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hi all
I posted a topic a wee while back regarding Santos Hernandez bracing pattern and Waddy replied with this -
“The fans are 7mm wide and 3.5mm high and triangular in cross section”.
I’m wondering how this would translate into the parabolic form re. narrower and higher and what dimensions that would yeild.
(I know, I know.)
Also would the reduced “footprint” of the brace be sufficient to serve it’s purpose.
Has anyone experimented with parabolic’s on fan / classical models.
just wondering
yours Geordie

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The "parabolic bracing" notion seems to refer to the lengthwise section, and not the crosswise section. I think you are splitting hairs in the wrong part of your career unless you have already built a bunch of classicals and exhausted all other fine detail.
The normal shaping lengthwise is to carve or plane a certain flat taper, which is more or less straight even if it might look somewhat parabolic. Usually the back taper stops at the bridge tieblock end, while the front taper is pretty short, 1-2 cm, unless you are in the "thick-in-front of-the-bridge" camp, and then you might want this taper to reach more or a lot more towards the bridge.

The crosswise section is usually triangular or rounded. The triangular ones are of course a little more efficient in stiffness per weight, but that does not necessarily make them better.

Same with the width of the braces. The 7mm width is old school. It's the width used religiously by Torres, and those who followed him before WW2. They are flat around 3mm and can be quite stiff especially if made round instead of triangular. More recent builders have gradually made the braces more narrow and taller. These are of course stiffer at the same weight. The small footprint is enough to keep it glued, and some might be even only 3.5mm in width (see Bream's 73 Romanillos)
On the other hand, I think that the old style braces have the advantage of crossing more grain and coupling better - I think they are able to keep the doming better if your thing is a deep dome.
Ruck, a famous builder, took wide braces to extreme even, replacing 3 of the 7 braces with wide veneer patches.

Romanillos have used several schemes, for example the widths and heights decreasing from 6.5mm for the center brace down to 4.5mm. all this is useless blabla unless you actually try it, and match the graduating stiffness of the braces to the graduating (or not) thickness of the top. I also found that it is important to find a certain balance between the two halves of the top.

The best thing you can do is not to overthink, but maybe pick a design you like the sound of, build several guitars, get the hang of it...Keep thinking, sure, but don't do it too much without actually building smth. It is so easy to lose control.

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Build log

Alex just gave the best advise I've ever heard !

There is NO magic brace size or shape.
I make mine 4mm wide x 5-6mm high to start with !
I started at 6mm X 6mm but found out it killed the warmth !
find what works for you !
If braces cross the top grain they stiffen it allot more than if they run parellel (sp)

Along with all the other criteria-top thickness,size & depth of box and scale length-plus the other not so easy to control ones !

Mike

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Mike Collins

I've been playing with the idea of laminating braces lately, in order to be able to carve them down further and have the same strength. You might want to look at this stuff:

http://www.lmii.com/CartTwo/thirdproduc ... heet+Stock

Rick

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Rick

I use the Torres standard fans of 7mm x 3mm and use his gable shape. Although many modern builders have tried to improve on his guitars, none have in my opinion. If it's not broke, don't fix it.

Too many people, especially those new to building, are overthinking the process, don't fall into that trap Geordie, build a few using tried and tested patterns, then start to change one thing at a time to try out new ideas.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

All these answers should give you food for thought !

Now make a guitar with which ever style you choose & you'll learn a bit on which way to go !


Mike

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Mike Collins

In addition to all the good advise given already, you can also think that in the traditional "Torres" classical guitar the thicknessing of the soundboard is the main control for stiffness, and the braces are primarily used to control the stiffness and the vibration patterns.

Therefore, they don't need to be all that tall to be effective. With the low wide braces, you can think of them as localized extensions of the soundboard. They are plenty stiff enough, actually.

As far as their weight is concerned, I weighed the tops and braces of my last three tops, all SE117 size. The top came in around 3 oz (cedar), while ALL the braces (spruce), harmonic bars included, added about .25oz.

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Expectation is the source of all misery; comparison the thief of joy.
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Actually, a couple of more things to think about --

Santos Hernandez were strung with "gut" strings, which - as I understand it - were/are stiffer than nylon strings. Builders tried to accomodate the change from gut to nylon by changing brace shapes from wide-and-low to narrow-and-tall.

Keep in mind that braces are just one element of a system that includes top stiffness - BTW, Hernandez tops were scary thin - bridge, and bridge pad, if any. It's probably a good idea to build a few guitars following a single system - until you've figured it out pretty thoroughly - before jumping into all kinds of "imporvements". After all, if Hauser, for example, could have built a better guitar, he would have.

Larry

The issue of strings is interesting. The gut strings made by Aquila have indeed very high tension ratings given, by they also warn about not tuning them to standard modern pitch! At 440Hz, the high e string would fail in a few minutes. Back then they were tuning them about a half-step lower than we do, if not a full step.

Another interesting very high tension modern string is the Goldin type made by Hannabach. They pull quite a lot more than common d'addarios, but feel ok on the hand. They add a real deal to the output (at least in a room) and don't sound that metallic, they are better than Savarez carbon's in this regard, but I am not sure the excessive tension is good in the long term.

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Build log

We're getting a bit away from the subject now, but I have afair bit of experience with gut strings as I use them on my lutes and have strung classical guitar with them as well, they do produce a sound that is almost impossible to reproduce with nylon strings, although Nylgut on one of my lutes (to save all the retuning time for practice) gave a passable impression. But for recording gut reigns supreme.

Richard Brune recommends that for original Torres guitars and for Torres copies that the best string for them is the Hannabach Goldins, they are more in the medium/high tension than high tension, but are the closest tonally to gut. I used them on my La lena on JOshua's recommendation. They are the string that is used by almost all of the 'Spanish' players and teachers at the RCM for the richness of the tone they can give.

This is using the Goldins, I would have done a comparison using some gut strings but.....

Caprichio arabe

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

hi al
Many thanks for the advice, as usual spot on.
I’m looking forward to getting back to collage next week - we’ll see how it goes.
Your right Colin I’ve had to much time on my hands lately and have a tendency to “over think” things.
Beautiful playing and tone Colin.
yours
Geordie

_________________
some tunes on acoustic and guitar synth.
http://www.youtube.com/user/TheGeordieAdams
http://www.myspace.com/geordieadams