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hi all - wondered what you consider the factors to be when you have it all ready to go and are ready to string er up. Short of testing to destruction ("oops, shoulda used lights i guess), is there a way to determine this?

All the factory guitars i have purchased/seen will state somewhere what the recommended maximum gauge is. How does a hand builder determine this?

Thanks!

adam

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"Everyone wants to BE something, but nobody wants to BECOME something" - William Cumpiano

I think with experienced builders, the descision is made long before they are ready to string up the guitar, like way back when carving the braces. Jody

yep .. its in the flex of the top, and the size of the braces.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

... and the height of the strings off the top, and the bridge mass, and...

Hmm... maybe my question was vague. OK then, given those factors, how do you use those to make that determination? Is there a formula? A given amount of flex beyond which you can't go beyond a certain tension? Something measurable?

Normally when an answer begins with "it depends on..." it is followed by some sort of "if this, then that". Is there such a thing on this one? Thanks!

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"Everyone wants to BE something, but nobody wants to BECOME something" - William Cumpiano

Ive asked this before and gotten about the same...I think you start with plans, and go with them. Or go with lights, and add mediums on the low, or....?

Which brings up the notion that if the guitar sounds too sloppy (loose) with mediums, maybe it would sound just right with lights?

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Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I

Most guitar makers think of themselves as 'artists' or 'craftsmen' rather than 'engineers' or 'scientists', and go by feel rather than measurements. That's changing, or, at least, there are more tech-minded makers these days who ware willing and able to talk about what they do and share measurements. But the guitar is a pretty complex thing, there are lots of things you could measure, and nobody has time to measure everything. If you want to find a formula for this sort of stuff, you're probably going to have to figure it out for yourself.

Partly, of course, this relates to the unavoidable fact that there are all sorts of opinions about what constitutes a 'good' sound, and all sorts of guitars that make it. You could very well come up with a formula that relates things like top deflection under string load, bridge mass, and string gauge in such a way that when you plug in value it will tell you what to do to make a guitar you'll like. Somebody else might hate that guitar. Another person, using a slightly different system of construction, or a different shape, might get wildly different results from yours.

You might find some useful information to start with in 'Left Brain Lutherie', by David Hurd. He talks a lot about top delfection measurements and what they might mean, although I don't remember much that specifically addresses your question. It's been a while since I loaned my copy out, and I have not gotten it back yet. There's also a book I've been meaning to get called 'Engineering the Guitar' that is supposed to be very good, but, since I haven't seen it yet, I can't say from my own knowledge.

I think I do remember some guy posting here 3 years ago about how he added medium strings, and his guitar imploded...

That makes an impression.

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Here is what a Parlor Guitar is for!
http://www.youtube.com/watch?v=oEa8PkjO6_I

Haha, yeah thats exactly the impression I am hoping to avoid! Well, I suppose maybe there is no hard and fast rule to this, perhaps the big factories make enough for the purpose of testing just for that reason, whereas the rest of us don't have that luxury. So I think what I will do, in the name of gathering another data point on the journey, is just put lights on it and see how it reacts, and if it looks stable after a few months, go with mediums.

What you say is true Alan.. most of my life has been filled with science and engineering of one form or antoher, but thats not why I am getting into this, and it would do well perhaps for me to remember that. Thanks for the responses!

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"Everyone wants to BE something, but nobody wants to BECOME something" - William Cumpiano

In my mind... you gotta take a look at what the instrument was designed to do and what it was based off of.

If you copy the design of instruments that were made to be played Live and unamplified -- they usually sound *Much* better with Medium gage strings.... (Old Martins, Gibsons, and basically all Factory instruments etc.) The tops and bracing are a bit heavier and stiffer for the more aggressive playing required to project out into the crowd. These do produce much more volume than a lightly braced instrument with light strings.... but only when you play them pretty hard. Think Factory Martin D-28.

In my own building so far... I have started out with light strings for the 1st 2 weeks or so... just to see how things go. If it still sounds too stiff after 2 weeks of playing with light strings... I put on Mediums and see how it goes.

My retopped dread sounds and plays much better with Mediums. My cherry Ditson GC sounds much better with lights.

Good luck

John

Here's the approach I've been following - and am also a novice luthier without much science to my buiding process (besides what I've gleaned from all the experts here who are so generous with their knowlendge).

I think we all agree (uh oh - did I really say that? ) that building lighter is preferable to building heavier - and the tradeoff is less structural insurance to the stress of heavier strings. So.. I build to the plans that I have, carve the braces as per a mix of the techniques I've learned from here, to get the top to have a breadth of sounds when tapping, (although trying not to remove TOO much mass - yep. judgement call) and when it's time to string it up, I use light strings and play with those for awhile. See how it sounds after the guitar adjusts to the tension - couple of weeks. If it's too quiet, and not so responsive, try mediums. Once the mediums are on, I'm very attentive to any bellying behind the bridge, or other indications that the guitar isn't handling the extra tension well.

Not too scientific, I realize, but with my somewhat rudimentary skills, the best I can do.