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bracing woods
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=53072		 Page 1 of 1
Author:  frwilliams [ Sat Apr 04, 2020 5:26 pm ]
Post subject:  bracing woods
Has anyone any thoughts from experience using either poplar or basswood for bracing. I know it can be used for liners but wondering about it. I have used poplar for necks and it is pretty good though not very pretty. Basswood not quite the same material, but I would be glad to hear your thinking. Stay safe in these uncertain times.
Author:  Alain Lambert [ Sat Apr 04, 2020 9:28 pm ]
Post subject:  Re: bracing woods
Spruce is your best option as far as weight/stiffness ratio.
Author:  klooker [ Sat Apr 04, 2020 10:21 pm ]
Post subject:  Re: bracing woods
Sorry, I have no personal experience; I've always followed the convention of using spruce.

If you want to pursue this, you should do some stiffness to mass testing with the woods you want to try and compare that to spruce. Bracing is needed to give structural integrity to the top but we want to minimize resulting mass & damping from adding that bracing, unless you want a less responsive instrument. Sometimes you may want a more laid back, less responsive instrument.

Kevin Looker
Author:  Alan Carruth [ Sun Apr 05, 2020 2:13 pm ]
Post subject:  Re: bracing woods
Material testing is the best path to an answer here.

'Stiffness to weight' is a structural function, not primarily a material one. The material properties that matter most are Young's modulus and density. Young's modulus is the primary determinant of the stiffness: two pieces of material with the same Young's modulus will have the same resistance to bending at a given thickness. Density tells you how heavy the thing will be.

Because of the 'cube rule' a tall narrow brace can be stiffer than a low, wide one. There are limits as to how tall and narrow you can go, of course: you have to think of the strength of the glue line between the brace and the top, for example. Very tall and thin braces might buckle in bending rather than break.

Toughness counts. Western red cedar is often significantly lower in density than spruce. Since the Young's modulus along the grain for softwoods pretty well tracks the density, it should make a good brace material: you make the braces a tad wider and a bit taller, and they'd have the necessary stiffness at a lower weight. WRC tends to split more easily the spruce does, and braces do tend to fail by splitting. It's not commonly used for bracing.

Keep in mind, too, that all of the bracing on the top of a guitar generally makes up only about 25%-30% of the weight of the top. Saving 10% of the brace weight would amount to about 2-3% of the total top weight. You can save more weight by looking for a slightly less dense top, or even by really optimizing the top thickness.

As I say, the long-grain Young's modulus (E) of softwoods tends to track the density pretty closely. This is probably because softwoods are all structurally pretty similar. Hardwoods don't follow the same plan, and are much more variable. There are some things that are botanically hardwoods, such as balsa, that tend to be lower in density than most hardwoods, with reasonably high long-grain E values. Some poplar is pretty low in density, and it is known to be reasonably tough, but without testing I can't say whether it's got a good enough E/density ratio to be a decent substitute. I suspect that with careful selection you could do well.
Author:  bluescreek [ Sun Apr 05, 2020 2:25 pm ]
Post subject:  Re: bracing woods
I have heard a poplar braced guitar. If you didn't know it you wouldn't tell . Sounded fine. The entire guitar was poplar , top back neck bridge fret board. Martin did this a few years ago.
Author:  Ernie Kleinman [ Sun Apr 05, 2020 8:35 pm ]
Post subject:  Re: bracing woods
Hi Ive used poplar in Kc and here in OK for back bracing on my tenor and baritone ukes. I have recycled the contractor grade posts. What I do is make a batch abt 1/4in thick and do a deflection test by hand . I also find that poplar is all over the map in terms of density and colour . Some of it is nearly white grey , light green , dark green etc.. You can also measure the weight with an inexpensive scale from HF > My preference is for the denser heavier stock. As others mentioned , I would probably use spruce. e. g. sitka spruce . as it is very stiff strong and light for guitars . I have occasionally used american sycamore. Again we picked out the densest pieces. for a CL guitar back. I like basswood for blocks , as it is light strong, and carves easily. . If you look at the older kay , harmony and budget guitars of years gone by . Many of them had poplar necks, and held up over time . Also I believe the older ladder braced guitars had used poplar for bracing on their tops . Experiment on scrap and see what works for you! Good Luck
Author:  oatesguitars [ Mon Apr 06, 2020 9:31 am ]
Post subject:  Re: bracing woods
Here’s an interesting article about this subject, not so much talking about the wood species but thickness width to weight relationships. https://www.ukuleles.com/Technology/bracemath1.html
As a part-time traditional bow and arrow maker I can tell you that “ spining” arrows to match the bow draw weight and design is essential for a good bow setup. Even though a bunch of arrows are made out of the same piece of cedar or spruce and are of the same diameter they have to all be sorted out into groups of the same weight and spine (stiffness) If you don’t do this, they will either fly to the left or the right. Many of the principles of self bow making apply to guitar making, I guess that’s why I love making both.
Author:  klooker [ Mon Apr 06, 2020 7:53 pm ]
Post subject:  Re: bracing woods
bluescreek wrote:
I have heard a poplar braced guitar. If you didn't know it you wouldn't tell . Sounded fine. The entire guitar was poplar , top back neck bridge fret board. Martin did this a few years ago.


