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Hey all! Starting to carve up my braces for 2 L-00's in the next few days. Haven't built and acoustic for awhile and thinking of trying something new for the brace carving. I used to start with a jig I had for my drum sander and then shape with a chisel. I know there is more than one way to skin a cat though and just was hoping to start a general conversation about brace carving and little tips and tricks! What do you got?


Thanks!

There has been a couple of threads recently, one of which is here http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=45526&hilit=boone+planes
Another here http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=45298&p=599067&hilit=boone+planes#p599067
But don't let that stop anyone who wants to pitch in

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thank you sir!

BTW, I started out just as you are doing, drum sander (now a home-made luthier's friend) and chisels.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Ill bet I could whip up that luthiers friend thing easily enough on my spindle sander! thanks again!

Carving braces with only a chisel is one of the few things that make me feel I'm doing something other than carpentry. Gets my in that Zen mode.

I like to use violin makers finger planes. IMO every guitar 'wants' a bit different bracing to optimize the sound, so I'll take a few shavings and check the tap tones/Chladni patterns.

Yep two words - finger planes.

My carving is almost entirely done these days with finger planes and I am also fond of taping some acetate on the top where the finger planes will be registering to avoid any marring. I use a sharp chisel to pare my brace ends down to either nothing or the respective height that I tuck into the kerfed linings, for me that .1" at present.

I have my own voicing method that works well for me and is repeatable and like Al said every top and bracing scheme is different and needs to be optimized by tapping, checking, and if need be the progressive removal of material in specific areas. Finger planes let us sneak up on how much material we want to remove.

From the original post not sure if the braces are being largely sized and shaped prior to installation and/or optimized after installation. I do all of the brace shaping after the brace stock has been glued in place. This makes using go-bars to glue my brace stock in place easy since the braces still have wide, flat tops when being glued in place.

I use a vacuum clamp for brace glue up so I am able to do much of the brace shaping with a bandsaw, spindle sander etc. I keep all the ends except the upper bout "X" legs and shoulder braces short of the ribbon lining. Final shaping is done with upside down chisel, curved chisel and sand paper. Final/final shaping and tap tuning is done after the sound board is glued to the rim --- for this reason I believe it's best to glue the back to the rim last.

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Ken Cierp

http://www.kennethmichaelguitars.com/

I like the finger planes too but I still use a chisel as well. Make sure you protect the top well if you only use a chisel, too many times have I slipped a chisel. The LMI 'glue' chisel is my favorite as it had that nice curve to it.

What I find is that when I'm starting to shave the braces on a top, and they're heavy, I can remove a lot of material without making too much difference in the tap tones. At some point this changes, and you get into a range where fairly small amounts of stock removed start to make a noticeable difference. A few shavings after that you've gone too far.

Just for calibration purposes, I try to track the mass I remove when tuning the braces: it's not much. Like Waddy, I put them on tall and rectangular. I then rough trim them to shape, leaving them a quite a bit taller than I think I'm going to want them, before I start tuning. At this point I'll weigh the top, and try to remember to write it down. I seldom remove much more than about 10 grams of wood from the braces of a steel string in the actual tuning process; mostly below the bridge. In one case I only took off three grams. Typically ALL of the bracing weighs about 35-50 grams, depending, and a lot of that is the upper transverse brace and 'A' braces. Classicals are much more sensitive.

In short, I look at top brace shaving as THE critical operation in terms of sound production. There are lots of good systems for doing this, but I don't see taking all the braces to a certain size as a 'good' system. It may be good enough for Martin, but you really want to try to do better.

Could you elaborate a little further, Alan, on how you know that you've gone too far ... is there a pitch that acts as a red warning light ? ...if so, what is that pitch?

Also, if you ploughed on regardless with a top on which you have "gone too far" , and glued it up, what would be the resultant effect on the sound of the guitar ?

I use the Chladni' method of 'free' plate tuning. Essentially it makes the 'tap tone' resonances visible, and separates them out at their respective pitches. The shapes of the modes give you information on the distribution of mass and stiffness in the plate, and the pitches tell you something about the ratio of stiffness to weight. I know I've taken the braces down too far by the mode shapes, and pitches to some extent. I tend to stop as soon as things are no longer getting 'better'. Sometimes you can't get just what you're looking for, but I think it beats shooting in the dark.

I wish I could be more specific.

I record the tap of every top I make at several points along the way -- free plate preliminary, intermediates 1, 2, and sometimes 3, final free plate, top joined to sides, then box closed, box closed with dummy bridge stuck on, then finally strung up. This database has allowed me to compare current builds to the taps of my favorite past builds (of the same shape), and in that way helps inform my final brace-carving. As a bonus, when I stack a bunch of the separate tracks together, it makes a wonderfully mellifluous, random percussive rhythm that at times takes on a strange natural synchronicity.


Ken Jones
Mountain Song Guitars

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Mountain Song Guitars www.mountainsongguitars.com

We all have our little tricks. I do preshape braces and glue them on. I don't do much refinement until the guitar is strung up a month or more. That is when I do my tweaking. As Alan points out , you can go from Great do dead in one swipe.
There is much you can learn by playing with guitars and taking them to that point. Learning where it will fail is often better than knowing where it will work.

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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

John Hall wrote:
"...you can go from Great do dead in one swipe."

And vice versa.

One time I got an odd looking mode on the top of a Classical guitar, and put it together to see how it would sound. It seemed OK so I shipped it off. The customer e-mailed back a few day later to say it was the most uneven sounding guitar he'd ever played. He tried several different types of strings, with no luck, and finally shipped it back for his refund. I kept REALLY careful track of that mode on the next few Classicals, and figured out how to convert it to a more normal shape by taking wood off the lower ends of the outer fans. I reached into the problem guitar with a finger plane and took two shavings 2" long off the lower ends of the outer four fans, and the problem was solved. Now I know what NOT to do.

that is my point Alan. It is hard to say just what you have to do until you built a few and can understand the cause and effect relationship of what you do.

how much have you discovered by simple explorative carving?

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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

John Hall asked:
"How much have you discovered by simple explorative carving?"

If by that you mean more or less random brace profiling outside of my usual zone, I have not done much of that in years. Basically, I have a system that works well for me, and stick with it. I have used Chladni tuning on student guitars with straight or scalloped bracing, and gotten them to work well, so the technique seems to be broadly applicable. For my own instruments, though, I tend to stick with a 'tapered' brace profile. Since I don't trust my own hearing very much, I rely on input from customers and students to refine my practice, and seem to be making slow but steady progress. At some point I expect I'll know what I'm doing.

You are all teaching me so much! Even if its over my head its a great read! Thanks

I heartily recommend to you the Gore/Gilet books. They may seem pricey, but they're worth every penny.

Voicing the top is one area where it is well worth it to invest the time and money to take a class or get someone to show you. Obviously, find someone whose guitars have a sound you like. I chose Kent Everett.

It is an especially valuable experience if you have already built a few and tried to use some of the various voicing methods. I had been tapping on everything in sight for several years, built equipment for and tried Chladni testing and also had worked with deflection testing even corresponding and talking with David Hurd who wrote the Left Brain Guitar. I was making slow progress. Then I spent one day with Kent in his class and it was like one big ahhaa moment. What I learned is done by feel but could also be done tapping. Since I have 20+ years of high performance aircraft ops on my hearing the method I learned is perfect for me.

Not saying really that you need to take a class but spend some time working at it (what you're doing here is perfect ) then, at some point, see if you get someone who really knows what they're doing to show you how they do it. Once you have one way of getting it right or at least close, then you are much more likely to have success with other methods.

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Steve Smith
"Music is what feelings sound like"