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I am asking about building with lighter woods verses heavier woods. I mostly build nylon strings guitars.

I thought I would ask the question whether a denser, stiffer spruce is better bracewood (or does it matter?) Or a lighter, less stiff wood is not good for brace wood? I do know that if you use the lighter wood, make the braces deeper to get the same stiffness however now the top is heavier and is it less responsive? Should we rule out using red cedar for bracing – it deflects a lot but is also very light.

Is this a good observation, the stiffer wood is a better sound conductor? or maybe it’s like using spruce vs cedar for a top, there is a quality of sound issue by using (red cedar)?

I thought, why not ask on the forum?


Blake Dixon

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Blake Dixon
Kelowna B.C.

I think the reason most people stay away from red cedar for brace wood is it's splittiness...

As I understand it, lower density wood will generally result in lower weight for the same stiffness, but of course the braces will need to be taller. Brace profile also contributes to the stiffness/weight ratio, with triangular profile being easy to carve and lighter weight than parabolic. So really tall triangle cedar braces will probably give you the lowest weight after carving to the stiffness you want.

But cedar and redwood split easily, and split braces can mean a retopping, so spruce is generally more adviseable. And triangle profile seems like it puts a lot of stress on a small amount of the wood, so when I've used redwood braces in the past, I went more parabolic, thus losing some of the weight savings.

So all in all, I'd say tall, triangular, light weight spruce braces are probably the best. But the weight savings is very small in any case, and a lot of people like dense red spruce, so there are no hard rules.

If you measure the Young's modulus along the grain of a bunch of different pieces of softwood, you'll find that it pretty well tracks the density in the same way for all the different species, with less scatter than you might think. Young's modulus is a measure of potential stiffness: two braces the same size made with wood of the same Young's modulus will have the same stiffness. In general, braces (or tops) made with lower density wood will need to be taller (or thicker). However, since stiffness goes as the cube of height (thickness), while the Young's modulus relationship is pretty linear in the range we're working in, the lower density stuff will end up lighter at a given stiffness. But not much.

One thing to keep in mind is that most of the mass of the top is in the top. Braces often end up being about 1/3 of the total, or less, and that's including the big upper transverse brace that adds a lot structurally but doesn't affect the sound much. If you use the lightest brace stock you can get, as compared with the densest, you might save about 10% of the weight of the bracing. That's 10% of maybe 30% of the total weight of the top: 3%. You could take off that much by zoning out when you sand the top. The place to save weight is the top itself.

Now; that added mass and stiffness will have an effect on the way the top works. If you use dense, and therefore heavy, bracing on a light top, and don't reduce the size appropriately, you could end up with a sound that's not what you'd hoped. It's nice to have some way to measure things as you go, and make changes. Some folks will do deflection tests on their brace stock and tops, ans keep track of what worked so they can repeat it. Others use 'tap tones' or some other method, like the 'Chladni patterns' I use, to check on how well the top and braces are working together. There's no one 'right' system, but it's nice to have some way to do this.

It can be argued that a good guitar is the product of a lot of little details, all of which are important. It's hard to argue with that. A few grams here and there in the bracing, or the bridge, may make the difference between a 'nice' guitar and a 'great' one. It's really hard, though, to break it down, and say why a particular instrument succeeds when another doesn't. In general, small causes will tend to have small effects (except when they don't), and it's usually more productive to pay more attention to the big stuff. Usually.

Alan, I always really enjoy reading your posts. You are very clear and informative. Thanks for taking the time to share your knowledge.

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We are all in the gutter but some of us are looking at guitars.

with what Alan stated I find spruce is as good as you can get , the one thing I do look for is run out. I do prefer my braces with as little as possible . Also to take this discussion a little farther , the shape of the brace will influence the stiffness . A cross section shape can make a big difference in the way the brace will act.
A 1/2 in sq brace is about 1/3rd as stiff as a 1/4 by 1 in yet it is the exact same amount of material. The point I want to make is that many builders especially new ones don't understand the effects this has on tone and the way the guitars acts under load. If making a guitar light and floppy was the secret we would be bracing paper , the key is you have to learn and understand the way a brace and other parts of the process aid and detract by adding stiffness and manipulating dampening properties. Why do some guitars that were made against the rules sound do good when others that were made to a print and are supposed to sound good don't?
Learning to mate the materials and how to make proper glue joints and attaining proper geometry , and placing the braces where the belong. Balsa is one of the lightest woods we use commercially but it wouldn't make a very good guitar. On the other hand Oak is a heavy wood but it sure won't make a good brace.
As pointed out cedar , redwood , they are light and reasonable strong but the brackishness of this wood doesn't make it good for braces. Think of brass , lead and steel all can be cast to make a bell but brass will make a much better one.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

As John says, you can't just think about one thing at a time. A tall narrow brace will have the lowest mass for the stiffness, but you need to think about other things too. There seems to be, for example, a minimum gluing surface requirement: lute braces tend to be rectangular, and about five times as tall as they are wide. They're really going for max stiffness and min weight so I suspect that's a good maximum ratio of height:width. Similarly, you could not make a brace by gluing the edge of a piece of paper to the wood surface: it would buckle rather than provide any support (unless it was rolled up into a tube, which is not really a 'brace' so much as a 'hard point').

One way to avoid 'imprinting' is to use more braces, spaced closer together. I like to use nine fans on my Classicals instead of the usual seven, and make them the usual height, but narrower in proportion, so there's the same amount of wood in the braces, but smaller unsupported spans in between. 'Lattice' and especially 'honeycomb' tops carry this to the extreme.

There's no magic in a blueprint. People discuss the pros and cons of 1/4" vs 5/16" bracing as if that were a key in itself. What matters is how the braces work with the top. The best makers figure out how to make that happen consistently, and may pay far less attention to some of these specs that you might think. If the brace stock is light, soft wood, I might well make it a little wider, to get more gluing surface, knowing that the low density will end up giving a lighter brace. OTOH, why not use the heavy stock for the UTB, where weight is much less an issue and you want all the stiffness you can muster? Think about what you're doing, and you'll have a better idea of how to do it.