Official Luthiers Forum!

Hello all - I'm new to posting here on the forum but have been reading for a while...

I am wondering what ideas folk have on building devices for measuring the deflection of the top under simulated torque - i.e. applying to the bridge position of the braced soundboard
an artificial analogue of the string tension for the particular gauge strings that your guitar will have on it, and measuring the deflection at various points on the soundboard (whilst it is clamped around the edges as if attached to the sides).

I am keen to get into this (similar to that used in the Siminoff book) as I like the systematic approach. Does anyone actual carve their braces whilst the soundboard is under load in this way, to see how it reacts to every bit of wood removed?

Thanks in advance.

Rob

http://www.stewmac.com/shop/Tools/Speci ... Gauge.html

Looks like all you need is a dial indicator and a metal bar, and two feet.

Or, if you don't have a Grainger account you can buy one from Stew-Mac..

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Old growth, shmold growth!

I'm not sure that many of us use the approach you describe. However, an 18" span and a 5lb weight seem to be a bit of a 'standard' for top deflection jigs.

That thing seems to be used for measuring top deflection so you can tell how much the top moves with the string on, which helps in neck resets. However I never had to use anything like that because it's not hard to estimate how much the top will move (and it's never a bad idea to overshoot a bit anyways, since the action always goes up, not down with time). I guess it could be useful with that thing and weight to tell you exactly how much a top has deflected, but you really don't need .001" accuracy for this.

I don't get how Stewmac charges so much for tools that are nothing more than a dial indicator and some simple metal bars, and they could have used high quality dial indicators from the USA or Japan, but instead they use the same cheap Harbor Freight dial indicator that retails for less than 15 dollars each. Probably much cheaper for them seeing that they probably buy those in bulk. Not saying HF dial indicators are junk (if anything they do exactly what they say it will do) but when they charge 300 dollars for a jig that's nothing more than some wood and dial indicators, they could have used something better.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Or $69, in this case

I'm talking about the neck jig by the way, not this particular jig.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Hi chaps, thanks for the replies. I was more referring to a method of artificially inducing the torque at the bridge location of a rough braced soundboard, before
closing the soundbox. So deflection tuning would be a better name for it - applying the same torque that the strings would, but whilst you still have access to the braces
and can carve them to give a particular deflection and thereby tune the board.

Any thoughts on that would be great.

p.s. see Siminoff's "Luthier's Handbook" page 84 onwards. Interested to hear from people who actually use this technique in their routine.

Thanks,

Rob

IMHO, Ditch the Siminoff book, it contains a lot of bad advice and bad science.
It is a shame it is still retailed by the luthier suppliers.

Hmmm. Interesting. Can you give an example of the bad advice? For a luthier on the steep learning curve it can be difficult to sort the wheat from the chaff...

Anyone else agree that this book should not be trusted? The guy seems to have a lot if years of experience. If this book has dodgy info in it then people like me should know that before we waste too much time...

Perhaps this has been a topic of heated discussion already on the board - off to have a look!

Rob




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It's quite a few years, and I no longer own it.
But for starters, his concept of tuning each brace to a musical note before gluing it on..........really!

Siminoff made his reputation in mandolins not guitars anyhow.
But he seems to have been a master of self promotion.

Yep, I have to say that his tuning technique of treating braces individually seemed far fetched. But I don't yet have the experience to contradict someone like him - we learners have to start out by treating the info in the books we buy as true and honest, otherwise how can you make progress?

I am now very keen to find out more about potentially misleading or erroneous info in these books - yes, you have to experiment and learn by building yourself with the right attitude, but you also need a bit of help. If you're lucky enough to be taught by a real person that's fantastic, but for many of us the books are the teacher.

And excellent forums like this one, of course...


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Yep, I have to say that his tuning technique of treating braces individually seemed far fetched. But I don't yet have the experience to contradict someone like him - we learners have to start out by treating the info in the books we buy as true and honest, otherwise how can you make progress?

I am now very keen to find out more about potentially misleading or erroneous info in these books - yes, you have to experiment and learn by building yourself with the right attitude, but you also need a bit of help. If you're lucky enough to be taught by a real person that's fantastic, but for many of us the books are the teacher.

