Official Luthiers Forum!

So being a new builder the first few guitars that my dad and I made were naturally over braced. They are still great sounding guitars, but there is just a little too much meat on their bones. I am trying to slim them down and find the sweet spot each guitar has.

I want to loosen up the guitar without compromising the structural integrity of it. I Realize that the main area of concern is around the bridge plate, and the braces resisting the force of the strings. With the lower legs of the X and a tone bar running across the bridge there is quite a bit of stiffness in that region. Now the question for me is how much can I loosen up the area near the bottom of the guitar.

Generally on our larger body guitars we have had 2 tone bars which have 2 scallops in them one near the bridge plate another approximately 3" from the rim of the guitar. While this has produced good guitars they have sounded a little "tight". By bringing the lower tone bar down to nothing before the second scallop I have loosened up the guitar and I am getting a far louder and clearer tap tone than I have ever heard on one of our guitars. The stiffness along the grain was definitely reduced though.

My inexperienced opinion is I am probably getting closer to where I need to be, but when you feel a top that is more flexible along the grain at the bottom of the lower bout than anything you have built it starts to make you think a little.

So here comes the impossible question to answer, knowing that there is decent stiffness around the bridge plate would you be concerned with some added flexibility near the bottom of the guitar? I know this is one of those things that is really hard to answer without the top in your hands.

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--Kyle Burner--

Kyle: Won't comment on the tone bar but will say something about your bridge plate. It is much wider and I think thicker than what I would use.Looks to me like it is .125 plus or so.....???
Tom

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A person who has never made a mistake has never made anything!!!

nope approximately .092

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--Kyle Burner--

I don't have the experience to help, but I'll give my opinion to compare with more expert opinion later.

I don't think the mass/stiffness you removed at the bottom of the lower tone bar will be a problem. It will likely help the sound too.

Like Tom, I'm concerned with the size of the bridge plate. Smaller may help the tone.

Also, you might consider reducing the stiffness of the finger braces. They look full height for part of the length. You might taper these from full height in the center down to nothing at the X-brace and nothing at edge of the lining.

So don't go by my suggestions......wait on more experienced opinions.

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Formerly known as Adaboy.......

For me, the really imortant area of the top is between the soundhole and bridge. I don't think it's any accident that the two most successful bracing patterns, Torre's 'fan' and the Martin 'X', both concentrate wood in that area.

I tell my students that the part of the top that's over the tailblock is all about sound, and has very little do do with structure, while the top at the neck block is all about structure and has very little to contribute to the sound. That's a simplification, of course, but it's still rather surprising how thin you can make the top at the tailblock without trouble, just so long as it's solid from the bridge up.

The 'Chladni tuning' method that I use seems to yeild guitars with a 'clear' and 'bright' sound. At first I found that I was taking a lot of material off the top behind the bridge to get the bass into balance. Then I got smarter, and started to taper the tops out before I put the bracing on. These days, I figure out how thick I want to make the top, based on it's stiffness along the grain, and make it a bit thicker than that at the neck end, and thinner at the tail. Depending on how I'm feeling about that top the total taper might be from .5 to .8mm (.02"to .03") It seems to work for me.