Specific mobility

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TallDad71
Blackwood
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Specific mobility

Post by TallDad71 » Fri Apr 09, 2021 10:17 pm

Trevor
I have spent some time measuring the specific mobility of some of my builds they fall anywhere between 15 and 18. Your book suggests that 18 is a good target value, I wonder if you could elaborate as to why?

My latest build has a specific mobility of 19.42. However the X braces at the small peaks are lower than usual, the result being some bowing in the soundboard under full tension. My first thought is that more than 18 is perhaps synonymous with braces that are insufficient.
Alan
Peregrine Guitars

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Trevor Gore
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Re: Specific mobility

Post by Trevor Gore » Sun Apr 11, 2021 9:51 am

The book says "Steel string guitars with monopole mobility greater than 14 x 10^-3 s/Kg are exceptional instruments indeed...." (p. 1-89)

Note that in Fig 1.7-8 the guitars below 14 are all wood X-braced guitars and the one above 18 is falcate braced with CF. That tells you something about responsive guitars...

North
Wandoo
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Re: Specific mobility

Post by North » Sun Apr 11, 2021 10:24 pm

TallDad71 wrote:
Fri Apr 09, 2021 10:17 pm
I have spent some time measuring the specific mobility of some of my builds
How do you measure monopole mobility ? Exactly as in the books? I have the feeling that I struggled a bit with some units there. I will have to check some guitars again. Thanks! :-)

seeaxe
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Re: Specific mobility

Post by seeaxe » Mon Apr 12, 2021 9:44 am

North wrote:
Sun Apr 11, 2021 10:24 pm
TallDad71 wrote:
Fri Apr 09, 2021 10:17 pm
I have spent some time measuring the specific mobility of some of my builds
How do you measure monopole mobility ? Exactly as in the books? I have the feeling that I struggled a bit with some units there. I will have to check some guitars again. Thanks! :-)
A timely question! I'm about to check some of my guitars and was about to follow guidance in the books, but wondering Alan whether you would care to post your method/set up? It sounds simple enough but always good to see how others do it. Especially when you haven't done it before :)
Richard

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