Official Luthiers Forum!

Clearly the square foot of gravel, if the internal voids aren't exposed to the external air volume. I think it's pretty clear that the 80 grit surface would have more area - the scale of the roughness is larger. But this won't amount to a hill of beans if the time scale to transfer the moisture is comparable to or less than the time scale over which the humidity is changing.

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Jim Kirby
kirby@udel.edu

I'm sorry, anyone that hangs a guitar on the wall is NUTS!
Uhh, unless you fill it with soil and plant an ivy.
Instruments belong in their cases unless they are being played. If you feel differently, expect cracks and "accidents". Circulation from cold to warm and low RH to hi RH runs from floor to wall to ceiling and back around. NOT a good place to put a guitar. Would you folks finally realize that a handmade guitar belongs in your hands OR in your case (with humidification monitoring) ???!
The only exception is a humidified room...well, nah, that's only for Taylors...
DUHH!

I have only built a few guitars and most were from quartersawn backs and sides or close to quartered. I have only made two with flatsawn material and both because of quilted figure. You just don't get quilted or pommele figure unless the wood is flatsawn. I don't have these guitars in my possession. One is owned by my brother and the other by his son. They have not had any problems with them as far as I know. My nephew plays his a lot and in all kinds of conditions. They were build in a humidity controlled shop and the material acclimated for a few years (I build now and then).

My opinion on the beauty of wood is that quartersawn material is just as attractive as flatsawn. In fact, I like it better. Gives the instrument a look of simplicity even with curly wood. When I go to a classical guitar concert, I am much more interested in the sound of instruments than how they look. The music is the most important part of the instrument. Why take away from it.

Ken

Who the heck is Thom Hartmann, and is this politics?

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Jim Kirby
kirby@udel.edu

I have to admit that I'm still horrified that "flooding with Cyano" s considered an acceptable practice for wood that is questionable in that it may contain checks.
My experience having repaired guitars with exisitng cacks is that Cyano repairs, even with refinishing, sooner or later show up again, no matter what.

I simply would not build a guitar for a client using wood which I knew to have an exisitng check within the pattern, cyanoed or not. This is one reason that at this point I favor (the very stable) E.I. rosewood which I can still get well quartered and in a quantity sufficient where I can pick the best and most appropriate sets.

Great thread Chris. The main reason you see so many flat sawn guitars by well known builders is the buying public.
IT'S WHAT SELLS. Most buyers are driven by looks first. Yes they want a good sounding guitar with great action and all the other good playing qualities but IMHO looks is still the #1 criteria. After all why spend thousands on a guitar and not be happy with the way it looks. I too have over 50 years of woodworking experience having built a lot of Queen Anne repros.
The most stable wood was always mahogany. I have to agree with what Rick Davis said. Most ebonies are prone to cracking. If you have never looked at ebony cants you would be shocked at all the cracks this wood can have even with the ends waxed. Most of these woods arrive with the whole board or cant waxed. Good for the wholesaler that sells this wood to various US dealers. Not so good for people like myself that have to process it. It is always soaking wet. So what does one do with all this lousy flat sawn prone to cracking wood? Toss it, burn it, take a chance and use it. Lets be honest about this. Sawyers don't like to qs wood. Way too much waste. Also a lot of these exotics are not wide enough to get qs bords in sufficient width for guitars. The more waste the higher the cost and the higher the sale price. That is unless you don't mind selling your wares at a loss. I have found some flat sawn woods to be very stable and others not. Most cocobolo seems to be OK flat sawn. I can usually get a good feel for most woods when re-sawing. Some will come off the saw perfectly flat and others will cup within minutes. While the RH you build in is important the MC of the wood is much more important. If a wood is dried to 6-8% MC it will never go back to it's wet MC unless you soak in a bucket. The width vs the thickness of a guitar back is another factor. Narrower pieces will tend to move a lot less. If we can educate the public into accepting 3 and 4 piece backs it would make for more woods being available and utilized and a more stable product. Just my $2.00 worth. Oh and one more thing. Try buying lumber sight unseen and see what you get.

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Best thing I've read here.

Fractal geometry tells us the opposite, in my admittedly humble understanding of the issue. If a surface is fractal, it's area would be greater when measured on a smaller scale of angular variations. Does a sanded wood surface have a fractal model? I don't see why not, especially since we are talking about the transfer of particles the size of water molecules. Is that model dependent on the scale of the sanding grit? That's the rub, and I don't know. But perhaps someone more expert will join in. The issue is far from simple. For example, see: http://www.imagemet.com/WebHelp/spip.ht ... meters.htm which has a section that goes into moisture retention. I don't pretend to understand all the math. Just suggesting that the answer may be contrary to our first intuitions. The answer seems to me to depend on the characteristics of the surfaces in between the scratches measured on the scale of the sandpaper. It may turn out that the sanding grit is irrelevant to the transfer area on a molecular scale.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

And here I thought that was going to be the least contentious thing I said........

