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From: snichols@magnus.acs.ohio-state.edu (Stephen M Nichols)
Subject: Scalloped braces

     There was a thread on here recently about "post-production scalloping" --
i.e., whether or not one could scallop (is that a verb?) the braces on a guitar
after it had left the factory; I talked to a luthier friend (J. Thomas Davis,
in Columbus, OH) about this yesterday, and he made some very interesting
points.
     Tom feels very strongly that this is a bad idea, for the obvious reason 
that it weakens the guitar's top.  What was interesting, though, was his 
explanation.  He noted that there are two dimensions of a brace -- the height 
and the width -- and claims that doubling the width of a brace makes the top 
twice as strong, while doubling the height of a brace makes the top *EIGHT*
times as strong.  The best tone, of course, is generated by a top the vibrates 
as freely as possible, so the trick is to come up with a bracing arrangement 
that provides strength while still permitting vibration.  One could produce 
very wide braces, but that would put more brace mass in contact with a wider 
spatial area on the guitar's top, thus dampening vibration; not good.  Plus,
brace height adds much more to the top's strength than brace width, so wide 
braces aren't much good for strength either.  The best combination, says Tom 
(and he builds his guitars this way -- and they sound fantastic -- and there is
something like a 3-year waiting list to get one) is to use thin, tall braces.  
Plenty 'o strength, and yet little of the brace actually in contact with the 
top, so plenty 'o vibration too.
     The point of all this is that scalloping, which he concedes does improve 
the tone, is exactly the opposite of what one should do -- it reduces the 
height of the brace, which is the most important component of its strength.  
Far better to reduce brace width.
     Tom says that C.F. Martin knows all this very well (he's an authorized 
Martin repairman), and he says the main reason they produce any guitars with 
scalloped braces is customer demand.  He also says they pick out only the 
strongest tops for guitars that are going to have scalloped braces -- which is 
another good reason NOT to do it on a guitar that's already left the factory: 
you don't know if your particular instrument has a top that would've stood up 
to scalloped bracing in the first place.
     Bottom line, then: post-production scalloping will improve the tone, but 
you will very likely have probelms with the top if you do it.  A much more 
fun/less expensive way to improve tone: play the hell out of the guitar.

-- Steve Nichols