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I am trying to get a better understanding of the pro's and con's of top bracing size and layout. I would imagine that if the braces are too heavy then the sound of the guitar is "tight" and not heavy enough and the structure may be in question. Can anyone fill in the finer details on this topic? (pictures are always helpful)

Thanks!

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Brad
Avon, OH

Brad,
You have asked a question that is sort of like "why do dogs pee on tires?"

There are as many ways to brace a top as there are grains of sand ont he beach. The archives are full of pictures, details, discussions, and most everything you would want to know about top bracing.

Try doing a search of the archives. I'm sure you will be reading for quite a while!

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Reguards,

Ken H

This may sound too simple but just like the old adage that you can always take some off wood but you can't always put it back. I feel it is better for a new builders to build using proven and slightly over braced schemes

As you gain experience in voicing you will naturally migrate to lighter bracing where and when appropreate

To try to jump directly into light bracing schemes with out experiencing the basic and proven bracing schemes and learning how to tweak them by voicing, or to try to set a rule that this brace should be this thickness or height is akin to trying to run before you learn to walk.

Brad,
I'm just in the process now of creating the bracing on a 13fret guitar that I've never built. I was told by a very well respected luthier that the first thing to start with is the bridge shape. Make a mock up of it out of poster board. Calculate the scale length and find the location from the fret you are joining your neck/body to the saddle. After you have this, you can figure out where the X will fall over the bridge wings. This is basically the splay of the X. If the X exits the sides of the bridge wings it will open up the lower bout more and be more bassy and floppy sounding. If it is tighter, meaning the X will exit at the top(back) inside of the bridge wings, it will be more focused and mid rangy. This of course is an over generalization, and depending on wood stiffness and brace thickness and height, things could change.

If it is a big lower bout, around 16", then you might want to make the exit of the X braces be near the corners of the wings, but exit closer to the inside back of the bridge. From here, you calculate the location of all other braces. I can't really get into that because that opens another whole can of worms. To many competing theories on this, and all work well if you know what you are doing. But Michael gave you good advice by sticking to some plans and following them closely.

I know I've over built my first 2 guitars, and now starting #3 & 4. I've built several other types of instruments in between these 2, and now feel more confident in the feel of wood in relationship to sound. I've got a long way to go, but I do have access to a Luthier who has built over 300 instruments. So I guess that is why I feel so confident.

Good luck and ask lots of questions. I think a good way to start is get John Mayes Advanced Voicing and Top bracing videos. You will be able to hear and see the braces being carved.
Tracy

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Tracy
http://www.luthiersuppliers.com

Thanks for some of the feedback. I will certainly look through the archives and I am sure I will find a bunch of information.

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Brad
Avon, OH

[QUOTE=Hodges_Guitars]Brad,
You have asked a question that is sort of like "why do dogs pee on tires?"[/QUOTE]

Unh Huh!  And why do they?

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

ToddStock wrote:
"Al C. is the guy to address this question, and cover the conflicting requirements of strength and role as 'graphic equalizer' for the top."

....in my dreams.....

Premise #1: The 'usual' bracing schemes are standards because they work well (whatever 'well' means). A lot of people have been experimenting with them for a long time. If there were huge improvements to be made with standard materials, they'd have been made by now and _those_ would be the standard designs.

Premise #2: Factories have to build with the expectation that the weakest set of bracing is going to end up on the weakest top. They can't take the time to test their wood for strength, and must over brace as a matter of course to be safe. You can probably reduce the sizes of normal factory bracings a bit. A BIT!

Premise #3: You'll get the best results if there is some sort of rough balance between the bracing and the top. You could make a top that was thick enough to take the load with no bracing, but that would weigh a ton and have no sound. You could make a top of tissue thickness, and put on really heavy braces, but that would probably sound pretty uneven, and, I suspect, 'tight'.

My friend Mark Blanchard always says to remember that the top is the sound. The bracing is there to help out, and fine tune, but it's the top that either makes it or doesn't.

So: start with your top, and try to figure out how thick you need to make it so that it will work right. If you can test the wood properties, that's a real help. Otherwise, use any info you can get: tapping, feeling the flex, chicken entrails, whatever. Get some idea of how this top 'wants' to work. If it's light and soft you might want to leave it thicker. If it's dense and stiff (Red spruce!) then thin it out some more. If you're looking for a bassier sound you might want to graduate it thinner toward the tailblock; for more 'brightness' thin it toward the wings. Or look for a top with a different stiffness ratio.

Think about what you want the guitar to do. If you're making a Dread for Bluegrass, then you will want to at least think about scalloped bracing. This will give you the 'thump' you want. If it's a fingerstyle box you might want to go to some sort of 'tapered' bracing scheme.

If the top is floppy in the cross grain direction you might try opening out the brace angle a little, so that they run more 'across' the grain. If it's stiff, go the other way.

If the top is soft you might want to make the bracing wider for more glue surface, but generally the highest stiffness/weight ratio comes from tall, narrow bracing. OTOH, don't bother to get too carried away: all of the bracing typically only amounts to about 1/5 of the weight of the top without the bridge. Generally the bridge weighs about as much as _all_ of the bracing put together. Shaving a couple of percent off the braces is not going to help you a lot. In any event, the tallest, narrowest bracing, on lutes, is usually five times as tall as it is wide, so don't exceed that ratio.

Don't get too carried away, adding lots of braces, particularly if they're tall and narrow. Structurally al you're trying to do is control the amount of 'belly' and, even more important, 'sink' in the top. 'Control', not 'eliminate'.    

Most steel strings use asymmetric bracing, and that gives the 'normal' sort of sound. Symmetric bracing tends to work a little better for more 'modern' or 'progressive' styles, like fingerstyle or jazz. Maybe.

When you're voicing, remember that the bracing at the head end is mostly there for strength, and doesn't effect the tone much (yeah, I know, the 'popsicle stick'. I don't use it). The bracing near the tail block doesn't have as much effect on the strength, but effects the tone a lot. The critical area for strength is between the bridge and the soundhole.

Cap the X crossing(s)!

All of the statements above reflect the opinions of the poster, and may have little to do with reality as you experience it. Subject to change without notice. Caveat emptor. De gustibus non disputandem. Cogito ergo sum. Veni, vidi, vici.

Rats! Left one out!
Quid est pro cenam.

Alan...great response.

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Brad
Avon, OH

I made a arch-top dulcimer to thin between the bridge and tail looking for bass response and got the dreaded mandolin center seam crack, Durn consequences!

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"It's a Tone Faerie thing"
"Da goal is to sharpen ur wit as well as ye Sgian Dubh"
"Sippin Loch Dhu @Black lake" ,Kirby O...

Just remember, it takes alot of time to put the 'first' one together, thats why your better off using a ready made plan. Unless your really knowlegable in the design area. I am hoping Im not making mine just a nice GSO. (Guitar Shaped Object) A known plan is essential in this biz, to start anyway.

 

 

Warning ***  I have zero experience 

But... I may have some good idea's???  From Martin I ordered a "ready to glue" set of top bracing for 21 bucks.  I have marked them with felt pen saying "Do not use". 

When I do my first top bracing in a few weeks this reference set of bracing will be one of the many aids I use to not destroy my first effort.

Is this a good idea?????

AND...  I highly recommend John Maye's "Advanced Voicing" DVD.  Watching and listening to John voice several tops is a priceless tutorial that explains top thickness, sound tapping, scalloping braces and much of what was said above in this post.  If you only buy one of his DVD's that's the one to get.

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Rick Hubka
Chemainus BC Canada