And excellent forums like this one, of course...


Sent from my iPhone using Tapatalk

Yep, I have to say that his tuning technique of treating braces individually seemed far fetched. But I don't yet have the experience to contradict someone like him - we learners have to start out by treating the info in the books we buy as true and honest, otherwise how can you make progress?

I am now very keen to find out more about potentially misleading or erroneous info in these books - yes, you have to experiment and learn by building yourself with the right attitude, but you also need a bit of help. If you're lucky enough to be taught by a real person that's fantastic, but for many of us the books are the teacher.

And excellent forums like this one, of course...


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Skip directly to the Gore/Gilet books. Don't say they're too expensive, they will advance you very rapidly and are worth every little penny.

Indeed

Thanks for the advice. I'm more than happy to pay for quality information!


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Best guitar related money I've ever spent.

I bought it the day it was released then the next year did a 3 day course with Trevor Gore.
I recommend it highly

While I've not really read through the Siminoff books, I'll admit it sounds a bit whacky, but by tuning each brace he is effective putting the same brace down (sort of) every time on each build. That is he's balanced the stiffness and weight of each brace in a way that makes since to him. Maybe it's not as goofy as it appears at first glance. After all it's not all that different than what Trevor G. does with his top selection.

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Jim Watts
http://jameswattsguitars.com

It's goofy,
He also has this dinky string tension device that tells you how to increase your string tension by increasing gauges

And it's very different to Trevor's approach

Jeff, My main point was that he's at least getting some vibrational repeatability to his braces, whether that's his main goal or not. Trevor is also tuning his tops to a consistent vibrational response with input from his equations, so in my mind there's some similarity (very little mind you) but I'll trust you that Siminoff's approach is goofy.
One thing I really like about Trevor's book is that he backs up his work and doesn't just claim it to be true because he said so, so there's a big difference there between the two for sure.
So to Rob, I would also recommend Trevor's set of books as some of the best "bang for the buck" in lutherie training.

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Jim Watts
http://jameswattsguitars.com

Thanks chaps - very interesting. Sounds like a Christmas present to my self!

At some point I would like to acquire the responsive guitar, but have to save up for that...

Cheers,

Rob


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Rob, full review by R. M Mottola for American Lutherie here, if you haven't found it already. And thanks for the kind words, Gentlemen.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Gore/Gillet is the best I've seen. Responsive Guitar......not as much though there are good things in the book. I do like the simple way Somogyi focuses on the 3 ways the bridge can move: bounce up and down, rock sideways, rock front to back. And you'll see a visual representation of the distribution of stiffness in the soundboard if you haven't already wrapped your head around how that works. Much more info in the Gore/Gillet books. You'll learn the bridge movements relate to particular viration modes (monopole etc.). And you'll learn there is more to excite the monopole mode than just the main top frequency and much, much more.....just giving an example.

The Gore books have the best, engineering model on a how a guitar functions. While not perfect I'm sure, it's the best I've seen.

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Formerly known as Adaboy.......

"you have to experiment and learn by building yourself with the right attitude"

Very ,very true.

"Responsive Guitar......not as much though there are good things in the book"

How the mighty have fallen! I guess I'm glad I didn't buy the books.

"Trevor is also tuning his tops to a consistent vibrational response with input from his equations, so in my mind there's some similarity (very little mind you) but I'll trust you that Siminoff's approach is goofy."

This is probably good if you want your guitars to sound pretty much the same? I would like to get a peek at Trevor's book to see if it would fit with my particular style of building, but at this point don't have the funds.

I have learned things from even the dodgyist of lutherie books, but take everything I read with a grain of rock salt sized salt.

"you have to experiment and learn by building yourself with the right attitude"

Worth repeating! The guy who bought all those specialized lutherie tools and books and now has them for sale as "barely used" should have heeded this advice. Without actually working the wood you won't get the skills needed to build a good guitar.

As to the original question here is one possible solution:
Although not built for the OP's purpose (it's a travel guitar where the neck stores inside the body), it does allow access to the braces while the guitar is strung under tension.