Official Luthiers Forum!

[QUOTE=grumpy] Are you discounting the value of measuring it and keeping track or
this value for future reference? It seems to me that you are.



Almost.
I am offering another view, another method of measuring. I flexed and
bounced tops and kept notes for years. Instead of numbers, I wrote and
described, to myself, what I felt.

[/QUOTE]




This is a perfectly valid and repeatable way for you to work Mario, as
your instruments have proven time and again. 
But it is uniquely you...because I or the next person could use an
entirely different set of adjectives to describe what's going on, which
might mean little to you or a luthier down the road.  It
is a sense and a feeling that is intuitive only to the individual
person.  This is bit like using words to describe tone....one
man's midrange is
another man's mud.




Numbers are a language common to everyone (one reason why engineers
spec out speaker cabinets in terms of frequency response).  I
personally am still
working on my first acoustic instrument, so I have yet to develop any
kind of intuition on top flexure (with and without braces) and how it
will correlate with the tone of a completed instrument.  But I
will venture that I could understand the meaning of Andy's seven
deflection correlations better than seven of your personal descriptions
of those same tops (when it comes to flexure at least). 



What numbers like Andy's do for me is to provide a flexure benchmark to
shoot for (knowing that my top will need a slightly different
thickness) and save myself the cost and work of 6 other tops that I'd
have to carry to completion in order to learn how they would
work.  As an inexperienced builder, I feel that quantitative
measurements like these give me a little bit of a head start.



It would not be difficult at all to standardize these kind of
deflection measurements...the jig pictured above is almost there (the
5# barbell just not the best for load distribution IMHO).

[QUOTE=azimmer1] John there are ton of ways to do deflection testing.
I do it with 2 wooden rods placed a fixed distance apart and use a 5# weight ...[/QUOTE]
Thanks, Andy.
What's the spacing between the support rods?
Are you measuring your deflections in thousandths of an inch?
And what's your 'standard width' for soundboards that go into the jig?

Thanks

John

because I or the next person could use an
entirely different set of adjectives to describe what's going on,

Correct, but you missed what i hoped you(and everyone else) would catch.

I'm trying to teach you how to use your intuition. I want to teach you how to learn.

See?

Numbers and specs are simple, and easy, as you state. It's easy to share numbers. But I'm not here to give you numbers. Andy and the others can do that.  No, I want you, and Andy and the others, to learn to supplement the numbers with intuition. Not something you can share easily, sorry, but most undoubtedly something you WILL use.

A rote music teacher will teach you a song, note for note. Yay! you learned a song. A good teacher will first teach you the theory, then a song to use the theory, so you can then learn any song you wish, without the teacher's aid. Then a great music teacher will also teach you how to listen.

No, I'm not placing myself upon a pedestal as a great teacher. I'm not. I have difficulty getting my thoughts across. Perhaps it's the language barrier, but I really think it's just 'because'. But I do know what i do know, and I do know that writing down what you felt will make you think deeply about what that was, and in turn, you'll realize you knew much, much more than you thought you did. Once you do so, you'll realize how you can teach yourself.


"learn by first teaching" is a cute quote, but it is very true. What's not often realized is, teaching yourself what you already know, but don't yet realize you know, is often the most difficult teaching assignment, and the most revealing.

So, go ahead and write down the numbers your jig gave you, and share them with your buds. But do yourself a big, big favor, and explain what they mean, to yourself. In writing. And re-read it every few months, or every few guitars you build. It will open your eyes, as well as a whole new world.

I'm sure David Hurd's notebook would be an awesome read, as would Al's and Rick's...(mines is just plain weird...<bg>)

[QUOTE=letseatpaste]Nope. An I-beam would have a higher stiffness/weight ratio than a rectanglur shape with the same dimension, but would not be as stiff overall.[/QUOTE]

I stand corrected. I should have said an I-beam retains most of the stiffness of its solid counterpart at a fraction of the mass. Here is a source with equations for the differences in geometry:

Link

John A
you are certainly asking the right questions
My standard plate width for measuring has been 16 inches.
For all SJ's and bigger the plates can be a bit wider and you just have to account for that with your data.   The same plate thickness at 2 different widths will deflect differently.

As far as separation of the rods, I would have to go out to the shop and measure. I think it is around 18 inches or so. I measure in thousandths of an inch deflection. That will all depend on your dial indicator. I like my digital one because I can zero it easily once on the plate. I don't have to count laps of dial

_________________
Andy Z.
http://www.lazydogguitars.com

Mario
It is interesting what you say about teaching. You are so correct.   I know bringing up ES is taboo, but he never answered many questions in his class directly. It got to the point some were very frustrated. He taught us concepts and made us use our brains to answer the questions ourselves. He was basically teaching us how to "listen"

BTW, I was only providing numbers so others could get a better feel of the cube rule. Sometimes seeing numbers makes it easier to grap a concept.

