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PostPosted: Sat Apr 13, 2019 12:07 pm 
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Joined: Mon Aug 23, 2010 11:42 pm
Posts: 1444
First name: John
Last Name: Parchem
City: Seattle
State: Wa
Zip/Postal Code: 98177
Country: USA
Focus: Build
Status: Amateur
I had a niece build a tenor ukulele in my shop. We ended up with an interesting wolf note on the high G string or the A string tuned to a G. Actually a little flat or a little sharp no problem. We put strings on the Uke and strung it up with the neck clamped in a vice as shown in the picture and all of the strings sound great. I took it out of the vice and the G string sound awful it died right away and there was a rattle. Trying to track down the problem I cleaned up the rattle tightening the tuners and cleaning up the nut slot but the G note still just died. It was weird as everything I touched around the neck made the problem go away. Interesting enough while playing a C cord (just fretting the A sting on 3 fret) all sounded great again. A capo clamped on the headstock cleaned it up as well.

With this information I took a spectrum plot tapping the neck with the strings tuned to pitch muting the strings and lightly holding the neck. I have a steep peak right on 392 Hz (that G string).

It is a spanish heel neck. Sort of in the middle of the road for neck thickness. Other than telling her to always have a capo on her headstock, are there other clever solutions. Most of the ones I thought of are invasive, like replace the flat 4 mm rosewood fretboard with an ebony fret board, maybe making it 5 mm sloping to 4.5 mm at the 12 fret to get it heavier and maintain my setup. Or pull the fretboard and install a metal bar in a truss rod slot.

Thanks for any ideas.

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PostPosted: Sat Apr 13, 2019 12:45 pm 
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Joined: Thu Jul 28, 2016 12:35 pm
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First name: Hans
Last Name: Mattes
City: Petaluma
State: CA
Zip/Postal Code: 94952
Country: United States
Focus: Build
Status: Amateur
Have you tried adding a bit of weight to the headstock to lower the neck's resonant frequency? If that works, thinning the neck a bit to lower its stiffness should have a similar effect.


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PostPosted: Sat Apr 13, 2019 12:50 pm 
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Joined: Mon Aug 23, 2010 11:42 pm
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First name: John
Last Name: Parchem
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State: Wa
Zip/Postal Code: 98177
Country: USA
Focus: Build
Status: Amateur
Hans Mattes wrote:
Have you tried adding a bit of weight to the headstock to lower the neck's resonant frequency? If that works, thinning the neck a bit to lower its stiffness should have a similar effect.


Thanks, Yes a capo on the headstock fixes the issue. Thinning the neck is a possible solution. I think with her carving there was some I could take off the side of the necks as well.

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PostPosted: Sat Apr 13, 2019 12:57 pm 
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Joined: Mon Dec 24, 2012 7:30 am
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Location: Canada
First name: Paul
Last Name: Dzatko
City: mississauga
State: Ontario
Country: Canada
Focus: Build
David Hurd wrote about a similar problem in his book Left Brain Lutherie
By decreasing the sound hole radius by 1/8 0f an inch he was able to drop
the ukuleles frequency of just over 190 Hz (close to the G strings 196 Hz)
by a semitone or so getting rid of a Thunky G string.

Paul


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PostPosted: Sat Apr 13, 2019 1:54 pm 
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Joined: Mon Aug 23, 2010 11:42 pm
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First name: John
Last Name: Parchem
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State: Wa
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pkdz wrote:
David Hurd wrote about a similar problem in his book Left Brain Lutherie
By decreasing the sound hole radius by 1/8 0f an inch he was able to drop
the ukuleles frequency of just over 190 Hz (close to the G strings 196 Hz)
by a semitone or so getting rid of a Thunky G string.

Paul

Thanks Paul, The top resonance is not quite on A 211 Hz. That really threw me for a bit. It is the neck that start vibrating at 392 Hz. I think I just hit the lottery in terms of exactly hitting the G with the neck.

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PostPosted: Sat Apr 13, 2019 2:04 pm 
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Is it of short duration? If so, with the rattle, it sounds like it could be a true wolf note. I'd be concerned that taking off enough neck wood to fix it would be too much. Does it respond to weight added anywhere else?

A guy in our luthiers group had a similar problem. He tried a different brand of strings and it went away.

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PostPosted: Sat Apr 13, 2019 2:47 pm 
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Joined: Mon Aug 23, 2010 11:42 pm
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First name: John
Last Name: Parchem
City: Seattle
State: Wa
Zip/Postal Code: 98177
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Pat Foster wrote:
Is it of short duration? If so, with the rattle, it sounds like it could be a true wolf note. I'd be concerned that taking off enough neck wood to fix it would be too much. Does it respond to weight added anywhere else?

A guy in our luthiers group had a similar problem. He tried a different brand of strings and it went away.


Yes short duration. As I tune it up between F# and G still sounds good. When I get get very close to G the sustain goes away and I had the rattle. A finger on the nut, a capo on the head stock or even on the neck close to the nut makes the the problem go away. Different brand of strings is a good idea as the resonance changes under tension. In fact pulling the nut causes the 1st fret to become a shorter scale 0 fret and the Uke sounds great no problem. I will try the new strings. Also the student left a bit of a squared off shoulder near the nut so I cleansed that up.

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PostPosted: Sat Apr 13, 2019 5:03 pm 
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Joined: Mon Aug 23, 2010 11:42 pm
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First name: John
Last Name: Parchem
City: Seattle
State: Wa
Zip/Postal Code: 98177
Country: USA
Focus: Build
Status: Amateur
Thanks All,

I calmed down, I went over the instrument fixed a few unrelated things, One change that might have helped was close to the nut the neck was a little squared off so I took that wood off to match the rest of the neck and I went to a different brand of strings. Sounds good now.

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