Official Luthiers Forum!

When you guys are doing your braces, is there a maximum amount of grain spacing you consider acceptable? For example, some of my finger braces can be cut from the offcuts from the top, however the grain spacing is obviously further apart from the outside of the offcuts. Is this acceptable for braces or would you stick to tight grained brace stock?

Cheers!

John

   Braces are in 2 catagorys , load and anti split. I want my X braces my tranverse brace and tone bars as tight as I can find. I make my own so I can select the quality of material.
   Finger brace and popsicle don't carry as much load so I will use more somthing wider but I prefer as tight as I have for all bracing
john hall

We recently examined about 500 Sitka, Cedar, Englemann & Adi tops and found that the tighter grained wood was [consistantly] weaker, in long di-pole stiffness. The tops with distinct darker grain lines and wider annual grain spacing were [consistantly] stiffer. This can be attributed to concentrated cellulose in the annual rings. Another factor to consider is grain run-out or the lack thereof.

Treat each piece of wood as unique and develop a metric to measure the stiffness. This methodology will eliminate any guesswork.

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tim...
http://www.mcknightguitars.com

good point. every tree is different. I like to do deflection testing. I do like more grains as we are looking at stifness in a different direction that on tops.
    

[QUOTE=Tim McKnight] We recently examined about 500 Sitka, Cedar, Englemann & Adi tops and found that the tighter grained wood was [consistantly] weaker, in long di-pole stiffness. The tops with distinct darker grain lines and wider annual grain spacing were [consistantly] stiffer. This can be attributed to concentrated cellulose in the annual rings. Another factor to consider is grain run-out or the lack thereof.

Treat each piece of wood as unique and develop a metric to measure the stiffness. This methodology will eliminate any guesswork.

[/QUOTE]



I agree with Tim.   

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Very interesting, Tim. I have found that some of the tops I have with wider grain spacing are just as stiff, if not stiffer than other tops with tighter spacing. I have one top set (sitka) that has unusually dark and prominent grain lines, much like you mention, and that top is extremely stiff, although somewhat unattractive because of the pronounced, and fairly widely-spaced lines.

I'll have to re-evaluate my bracewood selections. Recently, I bought some bracewood that had very widely spaced grain, and I've been afraid to use it. Now, I think I'll split it up and compare it with some other bracing stock I have.

Best,

Michael

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Live to Play, Play to Live

Yes. Tim is on the money, more celluose material (generally) means more stiffness. Runout is certainly a consideration to factor in.

Another thing that is worthwhile is to measure the density (mass / volume) of the material. All things being equal more dense woods have greater stiffness too.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

You can use denser wood for bracing; simply make them narrower so that the overall weight comes out OK. The only limit is the strength of the glue line between the brace ad the top: you need enough glue to hold the darn thing down. Lute braces seem to generally run about five times as tal as they are wide, so that's pehaps a good rule of thumb for the aspect ratio.