Tap tuning as a rough guide when shaving the braces

Construction and repair of Classical Guitar and related instruments
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Beowulf
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Re: Tap tuning as a rough guide when shaving the braces

Post by Beowulf » Tue Jan 23, 2018 5:34 pm

Of related interest are Daniel Friederich's comments on his build process for guitar #830 which may be found online in Orpheo magazine No.2, page 34.
1971 Yamaha GC-10 (Hideyuki Ezaki)
2017 Yamaha GC82S (Akio Naniki/Naohiro Kawashima)

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Tue Jan 23, 2018 9:29 pm

One of the dfficulties for new makers is probably hearing the sound of a free plate and mentally defining it as a note as if on a piano . A guitar plate has a woolly sound and it takes a while to focus on it .
I hope another point will not be too off topic but I remember a piano tuner saying you need to focus on the first sound as you play the note. Before it starts to fade and alter it`s frequency . A guitar note declines in frequency and a guitar forum advised to listen for after the note declines and not the first impact of the note . The question is how long do you wait ? How resonanant is the guitar ?
If a chord is slowly strummed on a guitar would the early notes become out of tune with the later notes ?
In the violin thesis was he being subjective when he said players were "wrong". Is wrong a subjective word ? Sorry , this starts to get quite funny after a while , ---- but not unpleasant .

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Tue Jan 23, 2018 9:38 pm

I have to ask about a list I saw yesterday . It listed all the things Torres did not invent or initiate . He did not invent fan braces allegedly . Or invent larger guitars . All those type of things . But there was a sentence about his instruments being sanded and refinished and that made the wood thinner . Is that what has been happening over the years ? I was shocked to read that. Would that alter the tuning of his guitars? The only thing he did apparently was to glue them together better than other makers . That does not sound like much of a recommendation . Some don`t even sound very good . It`s all so confusing .

Alan Carruth
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Re: Tap tuning as a rough guide when shaving the braces

Post by Alan Carruth » Wed Jan 24, 2018 7:41 pm

A lot of what makes a guitar superior has to do with how well balanced it is, in a lot of ways. Torres may not have 'invented' much, but he did a lot to 'optimize' the design. The same could be said of Stradivari. For that matter, J.S.Bach didn't invent new forms either, but that doesn't reduce his importance as a composer.

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Wed Jan 24, 2018 9:35 pm

So what would you say was optimised and has that knowledge and experience filtered through to later generations ? I get the impression guitars have become heavier than he made them , which might be relevant to this topic . A practical attitude would be make it very light (till it breaks ) and then make it a bit thicker . Sort of "make lots of broken guitars first " and not just make lots of guitars . A bit extreme and maybe the opposite of what happens in real life.

Alan Carruth
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Re: Tap tuning as a rough guide when shaving the braces

Post by Alan Carruth » Thu Jan 25, 2018 5:59 pm

Guitars probably have gotten both heavier and larger since Torres, although that's arguable. He made a lot of different sizes, and I have not really looked closely enough at his catalog to be able to say whether his biggest ones were as big as many contemporary guitars.

One idea about why they have gotten bigger is that when a maker wants to copy an instrument they lay it down on piece of paper and trace around it with a pencil. This makes a slightly bigger outline than the original, and after a few generations the difference gets noticeable. That's a bit facetious, but still...

Bigger guitars do tend to be more 'bass balanced': although they may not have as much actual power as a smaller box that it properly made, many people seem to feel the added low end makes them 'louder'. Note that 'power' is something you can measure (at least in principle), while 'loudness' is a subjective impression. At any rate, for structural reasons as you make the guitar larger you have to 'beef it up' a bit to keep it from folding up too soon.

Travel has gotten easier, at least for people. I'm not sure instruments are any better off in the baggage compartment of an airplane than they used to be on the top of a coach: at least in the old days you didn't have an airline baggage ape tossing them out on the tarmac. It's entirely likely that we make them a bit heavier to withstand the rigors of travel. Ditto the rigors of winter in centrally heated houses, where the relative humidity can reach desert dryness. There may also be more of an expectation of cosmetic 'perfection' these days which is a bit easier to achieve in a heavier build.