I personally feel that keep a log of measured data is priceless, but just as important is to "feel" the wood at the same time to develop your own mental database of the tactile properties of wood. This 2nd database in the long run is WAY harder to perfect. The other database can be a great guide to developing your tactile database.

Since I don't have years and years of experience I need the measured data to be a tool to guide my tactile database.

Eric. Be careful, my numbers above are by no means a recipe for a guitar. You shouldn't use my numbers as exact number to guide you. I only posted them to show how the cube rule works with thinning a plate.

_________________
Andy Z.
http://www.lazydogguitars.com

Andy-
Thanks for the info.
Next time you are out in your shop (no rush) perhaps you could measure the separation between those rods- no rush at all on this, but I would appreciate it.
Thanks.
John

Thanks Mario, I totally agree with everything you wrote. 



Numbers help tremendously at the start, but I agree they can only take
you so far.  They are no substitute for experience, building your
intuition, and training your ear.



Andy, I certainly do think there is a recipe for building any
particular guitar, but obviously it is the skill of the luthier in all
aspects that ultimately differentiates a kit guitar from a really fine
instrument that allows the raw materials  to speak to their full
potential.  I do believe measurements can help bridge that gap,
especially for beginners.

Since I don't have years and years of experience

Nobody started out with years of experience. Nobody. We all started out with the same amount of experience: zero.

The is an interesting book called "Blink: The Power of Thinking Without Thinking" by Malcolm Gladwell. That talks a great deal about how experts can evaluate an object or situation without even knowing what they are doing. One example is the Tennis coach Vic Braden can predict a double fault 90% of the time and he has no idea how he does it. He's looked at tapes in slow-mo and can't point to any one thing that indicated that the server was going to double fault.

Experienced builders do the same thing. Watch a good builder sort through a stack of top wood some time. They pick up the boards and instantly either like or dislike the feel of the board. What they are doing, in my opinion, is checking the density, stiffness and damping just by handling the wood. A light, stiff board that sort of "squeaks" when your fingers run over it feels like a board that "wants" to be a guitar top.

You can get that skill by building lots of guitars. Grumpy's journal of impressions forced him to think about the qualities of the board and made it easier for him to get to the point where he can evaluate a board in a few seconds. Al Carruth measures the heck out of the board and keeps copious notes but I doubt the he really needs to do it any more if all that he was interested in was building a good guitar. (Al has other objectives as well.) I've watched him work his way through a pile of spruce and he does exactly what the other more "subjective" builders do. He picks out boards that are light, stiff and sort of "squeak" when your fingers run across it. Al's measuring was the method that helped him organize his experience. (Grumpy, I'm not trying to put words into you mouth. I'm just restating what I think you said in order to clarify the ideas in my mind. If I got it wrong, I'd appreciate a correction. (including the sigh if necessary ))

I use the cube rule when trimming braces. To reduce stiffness, I trim from the top of the brace. To reduce weight, I trim from the sides. I don't expect a large change in the tap tone or Chladni patterns if I trim from the side. If I think that a brace is only a little bit too stiff, I'll trim from the side to avoid going too far. I really don't think that it needs to be any more complicated than that.

Thanks for mentioning your setup, Andy---I'm going to use one like it.
So your tops are 16" wide and the bars the tops rest on are about 18"
apart perpindicular to the grain? Slide the dial indicator over, zero it out,
add the weight. Very simple!

[QUOTE=grumpy] [Nobody started out with years of experience. Nobody. We all started out with the same amount of experience: zero.
[/QUOTE]

True- but a lot of builders who are now 'pros' started out working in shops/factories that were turning out many guitars/year. Think about the list of builders who worked with Larrivee, for instance.

It really doesn't advance knowledge much to say: "I paid my dues, and I'm not giving you my knowledge- go learn it on your own." Our whole technological civilization- for better or worse- was built after scientists and engineers threw out the master/apprentice/secrecy/guild model and adopted the 'scientific' model of open publication of results, and replication and proof by other researchers.

Working on your own, you can do all the feeling and thinking and listening (and measuring) you want, but it can't replace having a few hundred tops per year run through your hands, with somebody like Jean Larrivee saying "too thick" etc...when checking each one.
Even taking a 'course' will not necessarily give you this info and skill, or even address this issue in a meaningful way.
So for the hobbyist, or person trying to get started on their own, it's really a matter of groping in the dark. Even doing measurements on good finished instruments is not an option for most- how many beginning builders have a rack of great guitars from known builders to measure? If you are building a few instruments a year, you are unlikely to make much progress 'reinventing the wheel', unless you are extremely disciplined and build a string of identical guitars (shape,wood species, etc) for the rest of your life.

