string "jacking"?

Construction and repair of Classical Guitar and related instruments
RJVB
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string "jacking"?

Post by RJVB » Mon Mar 18, 2019 10:24 am

This may be a bit too geeky a question and addressed to the wrong "crowd" but here goes:

Is there such a tool as a string "jack" or could you think of something that would serve to take the tension off the bridge/saddle (so it can be adjusted) without having to slacken or even remove all strings entirely?

I realise that this may be relevant/possible only for guitars that have an actual separated bridge that doesn't sit just in front of the string holder/tie block, and that that's something I've never seen in instruments I know to be "classical" and not "acoustic" (that includes all period plucked string instruments I've ever encountered). But I'm guessing *someone* must have experimented with arch-top design instruments for classical repertoire, no?

Thanks!
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Bolink baroque violin, Nadegini modern violin (both F.S.)

GerryM
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Re: string "jacking"?

Post by GerryM » Mon Mar 18, 2019 7:10 pm

Sure, they are pretty common in banjo where you may want to swap bridges quickly when experimenting. They can be made of 1/4" plywood cut into a L shape or using dowel sanded to oval shape with a small handle inserted into a hole. For a classical guitar I would lay down a protective sheet on the top before using a string jack to lift the strings.

Personally I seldom used one as it was simpler to just lay the bridge flat and rotate it up (in the proper direction of course). I had to only slightly touchup the tuning when the bridge was the same height as the original. I could swap a bridge in about 15 seconds. I used to make and sell banjo bridges and would often test every one that way.

Lovemyguitar
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Re: string "jacking"?

Post by Lovemyguitar » Mon Mar 18, 2019 7:26 pm

I would never do anything like that on a classical guitar -- it would put a lot of extra tension on the strings and thus on the bridge/top of the guitar. Classical guitars are lightly built and not meant for excessive tension like that. It isn't that big a deal to slacken the strings to change the saddle, if one so desires.

RJVB
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Re: string "jacking"?

Post by RJVB » Mon Mar 18, 2019 8:44 pm

GerryM wrote:
Mon Mar 18, 2019 7:10 pm
Personally I seldom used one as it was simpler to just lay the bridge flat and rotate it up (in the proper direction of course).
More or less how you'd do it on a violin, though there you'd slacken the strings first because the feet of the bridge and the varnish are both fragile.

Are they indeed referred to as string jacks (and available online under that name)? I've been using my finger until now but come to think of it: given the small distance between the strings and the coverplate a simple wooden pencil might do the trick.

@Lovemyguitar: if I were to do this to a classical or other kind of acoustic guitar with a similar bridge design I'd take care to distribute the tension equally, possibly all the way to the side walls. On a resonator like mine there's a steel cover plate that should be a perfectly safe base for a jacking mechanism to lift the strings a few mm. One will just need to take a lot of care when lowering the strings back onto the bridge in order not to collapse the cone (they're about the thickness of a soda can).

Of course, if there's nothing to adjust in a saddle (other than string depth) you can just as well slacken and re-tighten the strings once. It's a bit different if you have a bridge that needs adjustment for intonation/compensation purposes.
Gretsch G9240 "Alligator" wood-body resonator converted to non-metal strings
Bolink baroque violin, Nadegini modern violin (both F.S.)

Lovemyguitar
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Re: string "jacking"?

Post by Lovemyguitar » Mon Mar 18, 2019 8:56 pm

RJVB wrote:
Mon Mar 18, 2019 8:44 pm
...
@Lovemyguitar: if I were to do this to a classical or other kind of acoustic guitar with a similar bridge design I'd take care to distribute the tension equally, possibly all the way to the side walls. On a resonator like mine there's a steel cover plate that should be a perfectly safe base for a jacking mechanism to lift the strings a few mm. ...
Oh, I thought that you were proposing to do this with a classical guitar (silly me, "classical guitar forum" and all!). Ciao!

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Beowulf
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Re: string "jacking"?

Post by Beowulf » Mon Mar 18, 2019 9:18 pm

The saddle can be "tuned" for intonation by taking an electric guitar string and bending it into a U shape. Then with the strings at tension slide it between the string and the top of the saddle. Check the intonation by comparing the fretted note at the 12th fret to the harmonic at the 12th fret. Slide the U back/forward until the tones match. Mark that point on the saddle for each string and then shape the front of the saddle as indicated. I found this method in a book by John Bogdanovich on classical guitar making.
1971 Yamaha GC-10 (Hideyuki Ezaki)
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RJVB
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Re: string "jacking"?

Post by RJVB » Mon Mar 18, 2019 9:50 pm

That's interesting; I'm guessing it should work also with a metal string for acoustic guitar - a high E I presume?

What I don't get is how sliding the U back and forth would affect tone height, nor what to mark. I'm going to need to find a schematic somewhere.
Gretsch G9240 "Alligator" wood-body resonator converted to non-metal strings
Bolink baroque violin, Nadegini modern violin (both F.S.)

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geoff-bristol
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Re: string "jacking"?

Post by geoff-bristol » Tue Mar 19, 2019 1:07 am

A thing I use on violins - very simple - is a block of hard foam slightly higher than the bridge. When you slacken strings on pegs - especially with steel strings ( fiddle set up etc ) they tend to all go hay-wire and un furl at the peg etc. If you slacken them loose then prop them with the foam - they stay put on the pegs etc. Its useful for removing a bridge for minor tweaks.

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Beowulf
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Re: string "jacking"?