Blasphemy!

Poplar is cheap, abundant, and you can get super wide boards of it!

Where can one find more info on a Poplar acoustic, asking for a friend.

Kevin Looker
Author:  bluescreek [ Tue Apr 07, 2020 5:48 am ]
Post subject:  Re: bracing woods
that was an experiment at Martin. The guitar was a bland looking instrument but sounded very good. I have used poplar for necks in my early days to learn to make them.
Author:  Clay S. [ Tue Apr 07, 2020 9:09 am ]
Post subject:  Re: bracing woods
If you compare it to Sitka spruce it has close to the same "numbers" for weight, elasticity, hardness, T/R ratio, and others according to the Wood Data base. It might make an interesting low cost soundboard for an archtop guitar.
Author:  DanKirkland [ Tue Apr 07, 2020 9:27 am ]
Post subject:  Re: bracing woods
bluescreek wrote:
that was an experiment at Martin. The guitar was a bland looking instrument but sounded very good. I have used poplar for necks in my early days to learn to make them.


Poplar can make a great neck. I've rebuilt several Kay and Harmony acoustics that had poplar necks. If you add a good truss rod they work just as well as any other acoustic.
Author:  Ed Haney [ Fri Apr 10, 2020 11:32 pm ]
Post subject:  Re: bracing woods
I was just reading the Gore design book tonight by chance. If you happen to have it, page 4-50 has a table comparing some brace woods such as sitka, WRCedar, balsa, etc. Bottom line: spruce is the default choice due to stiffness and shear strength with a low density if no carbon fiber is used. If a composite brace is fabricated with carbon fiber then WRC works well to reduce mass.
Author:  Ruby50 [ Sat Apr 11, 2020 6:30 am ]
Post subject:  Re: bracing woods
L Francis Herreshoff was a famous yacht designer and builder and innovated a lot of materials and techniques. Masts are typically made of Sitka Spruce because of its strength to weight ratio, and he experimented with that and other woods. He used Ash for a few masts because he said it had a superior strength to weight ratio, but he stopped because he could not get long lengths.

We don't need long lengths. Has anyone tried Ash?

Ed
Author:  Clay S. [ Sat Apr 11, 2020 8:25 am ]
Post subject:  Re: bracing woods
One aspect of wood properties that has not been addressed is wood's tendency to "creep" over time. I have not been able to find good data on it for various wood species. Most of the research I have seen appears to be for softwood structural applications.
From what I have seen it seems like hardwoods tend to creep and sag over time more than softwoods. But I don't have data to support this conclusion. For this reason I would be reluctant to use poplar for brace stock, especially since a typical SPF offcut fished out of a dumpster, split up and allowed to age for a year or two can make perfectly good brace stock.
For an archtop top I might chance tulip poplar - with spruce bracing of course. [:Y:]
Author:  John Arnold [ Sun Apr 12, 2020 12:59 pm ]
Post subject:  Re: bracing woods
Quote:
For this reason I would be reluctant to use poplar for brace stock, especially since a typical SPF offcut fished out of a dumpster, split up and allowed to age for a year or two can make perfectly good brace stock.


I used various hardwoods for bracing, particularly in my early years. I have not noticed a tendency to creep compared to spruce, and some of those guitars are approaching 40 years old.
The 'SPF' grading includes Engelmann spruce, lodgepole pine, and white fir, among others. I prefer Engelmann over the other species in the group, but that does require that you pay a little attention. Sometimes they can be hard to separate.
While we are discussing framing lumber, I also see the 'hem-fir' marking, which denotes Western hemlock and Douglas fir. These are denser, stronger woods than those in the SPF grouping, and can also yield some useful bracing material.
I believe most are referring to yellow-poplar (tulip poplar) in this discussion. Huge and fast-growing, it is a very important commercial species in the Eastern US. The logs normally have thick, creamy sapwood and a greenish heartwood. Being from the magnolia family, it is not a true poplar. The wood tends to be harder and denser than the wood from true poplars, which are in the willow family.
It is normally straight-grained, and very easy to work and finish.
I consider yellow-poplar to be good tonewood (comparable to mahogany), though it is rather bland looking.....unless it has mineral coloration. This 'blue or rainbow poplar' can have bold streaking, ranging in color from blue, green, yellow, orange, purple, brown, to coal black.
Author:  Bruce Sexauer [ Sun Apr 12, 2020 3:23 pm ]
Post subject:  Re: bracing wood
A few years ago I made a tulip magnolia (Poplar) guitar with a Catalpa top. It is certainly as good as my average guitar, perhaps better than average. Took a while to sell it, of course. I used Adirondack bracing throughout, as I have for many years. That’s because I have a really developed sense of the structural capability of Adi, which is amazingly consistent from piece to piece and tree to tree, at least among that which I have acquired. Bracing is a critical variable in our work, and I’ll take any edge I can find.

http://www.sexauerluthier.com/MagCat.html
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