Until somebody has the candor to say: "I built a guitar and it's gotten rave reviews for tone. I'm going to use the deflection and other data from this guitar as my baseline from now onward. Here's the data from my logbook:....." , it's going to be mostly stumbling in the dark for the solo builder. And, until some consensus is reached for equipment/methods for getting and sharing numerical data, even publishing data won't have much meaning. There is some info about Chaldni patterns available right now, thanks to folks like Hutchins and Carruth, but that's about it, as far as I know. (I think I've read most of the books, seen the DVDs, etc.)

And folks who are 'out in the market', trying to compete for a dollar, are unlikely to do this. Many amateurs buy into the pro 'ethic' as well, since the idea of selling instruments is part of the 'plan for the future'. It's no accident that practically all the 'open source' work in instrument building has come from amateurs and 'outsiders' - Heron-Allen, Hutchins, Kasha, etc - not professionals competing with each other.

It seems to me that it is in places like the OLF, with an established culture of open sharing, where there is the best chance for an exchange of 'science' data for building good-sounding guitars.

Cheers
John

I hear you John, but do you hear Mario telling us not to share or to focus
on developing our senses? There's a continuum---which way do you
think he's sliding? Learn to listen to the wood in your hands. I'm going
to learn from deflection, but I'd also like to learn what a stiff piece of
wood actually feels like.

"places like the OLF, with an established culture of open sharing", John A.

Has a nice ring to it, doesn't it?

The Cube Stiffness Rule for Beams.

I'm glad you guys didn't "stiff me" over this knowledge.   

_________________
http://www.dickeyguitars.com

[QUOTE=JohnAbercrombie] .......Our whole technological civilization- for better or worse- was built after scientists and engineers threw out the master/apprentice/secrecy/guild model and adopted the 'scientific' model of open publication of results, and replication and proof by other researchers.[/QUOTE]
John,
That is not true. It is true for government funded research and universities, but not at all for private industry.
What do you think Patents are for, trade secrets, Intellectual property?
I work in the medical device field. We have no desire to give our secrets/knowledge away that cost millions of dollars to obtain. Our competitors have no desire to share with us and in fact take very strong measures to protect that knowledge.
All industries are like that.

Lutherie is not like that for the most part, we tend to share knowledge freely, but it seems to be changing. One recent example of this is in addition to ES is Kevin Ryan's recent patent on the fluted armrest. I think he has every right to do that.
Another example is the fanned fret patent. There are other examples.


[QUOTE]......
So for the hobbyist, or person trying to get started on their own, it's really a matter of groping in the dark...... [/QUOTE]
Or you can take a class from an expert, like say ..... Ervin.
I got tired of groping in the dark. I paid a large amount of my hard earned money to spend a week with Ervin. I am very pleased with the results. I highly recommend it.
Would you have me just give that information away for free and make it suddenly worthless? (Not that I could.)


[QUOTE]
Until somebody has the candor to say: "I built a guitar and it's gotten rave reviews for tone. I'm going to use the deflection and other data from this guitar as my baseline from now onward. Here's the data from my logbook:....." [/QUOTE]

It would still be stumbling in the dark because it is just one small piece of the puzzle. Deflection data without an understanding of how to brace, make bridge and bridge plates, select wood, tap tone, sides, the back etc. is meaningless.
You have a start from what Andy shared earlier. Does that help much?

[QUOTE] .......It's no accident that practically all the 'open source' work in instrument building has come from amateurs and 'outsiders' - Heron-Allen, Hutchins, Kasha, etc - not professionals [/QUOTE]

Great point, with a few exceptions.


BTW - I understand that there are those that want people to have taken the "course" to share information. Few, if any of the people seem to be listening to those that have taken the course saying with one voice that it was too much information, you need to take the course. That's the truth.

John,
Sorry if this seems argumentative. That is not my intent. I just want to reply with another POV for you to think about. I hope it is helpful.

_________________
"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

True- but a lot of builders who are now 'pros' started out working in shops/factories that were turning out many guitars/year.

I didn't even have a book on the subject. No internet, no luthier firend I could talk to, not eve a StewMac catalog to peruse. Nothing. A "A-2" mandolin blueprint from Elderly instruments, and a friend's similar Gibson mandolin to look at was IT. I built my first guitar with not even a plan. Both that mandolin and that guitar are still played today, and it was that guitar's tone and power that got me noticed. It's still my benchmark for tone and power. And it's held up to rediculous abuse for 11 years....

But i started studying wood much, much earlier than i started building. I began listening to, and studying, wood almost 4 years before I completed that first mandolin and guitar.