Post by Beowulf » Tue Mar 19, 2019 2:22 am

RJVB wrote:
Mon Mar 18, 2019 9:50 pm
That's interesting; I'm guessing it should work also with a metal string for acoustic guitar - a high E I presume?

What I don't get is how sliding the U back and forth would affect tone height, nor what to mark. I'm going to need to find a schematic somewhere.
Sure, a high e should work fine. By changing the position of the U string, you have changed the compensation slightly (in that the vibrating length of the string from saddle to nut has been altered) and thus "fine-tuned" the intonation of that string. A mark is drawn on the top surface of the bone saddle and the saddle is filed down so that the string is supported to that point on the front edge of the saddle.
1971 Yamaha GC-10 (Hideyuki Ezaki)
2017 Yamaha GC82S (Akio Naniki/Naohiro Kawashima)

RJVB
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Re: string "jacking"?

Post by RJVB » Tue Mar 19, 2019 10:08 am

@Geoff:clever idea; esp.if that foam you use is compressable and can thus be put under the strings while they're still at tension!
I recall the symptom you describe with the metal E string; must be the same with metal strings on a guitars with an open ("classical") headstock!

OK, so the tuning trick consists of lifting the string off the saddle so that it no longer vibrates from the front of the saddle but from wherever "inside" the slot the U-bend of the metal string is positioned. That's clever indeed for very small adjustments to *increase* the sounding length.

To come back to the idea that players of non-fretted instruments compensate automatically: they probably do but there's 1 caveat which seems to contradict the idea that compensation is required. I was taught to check for general trueness by improvising a capo and moving it up and down the neck, checking for 3 perfect fifths (assuming the open strings were tuned that way). I *think* the idea was to hold the capo perpendicular to the neck but it's possible of course that one ends up making small adjustments there too. (General and not just string trueness because of fingerboard wear.)

BTW: is there an English term for "sounding string length", i.e. a translation of the French "diapason"?
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Bolink baroque violin, Nadegini modern violin (both F.S.)

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Beowulf
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Re: string "jacking"?

Post by Beowulf » Tue Mar 19, 2019 3:21 pm

RJVB wrote:
Tue Mar 19, 2019 10:08 am
BTW: is there an English term for "sounding string length", i.e. a translation of the French "diapason"?
I have not seen the word "diapason" used in that sense in either English or French. Commonly: tuning fork, in tune, the French concert pitch standard: diapason normal, the just octave in Pythagorean tuning... :?
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RJVB
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Re: string "jacking"?

Post by RJVB » Tue Mar 19, 2019 3:38 pm

[url=https://fr.wikipedia.org/wiki/Diapason_(homonymie) wrote:wikipedia.fr[/url]]
En lutherie, le « diapason » désigne pour les instruments à cordes la longueur vibrante de la corde, par exemple sur la guitare la longueur du sillet de tête au sillet de chevalet.
Normally I'd use the same site to find the translation but here I'm not having any luck with that.
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robert e
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Re: string "jacking"?

Post by robert e » Tue Mar 19, 2019 4:14 pm

RJVB wrote:
Tue Mar 19, 2019 3:38 pm
[url=https://fr.wikipedia.org/wiki/Diapason_(homonymie) wrote:wikipedia.fr[/url]]
En lutherie, le « diapason » désigne pour les instruments à cordes la longueur vibrante de la corde, par exemple sur la guitare la longueur du sillet de tête au sillet de chevalet.
Normally I'd use the same site to find the translation but here I'm not having any luck with that.
via google Translate:
In violin making, the "tuning fork" designates for the stringed instruments the vibrating length of the string, for example on the guitar the length of the nut of head to the saddle of saddle.
The term "string jacking" suggested more intriguing things to me than what's being discussed here. Oh well! :lol:

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Beowulf
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Re: string "jacking"?

Post by Beowulf » Tue Mar 19, 2019 4:48 pm

RJVB wrote:
Tue Mar 19, 2019 3:38 pm
[url=https://fr.wikipedia.org/wiki/Diapason_(homonymie) wrote:wikipedia.fr[/url]]
En lutherie, le « diapason » désigne pour les instruments à cordes la longueur vibrante de la corde, par exemple sur la guitare la longueur du sillet de tête au sillet de chevalet.
Normally I'd use the same site to find the translation but here I'm not having any luck with that.
Ahh...so was the term originally used in violin making? I'm not sure if it is used in that manner universally by guitar luthiers? In any case the word is the same in English, so "diapason" would work fine and perhaps could be universally adopted to replace "sounding/vibrating string length"? :mrgreen:
1971 Yamaha GC-10 (Hideyuki Ezaki)
2017 Yamaha GC82S (Akio Naniki/Naohiro Kawashima)

RJVB
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Re: string "jacking"?

Post by RJVB » Tue Mar 19, 2019 7:52 pm

Beowulf wrote:
Tue Mar 19, 2019 4:48 pm
Ahh...so was the term originally used in violin making?
Well, luthiers make lutes, no? :)

The link could be the violin A string which is (at) the reference pitch. What's more likely is that it's related directly to the ethymology of the term: the (full) range of notes. Which on a string could be measured by the number of positions between the 2 opposite ends of the part that can vibrate ... i.e. the sounding length.

https://en.wiktionary.org/wiki/diapason
Gretsch G9240 "Alligator" wood-body resonator converted to non-metal strings
Bolink baroque violin, Nadegini modern violin (both F.S.)

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