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How to tell an overbraced top with tap tuning?
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Author:  senunkan [ Wed May 07, 2008 11:15 am ]
Post subject:  How to tell an overbraced top with tap tuning?
Hi,

I am about to close the box of my 1st guitar.
I notice one thing when I tapped on the topboard at the bridge area.
Without the back, the guitar sounded with a clear ping with some sustain, but not particularly high pitch though.
Then I pressed the back against the box (closed without gluing) and tap the topboard at the same area.
This time round, it sounded with a thud with no sustain.
Is this a sign of the top being overbraced?

The bracing pattern is loosely based on a Torres 7 fan with open harmonic brace.
Each of the fan braces measured approximately 7mm wide 3mm tall.
Back braces are about 17mm tall throughout (at the center and at the ends)
Top thickness is between 2 to 3mm.
As I don't have a thickness caliper, I could only measure at the edge.
It measured 3mm before I thin it down to around 2mm.
So those in the center should be between 2 to 3mm...

Image

Sen.
http://senguitar.blogspot.com
Author:  Alexandru Marian [ Wed May 07, 2008 11:50 am ]
Post subject:  Re: How to tell an overbraced top with tap tuning?
Hey Sen,

I see you've made some progress. I think you should wait for the back to be glued on. At this point you have no work left to do on the braces. Best would be put the bridge and strings as well.

I have used an open harmonic design for the one I'm working on now too. The top (Lutz) tapers from 2.6 to 2.2 and I'm pretty certain it is too stiff. I'll send you some tap tone recording before I glue it to the neck.
Author:  Barry Daniels [ Wed May 07, 2008 12:29 pm ]
Post subject:  Re: How to tell an overbraced top with tap tuning?
Trying to hold the back to the sides with your hands is what may be killing the tap tone. When you get it glued on it will probably sound better.
Author:  Jon L. Nixon [ Wed May 07, 2008 1:29 pm ]
Post subject:  Re: How to tell an overbraced top with tap tuning?
Wow, Sen, really nice work. At this point some would say that tapping will not give you useful information. After the back is glued on you can experiment with selective thinning of the soundboard, especialy around the rim. I have got a feeling that this one is going to sound great.... [:Y:]
Author:  senunkan [ Wed May 07, 2008 8:47 pm ]
Post subject:  Re: How to tell an overbraced top with tap tuning?
Thank Alex, Barry, JNixon for you encouragement and help.
I guess there is no substitute for experience. :D
For my next build, I'll take more extensive notes, probably including the tap tones throughout the shaping process.
After seeing and hearing some great builds from Alex, Waddy, I was inspired to try to make mine just as good.

Currently, I am working on a router attachment for my B&D RTX for cutting the binding.
Progress is slow but I am enjoying every bit of the process.
Thanks, I really appreciate all the helpful valuable information shared in this forum.

Sen.
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