My point? I was ale t teach myself how to listen to wood in little time(relatively) using the method i am giving y'all. I'm not saying to sop usng jigs and numbers. I, in fact, said you should(please read my posts completely). Y'all have the tools already for number gathering: I'm trying t give you the rest of the tools to take you to a new level. Whether yo use it or not, is up to you, but don't come complaining. Sheesh. It's not like i charged y'all for it....

I type with two fingers; this takes me a lot of time to write. If you don't like what I wrote, just pass it by, don't make me write further for nothing(like now). I know the majority here are lurking quietly, but the vocal minority here comes across as nothing more than spoiled brats who won't appreciate anything but spoon fed pablum. And you even want to choose the flavor of the pablum. Incredible....

Your deflection picture is running from neck to tail, aha, didn't catch that.

I've always thought of measuring from side to side, but never the other way.

Did you measure both directions?

That would give important information if you had both.   

_________________
http://www.dickeyguitars.com

I typed this up before I read Mario's post, so some of this is echoing what he said...

If I were trying to keep my own trade secrets, I think the last thing I would do is offer a class. The fact that the Somogyi class is even available is great, I'm saving my nickels so I can take it someday after I have some more guitars under my belt. Why should an education be cheap? I think we're spoiled by the incredible amount of info and advice that is readily available at literally no cost except our time and net connection... and we get upset that we can't have it all right now for free.

We've got one thread where everyone is upset that Dave-SKG's buddy doesn't understand the value of Dave's time and experience, and every other thread where folks are upset that you have to pay a fee to learn Somogyi's techniques, which are likely not easily or accurately relayed through an internet forum anyway. I bet 30 years ago some guys would be willing to pay an arm and a leg just for the info we have available for free today.

</end rant>

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______________________________
Jonathan Kendall, Siloam Springs AR

Okay, with a full belly(lunch!) and fresh perspective...

John, I think your issue is that yo think we're dancing around the subject and not "giving" the information you want.

Problem is, somethings can't be taught. What I wrote last night is one of those "things". It can't be taught, but it surely can be learned. I gave you the tools to go ahead and learn, what can't be taught.

I'm not asking for thank you's, or even an acknowledgment from anyone, but at least, don't be so ungrateful.

[QUOTE=grumpy] Okay, with a full belly(lunch!) and fresh perspective...John, I think your issue is that yo think we're dancing around the subject and not "giving" the information you want. Problem is, somethings can't be taught. What I wrote last night is one of those "things". It can't be taught, but it surely can be learned. I gave you the tools to go ahead and learn, what can't be taught. I'm not asking for thank you's, or even an acknowledgment from anyone, but at least, don't be so ungrateful. [/QUOTE]

Whew!

I obviously didn't communicate my thoughts very accurately, and not just to Mario.

First of all, in an ideal situation, the data would be coming from everybody building, not just the 'successful' builders with long waiting lists for their instruments.

Second, the way (public) science works is that after the data is published, it's entirely likely that somebody will come along and say: "We followed your method and couldn't replicate your results. Something else must be going on here."
It's very possible that after publishing deflection, resonance/spectra, Chaldni patterns, etc of a successful guitar, another builder could say:"Mario- I tried to build a duplicate of your great guitar, using your numerical data, and folks say it sounds terrible. So, either my listeners like very different guitar sounds, or something is going on that cannot be measured using our techniques. Let's change our focus to figuring out those other factors."

It's not just the 'one-way street' that some folks here imagine. You don't necessarily look for progress only from those who are already famous and accomplished- at least in science.

In the 'some things can't be taught' department: I heard this a number of times during a course I took (after I'd paid the $4K, not before!). On the 'can't be taught' list :
-French polishing
-evaluating wood for selection
-judging correct thickness for top/back woods
-judging bracing size/strength/taper

Since I spent my professional career as a teacher, I needn't say that I don't agree with this approach!

Cheers
John

<shrug>

A music teacher -can- teach you the notes, which one to use and when, but only you can learn to make great music.

My school teachers taught me the alphabet and words and sentence structure(to two languages, at the same time <g>), but that won't make me into a writer, in any language.

Some things cannot be taught. But all can be learned, if we first learn to learn.

If you go through life searching for the teachings to everything, you'll miss the best teacher of all. Yourself.

Back to the topic... It's important to remember that the "cube rule" is just a guiding principle, not a set in stone method of designing the strongest/lightest braces. There are a multitude of forces acting on a guitar brace or top. If you optimize for stiffness in one direction, it could be very weak in the other direction, or could be weak if a twisting force was applied to it.

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______________________________
Jonathan Kendall, Siloam Springs AR

I think a lot of you blokes spend far too much time looking for the short cut that doesn't exist.

Your time would be far more wisely spent caressing a chisel rather than a keyboard.

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Bob Connor
Geelong, Australia