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Thu Jan 25, 2018 9:13 pm

There are too many articles about Torres to keep giving references but the latest one I read mentions the bracing fitted by Torres and how they made the guitar top stronger than a violin top . I`m not sure I agree with that . Why would strength in that sense matter so much . Another article , this time about violins, mentioned Carleen Hutchins and that she regarded the soundholes as a "weakness"in the top . The whole point about the soundholes is to produce the flexibility for the top to move and for air to move in and out and produce a louder sound. Loud as in "a guitar is nowhere near as loud as a guitar ". And a violin has plenty of tone to go with it .So a physical "weakness " that gives volume and tone cannot be all bad . Torres is said to have made the guitar bridge wider. Almost going backwards after the changeover to fan bracing from ladder bracing. But the bridge is on the outside and ladder bracing is inside "as if there was no direct connection "(?). Maybe he sensed an over correction had been made and tried to get it in balance again .
In a violin (from some historical notes ) the "original "sound post was almost an afterthought . The bassbar was already accepted. Before the soundpost the violin was a quiet instrument . By adding the soundpost it became much louder and the tone improved .The bridge is about 1/4inch nearer the scroll than the post . That creates a rocking action in the top from the bridge that was missing before .
There are plenty of guitars with F shaped holes but strange versions of soundposts in the wrong places that could be improved .
Maybe this needs a new topic .

Alan Carruth
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Re: Tap tuning as a rough guide when shaving the braces

Post by Alan Carruth » Fri Jan 26, 2018 6:12 pm

I studied with Carleen Hutchins; she was quite aware of the pros and cons of most of the features of the violin. I never heard her mention the F-holes as a 'weakness', though. At any rate, as I keep emphasizing, comparing the guitar and the violin is a fraught exercise: they are much different beasts in spite of a lot of common heritage and seeming similarities.

Many people do regard the guitar sound hole as a 'weak spot', and, in some sense, it is. However, on the guitar structural stiffness is the thing that sets most of the limits, and some models show that the sound hole area is more than strong enough so long as the top stiffness is OK. Guitars do, of course, tend to swallow themselves through their own sound holes over time, but they would distort in much the same way if the hole was someplace else, I think. It's not the hole that causes the problem, it's the nature of wood under stress.

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Fri Jan 26, 2018 7:12 pm

What do you think of the JLD Bridge system ? I used one to stop a top bellying up with normal tension strings. It brought the top back to a normal position and to me it seems to make any other reinforcements unnecessary . It could also allow a much narrower bridge without any cracking . I think I am still relevant to the braces topic . Bert Eendeback from the Netherlands has a good site with a section about Tapping the top . And a Jansen (Sweden ?) pdf that would not be recorded in my bookmarks says a lot about bridges .They show graphs for tapping as each part is added to the top and then the bridge is attached and all the readings drop down . Some foreign writers use similar phrases but it is very easy to almost get an opposite meaning depending on how you read it . A bit like Australians rising note at the end of a sentence that makes everything sound like a question .

Alan Carruth
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Re: Tap tuning as a rough guide when shaving the braces

Post by Alan Carruth » Fri Jan 26, 2018 7:38 pm

I've seen the JLD setup, but never used one. It would certainly reduce or eliminate the torque load on the top, but adds mass.

The resonant modes of the top can either rise or fall in pitch when you glue on a bridge. The bridge on a Classical guitar is, of course, one of the major cross grain braces on the top, so it can add a lot of stiffness in that direction. It's also the heaviest brace on the top, and can weigh as much as all of the other top bracing together. Most of the mass is in the tie block and saddle area, which is also quite stiff, of course. The wings have some stiffness as well, and the length and thickness of the wings are important variables. Whether the pitch of whatever modes are affected will rise or fall depends on the balance between mass and stiffness of the bridge as a whole, and in parts. The stiffness of the wings for example, can have a fairly strong effect on the 'cross tripole' mode pitch, and the bridge length can influence the 'cross dipole'.