You're probably right, Howard. It's not a safe assumption. Just something I read from someone I respect that made sense on the surface. I'm not going to put a lot of effort into trying to prove it one way or the other. Talking about it more would be pure speculation and as my friend's grandma used to say, "Speculate in one bucket and pee in another and only one of them will fill up."

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http://www.chassonguitars.com

I'm not positive, but pretty sure that coarser grit = more surface area, even if fractal geometry is accounted for. And even then, you can't get into the full potential of fractal surface area, since the grits are all glued to a paper so you can't have "overhangs". Well, maybe a little bit of overhang if the side of a grit scratches on a piece of wood, but definitely no notches cut into the ceiling of that notch, like the last line in the image.

You can still get into fractal business without overhangs in the grooves-within-grooves line, by cutting a smaller groove into the angled surface of each of those grooves, and then an additional groove in the angled surface of each of those grooves, and so on. But in any case, the larger grooves you start with, the more surface you can get before you run into the real-world limit of how small of grooves you can make. And that's assuming the sanding grits are rough enough to create grooves-within-grooves. If they're fairly smooth, faceted crystals, then they'll cut smooth grooves more like the "coarse grooves" line in the image... although there are a whole lot of grits on the paper, so even if one grit makes a smooth groove, another will probably come along and scratch another notch in the side of it, or cut across it, and various other things to rough it up.

But yeah, I'm going to say that sanding the inside to 600 grit will help. Or better yet, scrape the plates before gluing the braces and don't ever rough them up after that.

And the pile of sand has way more surface area than an equal size pile of gravel. But that has "inner surfaces", so not a fair comparison to a sanded wood surface. If you make two solid cones the size of the piles, coat them in glue, and pour gravel on one and sand on the other so only the outer surface is considered, then the gravel will win.

Now if you pour activated carbon on one of the cones...

Maybe it is possible to test this. Take one plate of rosewood that you are certain has been dead straight and flat for a long while. Sand one face as smooth as possible and the other with 80 grit or 40 or whatever. If it starts cupping or twisting....

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Build log

The sand or gravel would have a greater surface area to volume ratio ... , the on a two dimensional plain the finer sanded surface would have less surface area on that plane... If that makes sense

This is a great read fellas. Thanks.

I was jut thinking...... we should get Mandelbrot to weigh in on the topic, but I forgot that he passed last Fall. I attended a lecture he gave at a math and art conference while I was in undergrad school. What a guy! Has anyone ever thought of doing a guitar with a fractal theme, or using his amazing tiles as a decorative theme. What about Escher?....... his tesselations (especially hyperbolic) would be great ideas for rosettes and such.

Thanks for the thoughts my friends.

Love, Peace, and Hair Grease,
Hans

I don't think the discussion of whether flatsawn wood cracks more or less than Quartersawn is the right discussion..... Likely everyone here has seen plenty of guitars with cracks in perfectly quartersawn wood......

I think the crux of what I have seen boils down to the behavior of the crack and the ease of repairing/hiding it....

When Quartersawn wood cracks - it tends to follow grain lines.... so you have a nice, straight crack... whose fix will likely be hidden by the contrasting grain lines.... The cleats are also easy - as they follow a straight line...

When Flatsawn wood cracks - it tends to wander all over the place through otherwise unblemished wood.... It doesn't have the decency to follow grain lines... it just goes twisting around wherever the spirit carries it.... like the OP's original post shows.... so can you end up with this squiggly dark wandering "Crack" going across some extremely uniform colored section where the crack fix happened... and it looks like a crack.... Cleating it requires a whole handfull of itty bitty cleats all over the place.

That's my take on it at least....

Thanks

As a novice luthier...but 30+ years of experience laminating woods together, the issue is with each piece of wood and SEASONING...not necessarily the cut. I fix a lot of antique wood items and SORRY TO SAY there are no combination of woods glue up in multiple grain directions that will withstand the forces of nature and time. It's just a matter of when it will fail. Either cracking will occur or bracing and laminations will fail. That's why the repair and restoration business is available.
A quarter sawn grain WILL expand and contract evenly between grains all across a brace.That is good.. so stress along a counter grained brace is even across the back and less likely to split along a grain line. A (well seasoned) flat sawn back can also contract evenly against a counter directional brace. I see the bigger issue with flat sawn is the effect of moisture/humidity and the woods desire to cup and twist. To minimize this stress, I would tend to make a flatsawn back/side a bit thinner to reduce that tendency to pull on the interior bracing.

