Falcate #2 Tapping Results

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chrisbaer
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Falcate #2 Tapping Results

Post by chrisbaer » Fri Nov 09, 2018 11:47 am

Hello again, everyone! So, my second Falcate guitar is well underway... The box is closed and bound and the BO/BO neck fitted.

Carpathian Spruce top with a target thickness of 2.67mm - I think I may have gone a touch thinner after leveling the rosette.
EIR back and sides with a target thickness of 2.26 - I believe I'm right on the money here.
I have only the bolts in the side mass blocks, but they're heavy at 20g each.

So, here's the results!
Falcate 2 Top Bound.png
T(1,1)1 is 100Hz, which I take as a win!
T(1,1)2 is 187Hz which I think is a bit high, yes? Some more side mass, maybe?
T(1,1)3 is 211Hz (the back tapped at 209), so I think I actually have a live back, yes?? The main back brace is only slightly scalloped, so I do have room to work.

Any suggestions, or does it look like I can proceed to finishing and putting the bridge on?

Thanks!!

Chris

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kiwigeo
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Re: Falcate #2 Tapping Results

Post by kiwigeo » Fri Nov 09, 2018 12:34 pm

I wouldn't be playing around too much with everything. Once bridge is on I'd expect a few Hz drop in main top frequency. I sometimes stick a bit of mass on the top roughly equivalent to the bridge mass to see where things might go with the top frequencies. I'd probably be aiming to keep the bridge as light as possible.

Have you thinned the top around the periphery of the main bout as per G and G? If you haven't yet done this then I'd leave this step out as it will also alter top frequency.

Back frequency looks a little low to what I normally get but looks to me like you're getting some coupling going on.

Trevor will no doubt pop in and add some (more) learned comments.
Martin

johnparchem
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Re: Falcate #2 Tapping Results

Post by johnparchem » Sat Nov 10, 2018 1:54 am

I am with Martin, I would not touch anything now until you see where you are at with the guitar strung up. On my classical guitars the top resonance goes up a bit when I glue on the bridge and down a bit when I string up the guitar, so not a big change from the point you are at. On my steel strings I see a drop of about 10 Hz in the top resonance from just closed with no bridge to strung up.

chrisbaer
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Re: Falcate #2 Tapping Results

Post by chrisbaer » Sat Nov 10, 2018 3:43 am

Thanks, John and Martin!

I only thinned the perimeter of the top very slightly, given that I had already gone a touch below the target thickness.
The bridge is walnut and is pretty light at 18g with holes drilled and the saddle slot routed.

I think my main focus with this guitar is that the back be as "live" and resonant as I can make it.
What are some hallmarks of a truly live back? Higher dB on the T(1,1)3?

Thanks again for all the help!

Chris

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Re: Falcate #2 Tapping Results

Post by johnparchem » Sat Nov 10, 2018 4:40 am

chrisbaer wrote:
Sat Nov 10, 2018 3:43 am

... I think my main focus with this guitar is that the back be as "live" and resonant as I can make it.
What are some hallmarks of a truly live back? Higher dB on the T(1,1)3?

Thanks again for all the help!

Chris
To me it is the way it couples with the top also I get a much more complex final tap spectrum with more spikes (like yours) providing an almost choir like voice. I would not do anymore tuning of the back or the back resonance will get too low. I follow Trevor's guidelines of three semitones above the top.

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Trevor Gore
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Re: Falcate #2 Tapping Results

Post by Trevor Gore » Sat Nov 10, 2018 11:26 am

johnparchem wrote:
Sat Nov 10, 2018 4:40 am
chrisbaer wrote:
Sat Nov 10, 2018 3:43 am

... I think my main focus with this guitar is that the back be as "live" and resonant as I can make it.
What are some hallmarks of a truly live back? Higher dB on the T(1,1)3?

Thanks again for all the help!

Chris
To me it is the way it couples with the top also I get a much more complex final tap spectrum with more spikes (like yours) providing an almost choir like voice. I would not do anymore tuning of the back or the back resonance will get too low. I follow Trevor's guidelines of three semitones above the top.
I recommend 4 semi tones but no closer than 3.

With the T(1,1)3 already at 211Hz, 4 semi tones separation is T(1,1)2 = 170Hz and T(1,1)3 = 214Hz. So leave the back and proceed to finishing. Trim to 170Hz with side mass after you've got it strung.

chrisbaer
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Re: Falcate #2 Tapping Results

Post by chrisbaer » Thu Nov 22, 2018 2:07 am

Good morning (or otherwise) to everyone! It's the day before Thanksgiving here in the States and I've just finished up my second Falcate Guitar - now I get to spend the rest of the day cleaning house!!

Thanks so much to this great forum and to Trevor and Gerard for their excellent book! Both have been a boon to my guitar building.

So, everything is finished (aside from some fretwork) and I've added 157g of side weights to each side (for a grand total of 356g including the bolts) to lower T(1,1)2 to 170Hz.
Falcate 2 final.png
Unfortunately, it looks like T(1,1)3 lowered a bit as well, which I didn't want. That could be just that particular tapping - maybe I'll go back and do it again once it's broken in a bit more and see if things have changed.

Also, it seems like there is very little bridge rotation - I think I need to get some of that fancy 'luthier's clay' to get a proper measurement! It should loosen up a little over time, too, right?

Any thoughts as to why my T(1,1)3 is so low? I followed the plans closely and used Mahogany braces with a GPa of 9.05, which seemed a reasonable number.

Some thoughts:

It really is an excellent sounding guitar! My wife says it sounds like an entirely different instrument! It has some nice, chimey trebles and a decent bass (although nothing you'd call 'booming') and is nice and loud. It has a very complex tone. I'm very pleased!

The intonation is excellent and open chords are in tune!

I can feel significantly more vibration in the guitar as I play - I suppose that's the 'responsive' bit!

All in all, a big jump forward for me.

Thanks again for all your help!

Chris

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Trevor Gore
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Re: Falcate #2 Tapping Results

Post by Trevor Gore » Thu Nov 22, 2018 10:37 am

I'd call that a win! Well done!

The T(1,1)3 is ~ 3.5 semitones above the T(1,1)2, so far enough away. It would have dropped from 211Hz to 205Hz mainly because of the bridge mass dropping the T(1,1)2 and causing less repulsion upwards of the T(1,1)3.

It's hard to say why the T(1,1)3 is lower than you expected. I don't know if you did any scalloping, but it's pretty sensitive to that. If the G 3rd fret 6th string is OK, I'd be calling it done.

Happy Thanksgiving!

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kiwigeo
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Re: Falcate #2 Tapping Results

Post by kiwigeo » Thu Nov 22, 2018 11:29 am

Nice work Chris. Getting the back frequency right can sometimes be a P in the A. I've only managed to get a nicely coupling back on one of my last three Gore builds. You could try and beef up the main lower back brace by scalloping the brace and then gluing in some more brace stock and then shaping same....your hand will get tired from hours of working through the soundhole but it's not impossible to do. I actually popped the back on one build and did the brace surgery before re-fitting the back. But in the end you you have a nice sounding guitar whether or not you obsess about the back coupling or not.
Martin

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