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Sat Jan 27, 2018 9:58 pm

I used a JLD to get a laminated top to regain it`s normal shape. It was a cheap option but did not spoil the sound and made the top safe again.
I noticed the name Carleen Hutchins and expect she would have thought through ideas like soundholes as a weakness . She would most likely have enjoyed any challenging ideas like that . You must have been very happy to work with such an important thinker about violins .
I am looking at guitars as physical mechanisms to convert string vibrations into sound rather than as cultural icons . The guitars with f holes and no circular holes are a puzzle to me . Do they use any kind of soundpost ? That`s just a normal thing to expect when I see that design . The string tension is held at the end block . Stepping out from what we are used to ---when did the very odd idea of gluing a bridge on the middle of the top get started? With the desire to make guitars louder is that idea becoming obsolete? Gut strings never imposed the stress of hard tension strings on the bridges .
Bert Eendeback says the thinning of the edges is important for tuning ,and altering braces after assembly is for fine tuning. So that`s useful info for this topic. I have often seen comments that the top tuning will change after assembly but not by how much (roughly ).Nobody gives a hint about that . But if you go too far you can stop and use a JLD . I am trying to separate the leverage control needed (strings trying to twist the bridge and top ) from the very subtle business of vibration that happens without very much to see apart from the stings moving .

Alan Carruth
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Re: Tap tuning as a rough guide when shaving the braces

Post by Alan Carruth » Sat Jan 27, 2018 10:39 pm

amexcua asked:
" The guitars with f holes and no circular holes are a puzzle to me . Do they use any kind of soundpost ?"
No. Lloyd Loar lifted the idea of F-holes from the violin when he went to work for the Gibson company in the '20s: Orville Gibson's originals had elliptical holes and glued on bridges. The F-holes certainly do alter the timbre somewhat; they 'listen to' differet internal air resonant modes, among other things, but F-holes and a sound post don't automatically go together. Early violins had F-holes and no post.

"Stepping out from what we are used to ---when did the very odd idea of gluing a bridge on the middle of the top get started? With the desire to make guitars louder is that idea becoming obsolete? Gut strings never imposed the stress of hard tension strings on the bridges ."
That goes 'way back, so far as I can tell. It's not all that odd.

"I am trying to separate the leverage control needed (strings trying to twist the bridge and top ) from the very subtle business of vibration that happens without very much to see apart from the strings moving ."
As are we all!

Static torque on the bridge is a function of how high the strings are above the top (actually, the bending center of the top, which is someplace below the surface, but that's a small quibble). Flamenco guitars reduce the static torque by lowering the height of the strings off the top, and that allows for a much lighter structure. If all you had was string tension, acting in plane with the top, you could make it almost paper thin. That would not guarantee great sound, I think.

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Sun Jan 28, 2018 6:59 pm

I never had any interest in the large amplified steel guitars but I was very disappointed with them yesterday when I read that one type was described as "of no musical interest without amplification ".

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Mon Jan 29, 2018 11:19 am

The Goolgle boxes on my homepage today included the JLD system so I looked at it again . They show a cross section diagram of how a guitar bridge will twist the top out of shape. They say the force is about 250 lbs. So now weigh that strong force against the "added mass " of a JLD --a small wooden block and a spruce rod pressing on the tail block. That will release all the strain on the top and leave it free to vibrate . So no comparisons with any other instruments. It works on a guitar for a very logical reason .
Think of an opera singer being held by a top wrestler who is twisting her neck sideways . She can`t sing properly like that . To tell the truth I like that image quite a lot . Don`t let her go till I get out of range mate .

amezcua
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Re: Tap tuning as a rough guide when shaving the braces

Post by amezcua » Mon Jan 29, 2018 7:09 pm

I have another question about bridges now. I read that a bridge should be as stiff as possible because any twisting will soak up energy. (?)
Well it`s glued to the top so it would pass that vibration into the top . Has somebody been making up physical laws that sound plausible ? What would happen if you made bridges with carbon fibre? That would be ultra stiff . Would you get lots of stress cracks at the edges ? Somethings got to give .
In there was a way to use bridges without wings would makers colour them in like a Groucho Marx mustache to keep the traditionalists happy ?

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