Well Seasoned Wood is the biggest factor.....just my opinion.
Kent

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Kent, by thinning the plates further you increase the capacity and willingness of the wood to move with RH changes, thus to potentially develop cracks. It is my (unfortunate) experience that regardless of the cut, by thinning the plates further you increase the possibility of cracks to appear. Besides, for me at least, thickness is entirely determined by tonal and structural goals.
I prefer a great sounding guitar with a few cracks down the line to a dud with no cracks.
I entirely agree with your second statement though.
I always thought that quartersawn was more desirable because wood expands and contracts most tangentially, and least radially. Am I getting this wrong? It doesn't seem to matter much for some woods like mahogany or Spanish cedar. But IME, rosewoods and ebonies (with a few exceptions) tend to be much more stable when cut on the quarter. Since we ladder brace the back (most of us anyway), it seems to matter a great deal.
It is also a fact of life that a lot of tonewood now comes from smaller trees than before, some with too much internal stress to ever be stable. Another unfortunate fact of life is that I see more and more "tonewood" on eBay that should have never been resawed in guitar sets. The future catastrophe is written on the wood. Whereas it is ignorance or dishonesty from the part of the vendors, it probably varies, and alternates between both.
Personally I do not care much for the flat sawn "cathedral" figure of most woods, I find it distracting, almost vulgar. There are exceptions, of course.
You guys are kidding with the different grits, right?
As noted before, regardless of the cut, I always brace the back and assemble the box as dry as possible (30-35% RH). It seems to work, I haven't had a crack appear in a long, long time (knock on wood…).

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

I disagree. A guitar kept in its case is a guitar that gets played less often, and the point of these things is to get played, not to remain pristine. I encourage people to control humidity at room level and keep the guitar on a stand.

Besides, the most precarious moments in the life of a guitar are going into and out of its case.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Someone mentioned seasoning wood by keeping it in a humidity controlled environment for years. I think this is mistaken. "Seasoning" (the word) comes from exposure to the change of seasons. The more the wood has been responding to environmental changes before being used the better. I bring sets into the shop a few months before I expect to use them. Until then they are out of the rain, but without temperature and humidity control. If I lose a few, well, better that they revealed themselves now rather than later.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I think I may need more surface area on my head to scratch...

I would think the biggest problem with irregular grain would be irregular shrinkage. In some flat sawn you have areas that shrink differing amounts or in differing directions. Of course if you're a newbie like me and you build a guitar in the back shed during rain, then bring it in to an over heated room when done, the sitka spruce will likely crack, and then you can turn it into an instant "virtual vintage" guitar, using Behlen toner (the secret to good tone). Ha ha. Sorry I'm in a weird mood.




all the cracks are repaired, and everything sounds good... But I'm talking top instead of back here. (this top has a lot of character and looks like it was built a long time ago)...

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from "Your Owner's Manual" by Burt Hotchkiss.

Try seasoning sets outside in Buffalo NY. I guarantee you'll wind up with a lot of kindling.

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YIKES! That's a pretty harsh statement there, Haans. Seem to me that keeping a beautiful guitar in its case except when it’s being played is akin to keeping a bouquet of roses in the box they arrived in, except at dinner time.

I see you decided to man up and get rid of the political endorsements in your signature?

+1

"Conditioning" is a stage of the kiln 'drying' process and has nothing to do with seasoning/aging. It reintroduces moisture to the wood surface the purpose of which is to to equalize the MC of the kiln dried timber preventing cellular collapse and or casehardening of the wood surface.

Cheers

Kim

Absolutely right, howard.
An hour ago I pulled some wood for my next 3 builds.
Tazzie Blackwood back/sides/top. One plate had a tiny knot, 1/16", and it developed a 3" crack up the grain.
Looks like I'll be doing a spruce top, Tazzie back and sides,
and make something else that's smaller with the kindling.
Maybe it's Kizmet that the piece cracked.
I think I like a spruce top better anyway.
I've had that wood for about 4 years, maybe more.
Wood does what it wants, and I'm glad I waited!

What the heck is that, a bong ?

L.

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

"Shrinkage/expansion in a quartersawn board is greatest across the width of the instrument"



sorry, but this is not the way of wood....


michael keller
www.kellerguitars.cpom