.

How is it possible to ascertain for certain that the grain is near vertical on the outer edges?

[John Arnold]

Cross silk is a sure sign of vertical grain on a spruce top. Close inspection will reveal the 'near silk' appearance that is indicative of grain that is only a few degrees off vertical.

Red spruce trees are much smaller on average than Sitka. As a result, the edge of the top that is nearer the heart has growth rings that are much smaller radius that the rings on the outer part of the tree. This creates a situation where the angle of the grain can vary considerably from one edge of the top to the other. In other words, the less vertical grain will be on the heart edge.
Martin would often joint the heart edge of the prewar red spruce tops. Since the grain is generally wider and can be off-quarter on that edge, the only logical explanation for doing it is to reduce visible runout. Runout is evident where the two halves of the top reflect light differently.

[Monsoon1]

so the cut and grain is no particular clue about a boards stiffness...
well then how do you check for stiffness?

[Monsoon1]

and is soundboard stiffness even important for tone? is it at all an indicator of tone?

[Truckjohn]

Well... I think you have the answer to "How important is being perfectly quartersawn" from many posts on this forum - where folks observe that their favorite vintage instruments have some ugly tops when you really get down to it.....

But the trouble is "A man hears what he wants to hear.." Its literally true..

[Alan Carruth]

There are several ways to check for stiffness. The simplest one is by feel, and most luthiers will do this. Some folks can do it very accurately, but tests have shown that most people are not nearly as good as they think they are. Small differences in thickness can make a big difference in stiffness.

In all of this you need to keep in mind that what we're usually looking for is a way to make a top that's as light as possible and just stiff enough to keep from folding up too soon. Strength doesn't generally enter into it, since most woods will be much stronger than they need to be if they've been left stiff enough.

Some makers use static deflection to gauge how thick to make a top. Basically you support the wood at both ends, put a weight on it, and measure the deflection. This is a direct measurement of stiffness, and thus should be pretty accurate. As usual, there are complications from time to time; some pieces will measure different if you flip them over, for example.

It's also possible to measure the stiffness by looking at the way the piece vibrates. There's a known relationship between the vibration frequencies of a rectangular plate or bar, the size, and the weight, and once you've measured these you can calculate the 'Young's modulus', which determines the stiffness at a given thickness.

The problem with making these measurements is that you start to see that the stuff that 'everybody knows' is not necessarily true. OTOH in can make your guitar making more reliable, if, perhaps, less exciting. Watching tops self-destruct adds spice to the day, but it's not 'fun'.

[Truckjohn]

Originally Posted by Alan Carruth

Some makers use static deflection to gauge how thick to make a top. Basically you support the wood at both ends, put a weight on it, and measure the deflection. This is a direct measurement of stiffness, and thus should be pretty accurate. As usual, there are complications from time to time; some pieces will measure different if you flip them over, for example...

Al, I have seen this happen... Is this an indicator that there is more runout than "usual?"

[redir]

I would not be surprised if the time of day had something to do with the deflection testing measurement. I'm talking very very small numbers here. I've flipped them over and always get a different number but I presumed that to be because the plastic deformation had not come quite back to equilibrium. Probably should wait a few minutes before measurements.

At any rate, I do 3 iterations and take the average. Deflection testing is meaningless till you have enough data or perhaps when you get that 'Ah Haaa!' guitar, build one just like it and get similar results.

I've adopted deflection testing as my method and so far I like it. Prior to that I was doing the 'by feel' measurement of thickness but what does that mean? One method is to thin the top out till it sounds like a piece of sheet metal when you shake it. I wish I could attribute that method to the origianl designer but his name escapes me. I used that method for many guitars and when I now compare it to my deflection tests they match up pretty well so I like it.

The method I used was copied from luthier Brian Howard. Basically you choose a weight, in this case a brick, and you stick with it for the rest of your life. You take measurements and record them and after a while you get familiar with the results. Here's my set up. That brick and those anchor points will be with me forever and all those measuremts will be recorded and carefully noted. Over time I hope to have enough data for it to make sense. It already is after about 15 instruments.

[printer2]

Where Is My Brick? WHERE THE HECK IS MY BRICK!!!